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Bench Power Supply Packs a Lot into a DIN-Rail Package

เสาร์, 08/18/2018 - 21:01

We’re not sure why we’ve got a thing for DIN-rail mounted projects, but we do. Perhaps it’s because we’ve seen so many cool industrial control cabinets, or maybe the forced neatness of DIN-mounted components resonates on some deep level. Whatever it is, if it’s DIN-rail mounted, chances are good that we’ll like it.

Take this DIN-mounted bench power supply, for instance. On the face of it, [TD-er]’s project is yet another bench supply built around those ubiquitous DPS switching power supply modules, the ones with the colorful displays. Simply throwing one of those in a DIN-mount enclosure isn’t much to write home about, but there’s more to this project than that. [TD-er] needed some fixed voltages in addition to the adjustable output, so a multi-voltage DC-DC converter board was included inside the case as well. The supply has 3.3, 5, and 12 volt fixed outputs along with the adjustable supply, and thanks to an enclosed Bluetooth module, the whole thing can be controlled from his phone. Plus it fits nicely in a compact work area, which is a nice feature.

We haven’t seen a lot of DIN-rail love around these pages — just this recent rotary phase converter with very tidy DIN-mounted controls. That’s a shame, we’d love to see more.

JB Weld – Strong Enough To Repair a Connecting Rod?

เสาร์, 08/18/2018 - 18:01

JB Weld is a particularly popular brand of epoxy, and features in many legends. “My cousin’s neighbour’s dog trainer’s grandpa once repaired a Sherman tank barrel in France with that stuff!” they’ll say. Thankfully, with the advent of new media, there’s a wealth of content out there of people putting these wild and interesting claims to the test. As the venerable Grace Hopper once said, “One accurate measurement is worth a thousand expert opinions“, so it’s great to see these experiments happening.

[Project Farm] is one of them, this time attempting to repair a connecting rod in a small engine with the sticky stuff. The connecting rod under test is from a typical Briggs and Stratton engine, and is very much the worse for wear, having broken into approximately 5 pieces. First, the pieces are cleaned with a solvent and allowed to properly dry, before they’re reassembled piece by piece with lashings of two-part epoxy. Proper technique is used, with the epoxy being given plenty of time to cure.

The result? Sadly, poor — the rod disintegrates in mere seconds, completely unable to hold together despite the JB Weld’s best efforts. It’s a fantastic material, yes – but it can’t do everything. Perhaps it could be used to cast a cylinder head instead?

A Motion Coprocessor Without The Proprietary Layer

เสาร์, 08/18/2018 - 15:01

When you have a complex task that would sap the time and energy of your microprocessor, it makes sense to offload it to another piece of hardware. We are all used to this in the form of the graphics chipsets our computers use — specialised processors whose computing power in that specific task easily outshines that of our main CPU. This offloading of tasks is just as relevant at the microcontroller level too. One example is the EM Microelectronics EM7180 motion co-processor. It takes input from a 3-axis gyroscope/accelerometer and magnetometer, acting for all intents and purposes as a fit-and-forget component. Given an EM7810, your host can determine its heading and speed at a simple command, with no need for any hard work.

[Kris Winer] used the EM7810, but frustrated at its shortcomings decided to create a more versatile alternative. The result is a small PCB holding a Maxim MAX32660 ARM Cortex M4F microcontroller and the relevant sensors, with the MAX32660’s increased power and integrated flash easily eclipsing the EM7810.

As a design exercise it’s an interesting read even if you have no need for one. His write-up goes into detail on the state of the motion coprocessor art, and then looks carefully at pushing the limits of what is possible using an inexpensive PCB fabrication house such as OSH Park — you can get this chip as a Wafer-Level Package (WLP) which is definitely off-limits. Even with the TQFN-24 he picked though, the result is a tiny board and we’re happy to see it as an entry in the Return of the Square Inch Project!

It is perhaps surprising how few projects like this one make it into our sphere, as a community we tend to focus upon making one processor do all the hard work. But with the ready availability of inexpensive and powerful devices, perhaps this is an approach that we should reconsider.

Multi-switch Useless Box Is Useless In Multiple Ways

เสาร์, 08/18/2018 - 12:00

We’ve probably all seen (and built) a useless box, in which you flip a switch that activates a servo that pops out a finger and flips the switch off. [Coffeman500] decided to take this a step further by building a useless box with multiple switches. Flip one, the finger pops out to flip it back. Flip several switches, and the finger pops out and flips each back in turn.

It’s a smart build that [coffeeman500] says is his first electronics build. The compulsively switching brain of this is an ATmega328 driving an A4988 stepper motor driver, with one stepper moving the finger mechanism and the other moving the finger along a rail to reach each switch in turn. [Coffeeman500] has released the complete plans for this wonderful waste of time, including 3D models for the box and mechanism, plus the code. Redditors are already planning bigger and more useless designs with more switches, a pursuit that we fully support.

https://i.imgur.com/oVlNI0r.mp4

Via [Reddit]

Radio Antenna Mismatching: VSWR Explained

เสาร์, 08/18/2018 - 09:00

If you have ever operated any sort of transmitting equipment, you’ve probably heard about matching an antenna to the transmitter and using the right co-ax cable. Having everything match — for example, at 50 or 75 ohms — allows the most power to get to the antenna and out into the airwaves. Even for receiving this is important, but you generally don’t hear about it as much for receivers. But here’s a question: if a 100-watt transmitter feeds a mismatched antenna and only delivers 50 watts, where did the other 50 watts go? [ElectronicsNotes] has a multi-part blog entry that explains what happens on a mismatched transmission line, including an in-depth look at voltage standing wave ratio or VSWR.

We liked the very clean graphics showing how different load mismatches affect the transmission line. We also liked how he tackled return loss and reflection coefficient.

There was a time when driving a ham radio transmitter into a bad load could damage the radio. But if the radio can survive it, the effect isn’t as bad as you might think. The post points out that feedline loss is often more significant. However, the problem with modern radios is that when they detect high VSWR, they will often reduce power drastically to prevent damage. That is often the cause of poor performance more so than the actual loss of power through the VSWR mechanism. On the other hand, it is better than burning up final transistors the way older radios did.

Measuring VSWR without a transmitter is a bit trickier. A network analyzer can do it. While that used to be a pretty exotic piece of gear, it has become much more common lately.

A Tiny Steering Wheel You Can Print

เสาร์, 08/18/2018 - 06:00

Racing games are a great way to test drive that Ferrari you can’t quite afford yet, and the quality of simulations has greatly improved in the last 30 or so years. While there are all manner of high-quality steering wheels to connect to your PC or home console, many gamers still choose to play using a typical controller, using the thumbstick for steering. What if there was something in between?

What we have here is a tiny steering wheel you can print for an Xbox One controller, that mounts to the controller frame and turns rotational motion into vaguely linear horizontal motion on the thumbstick. It does come with some pitfalls, namely blocking a button or two and it also obscures some of the D-pad. However, for those of you driving in automatic mode without using the buttons to shift gears, this could be a fun device to experiment with. Files to print your own are available on Thingiverse.

It’s a neat hack, and there’s plenty of room to take the idea further and personalise it to suit your own tastes. While you’re there, why stop at steering? You could make your own custom buttons, too!

[via Gizmodo, thanks to Itay for the tip!]

The Wonderful World of USB Type-C

เสาร์, 08/18/2018 - 03:00

Despite becoming common over the last few years USB-C remains a bit of a mystery. Try asking someone with a new blade-thin laptop what ports it has and the response will often include an awkward pause followed by “USB-C?”. That is unless you hear “USB 3” or maybe USB 3.1. Perhaps even “a charging port”. So what is that new oval hole in the side of your laptop called? And what can it really do? [jason] at Reclaimer Labs put together a must-read series of blog posts in 2016 and 2017 plumbing the depths of the USB 3.1 rabbit hole with a focus on Power Delivery. Oh, and he made a slick Easy Bake Oven with it too.

A single USB Type-C connector

When talking about USB-C, it’s important to start at the beginning. What do the words “USB-C” entail? Unsurprisingly, the answer is complicated. “USB Type-C” refers only to the physical connector and detail about how it is used, including some of the 24 pins it contains. Then there are the other terms. “USB 3.1” is the overall standard that encompasses the Type-C connector and new high-speed data busses (“USB SuperSpeed” and “SuperSpeedPlus”). In addition there is “USB Power Delivery” which describes power modes and even more pin assignments. We’re summarizing here, so go read the first post for more detail.

The second post devotes a formidable 1,200 words to providing an overview of the electrical specifications, configuration communication, and connector types for USB 3.1.

Marketing at its finest

The third post is devoted to USB Power Delivery. Power Delivery encompasses not only the new higher power modes supported (up to 100W!), but the ways to use the extra 10 or 13 pins available on the Type-C connector. This is both the boon and bane of USB-C, allowing apparently identical ports to carry common signals like HDMI or DisplayPort, act as analog audio outputs, and provide more exotic interfaces like PCIe 3.0 (in the form of Thunderbolt 3, which is a yet another thing this connector can be used for).

It should be clear at this point that the topics touched by “USB Type-C” are exceptionally complex. Save yourself the trouble of a 90MB specification zipfile and take a pass through [jason]’s posts to understand what’s happening. For even more detail about Power Delivery, he walks through sample transactions in a separate post.

Turning Cheap WiFi Modules Into Cheap WiFi Swiss Army Knives

เสาร์, 08/18/2018 - 01:30

When the ESP8266 was released, it was sold as a simple device that would connect to a WiFi network over a UART. It was effectively a WiFi modem for any microcontroller, available for just a few bucks. That in itself is awesome, but then the hackers got their hands on it. It turns out, the ESP8266 is actually a very capable microcontroller as well, and the newest modules have tons of Flash and pins for all your embedded projects.

For [Amine]’s entry to the Hackaday Prize, he’s using the ESP8266 as the ultimate WiFi Swiss Army knife. The Kortex Xttend Lite is a tiny little WiFi repeater that’s capable of doing just about anything with a WiFi network, and with a bit of added hardware, can connect to Ethernet as well.

The hardware on this board sports an ESP8266-07S module, with two free GPIO pins for multiple functions. There’s a USB to UART in there, and a voltage regulator that’s capable of outputting 600mA for the slightly power hungry radio. There’s also an integrated battery management and charge controller, allowing this board to charge an off-the-shelf lithium cell and run for hours without any wires at all.

So, what can this board do? Just about everything you would want for a tiny little WiFi Swiss Army knife. There’s traffic shaping, port mapping, packet sniffing, and even support for mesh networking. There’s also an SMA connector on there, so grab your cantennas — this is a great way to extend a WiFi network, too.

This is a well-designed and well-executed project, and what makes this even more amazing is that this was done as one of [Amine]’s high school projects. Yes, it took about a year to finish this project, but it’s still amazing work for [Amine]’s first ‘high-complexity’ design. That makes it an excellent learning experience, and an awesome entry to this year’s Hackaday Prize.

The HackadayPrize2018 is Sponsored by:





Circuit VR: A Tale Of Two Transistors

เสาร์, 08/18/2018 - 00:01

Last time on Circuit VR, we looked at creating a very simple common emitter amplifier, but we didn’t talk about how to select the capacitor values, or much about why we wanted them. We are going to look at that this time, as well as how to use a second transistor in an emitter follower (or common collector) configuration to stiffen the amplifier’s ability to drive an output load.

Several readers wrote to point out that I’d pushed the Ic value a little high for a 2N2222. As it turns out, at least one of the calculations in the comments was a bit high. However, I’ve updated the post at the end to explore what was in the comments, and talk a bit more about how you compute power dissipation with or without LTSpice. If you read that post, you might want to jump back and pick up the update.

Back to Our Program

As a reminder, the LT Spice circuit we started with appears below. You can download that file and others on GitHub.

Output Z

Last time, we went over the design equations and even looked at a spreadsheet for figuring out the values. That spreadsheet assumed you wanted to pick a few items including the normal collector current for the device. In some cases, though, your driving design goal will be a certain output impedance. In that case, pick RC accordingly, and go through the same steps but you’ll compute Ic instead of selecting it and skip step 4. You can use this same procedure when the actual load you are driving is the collector resistor, which isn’t uncommon.

It is easy to see that RC is the output impedance if you do a little logic. Remember, this amplifier inverts. So Q1 is as close to off as it is going to get when the input signal is large. Assume Q1 turned all the way off. What would the output circuit look like then? A voltage divider made up of RC and RL. Like any voltage divider, the maximum power in RL is going to occur when RL=RC. If you have more of an engineering mindset, you can think of it as the amplifier’s Thevenin equivalent is a voltage source with RC as the resistor. Or, if you are more graphical, think of a voltage divider with a 10V input and a 100 ohm “top” resistor (R1). If you try values for the bottom resistor (R2) ranging from 1 to 200, it looks like this:

The voltage in R2 keeps going up, but the current goes down. When R2 is 100 ohms, the power maxes out at about 250 mW. This is why you try to match, say, a transmitter with an antenna or speakers with an amplifier.

You might want to control input impedance as well. For the input impedance case, you would have to control the values of Re, R1, and R2 which is quite a bit harder without setting up a lot of simultaneous equations or just iterating. It also will depend on beta, which is notoriously unreliable. If the product of Re and beta is a large number, you can approximate it as R1 and R2 in parallel, and that’s often good enough.

Note that in the above circuit example I just put a large resistor in as the load so it didn’t affect things much. But what if that resistor had been a 16-ohm speaker, perhaps?

Back to Capacitors

So why are capacitors important? Because the transistor needs a very specific set of DC voltages on its terminals and connecting an input or output to it is going to perturb that. However, we can isolate the circuit from any DC effects using a capacitor on the input and the output. That means we can’t amplify very low-frequency signals well — the capacitors will act like large resistors. But at higher frequencies, it won’t be any problem. You can see that in the simulation where some capacitors guard the inputs and the outputs.

If you want to see the effect in a less distracting way, check out this simulation. Here an input signal is riding a DC level. A voltage divider sets another DC level. With a capacitor between them, the circuit essentially shifts the input to a new DC level, like this:

The reactance of the capacitor, of course, depends on the frequency, according to 1/(2*π*f*C). That means the higher the capacitance, the lower the reactance at a given frequency. In this case, the 100 Hz signal sees the 10 uF capacitor as about 160 ohms of reactance. At 47uF, that drops to about 34 ohms. At 1 kHz, that will divide both of those values by another 10 (16 and 3.4 ohms).

Gain

The emitter resistor essentially introduces negative feedback which reduces our dependence on beta and makes things generally more stable. However, it also limits gain. If you suppose you have RE as a short-circuit — 0 ohms — you might think you could get infinite gain. But, in fact, you really just get a small internal resistance that is temperature- and current-dependent. At room temperature, though, it is generally just a few ohms at most. It would still increase the gain quite a bit if we could just short the emitter — in theory, up to the beta of the transistor. But without the negative feedback, we get all the other undesirable features we tried to avoid.

However, just as we use capacitors to isolate the input and output, why can’t we use a capacitor to short the signal to ground even if the DC path is through the resistor? As it turns out, you can. Try adding a capacitor across RE and watch the output go higher. Below, you can see the same output with a 47 uF capacitor across RE. Look at the scales. That 0.2V input signal now produces an output of over 5V, peak-to-peak. That’s a gain of about 25, or 5 times the DC gain.

Gain with bypass cap

The effect varies on the value of the capacitor and, of course, the frequency. Here’s the output with 10uF, 47uF, and 100 uF capacitors (first graph, below). The second graph shows the effect versus frequency. You typically want the reactance of the capacitor to be about 1/10th of the emitter resistance at the frequency where you will accept a 3dB drop off.

Three values of bypass cap Three different frequencies

Note that the capacitor works so well, that at some frequencies, we go beyond the allowable gain and clip (see the last graph). Depending on your design goals, you may need to be careful with that.

Selecting Coupling Capacitors

To know what value to assign the coupling capacitors, you need to know the impedance of the amplifier. That’s fairly easy to estimate, but with LT Spice we can do better. If you look at V2, you know it is putting out 50 mV and you can measure the current drawn from it. Ohms law will tell you that .05 divided by that current must be the resistance V2 “sees.” With C1 set ridiculously high (1F) and V2’s internal resistance set to zero, the circuit draws about 1.75 mA from V2. That’s about 28.6 ohms. So if you know the 3dB frequency you want you simply have to compute the capacitance using the familiar 1/(2*π*f*R) formula. Assume we want 10 kHz as the 3dB point. Since R is 28.6 you need at least 0.6 uF of capacitance. Of course, you can also reverse the formula and determine what your 3 dB point should be given a certain value of capacitor.

Here’s a little WolframAlpha tip. If you try to do the above calculation, you get the answer in scientific notation: 5.56 x 10-7. Sure, you can just shift the decimal point two to the right to get the exponent to -9… or is that to the left? However, you can also just add the words “engineering form” to your query, and you’ll get the answer to the nearest exponent that’s a multiple of 3.

Output Loading

The other problem you’ll often see is that you need to drive a low impedance load which can limit your gain since matching that impedance will prevent you from using a large RC. One answer is to use an output transistor as an emitter follower or common collector amplifier. This is a very simple setup where the input to the base appears practically unchanged on the emitter. So the gain of the stage is nearly 1. That might not seem like a great thing until you realize that the output impedance of such an amplifier is roughly the source impedance divided by beta. Remember, lower output impedance is good because you can drive a wider range of load.

Suppose your RC in the main amplifier is 1600 ohms and you would like to drive a 16-ohm speaker. If the emitter follower beta is 100, the effective impedance seen from the main amp will be 1.6K ohms and the output impedance of the stage will be very low. But because in this case, the emitter resistor is probably the load itself, you won’t want to put a capacitor in the output because it would block the path to ground.

Have a look at this design:

This is very nearly the same amplifier as before, but there’s no coupling capacitor on the output. In addition, the component values changed a bit. When Q1 is turned off, the maximum voltage will go to the load and this will transfer the most power when RL=RC so the output impedance at Q1 is 1600 ohms. This is a poor match for a 16 ohm speaker, but Q2 can get us in the neighborhood in the emitter follower configuration. It is true that beta isn’t reliable, so the match probably won’t be perfect, but it should be good enough for most purposes.

Here’s the output:

Compare that with the output of the original amplifier driving a 16-ohm load. You’ll need to reduce the input drive down to 50mV, but even then the output from the original circuit will be very disappointing.

Of course, Q2 is going to need to be a power transistor. You won’t be able to quite get all 15V on the base of Q2, but you could get close. After the emitter drop, you could have a Ve of about 14V and that’s a little less than 900 mA or around 13 plus watts. Picture a big device with a heat sink. Luckily, the simulation doesn’t care. But, of course, that’s also one of the dangers of simulation is that you can overstress the models and they don’t care.

The End?

As much as we’ve talked about the common collector amplifier, there’s a lot more to it. What if the collector load is a tuned circuit? Or the emitter bypass? You can construct lots of things including multistage amplifiers using this as a building block.

By the way, you might think that bipolar transistors are old-fashioned compared to FETs, but they do have their uses. Also, all of these amplifier configurations have corresponding FET designs. The ideas are the same but, of course, the design equations are a bit different. FETs operate on voltages and there are other peculiarities. For example, some types of FETs are normally on, so you’ll need a negative bias voltage to get them to turn off. FETs — especially MOSFETs — have very high input impedance which makes input circuits easy to design. However, they also introduce capacitance which can be tricky at higher frequencies. But that’s a topic for a future Circuit VR.

Semi-automated Winder Spins Rotors for Motors

ศุกร์, 08/17/2018 - 22:30

What’s your secret evil plan? Are you looking for world domination by building a machine that can truly replicate itself? Or are you just tired of winding motor rotors and other coils by hand? Either way, this automated coil winder is something you’re probably going to need.

We jest in part, but it’s true that closing the loop on self-replicating machines means being able to make things like motors. And for either brushed or brushless motors, that means turning spools of wire into coils of some sort. [Mr Innovative]’s winder uses a 3D-printed tube to spin magnet wire around a rotor core. A stepper motor turns the spinner arm a specified number of times, pausing at the end so the operator can move the wire to make room for the next loop. The rotor then spins to the next position on its own stepper motor, and the winding continues. That manual step needs attention to make this a fully automated system, and we think the tension of the wire needs to be addressed so the windings are a bit tighter. But it’s still a nice start, and it gives us some ideas for related coil-winding projects.

Of course, not every motor needs wound coils. After all, brushless PCB motors with etched coils are a thing.

Getting An RF Low-Pass Filter Right

ศุกร์, 08/17/2018 - 21:01

If you are in any way connected with radio, you will have encountered the low pass filter as a means to remove unwanted harmonics from the output of your transmitters. It’s a network of capacitors and inductors usually referred to as a pi-network after the rough resemblance of the schematic to a capital Greek letter Pi, and getting them right has traditionally been something of a Black Art. There are tables and formulae, but even after impressive feats of calculation the result can often not match the expectation.

The 30MHz low-pass filter, as QUCS delivered it.

Happily as with so many other fields, in recent decades the advent of affordable high-power computing has brought with it the ability to take the hard work out of filter design, Simply tell some software what the characteristics of your desired filter are, and it will do the rest. The results are good, and anyone can become a filter designer, but as is so often the case there remains a snag. The software calculates ideal inductances and capacitances for the desired cut-off and impedance, and in selecting the closest preferred values we modify the characteristics of the result and possibly even ruin our final filter. So it’s worth taking a look at the process here, and examining the effect of tweaking component values in this way.

The idealised graph produced by QUCS for our filter.

The filter we’re designing is simple enough, a 5th-order Bessel filter, and the software is the easy-to-use QUCS package on an Ubuntu Linux machine. Plug in the required figures and it spits out a circuit diagram, which we can then simulate to show a nice curve with a 3dB point right on 30MHz. It’s an extremely idealised graph, and experience has taught me that real-world filters using these designs have a lower-frequency cut-off point, but for our purposes here it’s a good enough start.

As previously mentioned, the component values are not preferred ones from a commercially available series, so I can’t buy them off the shelf. I can wind my own inductors, but therein lies a whole world of pain of its own and I’d rather not go there. RS, Mouser, Digikey, Farnell et al exist to save me from such pits of electronic doom, why on earth would I do anything else but buy ready-made?

My revised filter circuit with off-the-shelf component values.

So each of the components in the above schematic needs moving up or down a little way to a preferred value. What effect will that have on the performance of my filter? Changing each value and re-running the simulation shows us the graph changing subtly each time, and it can sometimes be a challenge to adjust them without destroying the filter entirely. Particularly with the higher-order filters with more components in the network you can observe the effect of individual components on the gradient at different parts of the graph, but as a rule of thumb making values higher reduces the cut-off frequency and making them lower increases it. In my case I always pick higher values for that reason: my nearest harmonic I wish to filter is at double the frequency so I have quite some headroom to play with.

The revised curve from the filter with preferred values.

Having replaced my component values with preferred ones I can run the simulation again, and I can see from the resulting graph that I’ve been quite fortunate in not damaging its characteristics too much. As expected the cut-off frequency has shifted up a little, but the same curve shape has been preserved without any ripples appearing or it being made shallower.

If I were using this filter with a real transmitter I would ensure that I designed it with a cut-off at least a quarter higher than the transmission frequency. In practice I find the cut-off to be sharper and lower than the simulation leads one to expect, and for example, were I to use this one with a 30 MHz transmitter I’d find it attenuated the carrier by more than I’d consider acceptable. It must also be admitted that changing the component values in this way will also change the impedance of the filter from the calculated 50 ohms, however in practice this does not seem to be significant enough to cause a problem as long as the value changes are modest.

We haven’t made this filter, but in the past we’ve featured another one I did make, and by coincidence it was in the same frequency range. When I wrote a feature on automating oscilloscope readings, the example I used was the characterisation of a 7th-order 30 MHz low-pass filter. It might even be one of the ones in the header image, pulled from my random bag of filter boards for the occasion.

What’s Behind the Door? An IoT Light Switch

ศุกร์, 08/17/2018 - 18:00

We’re not sure who designed [Max Glenister]’s place, but they had some strange ideas about interior door positioning. The door to his office is right next to a corner, yet it opens into the room instead of toward the wall. Well, that issue’s been taken care of. But the architect and the electrician got the last laugh, because now the light switch is blocked by the open door.

Folks, this is the stuff that IoT is made for. [Max] here solved one problem, and another sprang up in its place. What better reason for your maiden voyage into the cloud than a terrible inconvenience? He studied up on IoT servo-controlled light switching, but found that most of the precedent deals with protruding American switches rather than the rockers that light up the UK. [Max] got what he needed, though. Now he controls the light with a simple software slider on his phone. It uses the Blynk platform to send servo rotation commands to a NodeMCU, which moves the servo horn enough to work the switch. It’s simple, non-intrusive, and it doesn’t involve messing with mains electricity.

His plan was to design a new light switch cover with mounting brackets for the board and servo that screws into the existing holes. That worked out pretty well, but the weight of the beefy servo forced [Max] to use a bit of Gorilla tape for support. He’s currently dreaming up ways to make the next version easily detachable.

Got those protruding American switches? [Suyash] shed light on that problem a while back.

No SD Card Slot? No Problem!

ศุกร์, 08/17/2018 - 15:00

We feature hacks on this site of all levels of complexity. The simplest ones are usually the most elegant of “Why didn’t I think of that!” builds, but just occasionally we find something that is as much a bodge as a hack, a piece of work the sheer audacity of which elicits a reaction that has more of the “How did they get away with that! ” about it.

Such a moment comes today from [Robinlol], who has made an SD card socket. Why would you make an SD card socket when you could buy one is unclear, beyond that he didn’t want to buy one on an Arduino shield and considered manufacture his only option. Taking some pieces of wood, popsicle sticks, and paperclips, he proceeded to create a working SD card of such bodgeworthy briliance that even though it is frankly awful we still can’t help admiring it. It’s an SD card holder, and despite looking like a bunch of bent paperclips stuck in some wood, it works. What more could you want from an SD card holder?

Paperclips are versatile items. If an SD card holder isn’t good enough, how about using them in a CNC build?

PCB Junk Drawer Turned Into Blinky Mosaic

ศุกร์, 08/17/2018 - 12:00

We’ve all got a box full of old PCBs, just waiting to be stripped of anything useful. [Dennis1a4] decided to do something with his, turning it into an attractive mosaic that he hung on the wall of his new workshop. But this isn’t just a pile of old PCBs: [Dennis1a4] decided to use the LEDs that were on many of the old boards, creating a blinky junk build. That’s kind of neat in itself, but he then decided to go further, building in an IR receiver so he could control the blinkiness, and a PIR sensor that detected when someone was near the mosaic.

This whole setup is controlled by an ATMega328p  that is driving a couple of PCF8575 port expanders that drive the LEDs. These blink in Morse code patterns. [Dennis1a4] also used an array of DIP switches on one of the boards to randomize the patterns, and wired in a pizeo buzzer on another board to make appropriate bleepy noises.

Digital Dining With Charged Chopsticks

ศุกร์, 08/17/2018 - 09:00

You step out of the audience onto a stage, and a hypnotist hands you a potato chip. The chip is salty and crunchy and you are convinced the chip is genuine. Now, replace the ordinary potato chip with a low-sodium version and replace the hypnotist with an Arduino. [Nimesha Ranasinghe] at the University of Maine’s Multisensory Interactive Media Lab wants to trick people into eating food with less salt by telling our tongues that we taste more salt than the recipe calls for with the help of electrical pulses controlled by everyone’s (least) favorite microcontroller.

Eating Cheetos with chopsticks is a famous lifehack but eating unsalted popcorn could join the list if these chopsticks take hold and people want to reduce their blood pressure. Salt is a flavor enhancer, so in a way, this approach can supplement any savory dish.

Smelling is another popular machine hack in the kitchen, and naturally, touch is popular beyond phone screens. You have probably heard some good audio hacks here, and we are always seeing fascination stuff with video.

A Surprisingly Practical Numitron Watch

ศุกร์, 08/17/2018 - 06:00

Regular Hackaday readers are surely familiar with Nixie tubes: the fantastically retro cold cathode display devices that hackers have worked into all manner of devices (especially timepieces) to give them an infusion of glowing faux nostalgia. But unfortunately, Nixie displays are fairly fragile and can be tricky to drive due to their high voltage requirements. For those who might want to work with something more forgiving, a possible alternative is the Numitron that uses incandescent filaments for each segment.

There hasn’t been a lot of prior-art that utilizes Numitrons, but that might be changing, given how fantastic this wristwatch created by [Dycus] looks. With a multi-day battery life, daylight readability, and relatively straightforward construction, the Filawatch is likely to end up being something of a reference design for future Numitron watches.

[Dycus] has gone through three revisions of the Filawatch so far, with probably at least one more on the way. The current version is powered by a ATmega328 microcontroller with dual 16-bit LED drivers to control the filaments in the KW-104S Numitron display modules. He’s also included an accelerometer to determine when the wearer is looking at the display, and even a light sensor to control the brightness of the display depending on the ambient light level.

If there’s a downside to Numitron displays, it’s their monstrous energy consumption. Just like in the incandescent light bulbs most of us have been ditching for LED, it takes a lot of juice to get that filament glowing. [Dycus] reports the display draws as much as 350 mA while on, but by lighting it up for only five seconds at a time it can be checked around 150 times before the watch needs to be recharged.

Its been a few years since we’ve seen a Numitron watch, and it’s interesting to see how the state of the art has advanced.

[via /r/electronics]

Hanging, Sliding Raspi Camera Adds Dimension To Octoprint

ศุกร์, 08/17/2018 - 03:00

Are you using Octoprint yet? It’s so much more than just a way to control your printer over the internet, or to keep tabs on it over webcam when you’re off at work or fetching a beer. The 3D printing community has rallied around Octoprint, creating all sorts of handy plug-ins like Octolapse, which lets you watch the print blossom from the bed via time-lapse video.

Hackaday alum [Jeremy S Cook] wanted to devise a 3D-printable mount for a Raspi camera after finding himself inspired by [Tom Nardi]’s excellent coverage of Octoprint and Octolapse. He recently bought a wire shelving unit to store his printer and printer accessories, and set to work. We love the design he came up with, which uses the flexibility of the coolant hose to provide an endlessly configurable camera arm. But wait, there’s more! Since [Jeremy] mounted it to the rack with zip ties, the whole rig shimmies back and forth, providing a bonus axis for even more camera views. Slide past the break to see [Jeremy]’s build/demo video.

It’s great to be able to monitor a print from anywhere with internet access, but the camera is almost always set up for a tight shot on the print bed. How would you ever know if you’re about to run out of filament? For that, you need a fila-meter.

Getting Kitted to Teach your First Hardware Workshop

ศุกร์, 08/17/2018 - 00:01

I was always a sucker for art classes in my early days. There was something special about getting personal instruction while having those raw materials in your hands at the same time. Maybe it was the patient voice of the teacher or the taste of the crayons that finally got to my head. Either way, I started thinking: “I want to do this; I want to teach this stuff.”

Last year at Hackaday Superconference I got my chance. Hardware workshops with real hardware were so rare; I just had to bring one to the table! What follows is my tale of joys and woes bringing together a crew to take their first few steps into the world of cable-driven animatronics. If you’re thinking about getting your feet wet with teaching your own hardware workshop, read on. I’ve packed this story with as much of my own learnings as I could to set you on a path to success.

The good news is that Supercon returns every year. I you want to take part in some epic workshops like this one, grab a ticket for this year’s conference now. If you want to host a hardware workshop, the Call for Proposals is still open! Okay, let’s dive in.

2016 was the year of the tentacle

In July of 2017 I saw the call for workshop proposals go out. The year before that I had taken some inspiration from the Stan Winston Tutorial series to build my own cable-driven tentacle mechanism. That two-stage mechanism was a smashing success as a party trick, and I wrote a brief guide to building your own on these pages. With tentacle parts still loitering in my garage a year later, I figured: why not bring a tentacle-mechanism-building workshop to the Hackaday Supercon?

Victory Means… Determining the Scope of Your Workshop

Defining success was going to be my first challenge, and my focus needed to center on my target audience: the workshop attendees. Just who are these people? And how does this workshop make their Supercon just a little more awesome? I figured that these folk could come from all walks of life. From sleepwalks to moonwalks, they’re background in tinkering could be anywhere from 0-to-NASA (literally), and I needed to make sure everyone was having a good time. I realized that not everyone would finish, but I wanted to ensure that anyone could finish later on their own time so that all people could get to the same goal: a working tentacle.

With the audience in mind, I forged my thesis: I wanted workshop attendees to get a solid roadmap of principles for working with laser-cut materials, and I wanted everyone to walk away with something physical that’s either finished or finishable without extra guidance or tools. I wanted attendees to go back to their local hackerspaces and feel comfortable plugging designs into the laser cutter and getting parts out that fit together.

What’s Getting Assembled?

With about 2.5 hours to go from 0-to-tentacles, I was going to need to make some serious mods to the old design to make it sizable for a Saturday morning stint — only moments after a cup of coffee! First off, I realized that my old build was just too complicated. There were two controllers and two flexible stages. Honestly, building two of the same controller is just plain ol’ repetitive, so I cut my old design in half, almost literally. Instead of two controllers, we’d just have one. Instead of a long tentacle with four degrees of freedom, we’d make a shorter one with two. Behold: the Workshop Tentacle was born!

Workshop Tentacle was supposed to be easy to build, so it needed a small BOM. To get there, I redesigned the controller and tentacle to cut down on the number of unique parts. Less unique parts makes the missing screw that-just-flew-across-the-room-never-to-be-seen-again a little less precious. In the worst of cases, if I had left out a part across all kits entirely, it would only be a 30 minute drive from Supercon to the mother-of-all-mechanical-parts: McMaster-Carr. Most of my nuts and bolts were sourced there anyways, so if I made some gross mistake making the kits, I’d actually be able to get them back before the workshop finished.

I premanufactured everything I could. This meant instead of having attendees laser-cut the parts themselves, I’d spend 10 minutes discussing the key features of the laser cutter and what effects it has on your parts. Each kit only needed to drill out two identical parts, but the holes weren’t allowed to be misaligned, so we couldn’t use hand drills… or could we? I turned to my friend [Amy] with this question, and she gave me the pro-tip I needed: a drill guide. A drill guide was a supplementary tool for a hand drill that would guide it vertically into the hole ensuring a straight cut. Presto! With a drill guide, we could use hand drills! I ended up laser-cutting a custom one for just this particular purpose. It worked flawlessly.

Great Instructions Lead to Great Workshops:

In any given classroom there’s usually one teacher to about 20+ students. Getting peppered with 20+ questions every 20 minutes would spell doom to the instructor trying to get through their lecture notes. Lucky for me, I had one secret weapon that I could arm in advance: building instructions. Here’s a snapshot of what they looked like:

On delivery day my plan would be to (1) give a quick rundown of the kit and the workshop tools while highlighting the pinchpoints, and then (2) send them on their way building kits, using the instructions as a guide.

Instructions were now a must-have, but what were they supposed to look like? One one hand, I figured if my instructions halfway resembled Lego manuals, they might fly with most. Lego’s target audience starts at age 5 and manages to get by without a single written word of English (or Danish)! On the other hand, I had to remember why my target audience was here in the first place.

This was a group of attendees who could very well be inspired to build by the engineering domain. Shouldn’t I try to treat them like real engineers? In the end, I settled for a series of engineering-style exploded views. In the professional world, I might actually hand these off to a technician and expect them to come back with a tentacle. For this workshop though, I made a few extra notes in the drawings, figuring that “explicit would be far better than implicit.” In this case, just like Lego, each page had a part list of the necessary parts for that step. Hopefully, these instructions would keep most of us on the right track doing independent work. Of course, if anything else came up, they could still poke me with questions.

The Kit: the making of…

As for the actual kit-making, I needed to source a few thousand parts. For starters, I decorated all my CAD models with part numbers and vendor metadata and then exported a part list straight out of the software package. No manual bookkeeping needed! As long as my model wasn’t missing any screws, I knew exactly what I needed to order and fabricate.

Laser-Cut Parts

The end of September was coming up quickly. With about a month away, I needed to cut just over 450 pieces for all 15 kits. I had a couple options: cut them via a 3rd party or use my homebrew laser cutter in the garage. A 3rd party might really come in handy here, but they were going to charge me by the minute. Cutting at home would just cost me time and had the extra bonus that I’d be able to dial in any sizing tolerances as I see fit. I figured I’d try the cut-at-home route first.

my Millennium-Falcon-Piece-of-Junk doing its thing like a champ

Amazingly, the whole job only took about 9ish hours to complete without any major hitches! (Woohoo! Turns out you can build a production-worthy laser cutter at home if you put your mind to it!) Before cutting parts in bulk, I ran a few tests to find the maximum speeds at which I could reliably cut through parts. A few extra minutes of dialing in the numbers saved me hours before doing the same job as many as 60 times in some cases. I also spread those 9 hours out over the two weeks so that I wouldn’t go crazy idling in the garage while the laser did all the heavy lifting.

It was here in my first production run of laser-cut parts that I discovered an interesting phenomenon. Cutting away large chunks of material out of a sheet of Delrin tends to relieve internal stresses, causing the sheet to bend while cutting. To counteract the bends, I weighed down the sheet in as many places as I could. With all the effort I put into keeping the plastic from warping, I now wonder if 3rd party laser-cutter shops do any sort of fixturing before running a job. At the end of the day, I was glad that I was able to do the job myself rather than risk receiving a surprise batch of parts that were out of spec.

Special Parts

Most parts came in from McMaster-Carr except for a couple of specialty items. One of these is the spring guide, the flexible sheath that the cables ride in that make the mechanism work in the first place! Since these were made-to-order, I placed an order about a month in advance. (They barely came in on time, so I’ll be sure to give myself even more headroom next year!)

The next specialty item was a set of flexible shafts from AliExpress. These shafts form the core of the tentacle mechanism, which let the tentacle flex without twisting. I knew that these parts would probably ship by boat, so I also placed this order a month in advance.

Last on the specialty items were miniature wheel hubs. Each tentacle segment needs to be rigidly fixed to the flexible shaft. A hub with a set-screw did the trick perfectly. It’s a blessing that so many robotics-tuned parts which used to require a machine shop to make are now off-the-shelf items these days. The folks at Pololu were also very kind to give me a discount on a bulk order of their wheel hubs.

Bagging it all up

Probably my favorite part in this endeavor: bagging! Once I had all the parts in the living room, I just needed to put them in the right spot. Easy right?

I found a use for all those McMaster baggies!

To help with this adventure, I recruited a few friends. Using the part lists in the instructions, we were able to bag everything up in about 12 people-hours, thankfully shared among 3 people! I always wanted to have a crew of friends come over and bag a series of projects I made, whether that was for fulfilling my first Kickstarter or kicking off my first hardware workshop. There’s just something special about the ritual of your friends gathered in a part-bagging assembly line.

Bagging also turned out to be my biggest place for improvement. To help my attendees, I decided to bag up parts by sub-assembly. What that means was each page of the instruction had its own bag. This idea turned out to be overkill when delivery day came around. Since some tasks center around using the same tool over and over, it would be much more helpful to bag parts by type. In that way, they can do some bulk operations in one go, like heat-sticking all the heat-set inserts. Finally, if I bag parts by type, I can weigh them to make sure that they have the right number of nuts-or-bolts. This extra QA step would be a nifty nice-to-have if I plan to do 30+ kits.

In bagging parts and writing instructions, I realized that I’m almost scripting a behavior for my workshop attendees to perform. I’m… programming? Nevertheless, with instructions that are somewhat open-ended, I discovered that tentacle builders found their own way to navigate the kit. Knowing how folks wrapped their heads around the building process will help me re-jigger the instructions and bagging for the next time this workshop comes around.

Delivery Day

At long last: showtime! I split the workshop into two payloads. Let’s call them “Lecture” and “Lab.”

In “Lecture” I gave a quick rundown of the parts they’d encounter in this kit. I’m a shameless prophet of the idea that engineers should be constantly expanding their “vocabulary of parts.” The more parts you’re in-tune with using, the better equipped you are to solve a complex problem with a solution you can pull from your expansive mental bag of parts. (Hey, can I just stand on my pedestal once a year and say how engineering should be?)

In “Lab,” they built their tentacles. I gathered everyone’s attention for a couple minutes to go over some pinchpoints, but for the rest of it, they took to the instructions to get building. I’m a fan of the “inverted-classroom” model in a case like this one where everyone needs to do the same exercise. Here, they can go at their own pace and just poke me as needed.

Success! Nobody fell asleep! Image Credit: [Jenni]“Lab” turned out pretty well… unless you count the fact that nobody finished! With 2.5 hours alotted, we probably could’ve done with less of me talking and about 30 more minutes of kit-making. (4 hours would be ideal, but there are other fantastic workshops that you wouldn’t want to miss out on.) With the time limit closing in, I thought: what am I going to do? But, hey, this is a hardware conference. I invited everyone to join me on the nearby tables outside of the workshop areas to finish up. In about 45 more minutes, we managed to get through about 7 working tentacles! For the remaining uncompleted kits, everyone had the parts and instructions. If they had any further questions, they could drop me an email. With that, my first workshop came to a close and I wiped off the sweat from my brow. It was a mission accomplished.

If you managed to sit in on this workshop last year, thanks a bunch for joining me and supporting me with your enthusiasm. I had a blast putting it together, and I’d do it again in a heartbeat. SuperCon 2017 might’ve been the last SuperCon of the tentacle, but who knows what we’ll see this year?

Breakfast at DEF CON — The Greatest Illicit Meetup of All

พฤ, 08/16/2018 - 23:01

Every year we host Breakfast at DEF CON on the Sunday morning of the largest hacker conference in the United States. I think it’s a brilliant time to have a meetup — almost nobody is out partying on Sunday morning, and coffee and donuts is a perfect way to get your system running again after too much excess from Saturday evening.

This year marks our fourth Breakfast and we thought this time it would be completely legit. Before we’ve just picked a random coffee shop and showed up unannounced. But this year we synced up with some of our friends running the Hardware Hacking Village and they were cool with us using the space. Where we ran afoul was trying to wheel in coffee and pastries for 100+ people. The casino was having none it.

But to their credit, we were forbidden from bringing the food into the conference center, not into the greater casino. We ended up squatting in a restaurant seating area that wasn’t open until 5pm. The awesome Hackaday Community rolled with the venue change, and a fantastic time was had by all! For what it’s worth, this ended up being the best space for a Breakfast yet! There was plenty of room with many tables, and we had no problem filling all of the space.

Tindie and Hackaday were sponsors of the SMD Challenge this year (a timed soldering challenge going all the way down to 0201 packages that was also judged for quality). Jasmine announced the winner live at the meetup, that’s the image at the top of this article. I thought the award the Solder Skills Village made for the Most Dropped Parts was pretty epic. It’s a round pendant with a piece of carpet and a bunch of components that was on display during the meetup.

The number one piece of hardware people brought with them was badges. Since we’re doing in-depth badge coverage I won’t go into that here. But I’d like to mention that for the second year in a row, Brian McEvoy brought some epic hardware. Last year it was an OpenSCAD controller demo, this year it’s a custom mechanical keyboard design system.

Taking wide shots of crowds is frowned upon at DEF CON so what follows are posed shots. I made sure to ask all involved before snapping the image. DC27 is a long way away, I’m hoping to see many of these awesome folks much sooner than that when Supercon gets going this November.

DARPA Goes Underground For Next Challenge

พฤ, 08/16/2018 - 22:01

We all love reading about creative problem-solving work done by competitors in past DARPA robotic challenges. Some of us even have ambition to join the fray and compete first-hand instead of just reading about them after the fact. If this describes you, step on up to the DARPA Subterranean Challenge.

Following up on past challenges to build autonomous vehicles and humanoid robots, DARPA now wants to focus collective brainpower solving problems encountered by robots working underground. There will be two competition tracks: the Systems Track is what we’ve come to expect, where teams build both the hardware and software of robots tackling the competition course. But there will also be a Virtual Track, opening up the challenge to those without resources to build big expensive physical robots. Competitors on the virtual track will run their competition course in the Gazebo robot simulation environment. This is similar to the NASA Space Robotics Challenge, where algorithms competed to run a virtual robot through tasks in a simulated Mars base. The virtual environment makes the competition accessible for people without machine shops or big budgets. The winner of NASA SRC was, in fact, a one-person team.

Back on the topic of the upcoming DARPA challenge: each track will involve three sub-domains. Each of these have civilian applications in exploration, infrastructure maintenance, and disaster relief as well as the obvious military applications.

  • Man-made tunnel systems
  • Urban underground
  • Natural cave networks

There will be a preliminary circuit competition for each, spaced roughly six months apart, to help teams get warmed up one environment at a time. But for the final event in Fall of 2021, the challenge course will integrate all three types.

More details will be released on Competitor’s Day, taking place September 27th 2018. Registration for the event just opened on August 15th. Best of luck to all the teams! And just like we did for past challenges, we will excitedly follow progress. (And have a good-natured laugh at fails.)