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Inside a two-quadrant power supply – Agilent 66312A teardown and experiment

อังคาร, 10/09/2018 - 21:43

Kerry Wong did a teardown of an Agilent 66312A dynamic measurement DC source:

Typically, a lab power supply can only operate within a single quadrant. Take a positive voltage power supply for example, it can only output or source current. If any attempt is made trying to sink current into the power supply by connecting a voltage source with a higher voltage than the output voltage of the power supply, the power supply would lose regulation since it cannot sink any current and thus is unable to bring down and regulate the voltage at its output terminals.
The Agilent 66312A dynamic measurement DC source however is a two-quadrant power supply, it not only can source up to 2A of current between 0 and 20V, but also can sink up to 1.2A or 60% of its rated output current as well. Although lacking some key functionality of a source measure unit (SMU), Agilent 66312A can nevertheless be used in similar situations where both current sourcing and sinking capabilities are needed.

More details on Kerry Wong’s blog.

Check out the video after the break.

Free PCB Sunday: Pick your PCB

จันทร์, 10/08/2018 - 04:19

We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service. This week two random commenters will get a coupon code for the free PCB drawer tomorrow morning. Pick your own PCB. You get unlimited free PCBs now – finish one and we’ll send you another! Don’t forget there’s free PCBs three times every week:

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Be sure to use a real e-mail in the address field so we can contact you with the coupon.
  • Limit one PCB per address per month please.
  • Like everything else on this site, PCBs are offered without warranty.
  • PCBs are scrap and have no value, due to limited supply it is not possible to replace a board lost in the post

Be the first to comment, subscribe to the RSS feed.

App note: Minimizing light flicker in LED lighting applications

จันทร์, 10/08/2018 - 00:00

Another application notes from Richtek this time on LED lamps flickering. Link here

Applying LEDs in offline retrofit lamps seems straightforward, but should be done with care to achieve similar light quality as the conventional lamp that the user is trying to replace. Light flicker is one of the aspects that need to be considered carefully during LED lamp design to avoid customer complaints from the field. This application note explains the LED lamp flicker phenomena in relation to driver topology and LED characteristics, and provides solutions based on several Richtek LED drivers in combination with specific LED strings. A practical flicker measurement method is explained as well, that can be used to measure light flicker in LED lamps.

App note: Li-ion battery and gauge introduction

อาทิตย์, 10/07/2018 - 20:15

Richtek app note for Li-ion battery definitions and gauge introduction. Link here

SOC is defined as the status of available energy in the battery and usually expressed as percentages. Because the available energy change depends on different charging/discharging currents, temperatures and aging effects, the SOC could be defined more clearly as ASOC (Absolute State-Of-Charge) and RSOC (Relative State-Of-Charge). Typically, the range of RSOC is from 0% to 100%, a fully charged battery’s RSOC is always 100% and a fully discharged battery has 0% RSOC. The ASOC is a reference calculated by Design Capacity which is a fixed capacity from when the battery is manufactured. A fully charged new battery will have 100% ASOC, but a fully charged aging battery could be less than 100% because of different charge/discharge conditions.

Battery management is part of power measurement. The fuel gauge is responsible to estimate the capacity of battery in the domain of battery management. The basic function of fuel gauge is to monitor the voltage, charge/discharge current and battery temperature, and to estimate the battery’s SOC and Full Charge Capacity (FCC) of battery. There are two classic methods to do the SOC estimation which are Open Circuit Voltage (OCV) and Coulomb Counter, respectively. The other method is dynamic voltage-based algorithm designed by RICHTEK.

Free PCB coupon via Facebook to 2 random commenters

เสาร์, 10/06/2018 - 05:47

Every Friday we give away some extra PCBs via Facebook. This post was announced on Facebook, and on Monday we’ll send coupon codes to two random commenters. The coupon code usually go to Facebook ‘Other’ Messages Folder . More PCBs via Twitter on Tuesday and the blog every Sunday. Don’t forget there’s free PCBs three times every week:

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • We’ll contact you via Facebook with a coupon code for the PCB drawer.
  • Limit one PCB per address per month, please.
  • Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

Pocket high voltage generator quick build

พฤ, 10/04/2018 - 21:34

Aki made this DIY pocket HV generator:

There are times you find yourself looking for a relatively high voltage (100V to 200V often in my case) but low current DC power supply. I have zener diodes that are higher than 30V, which makes the lab supply useless, and filament LEDs with forward voltage over 60V. When I need to test them quickly, I used to hook up a simple rectifier circuit to a variable AC power supply (nothing more than a slidac with isolation transformer). While this gets job done, the setup is capable of supplying much too high current (1A or more), so I was always very nervous and extra careful in handling the circuit. All I need is a little HV generator that gives me around 200V DC and only capable of supplying a milliamp or less. Realizing that I do have such design available – one of the Nixie supply circuit – I just decided to put one together to use.

Project info on The LED Artist blog.

Two bits per transistor: high-density ROM in Intel’s 8087 floating point chip

พุธ, 10/03/2018 - 05:47

Ken Shirriff has a great write-up about the multi-level ROM in Intel’s 8087 floating point chip:

The 8087 chip provided fast floating point arithmetic for the original IBM PC and became part of the x86 architecture used today. One unusual feature of the 8087 is it contained a multi-level ROM (Read-Only Memory) that stored two bits per transistor, twice as dense as a normal ROM. Instead of storing binary data, each cell in the 8087’s ROM stored one of four different values, which were then decoded into two bits. Because the 8087 required a large ROM for microcode1 and the chip was pushing the limits of how many transistors could fit on a chip, Intel used this special technique to make the ROM fit. In this article, I explain how Intel implemented this multi-level ROM.

More details on Ken Shirriff’s blog.

#FreePCB via Twitter to 2 random RTs

พุธ, 10/03/2018 - 05:06

Every Tuesday we give away two coupons for the free PCB drawer via Twitter. This post was announced on Twitter, and in 24 hours we’ll send coupon codes to two random retweeters. Don’t forget there’s free PCBs three times a every week:

  • Hate Twitter and Facebook? Free PCB Sunday is the classic PCB giveaway. Catch it every Sunday, right here on the blog
  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs will be your friend for the weekend

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Check out how we mail PCBs worldwide video.
  • We’ll contact you via Twitter with a coupon code for the PCB drawer.
  • Limit one PCB per address per month please.
  • Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

DIRTY CABLES: a new cable editor

อังคาร, 10/02/2018 - 17:34

DirtyCables.com has a live preview of a new custom cable builder. This is a from-scratch rewrite of the editor at DirtyPCBs with new features based on your requests:

  • Isometric connector drawings with pin numbers save a trip to the datasheet
  • Improved connector selector with room for additional info
  • One to many “Y” connections. Same connector “U” connections
  • Bigger, cleaner interface

Check out the live demo, and read about the updates below. The new editor is in preview mode, saving and buying cables is disabled.

The editor is full screen and adjusts somewhat to different device sizes. Click “Add Connector” or “Add Wire” to insert a new part.

The add part dialog has been completely reworked. Choose the connector family to see a photo and isometric drawings with pin numbers. There’s room to add more information about the part in the future.

Click and drag to connect a wire and a connector. This is different than the click-to-select interface in the previous editor, and lacks the UI bugs. Pins, labels, and connections are handled by an open source library called jsPlumb.

Y-type one-to-many connections can be made for some parts. It’s also possible to do U-type connections that connect two pins of the same connector to the opposite ends of a single wire.

Click to flip the connector and pin order. The reverse view shows the bottom side isometric drawing.

Click the wire to edit the length. Click “X” to remove the wire and its connections. This is much more compact than the old editor and makes complicated cables look a lot cleaner.

DirtyCables.com will be the new dedicated  site for the Dirty Cables service. The new site has simple and clear navigation, and it gives us room to grow the cable documentation and resources. In the next year we hope to double the connector and wire options, and add 100 common pre-made cables to the store. Of course it would also be nice to have mating sockets for all the connectors.

It’s a big decision to move this service outside DirtyPCBs, but we’ve made a lot of progress in the last year. We have a solid supply chain, we can accurately estimate prices, and we have a procedure to evaluate cable samples before they ship. DirtyCables is currently in preview mode, but it should be open for orders early next week.

Try out the new cable editor preview here. Can’t wait to buy custom cables? DirtyPCBs’ cable creator is ready to take your order. Need to see the connectors? Try our cheap Dirty Connector Sample Kits.

 

 

 

Free PCB Sunday: Pick your PCB

จันทร์, 10/01/2018 - 05:15

We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service. This week two random commenters will get a coupon code for the free PCB drawer tomorrow morning. Pick your own PCB. You get unlimited free PCBs now – finish one and we’ll send you another! Don’t forget there’s free PCBs three times every week:

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Be sure to use a real e-mail in the address field so we can contact you with the coupon.
  • Limit one PCB per address per month please.
  • Like everything else on this site, PCBs are offered without warranty.
  • PCBs are scrap and have no value, due to limited supply it is not possible to replace a board lost in the post

Be the first to comment, subscribe to the RSS feed.

App note: Light guides

จันทร์, 10/01/2018 - 00:00

Light guide basics app note from OSRAM. Link here (PDF)

Light Guides are used wherever the light of a light source should be distributed homogeneously over a particular area, when there is a spatial distance between light source and the area which is to be illuminated.

App note: LED diagnosis in automotive applications

อาทิตย์, 09/30/2018 - 20:00

App note from OSRAM about different approaches on LED string diagnostic in automotive. Link here (PDF)

One requirement especially in automotive applications is the diagnosis of failures in functions and systems. Therefore light functions realized with LEDs like break light, daytime running light, low and high beam may require a diagnostics function. This application note describes some items which have to be taken into account, when a diagnostic function for a LED string or a multi LED module has to be realized.

Atari 5200 Playstation 2 dual-shock controller adapter

เสาร์, 09/29/2018 - 05:41

Dr. Scott Baker has developed an adapter that allows you to use Playstation 2 analog controllers on an Atari 5200, that is available on gitHub:

This adapter allows you to use a PS2 controller on an Atari 5200 gaming console. The 5200 was notable at the time for its use of analog joysticks, but the controllers that shipped with the console are pretty lousy. They don’t self-center and they have a mushy annoying feel to them. The fire buttons aren’t very tactile in nature. The controller in my opinion just doesn’t feel or work good. Nevertheless, you have to give the Atari 5200 some respect for trying to be a pioneer in the technology.
As such, several solutions have been proposed for using alternate controllers. There are adapters for Atari 2600 digital sticks, adapters for analog PC joysticks, my own handheld controller, etc. I decided to adapt the basic technique of my handheld controller to a PS2 adapter.

See the full post on Dr. Scott M. Baker’s blog.

Free PCB coupon via Facebook to 2 random commenters

เสาร์, 09/29/2018 - 04:42

Every Friday we give away some extra PCBs via Facebook. This post was announced on Facebook, and on Monday we’ll send coupon codes to two random commenters. The coupon code usually go to Facebook ‘Other’ Messages Folder . More PCBs via Twitter on Tuesday and the blog every Sunday. Don’t forget there’s free PCBs three times every week:

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • We’ll contact you via Facebook with a coupon code for the PCB drawer.
  • Limit one PCB per address per month, please.
  • Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

The ARM chip that wont cost an arm and a leg

ศุกร์, 09/28/2018 - 00:40

A small ARM developmentboard from SMDprutser, that is available on GitHub:

Searching the prerequisite Chinese websites to satisfy my shopping fetish I came across a neat little ARM Cortex-M0 chip which is an extremely good bang for buck. I believe it is the smallest chip available in a reasonable hand-solderable package (TSOP8). This board gives you everything to explore this marvel of this Chinese Semiconductor.

Project info at smdprutser.nl. It’s also up on Tindie.

BUS PIRATE: USB Micro B connector test

พฤ, 09/27/2018 - 18:20

USB Micro B is the connector of the moment, but we haven’t had a very good time working with it. The bog-standard Chinese generic Micro B connectors on Bus Pirate v5 and Bus Pirate NG1 break constantly. We tested a Micro B connector with through-hole support tabs on the latest Bus Pirate PCBs. It turned out really well.

Standard Chinese USB Micro B connector

A ton of mom and pop factories around Shenzhen churn these out by the bucket load. It seems like a great part: ubiquitous and cheap, doesn’t require a special board slot, versions with extended leads and centering pegs are easier to hand solder. Unfortunately, every connector soldered by every member of our team has eventually decided to exit the PCB.

This connector is optimized for paste stencil and reflow soldering. Most support should come from two solder pads under the connector that are impossible to reach with a soldering iron. Maybe it could be done with hot air, or the QFN “solder from the bottom of the board through a via” hack.

Connectors with supporting through-hole tabs

The generic Chinese connector (left) has six solder pads holding it to the PCB. Four can’t be reached with a soldering iron – the two under the front, and the two recessed pads at the back near the pins.

A Molex 47589-001 (right) with through-hole support tabs went into the next revision of the Bus Pirate boards. The tabs aren’t long enough to go completely through a 1.6mm PCB, but they can still be soldered in place from the top of the board. It’s much more expensive – essentially free vs $0.50 each – but we’re optimizing for hand assembly, not production.

Now we’re living the dream. The four tabs are really secure, and we don’t have to treat the prototype like glass. The next step is to find the most widely available Chinese equivalent.

 

 

 

IoT LED Dimmer

พุธ, 09/26/2018 - 06:21

Sasa Karanovic shared a how-to on making a IoT LED dimmer:

Making a IoT LED dimmer that you can control via your PC, phone, tablet or any other device connected to the network is super simple, and I’m going to show you how.
I’m sharing my three channel LED dimmer that you can use to dim single RGB LED strip or dim three separate LED channels. I want to be able to control lights above my desk and also mix warm white and cool white strip to give me more flexibility over lighting while I’m working, taking pictures or watching movies.

See the full post on Sasa Karanovic’s blog.

#FreePCB via Twitter to 2 random RTs

พุธ, 09/26/2018 - 04:43

Every Tuesday we give away two coupons for the free PCB drawer via Twitter. This post was announced on Twitter, and in 24 hours we’ll send coupon codes to two random retweeters. Don’t forget there’s free PCBs three times a every week:

  • Hate Twitter and Facebook? Free PCB Sunday is the classic PCB giveaway. Catch it every Sunday, right here on the blog
  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs will be your friend for the weekend

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Check out how we mail PCBs worldwide video.
  • We’ll contact you via Twitter with a coupon code for the PCB drawer.
  • Limit one PCB per address per month please.
  • Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

Trying a quick turn hand-assembly prototype service

อังคาร, 09/25/2018 - 22:07

These Bus Pirate v5 prototypes were hand-assembled by a random PCBA shop on Taobao. Assembly took two days and cost 80RMB (~$12) for each board, we provided the PCBs and components. Normally we relish a prototype build because it’s a source of so many design improvements, but this was an emergency.

The USB Micro B connector on the Bus Pirate v5 and the Bus Pirate NG1 keeps breaking. In fact, the connector on v5 broke while we took pictures for a post. We soldered it on well enough to finish the photos, but we need to replace the trashed board ASAP to continue working on BusPirate.com.

How it worked

We contacted a random PCBA shop on Taobao using QQ messenger. The assembler reviewed the gerber files and quoted 80RMB (~$12) to assemble each piece. That’s just the assembly cost.

PCBs and all the components came from our own suppliers. PCBs came from the Dirty PCB factory, parts came from JLC and a few Toabao suppliers. Sourcing the components for the “kit” took quite a bit of time, maybe the same as soldering a Bus Pirate. After two days we had the PCBs and parts in our Shenzhen office, then it all went to the assembler by same-day courier.

Communication with the assembler

The assembler relied on the BOM and the PCB silkscreen to stuff the board. They didn’t need an image of the schematic nor do they accept Eagle files. All interaction happened over QQ, which is pretty typical for everything in China.

They had a single question about the orientation of a component. The dots marking pin 1 of the BL1551s was on the wrong layer and didn’t get printed on the PCB. We’ll make sure all the orientation markings are clear for a speedier build next time.

The assembler found a problem with the parts we sent too. The 74HCT4066 is in the wrong package, it should be TSSOP instead of SOIC. We ordered a replacement part from JLC and chose SF shipping for 12RMB (~$1.90). The replacement arrived at the factory the next day.

The result

Finished boards arrived in our office two days after the assembler received all the parts, about 5 days after we ordered parts. Soldering is very good, but you wouldn’t mistake it for a board done in a reflow oven. All the components are stuffed in the right place and in the correct orientation. There’s a tiny bit of flux around the LEDs, but otherwise the board is super clean.

Bus Pirates have a row of unpopulated indicator LED footprints on the back of the board named LED1A-LED4A. These are the same as the LEDs on the front (LED1-LED4), and just open up more case options at no additional cost. The BOM we sent to the assembler specified LEDs for LED1-LED4, and made no mention of LED1A-LED4A. The assembler soldered LEDs to both sides of the board.

Our instructions were too ambiguous. The LED silk labels are PWR, USB, MODE, and VREG, not LED1-LED4. There was no way for the assembler to tell which LEDs were supposed to be populated, so they stuffed them all. In the future we’ll make sure the BOM names match the PCB silk, and explicitly state which parts are “do not populate”.

Does it work?

Powered up, programmed a bootloader, flashed the latest v5 firmware freshie build. Every board works and passes the self-test.

Quick turn hand-assembly

It’s super nifty to send away parts and get back assembled boards a few days later. If the orientation of every part is really obvious on the PCB silkscreen then the assembler can probably handle the build without any questions. The boards all work perfectly, and outsourcing the build really did keep the project moving at a critical moment.

Sourcing the parts and kitting the components took a lot of time. It would be a lot easier if the assembler provided common resistors and capacitor values so we don’t have to find them. There’s also a lot of caveats: this was all handled in Chinese, requires Chinese payment methods, and our Shenzhen office was able to coordinated everything.

Glowing mercury thyratrons: Inside a 1940s Teletype switching power supply

อังคาร, 09/25/2018 - 05:50

Ken Shirriff take a look inside a bulky DC power supply REC-30 rectifier, how it works and contrast it with a MacBook power supply:

We recently started restoring a Teletype Model 19, a Navy communication system introduced in the 1940s.14 This Teletype was powered by a bulky DC power supply called the “REC-30 rectifier”. The power supply uses special mercury-vapor thyratron tubes, which give off an eerie blue glow in operation, as you can see below.
The power supply is interesting, since it is an early switching power supply. (I realize it’s controversial to call this a switching power supply, but I don’t see a good reason to exclude it.) While switching power supplies are ubiquitous now (due to cheap high-voltage transistors), they were unusual in the 1940s. The REC-30 is very large—over 100 pounds—compared to about 10 ounces for a MacBook power supply, demonstrating the amazing improvements in power supplies since the 1940s. In this blog post, I take a look inside the power supply, discuss how it works, and contrast it with a MacBook power supply.

See the full post on Ken Shirriff ‘s blog.