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ถูกปรับปรุง 19 hours 27 min ก่อน

Calibrate a magnetic sensor

อังคาร, 11/20/2018 - 05:40

Liudr shared a how-to on calibrating a sensor:

First of all, what is calibration? In a general sense, calibrating a sensor makes the sensor provide the most accurate readings allowed by the sensor’s own precision. As an example, let’s assume for a moment that the earth’s magnetic field and any other stray magnetic fields are shielded and you have a uniform magnetic field generated artificially for the sole purpose of calibration. Let’s say that the field strength is 400 mG (milliGauss), equivalent to 40,000 nT (nanoTesla). Now if you align one axis of your magnetic sensor parallel to the direction of the field, it should read 400mG. If you then carefully rotate your sensor so that the axis is anti-parallel with your field, it will read -400mG. If you didn’t do a good job in either alignments, you will read less values, say 390mG, if you’re off by about 13 degrees, because only a portion of the field, which is a vector, is projected along your magnetic sensor’s axis.

See the full post on Liudr’s blog.

Free PCB Sunday: Pick your PCB

จันทร์, 11/19/2018 - 05:02

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: Overcurrent event detection circuit

จันทร์, 11/19/2018 - 00:00

Sample overcurrent detection circuit from Texas Instruments. Link here (PDF)

This is a unidirectional current sensing solution generally referred to as overcurrent protection (OCP) that can provide an overcurrent alert signal to shut off a system for a threshold current and re-engage the system once the output drops below a desired voltage lower than the overcurrent output threshold voltage.

App note: Active filtering in automotive audio applications

อาทิตย์, 11/18/2018 - 20:00

App note from Texas Instruments on isolating DC and high frequency noise in audio using their automotive op amps. Link here (PDF)

Phone calls, emergency alerts, and music are just a few of the reasons that a high quality audio system is vital in automotive infotainment and clusters. Operational amplifiers (op amps) are one of the most common building blocks of automotive audio circuits. Many designers choose to incorporate op amps into their automotive audio circuits in order to increase audio performance. Higher order filters, which can be created through a combination of second order filters, attenuate noise more aggressively than lower order filters. Additionally, active filters remove the chance of unwanted interference with the audio signal.

Free PCB coupon via Facebook to 2 random commenters

เสาร์, 11/17/2018 - 06:56

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.

CurrentRanger: auto-ranging current meter

เสาร์, 11/17/2018 - 06:35

An auto-ranging nanoAmp meter from LowPowerLab:

CurrentRanger is a nanoAmp current meter featuring auto-ranging, uni/bi-directional modes, bluetooth data logging options and more.
It is a highly hackable and affordable ultra low-burden-voltage ammeter, appropriate for hobby and professional use where capturing fast current transients and measurement precision are important.

More details on LowPowerLab site.

Check out the video after the break.

 

 

Teardown of an Array 3711A 300W DC electronic load

ศุกร์, 11/16/2018 - 05:54

Kerry Wong did a teardown of an Array 3711A 300W electronic load:

I have made many electronic loads in the past. For instance this simple harddrive cooler housed small dummy load, this more sophisticated constant current/constant programmable load and this heavy-duty electronic load that is capable of sinking over 1kW under peak load. In this blog post though, I am going to take a look inside an Array 3711A DC electronic load I recently purchased on eBay. You can find a video of this teardown towards the end of the post.

See the full post on his blog here.

Check out the video after the break.

#FreePCB via Twitter to 2 random RTs

พุธ, 11/14/2018 - 06:52

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.

Simple homebrew 6502 computer

พุธ, 11/14/2018 - 06:50

Sven Krasser blogged about his 6502-based homebrew 8-bit computer build:

After completing my VGA Generator project a while back, I’ve embarked on a new electronics project: building a simple 6502-based homebrew 8-bit computer on a breadboard. There are a bunch of similar projects online from which to draw ideas. Some projects set constraints such as only using contemporary parts of the 8-bit era, no FPGAs, no microcontrollers etc. In my case, I opted instead to keep the constraints minimal and the project simple.

See the full post on his blog here.

Check out the video after the break.

Making an e-Paper Etch-a-Sketch

อังคาร, 11/13/2018 - 04:18

Scott Baker has been working on making an Etch-a-Sketch using modern e-Paper displays and optical encoders:

Above you can see my prototype. I’m using a 4.2″ e-Paper display from Gooddisplay, together with the Waveshare breakout board. I have a couple of ENS1J-B28-R00128 optical encoders that I attained on eBay. I specifically chose these encoders instead of traditional electro-mechnical encoders due to the high numbers of pulses per revolution. A typical electro-mechanical encoder will net about 24 pulses per revolution. The optical encoders I bought on ebay are 128 pulses per revolution. Our 4.2″ ePaper has 400×300 pixels. To traverse the major axis would require 16 full turns of the electromechical encoder but only 3 turns of the optical encoder.
The hardware is so simple that there’s not much more to say. The encoders are connected to GPIO pins of a Raspberry Pi. Note that there are resistors inline on the encoder outputs as the encoders are 5V and the Raspberry Pi uses 3.3V GPIO. The e-ink display is connected to the SPI bus.

See the full post on his blog here and the GitHub repository here.

Check out the video after the break.

Free PCB Sunday: Pick your PCB

จันทร์, 11/12/2018 - 06:10

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: Blood pressure monitor fundamentals and design

จันทร์, 11/12/2018 - 00:00

Application note from NXP on blood pressure monitor fundamentals using their medical oriented MCUs. Link here (PDF)

Arterial pressure is defined as the hydrostatic pressure exerted by the blood over the arteries as a result of the heart left ventricle contraction. Systolic arterial pressure is the higher blood pressure reached by the arteries during systole (ventricular contraction), and diastolic arterial pressure is the lowest blood pressure reached during diastole (ventricular relaxation). In a healthy young adult at rest, systolic arterial pressure is around 110 mmHg and diastolic arterial pressure is around 70 mmHg.

App note: How to eliminate over stress of MOSFET during start-up of flyback converter

อาทิตย์, 11/11/2018 - 20:00

App note from Richtek about their embedded soft-start function to eliminate MOSFET stress. Link here

Switching Power Supply, compared to Linear Power Supply, is widely used due to its advantages, such as small size, light weight, high efficiency, etc. Flyback Converter, one of the switching power supply topologies, is most suitable for power supply systems that are below 150W because of its unique features of isolation between primary and secondary sides, simple circuit architecture, few components, low cost, etc.

Since switching power MOSFETs play a very important role in switching power supply converters, how to effectively eliminate over-stress of MOSFET during the start-up of flyback converters will be the main focus to be discussed in this application note. The three major aspects to be investigated are flyback controller design, feedback stability, and Snubber design.

Grbl_ESP32 development board version 3.1

เสาร์, 11/10/2018 - 06:25

A board to control your CNC machine with Grbl_ESP32 designed by Bart Dring, that is available on GitHub:

This is a Grbl_ESP32 CNC Development board. This is a quick and easy way to use and test CNC on the ESP32 controller.
Grbl is a great CNC firmware that has been around for nearly a decade. It was originally designed for the Arduino UNO and basic 3 axis CNC routers, but it has been ported to other CPUs and was the basis for many other CNC and 3D printer firmwares.
The firmware was written using the Arduino IDE to make it as user friendly as possible. If you have experience with Arduinos, this will not be much different.

Project info at Buildlog.Net Blog. It’s also up on Tindie.

Free PCB coupon via Facebook to 2 random commenters

เสาร์, 11/10/2018 - 05:34

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.

A simple 8-channel receiver voting controller for enhanced repeater coverage and usability

เสาร์, 11/10/2018 - 00:07

KA7OEI has written an article detailing a simple 8-channel receiver voting controller:

To simplify things, this voting controller sits in “front” of an ordinary repeater controller, taking the audio and COS inputs from the various receivers and outputting a single audio and COS signal.
If the repeater system in question uses subaudible tones, it is recommended that “discriminator” audio (e.g. that which has not been de-emphasized) that has not been subject to a squelch or tone detector audio gate be applied to the voting controller from the link receivers as well as any “local” receivers as this will assure that the voted audio will contain the subaudible tone.

More details on KA7OEI ‘s blog.

trigBoard – Ultra low power ESP8266 IoT platform

พฤ, 11/08/2018 - 05:00

Kevin Darrah writes:

The trigBoard is an IoT project that does one thing – it pushes you a notification triggered by a digital input. Well, it’s much more than that, but this is the inspiration. I wanted to design a WiFi board that essentially sleeps most of its life, but when that door switch, flood sensor, motion sensor, etc.. gets triggered, I just want a notification immediately on my phone. And that’s about it… a perfect IoT device in the background doing its job.

Project info on Kevin Darrah Wiki. It’s also up on Tindie.

Check out the video after the break.

#FreePCB via Twitter to 2 random RTs

พุธ, 11/07/2018 - 04:26

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.

SAMD21 LoRa development board with GPS

พุธ, 11/07/2018 - 04:24

Michael Krumpus designed and built a SAMD21 development board with LoRa radio module and GPS receiver, that is available on GitHub:

I’ve been doing some LoRa projects lately in order to learn as much as I can about this exciting new radio technology (see this LoRa mesh networking project and this LoRa weather station). ATmega328-based Moteino modules work great for a lot of projects, but I wanted a LoRa node with more processing power, more memory, and an onboard GPS receiver. The ATmega328 is just too constrained with memory — I’ve outgrown it. I really wanted a LoRa board with an ARM Cortex microcontroller like the SAMD21. This is the microcontroller used on the Arduino Zero. So, my ideal board is a SAMD21 with LoRa radio module and GPS receiver, all programmable with the Arduino IDE.
But, where is such a board? I could not find one so I decided to design and make one myself.

More details on Project Lab.

Free PCB Sunday: Pick your PCB

จันทร์, 11/05/2018 - 06:26

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.