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#FreePCB via Twitter to 2 random RTs

Posted on Tuesday, November 13th, 2018 in Free PCBs by DP | No Comments

BP

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

Posted on Tuesday, November 13th, 2018 in DIY by DP | No Comments

homebrew6502_003

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. (more…)

Making an e-Paper Etch-a-Sketch

Posted on Monday, November 12th, 2018 in hacks, R-Pi by DP | No Comments

epaper-etch-a-sketch

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. (more…)

Free PCB Sunday: Pick your PCB

Posted on Sunday, November 11th, 2018 in Free PCBs by DP | 5 Comments

BP-600x373

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:

(more…)

App note: Blood pressure monitor fundamentals and design

Posted on Sunday, November 11th, 2018 in app notes by DP | No Comments

an_nxp_an4328

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

Posted on Sunday, November 11th, 2018 in app notes by DP | No Comments

an_richtek_an010

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

Posted on Friday, November 9th, 2018 in dev boards, open source by DP | No Comments

20181007_153826

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

Posted on Friday, November 9th, 2018 in Free PCBs by DP | No Comments

BP

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:

(more…)

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

Posted on Friday, November 9th, 2018 in PIC, RF by DP | No Comments

R0300146

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

Posted on Wednesday, November 7th, 2018 in wireless by DP | No Comments

trigboard

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.

(more…)

#FreePCB via Twitter to 2 random RTs

Posted on Tuesday, November 6th, 2018 in Free PCBs by DP | No Comments

BP

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

Posted on Tuesday, November 6th, 2018 in dev boards by DP | No Comments

LoRaWAN_node_top

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

Posted on Sunday, November 4th, 2018 in Free PCBs by DP | 5 Comments

BP-600x373

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:

(more…)

App note: Common mode filter inductor analysis

Posted on Sunday, November 4th, 2018 in app notes by DP | No Comments

an_coilcraft_DOC200

App note from Coilcraft on the design and construction of common mode filter inductor. Link here (PDF)

Noise limits set by regulatory agencies make solutions to common mode EMI a necessary consideration in the manufacture and use of electronic equipment. Common mode filters are generally relied upon to suppress line conducted common mode interference. When properly designed, these filters successfully and reliably reduce common mode noise. However, successful design of common mode filters requires foresight into the nonideal character of filter components — the inductor in particular. It is the aim of this paper to provide filter designers the knowledge required to identify those characteristics critical to desired filter performance.

App note: How current and power relates to losses and temperature rise on inductors and transformers

Posted on Sunday, November 4th, 2018 in app notes by DP | No Comments

Coilcraft’s app note on temperature rise due to losses on inductors and transformers. Link here (PDF)

Core and winding losses in inductors and transformers cause a temperature rise whenever current flows through a winding. These losses are limited either by the allowed total loss for the application (power budget) or the maximum allowable temperature rise.

For example, many Coilcraft products are designed for an 85°C ambient environment and a 40°C temperature rise implying a maximum part temperature of +125°C. In general, the maximum allowed part temperature is the maximum ambient temperature plus temperature rise. If the losses that result in the maximum allowed part temperature meet the power budget limits, the component is considered acceptable for the application.

Free PCB coupon via Facebook to 2 random commenters

Posted on Friday, November 2nd, 2018 in Free PCBs by DP | No Comments

BP

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:

(more…)

N6QW Heathkit SSB transceiver

Posted on Friday, November 2nd, 2018 in DIY, RF by DP | No Comments

20181014_192406

Pete Juliano, N6QW,  has a nice build log on his newest version Heathkit 40M SSB Transceiver:

What are you thinking — I am not trying to break any world record? My XYL asked me that question today — why are you building another rig? Followed up by a snide comment that I had so many rigs now why do I need another one. Well the answer plain and simple because I can!
For the longest time in the late 60’s early 70’s my success rate with homebrew SSB transceivers was miserable. At that time I lacked the more sophisticated test gear and let’s face it some of the technology wasn’t that great. Crappy Analog VFO’s were high on the list of impediments! I also had to work and to give a fair share of my time to the family — it is that balance thing.
But today that is all changed –better test gear, better technology like Digital VFO’s and a bit more time. The latest project is to demonstrate that some of the components out of boat anchors can indeed be reworked to provide a very modern, very capable rig.

See the full post on N6QW blog.

Check out the video after the break. (more…)

Relays (DC): 99.9% less power and latching option

Posted on Thursday, November 1st, 2018 in tutorials by DP | No Comments

FH1F92ZJNOVN4LD

Technovative writes, “The purpose of this article, is to show a simple method to increase the power efficiency, and functionality, of standard DC actuated electromagnetic relay switches.”

Project instructables here.

#FreePCB via Twitter to 2 random RTs

Posted on Tuesday, October 30th, 2018 in Free PCBs by DP | No Comments

BP

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.

Battery monitor on a automotive relay form factor

Posted on Tuesday, October 30th, 2018 in DIY by DP | No Comments

001-Cover-1024x638

Jesus Echavarria made this battery monitor and wrote a post on his blog detailing its assembly:

Here’s one of the design I do last year for a client. He wants to measure the voltage of a car battery and set a couple of alarms when voltage falls below a defined values. Also, he wants to put the device in the relay box of the car, so the design needs to have a relay form factor to easy integration. So, after a couple of iterations, here’s the final design of the battery monitor.

Via Designing Electronics in Spain.

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