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Bi-directional voltage level translator – Board house test

Posted on Wednesday, August 17th, 2016 in DirtyPCBs.com, PCBs by DP | No Comments

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Lukas Fassler from Soldernerd shares his experience with DirtyPCBs:

I can think of a lot of situations where it could be useful. But the main reason for this project was to gain some experience with getting a PCB professionally manufactured by a board house. For several years I have done my own designs but I always milled and drilled them myself. This had pros and cons. I never had to worry about silk screens or solder masks because my boards never had any. On the other hand I suffered from the lack of plated-through holes. Vias were always a pain in the arse because I had to manually solder in pieces of wire to connect the two sides. And it was very difficult if not impossible to put a via below a component which made the layout challenging when working with ICs with many and/or tightly spaced pins.

More details at Soldernerd homepage.

#FreePCB via Twitter to 2 random RTs

Posted on Tuesday, August 16th, 2016 in Free PCBs by DP | 1 Comment

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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.

Dekatron tubes controlled by Arduino

Posted on Tuesday, August 16th, 2016 in Arduino, DIY by DP | No Comments

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Flathagen writes:

Interfacing dekatron tubes with a microcontroller is fairly easy, once you understand how the tubes work. Threeneuron’s Pile o’Poo of Obsolete Crap provides the necessary background information and schematics for making this work.
I used two russian OG-4 tubes. I prefer the orange look of the neon tubes rather than the purple look of the argon filled OG-3 tubes. The latter tubes just look to modern for my liking. On the above picture you can see how I have mounted the tubes on a rig alongside two Magic eye tubes.

More details at DIYcrap blog.

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

Light following bristle bot

Posted on Tuesday, August 16th, 2016 in DIY by DP | No Comments

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Facelesstech made a light following bristle bot and wrote a post on his blog detailing its assembly:

There is one thing missing from all my projects so far…..Something that moves. Bristle bots are very similar to hex bugs but are built from toothbrush heads and pager motors. I thought the idea of bristle bots was cool but they were no brains to them until i seen this blog post where you could control one with a light. Essentially this light following bristle bot is just two bristle bots side by side so it would be steered.

More info at Facelesstech’s blog.  Project files available on github.

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

25 watt hybrid EL84 tube amp

Posted on Monday, August 15th, 2016 in DIY by DP | No Comments

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Ray Ring from Circuit Salad has published a new build, 25 watt hybrid EL84 tube amp:

This is my new  hybrid guitar tube amp which utilizes a solid-state input stage, DSP reverb, and solid-state phase splitter. Only the push pull, class AB output stage utilizes tubes, namely two EL84’s run at 390 volts with cathode bias. The bias uses two 15 volt zeners which creates a bias current of about 26mA. This requires almost 30 volts of swing on the grids to drive the amp to saturation. This is accomplished with a little switch mode boost converter that generates 29 volts to drive the phase splitter opamps. All of the solid-state circuitry runs off the AC filament supply for the tubes. The solid state portion is basically my stomp amp design( also on this blog) minus the final power amp, which is replaced with the phase splitter.

More details at Circuit Salad’s homepage.

Free PCB Sunday: Pick your PCB

Posted on Sunday, August 14th, 2016 in Free PCBs by DP | 29 Comments

IRToy

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:

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App note: Voltage to current conversion

Posted on Sunday, August 14th, 2016 in app notes by DP | No Comments

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Using Apex Microtechnology’s power op amps for voltage controlled current sources (VCCS’s) application note, Link here (PDF)

Voltage controlled current sources (or VCCS’s) can be useful for applications such as active loads for use in component testing or torque control for motors. Torque control is simplified since torque is a direct function of current in a motor. Current drive in servo loops reduces the phase lag due to motor inductance and simplifies stabilizing of the loop.

App note: Programmable power supplies

Posted on Sunday, August 14th, 2016 in app notes by DP | No Comments

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Apex Microtechnology’s application note about programmable power supplies. Link here (PDF)

The programmable power supply (PPS) is not only a key element in automated test equipment, but it is also used in fields as diverse as industrial controls, scientific research and vehicular controls. When coupled to a computer, it bridges the gap from the software to the control task at hand. This application note examines the basic operation of the PPS, the multitude of possible configurations and the key accuracy considerations.

App note: Interfacing an I2S device to an MSP430 device

Posted on Saturday, August 13th, 2016 in app notes by DP | No Comments

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Interfacing an I2S device to an MSP430 device application note (PDF!) from Texas Instruments:

The MSP430 series of microprocessors are fast powerful devices ideally suited for use with the various wireless transceivers offered by Texas Instruments. In streaming audio applications, however, it is desirable that the microprocessor support an audio bus to allow for interconnection to an audio CODEC.
This application note describes how to create an I2S-like bus (left-justified mode) from an SPI bus using a 4-bit counter, a ‘D’ type flip-flop, and a dual inverter gate.

Free PCB coupon via Facebook to 2 random commenters

Posted on Friday, August 12th, 2016 in Free PCBs by DP | 2 Comments

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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…)

OTGW panel

Posted on Friday, August 12th, 2016 in DirtyPCBs.com, PCBs by DP | No Comments

OTGW-LED Panel

Onno designed and built his own OTGW panel with Dirty Board PCBs:

Added all together and had a working gateway. This gateway has also connections for status LED’s. However, I didn’t find anything about getting the LED’s connected and build in the housing. So there started the first idea of designing my own PCB. I’m someone who takes the difficult road just for the fun of it. And now I had a real goal for designing a real PCB. I downloaded the Eagle PCB design software and just started “drawing”.
After couple of hours (read: days ;o) ) I finally got it and managed to create my PCB. Yeah!

More details at Onno’s blog.

A low-voltage disconnect for 12 volt lead acid and lithium batteries

Posted on Thursday, August 11th, 2016 in DIY, hacks by DP | 2 Comments

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KA7OEI writes:

The avoidance of overcharging is usually pretty easy to avoid: Just use the appropriate charging system – but overdischarge is a bit more difficult, particularly if the battery packs in question don’t have a “protection board” with them.
Lead acid batteries (almost) never come with any sort of over-discharge protection – one must usually rely on the ability of the device being powered to turn itself off at too-low a voltage and hope that that threshold is sensible for the longevity of a 12 volt battery system.
Many larger (e.g. >10 amp-hour) lithium-iron phosphate (LiFePO4) do not routinely come with “protection” boards unless it is ordered specially: Such batteries include some of those “Lead Acid” replacements and some of the more “raw” LiFePO4 batteries available from many vendors, such as the 20 amp-hour modules made by GBS.
While it is also important to equalize LiFePO4 batteries when charging (refer to this post – Lithium Iron Phosphate (LiFePO4) batteries revisited – Equalization of cells – link) the more immediate danger in routine use is accidental over-discharge.
For lithium batteries, one may install “protection” boards that prevent accidental over-discharge and, in some cases, provide charge equalization – but such things are much rarer for lead-acid batteries, but such a circuit is quite simple and is applicable to either Lithium or Lead Acid batteries.

More details at KA7OEI blog.

Open hardware DSP platform

Posted on Wednesday, August 10th, 2016 in open source by DP | No Comments

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 Open source hardware digital signal processing platform from Paul Janicki:

The open hardware DSP platform is a range of small boards that can be plugged together to give you a flexible platform for processing all sorts of audio signals. If you want a simple crossover, a custom USB soundcard and headphone amp, or a fully fledged 48 channel mixer or synthesizer there should, eventually, be something here to do it. All board designs and information are released under the TAPR Open Hardware License.
Current board designs include a digital signal processor, 16 channel digital to analogue converter and single ended output stage, power supply, and single ended and balanced stereo analogue to digital converters. All released designs are hosted on GitHub.

Full details at Paul Janicki’s blog.

DIY ECG with 1 op-amp

Posted on Monday, August 8th, 2016 in DIY by DP | 1 Comment

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A DIY ECG made from single op-amp (LM741) and 5 resistors by Scott Harden:

I made surprisingly good ECG from a single op-amp and 5 resistors! An ECG (electrocardiograph, sometimes called EKG) is a graph of the electrical potential your heart produces as it beats. Seven years ago I posted DIY ECG Machine on the Cheap which showed a discernible ECG I obtained using an op-amp, two resistors, and a capacitor outputting to a PC sound card’s microphone input. It didn’t work well, but the fact that it worked at all was impressive! It has been one of the most popular posts of my website ever since, and I get 1-2 emails a month from people trying to recreate these results (some of them are during the last week of a college design course and sound pretty desperate). Sometimes people get good results with that old circuit, but more often than not the output isn’t what people expected. I decided to revisit this project (with more patience and experience under my belt) and see if I could improve it. My goal was not to create the highest quality ECG machine I could, but rather to create the simplest one I could with emphasis on predictable and reproducible results. The finished project is a blend of improved hardware and custom open-source software, and an impressively good ECG considering the circuit is so simple and runs on a breadboard! Furthermore, the schematics and custom software are all open-sourced on my github!

Project info at Scott Harden’s blog.

App note: Wear leveling in NAND flash memory

Posted on Sunday, August 7th, 2016 in app notes by DP | 2 Comments

Application note/Technical note from Macronix on extending the maximum endurance limit of NAND flash memories by wear leveling. Link here (PDF)

NAND flash memory is widely used in today’s embedded systems for code and data storage applications. Some applications are required to perform numerous Program and Erase operations on the NAND flash memory after system boot-up. NAND flash memories are generally specified with a limited number of Program/Erase (P/E) cycles per block. If the P/E cycles are not evenly distributed across the memory, individual memory blocks can exceed their endurance specification limit. To prevent this scenario from happening, a technique known as “wear leveling” is widely used in NAND flash memory management. Essentially, wear leveling is a way to average out the number of P/E cycles across all usable blocks in a NAND flash device so that the number of bad blocks created over time as a result of frequent PE cycling is minimized. Today, wear leveling has become a critical part of NAND flash management in embedded systems that require frequent Program and Erase operations.

Free PCB Sunday: Pick your PCB

Posted on Sunday, August 7th, 2016 in Free PCBs by DP | 35 Comments

IRToy 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: Understanding a digital transistor datasheet

Posted on Sunday, August 7th, 2016 in app notes by DP | No Comments

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Application note from ON Semiconductors about digital transistors where two resistors are built-in the transistor package. Link here (PDF)

This application note will describe the common specifications of a Digital Transistor. It will also show how to use these specifications to successfully design with a Digital Transistor.

App note: Using the Microchip Ultra Low-power Wake-up module

Posted on Sunday, August 7th, 2016 in app notes by DP | No Comments

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An application note (PDF!) from Microchip on using the Ultra Low-power Wake-up module to reduce system current consumption:

This application note describes ways to reduce system current consumption with the use of the Ultra Low-power Wake-up (ULPWU) module. The PIC16F684 and PIC16F88X are examples of deviceswith this feature.
The primary use of this module is as an ULPWU timer, but its functionality can be expanded to function as a temperature sensor and/or a low-voltage detector. The main and expanded functions of this module are explained in this document.

Free PCB coupon via Facebook to 2 random commenters

Posted on Friday, August 5th, 2016 in Free PCBs by DP | No Comments

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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…)

Hacking HAKKO 936

Posted on Friday, August 5th, 2016 in hacks by DP | No Comments

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Simon Ludborzs writes:

For many years I lived with dodgy epoxy fix on the handle, and finally swapped it out with a cheapie from eBay. All the HAKKO bits (tip, barrel, heating element) got transfered to the plastic handle and all was good in the world.
Except for the heater LED. Like all Hakko’s the LED only illuminates when heating. With a quick glance you can’t tell if your station is on or not.
So, I did the first rational thing – I googled it. Daniel had the same issue and his mod was quick and easy. I like quick and easy so I went down that route. With a twist, but I’ll get to that in a bit.

More details at Ludzinc blog.

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

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