App note: PCB layout guidelines for high frequency signaling products

High speed board design app note from ON Semiconductor. Link here (PDF)

There is an increase of devices and circuitry in usage of high speed, low consumption, small volume and lower interference. Hence PCB design is an important stage of electronic product design. It forms a connection between function and electronic components, and is also an important part of power circuit design. High frequency circuit has the higher integration and the higher layout density, making it necessary to know how to make layout more reliable. The use of multilayer board becomes a necessity and an effective means to reduce cross interference of signals, better grounding and lower parasitic inductance.

This application note looks at the different layout types, practices and guidelines, types of material and factors influencing the high frequency signal transfers.

App note: Calculating and interpreting power dissipation for polypropylene film DC-link capacitors

Tech note from Vishay on polypropylene film capacitor value calculation with temperature and power dissipation consideration. Link here (PDF)

Film capacitors can deliver high power density due to their low ESR and high ripple current capabilities, and offer the highest ampere per μF ratio of capacitor technologies. This feature, combined with their high reliability and long lifespan, make the film DC-link capacitor a central component for power inverters in industrial and automotive applications.

DIY MechBoard64

DIY MechBoard64 @

When the MechBoard64 was finally realized and presented on my blog, it soon came clear that a new mechanical keyboard was the missing piece in the creation of a brand new Commodore 64 (…well that and some new keycaps…). As I have no intention to become a Commodore 64 mechanical keyboard manufacturer, I’ve therefore decided to release all information regarding the creation of the MechBoard64 . This includes files for creating the keyboard PCB (Gerber, Excellon, BOM), the keyboard bracket (Illustrator, PDF, bend allowance drawing), 3D printed keycap adapters (.STL), the keyboard stabilizers (dimensions, material) and all miscellaneous parts (cables, screws, nuts, super lube). This way users can make their own keyboards, modify them to accommodate modern day keycaps, make groupbuys or start making batches for everyone to enjoy

#FreePCB via Twitter to 2 random RTs

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.

How to correctly set the motor current limit on an A4988 stepper motor driver

Michael posted detailed instructions of how to set up your A4988 stepper motor driver’s motor current limit:

One important thing to set up when using these drivers is the motor current limit. This is especially important when you’re using a higher input voltage than what the motor is rated for. Using a higher voltage generally enables you to get more torque and a faster step speed, but you’ll need to actively limit the amount of current flowing through the motor coils so that you don’t burn your motor out.

See the full post at

Check out the video after the break.

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App note: Guidelines on the effects of parasitic capacitance on clock accuracy due to board layout

Board design considerations like board thickness and layer stacking under a crystal when designing PCB for accurate clock crystals discuss in this app note from Maxim Integrated. Link here

Crystal oscillator is widely used in RTC applications. Clock accuracy, one of the key parameters in real-time clocks, partly depends on the parasitic capacitance of the PCB being employed. Optimizing PCB layout can achieve the desired clock accuracy.

App note: Basics of ventilator systems

App note from Maxim Integrated about the design of modern ventilator system. Link here

This application note provides an overview of ventilator systems with a focus on system design for precision measurement and reliable protection. It discusses the four key components of a pneumatic ventilation system: gas supply, gas flow mixture, inhalation and exhalation systems. Within each of the components are a variety of sensors including pressure, flow, humidity, and temperature sensors. These sensors provide feedback to accurately control solenoid valves to ensure the air volume, pressure, and air-oxygen mixtures are delivered to the patients at specified intervals. Included in the system design are several fail-safe features and alarms to ensure reliable operation in any condition.

Reverse-engineering and comparing two Game Boy audio amplifier chips

Reverse-engineering and comparing two game boy audio amplifier chips @

The Nintendo Game Boy contains an audio amplifier chip for sound through a speaker or headphones. In this post, I reverse-engineer this chip and compare it with the later Game Boy Color chip (reverse-engineered earlier). Unexpectedly the Game Boy Color uses an entirely different amplifier design from the original Game Boy, which may explain why the two systems sound different.

Building a chaotic oscillator from common components

cpldcpu writes:

A chaotic oscillator is an electronic circuit that can exhibit “chaotic“, nonperiodic behavior. A commonly cited example is Chua’s circuit, but there are many others. I always regarded these as carefully designed, rather academic, examples. So I was a bit surprised to observe apparently chaotic behavior in a completely unrelated experiment.

See the full post on Tim’s Blog.

HDSP clock with SCD5583 display

FlorinC’s HDSP clock with SCD5583 display:

Here is another interesting “intelligent” LED matrix display, whose name actually makes some sense (unlike HDSP-2354, among many others): SCD5583A. I reckon it means: “Serial Character Display with 5x5x8 dot matrix”. 3 is the code is for green (0 for red, 1 for yellow).

More details on Wise time with Arduino blog.


Drive WS2812B LED strips from a PMOD device, a lightdriver project @

I created a PMOD module PCB using KiCAD, that enables connecting WS2812B lighting strips to an FPGA board with a PMOD interface. The board was assembled by JLCPCB.
This is my first project using an FPGA, I plan to soon implement an SPI interface with the FPGA, to accept colour pixels via SPI from a raspberry pi, to then drive the LEDs appropriately. I am making use of the original Zybo board which uses a Zynq FPGA, although I’m not using the ARM portion of this chip as I want to learn VHDL.

Project files are available on GitHub.

App note: 48V buck converter helps MHEVs meet fuel emission standards

Maxim Integrated got you covered on designing all in 48V automotive compliant buck converter. Link here

Ever-tightening automotive fuel emission standards are becoming challenging. The gasoline engine needs the help of an electric motor to meet these standards, leading to the introduction of mild hybrid electric vehicles (MHEV) with higher battery voltages. 48V hybrids are in production today and are proliferating. A 48V buck converter with integrated MOSFETs in an advanced CMOS process helps meet these standards by withstanding high-voltage load-dump transients and operating with low EMI, low duty cycles, and high efficiency.

App note: Surge-proof your industrial sensor

Design solution for a robust and reliable power supply for industrial sensors from Maxim Integrated. Link here

Modern industrial sensors must operate reliably in harsh and demanding industrial environments where they are prone to large surge voltages and mechanical stresses. This places considerable demands on the DC power supply that they use. We consider the merits of different approaches to designing this DC supply, before presenting the most robust, reliable and efficient solution using a uSLIC™ power module.

Automatic keyboard switch tester

James made this automatic keyboard switch tester, that is available on GitHub:

It uses a servo to turn a robotic finger that slowly presses the switch down. When it detects that the switch has closed, it lights up the LED and waits 100 ms for the contacts to settle, before slowly releasing the switch until it detects that the switch has opened again. At this point it switches off the LED, resets the servo to the start position, and writes the measured activation and deactivation positions to the PC over the USB serial connection. In the event that the servo reaches the configured end point without the switch closing, or reaches the configured start point without the switch opening, it logs a failure instead. If the switch failed to reset, it won’t start another cycle until it does.

Project info at

Check out the video after the break.

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Low cost Carbon Monoxide meter

Dilshan has published a new build:

Today Carbon Monoxide (CO) meters are available in different forms. Overall, Carbon Monoxide meters sense CO fast and display the amount to the user and trigger alarm if it reaches a critical level. Compare with most of the DIY Carbon Monoxide meters, the project which we described in this article does not need any development platform or MCU / firmware. The Carbon Monoxide meter in this project design around using general-purpose ICs, such as NE556 and LM3914.

More details on Jayakody’s Web Log.

Check out the video after the break.

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App note: RC Snubber for Class-D audio amplifiers

App note from Cirrus about overshoot/ringing suppression in the output stage of Class-D amplifiers using RC Snubber. Link here (PDF)

High speed switching of power MOSFETs in the power stage of Class-D amplifiers results in output voltage over/undershoot and high frequency ringing on the output waveform. The over/undershoot places additional stress on the power MOSFETs, potentially reducing MOSFET lifetime or, in extreme cases, causing avalanche breakdown.

The high frequency ringing can couple to nearby PCB planes and cables and is therefore a source of radiated emissions. Radiated emissions can be particularly problematic in portable electronics where the Class-D amplifier may be some distance from the micro speaker and connected by a relatively long unshielded twisted pair or flex cable.

A full-duplex tiny AVR software UART

Nerd Ralph writes:

I’ve written a few software UARTs for AVR MCUs. All of them have bit-banged the output, using cycle-counted assembler busy loops to time the output of each bit. The code requires interrupts to be disabled to ensure accurate timing between bits. This makes it impossible to receive data at the same time as it is being transmitted, and therefore the bit-banged implementations have been half-duplex. By using the waveform generator of the timer/counter in many AVR MCUs, I’ve found a way to implement a full-duplex UART, which can simultaneously send and receive at up to 115kbps when the MCU is clocked at 8Mhz.

More details on Nerd Ralph blog.

Using the ADS1115 in continuous mode for burst sampling

Edward Mallon writes, “The 16-bit ADS1115 has a programmable amplifier at the front end, where the highest gain setting providing a range of +/- 0.256 v and a resolution of about 8 micro volts. But readers of this blog know you can already approach 14-16 bit sensitivity levels with Arduino’s ADC by oversampling with lower Arefs & scaled ranges. PA1EJO demonstrated a ADS1115 / thermistor combination which resolved 5 milli Kelvin, but we reach that resolution on our NTC’s using the ICU peripheral with no ADC at all. The beauty of time-based methods is that they scale gracefully with sensors that change over a huge range of values. So why am I noodling around with this ADC module?”

See the full post at