Adjustable Lab power supply

Xristost built a DIY adjustable lab power supply:

With the original schematic at hand I took the liberty to make a few changes. First of all I replaced two transistor-zener regulators with LM317L/LM337L. Circuits are calculated to produce 33V positive and 3V negative voltages. Thus total supply voltage for the opamps does not exceed 36V and therefor we may use standard ones. I also made changes in the LED drive circuit and a few other minor changes.

See the full post on DIYfan blog.

DIY current sensor capable of handling up to 15A

Utsav shared detailed instructions of how to build your own current sensor that can measure up to 15 Amps, project instructables here:

This current sensor can easily be used for measuring currents up to 15 Amps constant and can even handle about 20 Amps peak. I had previously built a shunt current measurement module using a home made shunt but it had a few limitations- The wire was quite long which may not be suitable for small devices. It also got rusted over time and one major drawback was heating at higher currents even at 10 amperes. Well, this module solves almost all of these problems in a more efficient design.

Check out the video after the break.

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High efficiency 4V supply QRP amplifier

Low voltage, high efficiency QRP RF amplifier project @

This is an example of a high efficiency QRP transmitter designed to work at very low supply voltages (3v-5v). It can produce 2 watts a 4 volt supply @ 70% efficiency. It uses small, inexpensive switching mosfets. The primary requirement for these mosfets is low output capacitance, a VDS of >20V, a logic level VGS and a drain current rating of a couple amps.

Check out the video after the break.

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App note: Bipolar transistors maximum ratings

Deep dive on to the maximum ratings of bipolar transistors presented in this app note from Toshiba. Link here PDF!

For transistors, the maximum allowable current, voltage, power dissipation and other parameters are specified as maximum ratings.
The absolute maximum ratings are the highest values that must not be exceeded during operation even instantaneously. When two or more ratings are specified, two ratings can not be applied to the transistor at the same time.
Exposure to a condition exceeding a maximum rating may cause permanent degradation of its electrical characteristics. Care should be exercised as to supply voltage bounces, variations in the characteristics of circuit components, possible exposure to stress higher than the maximum ratings during circuit adjustment, changes in ambient temperature, and input signal fluctuations.

App note: Comparison of SiC MOSFET and Si IGBT

App note from Toshiba on the advantages of Silicon carbide (SiC) MOSFET over silicon (Si) IGBT. Link here PDF!

Silicon carbide (SiC) comprises silicon (Si) and carbon (C) atoms. Each atom is surrounded by four different atoms in the form of a regular tetrahedron. SiC is a compound semiconductor with the densest tetrahedral arrangement. SiC has many crystalline structures called polytypes that exhibit different physical properties because of periodic differences in the overlap of tetrahedrons.
Compared to silicon, SiC has a wider energy gap where no electron states can exist (called a bandgap) between the valence band (i.e., an energy band filled with valence electrons) and the conduction band (i.e., an empty energy band in which electrons can be present). A wide bandgap provides a strong chemical bond among atoms and therefore a high electric breakdown field. SiC has an electric breakdown field roughly ten times that of silicon. Because of a strong atomic bond, SiC has greater lattice vibration and consequently conducts energy more easily than silicon. Therefore, SiC is a semiconductor material with good thermal conduction.

DIY air quality monitor

Dejan over at HowToMechatronics shared detailed instructions on how to build your own air quality monitor:

Have you ever wondered about the quality of the air you are breathing, or maybe, why you sometimes feel sleepy in the office or tired in the morning even after sleeping all night? Poor air quality can lead to many negative health effects as well as can cause tiredness, headaches, loss of concentration, increased heart rate and so on. Monitoring the quality of the air may actually be more important than you realize. So, in this tutorial we will learn how to build our own Air Quality Monitor which is capable of measuring PM2.5, CO2, VOC, Ozone, as well as temperature and humidity.

See full details at

Check out the video after the break.

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Cloning the ET-3404 6809 adapter for the Heathkit ET-3400

Dr. Scott Baker made the ET-3404 6809 adapter clone:

I’ve become somewhat of a Heathkit ET-3400 enthusiast lately, after building my ETA-3400 memory/io clone. I decided to also clone the ET-3404, which is a 6809 adapter board for the ET-3400. Why? Simply for completeness sake.
The official “experiments” for the ET-3404 aren’t all that exciting, they’re mostly focused around understanding the differences in the microprocessor. Differences such as addressing modes, register changes, etc. There’s not much flashy interfacing like you would find in the other labs. Nevertheless, the ET-3404 fit an important niche in history. Recall that back in the day all of this stuff was new, computers were expensive, and the ability to upgrade your trainer and learn about the 6809 would have been valuable.

Project info at

Check out the video after the break.

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Laser cut project plate

Layne designed a laser-cut project plate:

When I build electronics prototypes, it’s sometimes difficult to keep all the parts together without falling apart, especially if you need to move everything from one location to another. Between the breadboards, Arduino boards, programmers, FTDI cables, spare wires, and spare parts, I wanted to create a way to keep them all connected together without falling apart or losing anything. To this end, I designed a laser-cut Project Plate. It has holes for mounting an Arduino or Arduino Mega, a place for sticking a double-breadboard, and a series of customizable short boxes for holding parts.

See the full post on Wayne and Layne blog.

Building a chaotic oscillator from common components

Tim blogged about his chaotic oscillator build:

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.

App note: Load switches for mobile and computing applications

App note from Nexperia presenting simple load switches in mobile and computing applications. Link here (PDF)

There are several reasons why a circuit or subsystem is required to be disconnected from the power supply using a load switch. A very simple and very common reason is that it helps saving power. An unpowered subsystem can eliminate power consumption due to leakage or standby currents. In portable electronic devices, load switches can be used to prevent damage from electrical surges, incorrect battery insertion and other damaging events that can enter through the power source.

App note: Driving solenoids in automotive applications

App note from Nexperia about various solenoid driver used in automotive. Link here (PDF)

There are a wide variety of solenoid drive circuit topologies. Most of them use MOSFETs in various configurations and driving modes. In this application note four of them will be discussed: solenoid driver with free-wheeling diode, solenoid driver with MOSFET avalanching, solenoid driver with active clamp and solenoid driver with auxiliary boost circuit.

Building a DIY High density Philips Hue LED stripe

Erich created a DIY high density Hue smart LED stripe:

Philips Hue Smart LED stripes are great, but they have a disadvantage: the LED density is rather low: one LED cluster (WW, RGB, CW) every 55 mm. This leads to the problem that individual dots might be visible if the LED stripe is directly visible. Even if the LED stripe is used for indirect ambient light it means that individual dots might still be visible on the wall or ceiling. The solution is to create a ‘high density’ Hue smart LED stripe

More details on MCU on Eclipse blog.

App note: Power Battery Charger Calibration Fixture

Automated battery charger calibration fixture using Holtek’s ASSP MCUs. Link here (PDF)

Power chargers for electric bicycles, electric motorcycles and power tools, etc., are all calibrated before delivery, thereby correcting any charging parameter drifts due to external component tolerances. This will ensure the output voltage and current conform to their specifications. However, traditional applications are calibrated manually in production by using variable resistors, which reduces production efficiency as well as increasing manpower, thus increasing manufacturing costs.

App note: BA45F55xx with power line transceiver

App note from Holtek on power line transceiver found on their BA45F55xx MCU. Link here (PDF)

A Power Line Transceiver is a fire protection dual-line bus which is used as a data transceiver. The master gives a command to the slave using a voltage signal modulation method while the slave responds to the master using a current modulation method. In this way a complete communication system between a master and slave only requires two lines. This communication method is very common in fire protection related products.

App note: Op amps for MEMS Microphone preamp circuits

App note from TDK on design considerations of preamps used on MEMS microphones. Link here

A microphone preamp circuit is used to amplify a microphone’s output signal to match the input level of the devices following it in the signal chain. Matching the peaks of the microphone’s signal level to the full-scale input voltage of an ADC makes maximum use of the ADC’s dynamic range and reduces the noise that subsequent processing may add to the signal.

App note: Analog and digital MEMS microphone design considerations

App note from TDK about the things to consider when integrating analog and digital MEMS microphones into a system design. Link here (PDF)

Microphones are transducers that convert acoustic pressure waves to electrical signals. Sensors have become more integrated with other components in the audio signal chain, and MEMS technology is enabling microphones to be smaller and available with either analog or digital outputs. Analog and digital microphone output signals obviously have different factors to consider in a design.