App note: Proper resistance measurement test method for Bourns metal current sense

How to Measure low resistance accurately talked through in this white paper from Bourns. Link here (PDF)

Resistance value measurement tests typically use standard multimeters with two measuring wires. This measurement method is suitable for resistance values higher than 10 ohms, but is more prone to inaccurate results when measuring lower resistance values. This is especially true of current sense resistors with resistance values under 100 milliohms. Measuring resistance values less than 1 ohm requires the tester to apply a four-wire (Kelvin) measurement method.

App note: Advantages of sulfur-resistant film resistors

Special type of SMD resistors from Bourns that are resistant to most environmental pollution. Link here (PDF)

In recent years, the long term reliability of film chip resistors in a high sulfur environment plays an increasingly important role in a wide range of market segments such as industrial electronics, IT systems and telecommunications. Sulfurous environments have a negative impact on film resistors by reacting with elements, in particular silver. Sulfide growth can cause resistors to go open circuit.
The critical environmental factors of sulfur pollution are:
• Where oils, lubricants or fossil fuels are used
• Rubber seals, gaskets, grommets or molded coatings of affected material
• Air polluted industrial area or areas containing biological or volcanic gasses

App note: Precautions when measuring the rear of the package with a thermocouple on power devices

App note from ROHM Semiconductors when measuring thermals along exposed pads on power devices. Link here (PDF)

When measuring the rear of the package with a thermocouple, to measure accurately, the thermocouple must be in close contact with the package. A thermal pad for heat dissipation is exposed on the rear side and this thermal pad is connected to the drain due to the design of the package. Since high voltage is applied to the drain, the same voltage is generated in the thermal pad. If you attach the thermocouple here and connect the data logger, a high voltage will also be applied to the measuring instrument. In this case, measurement will not be possible unless the measuring instrument’s rating is higher than the applied voltage.

App note: LED electrostatic breakdown

Very brief reminder from ROHM semiconductors about LED electrostatic destruction. Link here (PDF)

LED products are classified as having a lower electrostatic breakage resistance than other semiconductor products. InGaN devices used in blue and white LEDs are more vulnerable to static electricity than other InGaAlP and GaP (red to yellow-green) devices.

Lab power supply build using old power bricks

Building a lab power supply from old computer power bricks:

Over the years, I have accumulated many used computer power bricks. Although I could just use them by themselves to power other electronics with similar voltage and current requirements, I thought I would combine a few of them together as the input to a linear regulator so that I can make a powerful lab power supply.

See the full post on Kerry Wong’s blog.

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Reverse-engineering a low-power LED flasher chip

Ken writes, “How do you make an LED blink? A vintage way is the LM3909, a chip from 1975 that can flash an LED for a year from a single flashlight battery. This chip has some surprising features, such as a charge pump that lets you power a 2-volt LED from a 1.5-volt battery. This IC was designed for simplicity, using just an LED, external capacitor, and battery. In this blog post, I reverse-engineer its silicon die.”

More details on Ken Shirriff’s blog.

App note: MOSFETs withstand stress of linear-mode operation

App note from IXYS talking about MOSFET operating in linear region in application like electronic load. Link here (PDF)

Power MOSFETs are most often used in switchedmode applications where they function as on-off switches. But in applications like electronic loads, linear regulators or Class A amplifiers, power MOSFETs must operate in their linear region. In this operating mode, the MOSFETs are subjected to high thermal stress due to the simultaneous occurrence of high drain voltage and current, resulting in high power dissipation.
When the thermo-electrical stress exceeds some critical limit, thermal hot spots occur in the silicon causing the devices to fail. To prevent such failure, MOSFETs operating in the linear region require high power dissipation capability and an extended forward-bias safe operating area (FBSOA).

App note: Digital inrush controller

App note from IXYS about their unique digital inrush controller using Zilog’s 8-bit Z8F3281 MCU. Link here (PDF)

Digital control allows distinctive solutions to control inrush current in typical AC-DC rectifier with capacitive load by limiting capacitor pre-charge current to a predetermined value at each half sine-wave cycle. Capacitor charge is spread over a number of cycles until capacitor is charged proportion of peak value of AC voltage source. Capacitor is charged according to timedependent pulse train. The pulses are designed in a way to provide substantially equal voltage increment applied to capacitor to keep peak of charging current about the same value at each cycle. Number of cycles depends on capacitor value and charge current. For a given capacitor value which is selected depending on desired ripples amplitude, the charge current is a function of number of pulses and its timing position with respect to rectified sine wave. Detailed algorithm of creating pulse train for Digital Inrush Control is described in the Principles of Operation section.

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 @ circuitsalad.com

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 howtomechatronics.com.

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 smbaker.com.

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.