Category

## Tutorials

Category

The 555 is a very popular chip, and for good reason. It is such a versatile timer. Learn about 555 measurements like how to measure the voltage divider inside the chip and what is going on with the signals in an astable multivibrator (clock) circuit. The key to a 555 circuit is connecting the threshold and trigger pins together. But, until you see the schematic and waveforms it may not be obvious why.

Measuring the effectiveness of a heatsink or the thermal load of a CPU requires thermal test tools. In this episode, learn how an IR Thermometer and a Thermocouple could be used on an electronics workbench. Many multimeters (DMMs) include the ability to measure temperature with a K-type thermocouple. See examples of when each measurement could be used.

## Behind the scenes of Thermal Tools Tutorial

Originally intended to use the episode to show how hot the Pi 4 would get. However, by the time I got around to producing it, a new version of Raspbian came out, resolving the temperature issues. To heat up the Pi, I used this toolset from GitHub: XXXXX.

A multimeter is the go-to-tool for electronics measurements. Knowing how to use it to measure voltage, current, diodes, and transistors can save time (and frustration) while troubleshooting. In this video, James explains how the multimeter works, so that you can understand them better. After watching, you will gain a solid DMM basics understanding.

## Behind the scenes of wbw’s DMM Basics

The first Workbench Wednesdays episode covered a pen-style DMM. Back when we were first developing the show, the intent was to be more of a review show and less of a tutorial show. That episode became a mix of both. So we decided to do a straight-up tutorial on DMM basics. Measuring voltage usually has not tripped up too many people, especially on an auto-ranging meter. The main thing to remember with current is to move the red lead back to the voltage input immediately after making a measurement. I touched on continuity briefly but hope to come back and cover that more in the future.

After watching this episode, I would recommend moving to the bench power supply tutorial. After a DMM, the bench supply is one of the most used tools.

Bench DMMs have an extra set of banana jacks called “sense.” Known as a Kelvin or 4-wire resistance measurements, these inputs accurately measure small resistors. Like, milliohms small. This video shows how to make a 4-wire measurement, prove when it is accurate, and alternatives to 4-wire.  See below for an explanation of the alternative method shown.

## Behind the scenes

Doing yet another DMM episode was a tough call for me. However, I am working on a project that requires me to characterize both a 1 ohm and a 100 milliohm resistor. The element14 community was kind enough to send me an MP720028 bench DMM. As shown in the picture, it has an extra set of banana jacks called “4-wire sense.” These connections make 4-wire resistance measurements. In this video, I show the same resistor measured with the traditional 2-wire and advanced 4-wire configuration. (Spoiler Alert! The 2-wire measurement was almost twice as big as the 4-wire!)

### Alternative 4-Wire Resistance Measurement

In the video, I show one optional method of using a multimeter with 4-wire resistance capability. The trade-off is that it requires at least two multimeters. Since the 4-wire measurement is making two measurements at the same time: voltage and current, the alternative method does the same thing. A bench power supply, ideally with current limiting, applies a voltage to the resistor under test (RUT). One multimeter is used to measure the current through the resistor and, another measure the voltage across it.

In a pinch, you could use the bench supply’s ammeter for the current, however, its precision is probably much less than the average DMM. Once the voltage and current are known, a little bit of ohm’s law determines the RUT’s resistance!

The Analog Discovery 2 combines all the equipment found on a typical electronics workbench into one small package. It packs an oscilloscope, logic analyzer, power supplies, spectrum analyzer, and so much more. As impressive as the hardware is, the Analog Discovery 2’s software, called Waveforms, is fantastic as well. You can configure it for any measurement situation, and it has extensive scripting capability. See if you should be considering adding the Analog Discovery 2 to your electronics workbench.

My day job causes me to travel on a regular basis. Sometimes that means taking my circuits with me. I picked up an Analog Discovery 2 so that I could take test equipment with me. It’s a small enough box that fits nicely into my bag. The one significant trade-off is that it requires a PC to be functional. However, for travel, that works out great.

The key functions the Analog Discovery 2 provides are:

• 2-Channel oscilloscope
• 2-Channel function generator
• Voltmeter (not DMM!)
• 2-Channel Power Supply w/ negative voltage
• 16 Digital Channels for Logic, Protocol, and General Purpose I/O
• Network Analyzer (Bode Plots!)
• Spectrum Analyzer
• Impedance Analyzer

There are probably other functions, but that covers the major ones. Years ago, I reviewed the Virtual Bench from National Instruments. While the Virtual Bench has better specs than the Analog Discovery 2, the difference in price points is staggering. You can get the AD2 for \$200-300.

Check out how some of the features work and my thoughts on this device in this Workbench Wednesdays review.