I do a lot in prototyping as part of my repair work on old circuit boards. Over the years, I have developed an array of circuit boards that come in handy when performing tests, whether I need to measure something or output a signal. Below are a few of my favorites.
Most of my testing is at low frequencies, so my primary connections are done using banana plug-to-banana plug test leads. Now, some of these may look crude, but the usefulness and the quick proto-typing is what were needed at the time.
The basic device is a simple trim pot. Nothing exciting on this, but it allows me to have a multi-turn pot put where I need one quickly:
The next circuit is a simple amplifier with an offset trim adjustment using the ADA4627. This circuit allows me to configure the amplifier as an inverter or non-inverter. Usage is up to ±15V supply:
Complexity gets stepped up a notch with this board. I am able to configure the SOT23-5 op-amp in any manner, plus have a trim-pot to help set the gain:
The next circuit is a bit short of a component, but was used to drive an input with a variable waveform at a known current value from 1μA to 100μA. This required a high-impedance differential op-amp set to measure the voltage across a known resistor value, R5. The missing component is a power amplifier, but in this case I was able to use a signal generator. Initial tests using a scope probe affected the current significantly, thus using the ADA4627 op-amps minimized any current being fed into the measuring circuit:
One program required measurement of MOSFET leakage current. This circuit allowed me to test either a SOT23, or a SC70 packaged device by applying a voltage and monitoring the output for abnormal drift that would indicate a high leakage current. I did find some bad MOSFETs, but after putting them through an oven for a few hours, the baking took out the moisture and the parts fell back into spec for the circuit:
One current project is working with a syncho/resolver measurement system that requires a high voltage reference voltage and a couple of other boards to clock in digital signals and read the digital result. Here is the current bench set-up:
The board on the right allows me to clock in digital signals where I can set the output logic level voltage from 3.3 Volts to 10 Volts (yes, I do work with some old logic boards at times). There are LED on the board to indicate a high or low rating. And the board allows me to drive up to 17 data lines.
The board on the left is a generic break-out board for a particular 70-pin connector. Several projects require this connector, but I have removed the polarizing pins to ensure it will work with all connector polarization variations.
The board in the upper left is a quad power-amplifier board (only one is stuffed in this set up). This board allows me to configure an LM3886 to accept any function generator input and then amplify the signal and provide up to a 1 Ampere current drive with output voltages swinging ±40 Volts. This acts as a basic linear amplifier, but is very useful when doing these quick proto tests.
I have others, but these are my mostly used boards. I may share others later. In the meantime, what type of useful test boards and test jigs do you use?