Homemade or Inexpensive Component and Circuit Testers

Hello ETO forum,

First, thanks to all the folks who have replied to questions and provided
guidance and knowledge:
colin55
Analog Kid
Nigel Goodwin
ronsimpson
jpanhalt
Tony Stewart
KeepItSimpleStupid
tvtech
ChrisP58
JimB
Pommie
eTech
rjenkinsgb
Les Jones

Really get a kick out of building electronic systems that provide a useful function.
Recently an arrangement was completed that uses a PIR sensor to activate
a 555 timer and turn some bright LEDs in a closet for a minute.

But it is actually rare when s circuit is built and it works the first time. And then
the part which I dislike begins: troubleshooting.

Some homemade troubleshooting tools have been developed. These first two
are, admittedly, very simple. But sometimes it is a simple issue that is tripping
you up.



Have done several projects that use PIR sensors to initiate an operation
based on human presence.

There is a resistor, capacitor, diode and transistor checker on my old Radio Shack DMM.
But while the transistor checker seems to work well on bi polar transistors
it does do that well on MOSFETs. This circuit proved useful.

The venerable 555 timer has been an effective element on several projects.



Finally, a project that releases a parachute payload from a kite has been
completed using a 433 mhz transmitter/receiver and a small servo.
Testing a servo became important and, while this servo tester is not
homemade, at $16, it is fairly inexpensive.

Barnabas Robotics Servo Motor Tester Kit | 180 Degree 9g Servo Motor + RC Servo Tester Controller + 6V Battery Holder

So it is conjectured that others may have developed circuits or systems for testing.

Is an oscilloscope a test instrument that is useful frequently
enough to warrant the expense?

Are there any other testing rigs that you would care to share?

Thanks.

Allen in Dallas

One of these is extremely useful - someone else on here mentioned them & since buying one one ebay it has had a lot of use!
There are many sellers of the same device.

A scope is invaluable for some things; I have three I use for various work - an old Velleman handheld one for quick testing, a good 200MHz dual channel and a four channel USB one, but I may not use any for weeks at a time.

A cheap logic analyser can also be extremely useful for certain projects or diagnostics; again, I have one from ebay that gets used in bursts and then not touched for ages, depending what I'm working on.

The majority of the time, just a good multimeter is enough.

ps. For a really simple servo tester, just use the 555 section of of this old project of mine:

rjenkinsgb said:

One of these is extremely useful - someone else on here mentioned them & since buying one one ebay it has had a lot of use!

Click to expand...

That was probably me I've recommended them a LOT.

It's great fun building the kits as well, and I've built 4 or 5 different ones, an even took one to work to use there. With the modern usage of 1% resistors it's difficult to read them, and testing them using one of these avoids any issues. It's also very handy for determining the connections of transistors, often the same marked transistors have different pin connections, and again it's easier to test them before you fit them.

Hello rjenkinsgb and Nigel Goodwin and the EOT forum,

Have studied the 'R C Failsafe' circuit and see how the 555 timer
section of the circuit could be used to verify the timer is working.

Have ordered the Transistor-Tester-Diode Triode Capacitance ESR Meter MOS NPN LCR-T4 Mega328.
Looks like the Tester is coming from across the pond so it will probably
be next year before it gets to Texas.

Has surmised and confirmed the good old digital multimeter,
which will provide voltage or current, is usually the best
troubleshooting amigo.

Thanks.

Allen Pitts

AllenPitts said:

Hello rjenkinsgb and Nigel Goodwin and the EOT forum,

Have studied the 'R C Failsafe' circuit and see how the 555 timer
section of the circuit could be used to verify the timer is working.

Have ordered the Transistor-Tester-Diode Triode Capacitance ESR Meter MOS NPN LCR-T4 Mega328.
Looks like the Tester is coming from across the pond so it will probably
be next year before it gets to Texas.

Click to expand...

Yes they come from China, but you can't argue with the price. Have fun building it

Has surmised and confirmed the good old digital multimeter,
which will provide voltage or current, is usually the best
troubleshooting amigo.

Click to expand...

Yes, it's the first port of call.

AllenPitts said:

Have studied the 'R C Failsafe' circuit and see how the 555 timer
section of the circuit could be used to verify the timer is working.

Click to expand...

To clarify, the timer circuit is configured to produce a servo-compatible pulse and varying the preset (or pot) position will move the servo through its range.

It can be used as a servo tester, in other words - or add a second preset and bypass one with a relay & the servo can move between two preset positions etc.