Build your own Test Equipment !!!

[amtech2005]

Hello , This is where "Heathkit" Schematics are more than Welcome !!!!!
We will be looking for up to date , Easy to build , compact , Various Test equipment fom 'A to Z" for everyones Modern Electronic Test Bench . I think there will be a bunch of information posted to build the neccessary Test equipment , that will be required to build the "VLF" Metal detector or the Pulse Induction Metal Detector you always wanted !!!.....You can Make a Specific Request , or Post a Cool Schematic !!!.......I hope this thread will be successfull...........And this should be my last "NEW THREAD POSTED" for a long time !!!.....There are enough topics now on this "Geotech Forum" to keep Everyone busy for a "Very Long Time" ......No Work Shortage or Bad Economy Here !!!!...............Thanks..............Eugene

[amtech2005]

Build your own Test Equipment !!!

Here is a link of vintage "free" Heathkit Schematics . Both tube type and solid state. Might be something here worth downloading for the electronic test bench : http://www.vintage-radio.info/heathkit/ ..................Eugene

[amtech2005]

Build your own Test Equipment !!!

Hello , What I have done is , I came up with a list of the 10 "Most Wanted" or required pieces of "Solid State" test equipment for the Electronics-Test/Repair/Hobby Bench. With exception of the Oscilloscope , all other 9 pieces of test equipment are kinda easy to build. I will post the complete list and schematics as soon as my time permits , or if someone has Ideas and Schematics , Please , post them here !!!...........Thank-You........Eugene

[Max]

Hello , What I have done is , I came up with a list of the 10 "Most Wanted" or required pieces of "Solid State" test equipment for the Electronics-Test/Repair/Hobby Bench. With exception of the Oscilloscope , all other 9 pieces of test equipment are kinda easy to build. I will post the complete list and schematics as soon as my time permits , or if someone has Ideas and Schematics , Please , post them here !!!...........Thank-You........Eugene

Hi,
the poor man scope could be some soundcard and PC... just a bit of electronics like some op amp... I think many magazines published that stuff from middle 90's till today.

That will be not good for many advanced purposes... but poor people will take advantage of existing, cheap computer equipment.

So, I suggest , instead of regular scope (CRT) project , some interface for soundcard based scopes: I think elektor magazine published some but cannot find anything at now.

PS: I suggest those in the list

1. inductance meter
2. capacitance meter
3. frequency meter
4. phase meter
5. ac/dc millivoltmeter
6. transistor hfe meter
7. free oscillator (1Khz to, at least, 1MHz )
8. low resistance meter (0.01 ohm resolution)
9. Q-meter
10. soundcard o'scope

Kind regards,
Max

[amtech2005]

Build your own Test Equipment !!!

Hi Max , Thanks for your input !! That's what makes the forum here so Great !!! 2nd opinions , or even 1st opinions. Here is my Top Ten list :

1. Of course number #1 is the Oscilloscope , 15 to 20 mhz minimum !!
2. A. Desktop Solder station "50 watt" maximum is good , with manual Temperature adjust.
and B. 30 watt solder pencil "Back-Up"
3. Signal Generator square/sine wave or a Function Generator.
4. Transistor Tester.
5. Capacitance Tester.
6. Inductance Tester.
7. D.M.M. "Digital Multi-Meter" or good volt/ohm/amp meter combo.
8. Logic Probe or an I.C. Tester .
9. Bench-Top power supply with "over-current" protect/shut-off
10. The most important for us at Geotech ?? A Good , Decent "BREADBOARD" for prototyping circuits !!!!!!
The above is a Great list but everyone has there own preference , so other suggestion's are Welcome here !!!................Eugene

[Fred]

Hi,
There is equipment that is very cheap to buy and that is not worth building.
The multimeter, soldering station are among them IMO.
The oscilloscope as a precision instrument , will be dificult to build correctly if a reliable result is intended.
The logic probe is not needed if you have the scope, but all other devices are easy to build and dont require dificult calibration.
Regards,
Fred.

[amtech2005]

Build your own Test Equipment !!!

Fred , This is great , Everyone will post what "Test Equipment" is absolutely Needed , or what is not needed at all . Another purpose of this thread is , if someone buy's a good "piece of test equipment" at a "Dirt Cheap Price" , And then they need a schematic , no problem , we can look for a link , or if the file fits here on this Forum , we can post it here . Everyone's post about test equipment is now very welcome !!!! ........Thank's...........Eugene

[gwzd]

The logic probe is not needed if you have the scope,

I have several scopes and I don't agree with you. A logic probe many times is faster to move around without lifting your eyes from the circuit. A cheap logic probe is not a big investment and at the same time a valuable tool if you are only interested in logic levels.
Regards,

[Fred]

I have several scopes and I don't agree with you. A logic probe many times is faster to move around without lifting your eyes from the circuit. A cheap logic probe is not a big investment and at the same time a valuable tool if you are only interested in logic levels.
Regards,

Hi,
You are probably right : i dont work much with digital circuits, but when i did i was looking for "semi-damaged" cmos IC´s with "dirty" outputs that where ruining the signals...but that may be special cases.
I do have a probe, i should try it again sometime...
Regards,
Fred.

Here is a LC meter .I made the Pic 16f84a version, working great and probably a must have for metal detector builders.

[gwzd]

Hi Fred,
Very interesting, I haven't seen before the version using the '628 comparators.

I made one based on the '242 a few years ago and used a LM311 for the main oscillator. I chose the 18 series because of the hardware multiply, and of course because I had a couple of chips lying around. The interesting thing was putting a digital potentiometer from Catalyst and measuring the capacitance of diodes as a function of the voltage, everything sent via RS232 to the PC and viewed with a very primitive VB6 software. I'll check around to see if I can find the code, I know where the schematics are.

I think Eugene has started a terrific thread!

Regards,

[Fred]

Hi gwzd,
That looks interesting, that way curves for diodes and transitors could be traced.The only problem is that the ´242 is a bit more dificult to find now and expensive.It´s similar with the F84 ...
Here goes a signal generator,well designed ,but in French.No much to read anyway.
Regards,
Fred.

[gwzd]

No Fred, you misunderstood me. It is not a curve tracer for diodes, what it measures is the capacitance of the diode depending on the applied voltage. I don't know if you have encountered this or not but when balancing bridges specially at a few hundreds MHz it is important to have matched diodes. You can, of course, buy them already matched, but you can do the work yourself by testing the capacitance, the forward voltage and the reverse leakage. A curve tracer should not be any problem to build, I have an old, from the eighties, Tektronix curve tracer and have never had the need for another one. That could be an interesting Saturday afternoon project.
Regards,

[Fred]

. I don't know if you have encountered this or not but when balancing bridges specially at a few hundreds MHz it is important to have matched diodes. Regards,

Ok i undertand now.so you build you own mixers? cool !.
Yes measuring only the capacity at a single voltage won´t tell you about real linearity matching...
regards,
Fred.

[gwzd]

Hi gwzd,
That looks interesting, that way curves for diodes and transitors could be traced.The only problem is that the ´242 is a bit more dificult to find now and expensive.

I never write absolute code, only relocatable one. So, adapting that for any of the 18 series would be no problem at all. By the way, I didn't know it was getting hard to get the '242.

It´s similar with the F84 ...
Here goes a signal generator,well designed ,but in French.No much to read anyway.
Regards,
Fred.

Did you know that Maxim is no longer manufacturing the MAX038? Then again there must be thousands of those chips around. I was playing around for a couple of weeks ago with some of the linear I2C and SPI controlled oscillators. Have a look at the LTC6904 for instance, it goes from 1kHz up to 68MHz in one go. The beauty of it is that it is very accurate, from the beginning I didn't believe much their claims about 1% frequency accuracy, but I must admit they were merely claiming a fact.
Regards,

[Aziz]

Last days, I measured the coil inductance with some environmental noise. The parallel LC resonant circuit is amplifiying on its resonant frequency everything induced in the coil, even noise. So this can be seen on a spectrum analyzer. It is not accurate enogh, but good for its simplicity.

The laptop MD will have some measurement instruments built-in:
- Scope (time-domain)
- Spectrum analyzer (frequency-domain)
- Lock-in amplifier (for other purposes than metal detecting)
- LC meter (for coils)
- Milli-Ohm meter (for coils)


Aziz