DMM layout or schematic

[rasco22862]

Is there a schematic for making a tester for DC (volts) with lcd?. I just want to make an "especific" DMM for testing germanium transistors gain.

Thanks

[Seljer]

my prediction is that you're going to have to get into microcontrollers if you want to do that


jsut take a $8 multimeter and permantly fix it into a transistor tester

[R.G.]

Look for "Digital Panel Meters". These are specific purpose voltmeters which come in an assortment of voltage ratings. There exists a 2.00V one and a 5.00V one - I think. It's been a few years.

They cost as much as a cheap voltmeter, though, about $8-10 for the cheapest ones.

[The Tone God]

While I don't play with Ges often I did make alittle uC based gain/leakage meter since I'm lazy. The uC takes the readings and does the math for me so all I do is stick in the tranny, hit a button, and presto the leakage and gain is given. Makes sorting so much easier.

Andrew

[jlullo]

While I don't play with Ges often I did make alittle uC based gain/leakage meter since I'm lazy. The uC takes the readings and does the math for me so all I do is stick in the tranny, hit a button, and presto the leakage and gain is given. Makes sorting so much easier.

Andrew

andrew,
would you mind sharing how you made that?

jonathan

[The Tone God]

andrew,
would you mind sharing how you made that?

Sure. I based it on R.G.'s tester. I use the uC's A/D to take the readings which replaces the DMM. I use a FET to replace the switch which is controlled by the uC. I regulate the voltage to the transistor and I use an external supply to make sure voltages are good. Saves on batteries also.

When you hit a button the uC reads the first voltage, turns on the FET, takes the second reading, then does the math and spits out the result on a display.

Hmm...maybe this is a good project to post in the Digital forum.

Andrew

[R.G.]

.. and you were no doubt surprised when the first post after your announcement was a request for how to build it??

[The Tone God]

.. and you were no doubt surprised when the first post after your announcement was a request for how to build it??

Yeah I knew I was walking into that one when I started to write the post but I'm a sucker.

Its actually a simple little project that I'm not particularly protective of so I'm willing to share it. I'll have to rearrange it somewhat to make is more accessible. It might be good for getting a few people into the digital forum as there are no complete projects there yet for people to try. Gotta trick the newbies into trying that digital stuff some how.

Andrew

[jlullo]

haha lucky for you i'm ignorant of microcontrollers!

seriously, thank you for sharing though

[RLBJR65]

This one looks easy, pcb art work and all! http://www.electronics-lab.com/projects/test/014/

[rasco22862]

In this layout what are the 1,2,3,4,5? ???I mean, i don´t know wich one is for the red lead, and so


Thanks

[RLBJR65]

Well looking at the schematic and data sheet. http://pdf1.alldatasheet.com/datasheet-pdf/view/67431/INTERSIL/ICL7107CPL.html

Pin 1 is for the Pos probe
Pin 2 is for the Neg probe
Pin 3 is + 5V
Pin 4 is ground
Pin 5 is - 5V

[petemoore]

  Someone posted a two transistor comparitor, when one voltage exceeds the other by a certain amount [adjustable with a pot], an LED lights.
  A bunch of these, adjusted to light at different voltages...[might load down the signal, I have one, don't remember where I got the schematic, Joe Davisson I think it was called 'low battery indicator'.

[R.G.]

 

Someone posted a two transistor comparitor, when one voltage exceeds the other by a certain amount [adjustable with a pot], an LED lights.
  A bunch of these, adjusted to light at different voltages...[might load down the signal, I have one, don't remember where I got the schematic, Joe Davisson I think it was called 'low battery indicator'.

Ding!!

One of the first things I made and tried to sell, back when the universe had first started coalescing out of primordial particles, was a battery voltage indicator made from... drum roll... an LM3914. It's like a reference voltage generator and a string of ten comparators complete with current limited LED drivers.

It would make a great way to sort JFETs into buckets, in this way:

The LM3914 can be ganged up in series so that you get more than ten LEDs. So you could divide the "good" range for your JFETs into as large a set of voltage ranges as you wanted to test. Buckets 0.1V wide would be easy. Put the LED beside the physical bucket(s). Then just pop a JFET into the socket and then toss it into the bucket where the light went on. This immediately segregates your JFETs into groups that are quite narrow. From there, alls you gots to do is to a finer test on the ones in the bucket. Or not. I bet any set of JFETs in the bucket would produce fairly good phasing.

Eh? The question was about testing Ge transistors? Ooops. Sorry. Mother Nature whacked me in the head with that one and it had to get out.

[rasco22862]

Man!, the PCB is not mirrored. I made the transfer and i got now a non Mirrored PCB. So i was trying to flip the ICs pins, and i got three broken legs.... Is there a way to fix the IC

[Papa_lazerous]

I like it   

Already got a nice DMM but I am going to make this one anyway,  Especially as it could be integrated into a little test rig or something

[Paul Perry (Frostwave)]

Man!, the PCB is not mirrored. I made the transfer and i got now a non Mirrored PCB. So i was trying to flip the ICs pins, and i got three broken legs.... Is there a way to fix the IC

I've had success soldering bits of wire to what is left of the legs, generally speaking if you have 2mm of leg left, you can dio it. Less than that, it's not easy... maybe just glue the chip on its back, solder solid wires into the holes & bring them up to what is left of the legs.
I feel for you, I really do...