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Old 14th December 2005, 01:01 AM   #11
Stocker is offline Stocker  United States
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Thanks, but this project has as one of the primary design goals:

Free or as close to it as practicable. It looks like I will have to buy one of the potentiometers at least.

The software is a nice doodad, but not required (by me, yet) at this point. Thanks for the heads-up, though. If I really had good timing I might be able to get myself a National Instruments NI-DAC and do this in my PC... not motivated enough to try (yet).

Let's see, I have so far
chassis
both transformers
all 3 meters
meter power supply section
1/2 the controls
current-sense resistors
cost so far: $0
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Old 14th December 2005, 01:27 AM   #12
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fwiw -- National Instruments now owns Measurement Computing AND Softwire --

but free is always good.
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Old 14th December 2005, 05:28 AM   #13
Stocker is offline Stocker  United States
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Not quite always.

If I were time-warped back to the good old CCCP, I would be #1 with a bullet...

But I don't think I should like to be given a free "nine grams"...

Seriously though: Since I am using voltage over known-value resistors to show current on my panel meters, theoretically, I could use a data acquisition card to do up all sorts of tricky stuff on the PC with the simple addition of a connector on the side of the tester's chassis.

Now don't get me started on adding features I can't utilize yet!
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Old 14th December 2005, 09:55 AM   #14
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the Heathkit transistor checker (does both BJT and FETs) uses a switchable range of currents -- you can do this with a resistor across the output and adjust pins of an LM317 -- the current is limited to I = 1.25/R (to the limitations of the LM317).

I have maybe a 1/2 dozen of these cards. You can deploy them for multiple purposes -- but they are a bit slow to do FFT. The Measurement Computing ones can do "Bipolar" down to 1 volt full scale, 12 bits (or up to 20 volts).

If you are using panel meters you might want to build a small isolation amplifier with an MPF102 -- and clamp the output so you don't pin the meter (ouch ) when it over-ranges.

Well, it's about 10 degrees here, 6:00 in the a.m. and the XYL is snorin like a GE locomotive haulin' coal out of the Powder River Basin. You've got mail.
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Old 14th December 2005, 10:36 AM   #15
lineup is offline lineup  Sweden
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What functions does a basic transistor tester have?

1. Select collector current
2. Select collector-emitter voltage
3. Measure base current
4. Measure base-emitter voltage

This would be fairly simple if you only will test bipolar NPN small signal.

If you want to test NPN, PNP small signal/power devices of JFET, MOSFET and BJT
you need several different circuits or one rather complex circuit
fed by a more complex power supply.
As mentioned above some sort of temp monitoring and/or temp control can be used to get good testing conditions.

If we to testing at DC-currrent add feature to test with AC-signals for all sort of transistors,
we are really into serious tough work to make a nice tester.

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Old 14th December 2005, 01:31 PM   #16
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Old 14th December 2005, 01:36 PM   #17
lineup is offline lineup  Sweden
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Quote:
Originally posted by jackinnj
http://www.tech-diy.com/TestEquipmen...rtpocket2b.gif
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Old 14th December 2005, 01:42 PM   #18
lineup is offline lineup  Sweden
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ePanorama also has links
to transistor tester circuits
http://www.epanorama.net/ transistortest

One of those links is to ESP Project 31
Schematic:
http://sound.westhost.com/p31_fig2.gif

Project:
Project: Full Featured Transistor Tester - Rod Elliot
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Old 14th December 2005, 01:48 PM   #19
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Stocker, _why_ do you need a transistor tester? Isn't it enough to use available data you can find in datasheets?
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Old 14th December 2005, 02:26 PM   #20
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perhaps he wants to make current mirrors, differential amplifiers, or a really acurate high speed comparator --

(I bemoan the fact that my favorite matched device, the Intersil HFA3102 doesn't seem to be made anymore).
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