In my opinion HOW to do this is very interesting, but the result
is a toy. I can't imagine who will use this tool. Here every
child know to handle with a digital multimeter and find quickly what have
in his hands, a npn, a pnp or a fet...
And a digital multimeter is cheapest than a pic based tool ( even 12c509 )
and can do more things.
Just a thought.
Vasile

On Wed, 11 Apr 2001, Dan Michaels wrote:

> Roman Black wrote:
> >Maybe as another suggestion for a competition
> >idea, what about a universal semiconductor tester?
> >Like three leads, A,B,C, and a 2-line LCD display.
> >You can clip it on any transistor or diode and
> >it tells which leg is which, NPN, PNP, fet,
> >darlington, etc etc, even measures beta and
> >saturation drop. All these things would be easy
> >to measure if you could adjust voltages and measure
> >voltages, say with a 16F876 or even a F628.
> >Just an idea. Hey, i'd like one!!
>
>
> Hey, Roman, I'll tell you what my idea is, and maybe you can tell
> me what is wrong with it :).
>
> I have been mulling this over for several months - even before
> that UK company started selling exactly what you mention above.
> My device would work with the little virtual instruments I have
> been producing, so it relies on a PC for control/display, rather
> than having its own LCD. This does make it easier to extend to
> different devices, since all you have to do is change the PC
> s.w. rather than the PIC firmware..
>
> The plan is to have it work symmetrically on 3 pins, and
> automatically identify transistor C, B, E, etc, as the first step,
> then go on to test and identify the type of device. Should work
> with BJTs, FETs, SCRs, diodes, etc.
>
> The key is to use 6 pins in groups of 2 for different stim and
> record regimens. This is purely digital, but with more complex
> circuitry could be made more sophisticated. The current design
> was made to be easily added to an existing device. It would not
> work with zeners > 5v.
>
>   PIC
> -------+
>        |                                   D.U.T.
>    RB7 +-----3.3K----+-------> A ------------+
>        |             |                       |
>    RB6 +-----330-----+                       |
>        |                                  | /  e
>    RB5 +-----3.3K----+-------> B ---------|
>        |             |                 b  | \  c
>    RB4 +-----330-----+                       |
>        |                                     |
>    RB3 +-----3.3K----+-------> C ------------+
>        |             |
>    RB2 +-----330-----+
>        |
> -------+
>
> The D.U.T. connects at A, B, C. The 330 R's are in my existing device,
> but could be eliminated in a dedicated device. Basically, you use
> pins RB2-RB7 as either outputs hi/lo, or as inputs for sensing.
> Of each pair, normally one will sense while the other stimulates.
> Flipping the pins in a pair changes the level of stimulation.
>
> To test diode action between A and B, set RB7=out_hi, RB6=in_sense,
> RB4=out_lo, RB5=in_sense. For diode conduction A->B, both RB6/RB5
> will read low. By doing the inverse to that just described, you can
> show no conduction in the reverse direction.
>
> You go thru this regime for all pin combinations, discover you
> have back-to-back diodes, and it's a PNP with the base at B.
> Discovering whether A or C is the emitter/collector takes a
> dynamic measurement.
>
> By connecting 3 A/D channels to points A/B/C, and also possibly
> using 3 more digital pins with 33K R's, you can measure more
> complicated parameters, like beta, etc.
>
> There are probably many improvements that can be made to this basic
> idea. Of course, you could go whole hog and do curve tracing/etc.
>
> best regards,
> - dan michaels
> www.oricomtech.com
> =======================
>
> --
> http://www.piclist.com hint: To leave the PICList
> mailto:piclist-unsubscribe-request@mitvma.mit.edu
>
>

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads