Dan Michaels wrote:
>
> Roman Black wrote:
> >Maybe as another suggestion for a competition
> >idea, what about a universal semiconductor tester?

> 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.

>
>   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-----+
>        |
> -------+


Hi Dan, yes I think that is a good start, but you really
need analogue inputs to make this work well. Also it would
be nice to have analogue outputs... TI make some quad D-A
converters at 10 bit and 12 bit, not too expensive.

I think I would prefer to have a 15vdc supply, and be able
to adjust this via the DACs. Then measure the result via
the ADC inputs. Could use 2x 9v batteries to make it portable.

Your procedure seems good, to check for obvious diode
junctions first, then explore the possible variations.
Testing Vsat well would maybe require a larger current
source, I like to test stuff at 500mA or 1A etc. I'm not
sure how this would be handled or even if it is necessary.
:o)
-Roman

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