Then I would suggest you're working with engineers
who are not
particularly knowledgable about practical electronics. If they're (say)
mechanical engineers or civil engineers, then no problem. If they claim
to tbe electronic engineers I'd probably dispute that claim.
I agree, last year they couldn't even build a set of LED Christmas tree lights
without blowing them up, never heard of constant current drive !!! I'm not
Do you own a suitably large LART?
I must have told the story of the 362.8 ohm resistor. In case I haven't,
it goes like this.
I was working in a lab at a university over here when some final year
engineering student asked me for a 362.8 ohm resistor 'as there are none
in the drawer'. I said that I was not suprised, and asked him what on
earth he needed it for.
The answer? An LED current limiting resistor. Apparently he'd taken the
well-known formula R=(Vsource-Vforward)/Iforward (which I may add, he
couldn't derrive), stuck in his PSU voltage, the LED forward voltage and
typical current form the data sheet and calculated a resistor value.
It took me a long time to convince him that a 390 ohm (which we did have)
would be fine. As would a 360 Ohm (I think I could have found one of
those). Or even a 330 Ohm. Heck, a 470 Ohm would have given some light
output, just a bit dimmer than the data sheet value.
In our incoming test group one of the electrical engineers didn't know
V=I*R. Some of the other electrical engineers didn't have a clear
concept of how a transistor operates. I feel fortunate that our school's
EE program went into the basics in depth and built from there.
--
Eric Dittman
dittman(a)dittman.net
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