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Wow.. Slipped up with ISIS simulation

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Ian Rogers

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Just a word of warning to all of those who use Proteus ISIS..

I have been tasked with designing a large LED remote display... Easy peasy, or so you would think.

First step was to select four 3" Common Anode LED displays.. Then four transistor array chips.. Four shift registers and finally a small pic...

All the parts are modelled in ISIS so off we go. Placed the components hooked everything up... Wrote a program to take RS232 input and display a four digit number... Hour tops and it was working... Ordered all the parts, built the Stripboard programmed the pic...................... Nothing!!!

Works in simulation.... Aha!!! I hear Nigel saying.. "Don't rely on simulation".... Bah humbug!!! He is totally correct..

Pic12f1840... serially hooked up to four 74HC595 shift registers.... Paralleled to four ULN2002A darlington buffers.. paralleled to four seven segment CA LED modules...

ULN2002A???? After reading the datasheet, I found that for some reason ( god knows why ) only the 2002A has a 7V zener on the input.... This means a voltage of around 13v is needed to drive them...

I contacted Proteus explaining that I had bought oodles of these and now are useless to me... They agreed that the model was wrong and has to be like that as the simulation speed would decrease dramatically if the 7v zener was modelled.. I know its my fault as I didn't consult the datasheet beforehand.... All the other drivers in the range are able to be driven with 5v...

So.... Again I say "Read the ***** Datasheet" I am eating my own words...


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You, Ian the Wyle Coyote slipped up? Say it's not so! My world is in Caos. :woot:
Just kidding ya Ian. :)


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Works in simulation.... Aha!!! I hear Nigel saying.. "Don't rely on simulation".... Bah humbug!!! He is totally correct..
hi Ian,
Saying, "Don't rely on simulation" is incomplete, it should be "Don't rely on simulation to do the design".

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