Transistor Affecting Timings?


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  1. #10
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    Default Re: Transistor Affecting Timings?

    Those look like ceramic resonators. (?) The ceramic resonators aren't that accurate and I bet that the actual frequency differes ever so slightly between the two so your timing drifts. Capacitance in the breadboard may also have an effect on tha actual frequency.

    If you really need to keep them in sync then I'd suggest driving both PICs from one oscillator or sync them thru one of the spare I/O's but I suspect that's not physically possible (?). Next suggestion is to use crystals instead of resonators, moving on from there there's almost no end to how much you want to spend to be accurate - temperature compensated?, oven controlled?, rubidium? - you name it.

    /Henrik.

    EDIT: I looked at a couple of resonators and they had a frequency tollerance of +/-0.5% typically. If you're unlucky and get one at +0.5 and the other at -0.5 (very unlikely but still) the difference between the two is 1%. Your 1000ms delay becomes 995ms on one and 1005ms on the other.
    Last edited by HenrikOlsson; - 19th April 2012 at 06:24.

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