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Valen
Experienced Roboteer
Joined: 07 Jul 2004
Posts: 4436
Location: Sydney
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Watch for power conditioning, automotive stuff has stupid transients -30 to +60v spikes aren't unheard of. I like something like a 10 ohm resistor followed by a diode, a zener of around 16-18 volts then a decent cap.
What environment is it going in, if its engine bay look for automotive grade chips and try to stay away from electrolytic caps.
put something like a .1uf ceramic cap on the power legs of the IC
Can you scope the input and see if your getting nice square waves? if its a bit wobbly you could run into issues where a bit more noise on the line will make the IC run several counts, like the need to debounce a switch input. if you are getting a sine wave type input you may want a comparator buffer type input with hysteresis.
Also wire up the other inputs on that chip to something, leaving them floating can cause bad things.
CMOS is rather more static sensitive than TTL so watch for that, also its current output is lower so keep that in mind.
Is your ECU looking for pulse inputs? because that circuit is going to basically be putting out a 50% duty cycle square wave,
when pulse 1 comes in it'll go high, and stay high until pulse 2 comes in. _________________ Mechanical engineers build weapons, civil engineers build targets
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Wed Nov 10, 2010 2:59 pm |
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