Turn relay on/off with pulse. Pulse-on, Pulse-off

djsfantasi

Joined Apr 11, 2010
8,258
@crutschow : what’s the purpose of R3 and C4? And is R1 really necessary? And although the CD4013B power connections aren’t shown, shouldn’t a 0.1 uF decoupling capacitor be connected between Vcc and ground? Just asking for my own curiosity.
 

crutschow

Joined Mar 14, 2008
29,511
what’s the purpose of R3 and C4
Do you mean R3 and C2?
They provide a power-on reset in case you want to insure that the output will be off when power is first applied.
And is R1 really necessary?
Yes, if the input is from a mechanical contact.
R1 and C1 provide contact bounce protection by generating a delay in the D input feedback, so that the FF can only change state once for the duration of any input contact bounces.
shouldn’t a 0.1 uF decoupling capacitor be connected between Vcc and ground?
Good idea.
 
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djsfantasi

Joined Apr 11, 2010
8,258
I m
Do you mean R3 and C2?
They provide a power-on reset in case you want the output to be off when power is first applied.
Yes, if the input is from a mechanical contact.
R1 and C1 provide contact bounce protection by generating a delay in the D input feedback, so that the FF can only change state once for the duration of any input contact bounces.
Good idea.
I meant C3 and R4.

I got the power on reset part. And my understanding of the problem was that the input was NOT a mechanical contact. If it was, I understand.
 

MisterBill2

Joined Jan 23, 2018
11,605
I just came across this thread, the functionality seems to be similar to a project that I repaired many years ago.
But I have a big question, which is what sort of motor reverses instantly? And one work-around for a short counter pulse is to use the greater or equal function instead of only the equals function.
And with an encoder like the one shown it might work to have the counter count up and then count down. Some of them will work that way.
And please describe whatever the actual solution was so that we can all learn something.
 
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