Pulse generator

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marsheng

Joined Aug 9, 2008
5
The 555 needs the trigger to drop before the output pulse reaches it's timing period. I have been using a RC circuit to get a short pulse but with all the RF around (car engine compartment) , I don't like that solution.

What can I use to get a timed output (5 us) independent on the input signal length. IE 100 Hz square wave in, 5us pulses out?

Thanks Wallace

 

k7elp60

Joined Nov 4, 2008
555
You could use the 555 in a one-shot mode(Monostable), with a resistor of 10KΩ, and a capacitor of 470pF the time would be very close to 5uS.
 

Wendy

Joined Mar 24, 2008
21,840
The 555 needs the trigger to drop before the output pulse reaches it's timing period. I have been using a RC circuit to get a short pulse but with all the RF around (car engine compartment) , I don't like that solution.

What can I use to get a timed output (5 us) independent on the input signal length. IE 100 Hz square wave in, 5us pulses out?

Thanks Wallace

You do realize the TOS specifically bans automotive mods? What are you doing with this circuit?
 

Thread Starter

marsheng

Joined Aug 9, 2008
5
You could use the 555 in a one-shot mode(Monostable), with a resistor of 10KΩ, and a capacitor of 470pF the time would be very close to 5uS.
I may not have explained the problem correctly. This is for a motorcycle ignition. The input could be an inductive pickup, hall effect or opto. Either way on the rising edge (or falling) I need a pulse of fixed width out. The pulse out is in the region of 5 us. The maximum input frequency is 15000 rpm or 250hz. The duty cycle of the input signal varies with input device hence I need the rising edge only to trigger a pulse.The 555 needs the trigger to be reset before the output times out.

Thanks Wallace

 

Thread Starter

marsheng

Joined Aug 9, 2008
5
You do realize the TOS specifically bans automotive mods? What are you doing with this circuit?
Devices are made by engineers, like you and me. The level to which you rise it governed by the following.

Rules are for fools and a guide for the wise.

If you have a simple solution to my electronic problem. Please let me know. This is what the forum is for. Thanks
 

Wendy

Joined Mar 24, 2008
21,840
This forum has rules, which are clearly spelled out in the ToS. Failure to honor the ToS can have concequences. The minimum is closing of the thread, the max we'll discuss if we get there. In any case, my job is to enforce the ToS.

The All About Circuits forum Administrative Team has elected not to host discussions of automotive electrical system modifications/enhancements due to safety concerns, the potential of legal ramifications and the possible circumvention of vehicle regulations at the state and federal level.

This thread is against the AAC forum rules, Chapter 6, as seen here:

http://www.allaboutcircuits.com/l_tos.html


Automotive modifications of any kind are strictly forbidden. Therefore, this thread will be closed.

You might find answers to your questions in one of these forums:

http://forum.allaboutcircuits.com/sh...ad.php?t=54400

Please do not attempt to violate our ToS again. It is not for you to decide what the rules are. I did not create these rules, but I do enforce them.
 
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