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Basic Electronics » How to stop a flip flop counter from... hum.... counting?

January 12, 2010
by Frozenlock
Frozenlock's Avatar

Hello everyone,

I use a flip flop counter to... well... count. :P

Problem is, I want it to STOP counting when a certain events occur. Is there a way to make this happen?

Would using an output of the MCU be an elegant design? By setting the output at 5v, the signal going to the flip flop counter would become "invisible". No more up-down, no more increment.

Any ideas, comments?

Thanks in advance!

Frozenlock

January 18, 2010
by hevans
(NerdKits Staff)

hevans's Avatar

Hi Frozenlock,

Could you post information about the particular counter you are using. Most digital counters have an enable pin which will stop the counter from counting.

Where is the signal you are trying to count coming from, and why are you trying to count it? Sorry for all the questions, but knowing what you are doing will probably help us help you, and we might all learn something neat too!

Humberto

January 19, 2010
by Frozenlock
Frozenlock's Avatar

Sure, here are some details...

The counter I use is the cd74hc4020.

Related to my other question Power a piezo with a ceramic resonator, I now want to count how many cycle the resonator produce before an event X. Being in the MHz range, I can't use the MCU to "read" the counter quickly enough, which is why I want to stop it.

January 19, 2010
by mongo
mongo's Avatar

A simple way to stop counts is to add a gate to the input. It can be a NAND gate, NOR gate, or anything else that has two or more inputs and compares them for an output.

When the event happens, it triggers the other input and effectively stops the count pulses from getting through to the counter.

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