Re: How to count pulses per second ?

In article <1171404350.522626.261940@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Mike C <tiberian5@xxxxxxxxx> wrote:
Hi, I'm hoping someone could help me create a very basic circuit which
would:

Count the number of pulses it receives per second (from a 555 timer,
or a switch, for example) and if the number of pulses per second is
equal to, or greater than 10 it turns on a transistor.

So basically it should check every second if a clock frequency of 10Hz
is being met - if so, a transistor should turn an LED on and keep it
on for as long as 10Hz a second is hitting the circuit. As soon as the
clock stops, or the frequency goes below 10Hz, it should turn off the
LED.

Is the "check every second" really a requirement?

If not, the question can be rephrased as "if the pulses have a period
less than or equal to 0.1 seconds"

I suggest a couple of retriggerable oneshots like the HC122. Both are set
for a 0.1 second time. The first is triggered simply by the pulse. The
second has the AND inputs of the trigger used to combine the pulse with
the output of the first.

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