limiting pulses

novice

pulses

if

but

any

Feed the pulses into a counter and one input of an AND gate. Invert the most significant output bit of the counter and feed it into the other input of the AND gate.

Connect a 1/60th Hz oscillator to the reset pin of the counter.

At the start of each min the counter will be reset and the AND gate will allow subsequent pulses through to it's output. The counter will count the pulses until the required number is reached and then block the AND gate until the 1 min expires.

If you need to be able to change the number of pulses allowed then configure the counter as a down counter and pre-load it on reset.

--
I'm pretty sure that way won't mostly work because the MSB won't
always be the boundary which defines the target number.  What you'd
need to do would be to decode that number and use the decode to
inhibit the counter _and_ the pulse gate until the one minute reset
came around and started things up again.

What to do if the one minute is a rolling period? You could get 90 pulses in

30 seconds, a 20 second pause then repeat, then some 1 minute periods it's okay, others it's not. Ditto if you get 90 seconds of nice slow pulses then a rapid-fire 15 seconds. More detail on the input required.

Ken

then

Yes I wondered about that. Not hard to do it either way with a single chip micro.

Yes that will be interesting to see. I'm hoping that Kay isn't related to a troll we had a few weeks back. "She" was also a beginner with a suspiciously challenging problem.

Ah yes. If the count exceeded twice the limit it would start letting them through again. You are right - you need to inhibit the count once the limit is achieved.

configure

Agreed.

--
Perhaps, but from the OP's post, it sounds like what s/he wants to
do is allow _up to_ a certain number of pulses to pass through a
gate in one minute, regardless of the pulse rate or change in the
pulse rate of the input stream.  So, if 10, 10 microsecond pulses
show up when the counter is enabled, then nothing for, say, 30
seconds, then 1000 pulses for the next minute, then nothing for the
third minute, the tally would look like this:

T min 0              1              2              3
      |              |              |              | 
n     0             150            150             0


OTOH, if, during the first minute, 10 ten microsecond pulses are
followed by 10 one millisecond pulses, and then by 25, 100
millisecond pulses, then by 50 one second pulses, then nothing for a
few minutes, the tally would look like this:

T min 0              1              2              3
      |              |              |              | 
n     0              95             0              0

--
I'm assuming here that the gating periods are contiguous and that
the counter will be disabled after it gets to the target count, then
re-enabled and reloaded at the beginning of the next period   

That being the case, counts will be lost if the number exceeds the
target in any given period, but will roll over into the next period
if they don't.

Yes, the contiguous nature of the gating is rather important. However I read it as the OP didn't want more than 'x' pulses in any one minute period, which suggests that regular gating like that isn't going to cut the mustard. Like I said, more data required from the OP - the spec isn't too clear.

Cheers.

Ken

Sorry for being so vague, I'll try and elaborate further. Firstly let me say that I'm a complete amateur and the replies so far have made little sense to me ! My fault not yours. Also nothing to do with the troll, it's my first visit to this group.

Back to the problem at hand. The pulse count per minute was a bit misleading, it maybe should be a maximum average over different lengths of time. The input pulses would be at the rate of between 1 and 4 per second, but I want the outputted number of pulses to be restricted to a maximum of 3 pulses a second, however any pulses below this maximum would be let straight through, the pulse rate would vary all the time, (maybe 1 per sec for ten seconds, then 4 per sec for 15 seconds, then back down to 2 per sec for 30 seconds). Does that make any more sense?

So for example if the pulse rate was 3 or below per second the output would show the true input, whether it be 1,2 or 3 pulses per sec. But if the input went above 3 per sec (4,5,100 whatever) the output would still only show the maximum of 3 pulses per second. The input would be in millivolts, the output is not as important but a maximum of 5 volts. Hope this is of some help, if not get back to me. Thanks again.

In article , Kay wrote: [snip]

Would this get the effect you want? ________ _______ ________ | | | | | | Fin >--->| Measure|-->| Clamp |--->|Generate|---> Fout | Fin | | Result| | Fout | |________| |_______| |________|

Measure the incoming frequency and use the Result to set the frequency of a local pulse generator, but limit the maximum value of Result with a clamp.

For all values of Fin that produces a Result less than the clamp, then Fout = Fin.

For all values of Fin where the Result is clamped, then Fout is fixed at Fout(max, clamped).

For the low frequencies that you mention it is probably better to measure Fin's interpulse period, and use that to set Fout's period. Fout(max) would then be set by limiting the minimum value of the Fout period.

--
Tony Williams.

--
I think you've set yourself an impossible task if you want to output
pulses as the input pulses occur, in that it takes time to measure
their frequencies/repetition rates and you won't know how many
pulses to output until after the measrement's been made and the
pulses have already happened.  

However, if you could measure the number of input pulses in a one
second period and then output the proper number during the next
second, (while at the same time measuring the number of new pulses
coming in) that might be made to work.  Will you have fractional
numbers of pulses coming in every second?  If you describe your
application, maybe we can come up with something that'll work.

If you describe your

Looks like I'm going to have to come clean, didn't want to give too much away for reasons you will find out!

It's for a magic illusion, to show a magicians skill at 'mind over body' in controlling his heart rate. Basically a heart rate monitor would be worn to measure heart rate. Using the magicians skill the heart rate would not exceed a maximum, indeed it would reach a certain rate and then remain constant. But in order to show there was no con the heart rate would be constantly measured, starting off low and gradually rising to(but never going over) the desired rate, remaining steady and then falling back down again.

Is it all crystal now? The heart rate monitor would be of the type worn across the chest with the rate transmitted by radio to a wristwatch receiver. An audience member would check both the monitor and the wristwatch, they would find nothing wrong, they're perfectlly normal, they could even use their own monitor if desired! But in order to verify that the reading was true the pulse would be taken by the old fashioned method and the two rates compared - they would be the same.

I've already worked out how to get the signals from the body to the monitor, it's just the limiting of the maximum pulse rate needed. So the device would need to measure the electrical pulses from the heart, allow through all pulses as normal up to a certain rate and once that rate is exceeded 'cap' the upper limit so that any pulses sent to the monitor don't exceed that limit. Thus showing that the illusionist is able to control his heartbeat by 'mind over body'.

--
Cute.

Actually, the circuitry's pretty simple.

What you need is something that measures the period between
heartbeats and compares that against a reference with a fixed
period.  If the time between heartbeats gets to be lower than the
time between reference "beats", then reference beats are sent to the
transmitter, otherwise heartbeats are.

Want a schematic?

I'd appreciate the schematic very much, whether I'll understand it is another matter! But yes please.

--
OK.  It's on alt.binaries.schematics.electronic under "limiting
pulses (from seb)"

Thanks for the schematic, I just about make sense of it! Just a few questions, excuse the ignorance.

1)Is a power source needed, if so what should it be. 2)IC's U2 and U3 are both listed as 74HC00 types, on the diagram one is a NAND gate and the other NOR gate, are they the same processors wired differently or two different types entirely.I've only managed to get hold of the NAND type(and I'm still one short!). 3)How are the caps at the bottom left of the diagram wired into the circuit, if at all. 4)I have been unable to get hold of a 2n4401 transistor, my supplier says they've been discontinued.Can I substitute a different one, which.

Finally, I am going to attempt to build the circuit but being a complete amateur I know I'll screw things up somewhere. Would you consider building the circuit on my behalf, for reasonable payment, or recommend someone who can. Postage would be to the UK. Let me know if you're willing and how much you want and I'll get back to you. Once again thank you for your time and effort.

--
Yes. With the devices shown it should be 5V.  However, by changing
the HC00's to CD4011's the supply can lie anywhere between 3V and
18V.

Many thanks for that ! I look forward to your e-mail.

Can you elaborate on this please I don't quite understand. Are all four caps wired to each chip, and which pins do they connect to? And are all the IC's (U1,U2,U3,U4) connected to the caps or just the U1's and U4? Cheers.