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LED / Tap Tempo Readout project

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Hi Whiz Kids,

I am a newbie here and I need help..... I need a circuit that will flash an LED based on a tempo tapped into a momentary contact switch. It needs to work with a 9 volt supply.

It will only need to control one LED. The duration of the tempo cyle could be from 10ms up to 2 seconds or so.... (that's not too critical on the top end.)

The momentary footswitch will send this "tapped" tempo to a audio delay unit and to this LED flasher.

Anyone have any ideas on this one?

Thanks, Steelroller


Well-Known Member
You need a microcontroller for this (or a big board full of logic chips). You put the switch on an input port, read the switch thirty or a hundred times a second or so while a timer is operating, save the times of the switch activations to memory, then use the sequence of timestamps to reproduce the tempo in playback mode.
Whew.... I was looking for something easy.... this sounds incredibly tough...
I have no idea even where to begin in designing that type of circuit....

But thanks for the reply....



Yeah, not too easy steel. What you're describing is basically recording a pulse train (your taps) and then looping it back later. It's not too hard to do with a micro controller but you'd need to learn how to program them. Basically what you would do is record time stamps every time the button was pressed and store them in memory, and when the other switch was hit it would play back those recorded time stamps as an exact replica of your initial sequence, and then loop (if you wanted it to)

Microcontroller - Wikipedia, the free encyclopedia
for some initial reading. Getting setup with the software and programming hardware you need can be a little intimidating but the chips themselves can be quiet small and easy to work with as long s you can handle the programming side. Basic knowledge of electronics is really required as well.
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Hi, yeah.... I understand.....that's a shame.....too much work for convienence .... :)

Ok, let's try a different approach.....

Is there an easy way to make an LED stay on (or off depending on condition) using a momentary contact switch? I sure hope so....

Again, the supply is 9v..... switch is a momentary pushbutton.....

Thanks Again,



Describe EXACTLY the conditions you want to trigger the LED on or off. We can help you then. You'll learn soon enough that there is no such thing as too much information on forums like this, but you'll see a million posts asking for more details =)
You guys are great !!!!

Ok, It is basically a momentary switch that triggers channel switching on a guitar amp. I have a 9v supply at my pedalboard for powering effects processors.

So, we have a momentary contact switch that needs to light (and keep on or off depending on status....I would like to use a dual color LED (green/red) to show channel status. A push on/push off will not work because you have to hit it twice to toogle the amp then.

I would imagine it to be some type of latching IC ... is that correct?

But again, I am VERY newbie.... so handholding or oversimplification is a good thing in my case... I can follow a schematic fairly well though... unless it becomes super difficult...

Is this enough info to go on??? Thanks



I would not recommend fooling around with production audio equipment as a good project for your first go =) oopsies get to be VERY expensive. You would need to tap into that momentary switch (if you feel comfortable with that) and feed it into a JK flip flop (the latching IC you were thinking of) the flip flop may be able to drive an LED directly but drivers are often needed. You either need to duplicate the debounce circuit the momentary button you're tapping is using or tap it AFTER the debounce filer for the momentary conact or the output of your little LED circuit won't match the real state of the channel switcher. Simple is not always easy.

Just an example. Take a look at my avatar and tell me what animal that is. Likely you'll see a cat. Find a computer that can say the same thing based on the image alone and I'll pay you 100 bucks =)
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I guess I lose $ 100.... it's that kind of a day....

I really am not messing with the amp itself.... I've already built the footswitch and it works fine albeit it doesn't show me which channel I'm on without going over to the amp and looking.

So, if I understand correctly.... the momentary switch is pushed.... it switches the amp and also feeds a flip flop.....which can possibly trigger the LED on the floorboard to change colors or go on or off as the case may be.... ???

That would indeed work.... but now the tricky part for one not equipped with tremendous electronic design knowledge....

Would you recommend a 7476 for this job? If so, I will have to limit the input voltage down to 5 volts....correct?

Then I'm not sure what the individual pinouts would be....

Would every push of the switch then clear? Does the clk pin get the output of the switch as a trigger?

I know I'm not stating it correctly.... sorry


Start a new thread that describe your project as you've learned how to describe it so far, describe your pedal as well, I'm not so good with the discrete digital stuff, I always throw a micro controller at problems like this, but you don't need one.
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