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I am doing a project that requires me to have a small compact system using a DC power battery source, but I also require it to switch between two frequency signals, such that the LEDs stay in one for a few seconds after pressing a button, but then switch back to a "default" signal until it is pressed again.

I have looked at using a 555 or a thyristor circuit, but I can't figure out how to switch between the two signals, much less for it to switch back a default one after a certain amount of time.

I am looking to do this entirely with an analogue circuit, or at least not using software. I need to do it that way only.

JRE
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  • A very warm welcome to the site. You're quite clear that this shouldn't be done by a microcontroller, so you shouldn't get any 'use a microcontroller' answers. Please edit your question and add lots of detail about what your source frequencies are, if they're fixed/changing, what their voltage and power are, what 'switching between them means' and much more. Thanks and, again, welcome. – TonyM Mar 14 '22 at 13:06
  • Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. – Community Mar 14 '22 at 13:16

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It sounds like you are trying to flash some LEDs at one rate until a button is pushed, and then change the rate for a given time.

You can do this with two 555 timers, setup one timer in monostable mode and have your button trigger that. The other timer is set in astable mode. Use the output of the first timer to vary the control voltage of the second.

To make the rate lower when the monostable is on, connect the output of the first timer to the control voltage pin of the second through a resistor. If you want to have the rate get faster, you need to use an inverter circuit which can be done with a transistor.

Here is a basic circuit to do this, that should give you a starting point. In the waveform, the monostable is triggered after 20 seconds, the rate of the astable increases for roughly 15 seconds and then goes back to the lower rate. two speed pulse generator two speed pulse generator waveform

GodJihyo
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