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What do I call this thing?? Help me name it, so I can search for it :)

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So, I find myself needing a simple circuit, but I havn't got a clue as to what it's called  ???

I hope that, if I describe the circuit you can help me name it.


You have all used/built/seen this thing; there is a simple push button, and everytime it is pressed the circuit changes state/output.

All of the states are cyclical, meaning that when you reach the last state, and press the button again, it returns to the first state.

This type of circuit is found on numerous toys, hifi's and the like. Eg. when you press the source button on a tv-remote, it cycles between all the sources again and again.

I need three these states:

* Both outputs off
* Output 1 on, Output 2 off
* Output 1 + 2 on
The outputs will drive a miniature 5-12V relay each

Thanks in advance  ;D


Oh no .. it does not work that way .

--- Quote ---The outputs will drive a miniature 5-12V relay each
--- End quote ---

I have see such designs  in Disco light systems.

Basically , you are NOT looking for one part solution , but for an complete circuit .

They must called as " opto-coupler  switches "   the IC at list , and I had found some in high end preamp's.
Instead  of mechanical switches  on the sound inputs , they use those , because it eliminates sparks and noises caused by common mechanical switches .    ( Input selectors )

I do not have an schematic to share , but  lets hope that my reply will help you , even by just a little.

A state machine. The usual method for arriving at a logic circuit to realize this is to write down all of your inputs and outputs, describe their values for each state, draw any possible paths between states, then implement those paths with logic functions. There are other methods for minimizing the resultant logic circuits. Is this what you're thinking of?


So you need some kind of machine with a finite number of states. Hmm...

Without knowing any details of your implementation goals or target, here is a suggestion:
You can use discrete logic ICs and implement a Shift Register Counter (or more precisely a ring counter) with three flip-flops (ff0, ff1, ff2). The output of each flip-flop represents the corresponding state. If "high" then the state is active.

Each primary output is activated by a relay driven by a BJT transistor (with a protection diode in parallel of course). The base is driven by the outputs of the flip-flops, but with a twist:
- Use a diode from ff1 to output 1 transistor base
- Use a diode from ff2 to output 1 base and another one to output 2 transistor base.

(Note: According to flip-flop characteristics, you can also drive the relays directly)
(Second note: a transistor-only implementation is also possible)

However, please familiarize yourself with the wonderful concept of "de-bouncing" before proceeding.

If you have experience and hardware to work with microcontrollers, you can also try using a cheap, 8-pin MCU.


i'll go with the mcu. here goes the ugly sketching...
you'll need (N+3) pins mcu = Vcc, GND, input and N-output.
number of state = 2^N.
the cap is for debounce i think, but i could be mistaken.
instead of directly connecting to relay, you can use bjt to cope with higher current if necessary.


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