Electronic – Circuit changing the color of an led with a button

Input selector in one of my amps worked that way (until I blew the chip up and had to recreate the selector since I could not get another chip).

I do not particularly like programming microcontrollers (why else would I make a dual frequency counter with a lot discrete logic chips?), so I always look for a way to avoid using one.

I made this with real buttons in mind (so I added debouncing). If you actually want to control this with logic output from some detector or chip (that does not need debouncing) you can get rid of R1-R4 and C2-C5. If your control signal is active low ("0" when the button is pressed) then leave the inverters. If your control signal is active high ("1" when the button is pressed) then you do not need to use U2C-U2F and just connect the control signals to the anodes of D1-D4.

How this works: When "1" appears on the anode of, say, D1, it also goes to the input pin of U1. The flip-flop is triggered by the riding edge of the clock. To allow for the input pin voltages to settle to their final values, a circuit made of U2A, R5, C1 and U2B delay the riding edge by a few ms. Actually, you could probably get rid of R5 and C1 too, the propagation delay of U2A and u2B would probably be enough, but I have no way of testing it without building it.

R7 and C6 reset the flop-flop to "0" (all LEDs off) state when the power is turned on, otherwise at each turn on it would get a random state.

I noticed the "model-railroad" tag, and this question takes me back to the trains of my childhood. That feature was present, and of course it was done by a mechanical rotating switch, and you would interrupt power momentarily in order to activate it.

You could do the same thing using a microprocessor. You can get them with on-board EEPROM in which you can save a counter value. This count will dictate which light pattern to run. You would want to provide enough power storage (capacitors) to let it complete the EEPROM write. Also enough to keep it from switching to the next pattern if there are glitches (of which there are plenty when power is taken off the track using the wheels).

The rest is straightforward microprocessor work, but of course it's not trivial if you've never worked with them before. The chip I looked at costs a dollar, looks just like a 555, and if you only need 2 LED's and can run them at 10mA each, add a resistor for each one and you wouldn't even need any transistors to drive them. Then the rest, as they say, is a "small matter of programming".