The application demands that two selectable leds to replace one, with any added circuit drawing power from across the feed to the led.
No need for fancy ICs – the attached flip flop circuit using humble CMOS 4069 inverters has served me well since the 1970s working from 3-15V supplies.
Any high input impedance inverters will do so why not use the mosfet led drivers themselves (Circuit 2) thus eliminating the IC ?
I am suitably humbled, because circuit 2 is exactly the sort of thing that I tried, and failed, to come up with before I tried the D-type circuits.
Mike went on to point out that the diode clamps in my original circuit would stop the circuit 2 scheme from working unless low gate voltage mosfets could be found.
However, my clamps were there to prevent both leds from being off simultaneously should the CMOS hiccough – allowing the supply voltage to rise and blow up the power supply.
Mike’s circuit 2 looks a lot more robust and is going to hold at least one fet on all the time, so I think my diodes could go and a resistor could be added in parallel with each of the leds to increase gate drive.
There are a whole bunch of mono, bi and n-stables on this blog and they were mostly hyperlinked until some IT changes at EW disconnected them all. As I can’t face putting all the links back in the right places, here is a list instead.
A 74HC74 hysteresis mystery
Hysteresis mystery solved, probably
Two leds for one
And now the pcb
Simple circuit selects LEDs? – a tri-stable
More push button bistables
A 74HC4060 monostable?
Thoughts on another EEVblog – a power on-off bistable