NAND LED Flasher Circuit

257

03:55:46

Oddly enough, *This* circuit works fine on the bench (in real life) but for some reason EveryCircuit cannot find the solution.  I guess everybody has their limits.  Anyhow, this circuit will (in real life) flash the LED, the speed being set by the 100K potentiometer.  Guess you'll need to build it to be sure.  I would suggest using a 4093 for your NAND, and remember to tie all unused inputs to ground (0V) before starting it up, lest you end up with weird results.

The circuit on the right side works with a 7400.  But it will flash the two LEDs "opposite" each other, because they're on opposite sides of the  "flip-flop" that we've built, there.  Again, not EveryCircuit's cup of tea for some reason, but it runs in real life, so I included it here.  If nothing else, I can find it here faster than in my notebook, so it still serves...

published 12 years ago

anodorotante

12 years ago

The NAND has the same input so it will always return 0 and this is why it cannot find a solution i guess. Try changing it

LongFist

12 years ago

The capacitor charges and discharges (the rate of such is controlled by the 100K potentiometer) which shifts back and forth across the threshold voltage to "trigger" the gate's on/off (flashing). So contrary to popular disbelief, it really does work...

hurz

12 years ago

No, the Nand is wired like a single inverter. The problem seems to be the simulator tries to find an Opterating Point to start and get in trouble. Put a 1Meg in parallel to the condensator at least the simulator find its OP. But this curcuit needs an schmitt trigger with hysteresys to work fine. Anyway, simulating digital elements together with analoge ones is not an easy task

hurz

12 years ago

The single gate solution normaly does not work in real without schmitt trigger

Secuture

12 years ago

Oh yes hurz has right abour single gate one. It will be need to use nand with schmitt type triggering built in to work in sch simple way . Nlrmal nand will rather be very noncooperative unless u provide a proper positive feedback

LongFist

12 years ago

It was a Schmitt - type NAND, and I forgot to note this. Oversight corrected...

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