Hi to everyone. I have to make a projec in which 4 sets of 4 LEDs have to turn ON and turn OFF, in sequence. Something like a decade counter but using only basic componentes. The thing is that for one set, each light has to be ON for a specific time, say 25 seconds, then turn off, inmediately the next one turns on for 10 s, off, and inmediately the next for 5 s, turns off and the last one for 20 s, turn off and repeat everything again, so that all the sequence lasts for 60 seconds (1min +- 1%) , each set must not have the sime timing (no other set can have de 25, 10, 5 and 20 s combination) but they all must have a sequence period of 60 seconds.
The only components I can use are: capacitors, inductors, resistors, bjt transistors (2n3904, 2n3906) and voltage regulators and that is why I added the name "purely analog", because I can not use discrete gates, but I can make them with the components I mentioned.
I must do it with the less component count possible, so I thought about doing something like a ring oscillator with inverters, because it is simple to build a inverter with transistors, only one is needed, and use some large capacitors and resistors for the delays, but it must have the sequence above, in which one light is ON and AFTER it turns off the next turns ON, which is something a ring oscillator does not meet.
I have not been able to make a ring oscillator with a "variable" time between inverters and to make them turn off automatically after that time and "pass" the "logic High" to the next inverter in the sequence.
In my mind is a matter of charging a capacitor up to a voltage, use a comparator to trigger the output to HIGH, from that time start to count the seconds, after the capacitor reaches a maximum voltage start to discharge it and when it falls to a voltage specific voltage, compare it again and that would set the output to LOW, and make sure the time between HIGH and LOW is the time I desire, and also send the signal to the next stage to start.
I would really thank anyone here who could suggest me any ideas on how to make this, the charge and discharge circuit for a capacitor and a voltage comparator (without opamps). I have done my search for some time right now but I am still confused
. Thanks a lot!