How to make push button switch with auto off after about 5 seconds.
Output circuit is high (active) for max 5 seconds when I keep pressing push button.
Output will be low after this time or when I release push button.
To reactivate, I have to release push button and press again.
I think that it's using a capacitor charging with some transistors. But how to make it work?
Electronic – Push button with auto off
buttontimertransistors
Related Solutions
If you had a resistor tied to the battery only, yes less current would be driven by that 1 MOhm resistor, but actually less heat is generated. Heat is generated from the power dissipated (as heat) by the part. So power is V * I which is (for a one resistor, one 12 V battery setup) 12 V * (12 V / Resistance) using I = V/R to calculate I. So as resistance goes up, power goes down for a constant voltage.
I don't know enough to reliably help you with your main problem, just thought I would contribute what I could.
What you need are 5 bi-stable switches, something like the T flip-flop (well, not exactly but similar).
You can do that with either:
- a microcontroller, as RedGrittiBrick pointed out
- 5 T flip-flops with their input at logic '1' and your switches commuting their CLK
- any other bi-stable logic circuit
Note that, in order to create a logic input from a switch, you need a pull-up and pull-down circuit, for instance using a resistor as pull-down and the switch as pull-up:
simulate this circuit – Schematic created using CircuitLab
Best Answer
This is the basic idea (functional), but it may need to be tuned like R5/C2 time constant, switching spikes on transistors (add little capacity to slow it), width of trigger pulse, etc...
Edit: You get better result with R3,R8=1k , and C2= 68uF (almost exact 5sec)
(green is button press, blue is output voltage)