# Constant power supply with countdown timer triggered by a momentary switch

Can I make a 1 or 2 NE555 timer delay switch adjustable module from eBay,or any other simple components ?

Momentary switch closes = power ON and start of a countdown timer of 0.3s. Mentary switch opens = no influence, holding the momentary switch up or down = no influence,timer must stil1l run and if the momentary switch is not closed again to reset the timer to 0.3s than the power must be off.So in this way only clicking it about 4 timer per second will keep the power on and uninterrupted.

If you are interested what I would use this for (it is a pedal assist system): I am trying to tun a 24-42VDC 100-1000W motor with this,clicking the momentary switch means the pedals are moving,not clicking it or holding means the pedals are not moving and the power to the motor should be shut down.

Most of the 555 monostable circuits won't satisfy your requirement that it times out if the input is held in the high or low condition. This one does. Opening and closing the switch will cause a pulse to be transferred across the 1 $\mu$F capacitor. The 100k resistor will pull the trigger input high again in a time determined by RC. In the example this is $100k \times 1\mu = 0.1 s$. Adjust R and C to your taste.