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.


I think you are looking for an edge-triggered retriggerable monostable.

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Figure 1. Schematic from http://www.talkingelectronics.com/projects/555/Page1-555.html.

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.

You will need to modify this to suit the position of your switch - connected to + or - rail, etc.

  • \$\begingroup\$ This is very good but can this be made with few capacitors and transistors and a singe 20A Relay ? \$\endgroup\$ – EFRANKENSTEIN Jun 11 '17 at 21:38
  • \$\begingroup\$ You specified 555 in your question. Yes you can make a monostable with transistors. Web search will get you plenty of designs. You probably need more sophisticated control than a 20 A relay for a pedal assist. The switch-on will be full power and will be hard on the motors, gears and drive train. You need variable power control. \$\endgroup\$ – Transistor Jun 11 '17 at 22:21

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