Electronic Switches - What switch remains on for a certain time?

Ryan Russell

Reputable
Feb 6, 2015
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Hello all electronic peoples, I had a quick question

I am running a 12V DC Motor that I need to remain on for approximately 30-40 seconds when a button is pushed only once.
I can currently do this by holding the button, but I need to be able to simply push the button once and for it to run the circuit. The button also must return to it's original position.
This circuit must be pretty tight, so running a board with a 555 or other chip will be difficult.
Are there any switches that remain on for a certain amount of time, or slowly return to their original position while keeping the circuit closed?

Thank you all for your help :D
 
Solution


Switches come in three main varieties. There are maintained contact switches such as toggle...

Ralston18

Titan
Moderator
Not so much a matter of a switch per se.

Since you mentioned "555" then you probably have some idea of the circuitry needed.

Google "timer circuit images".

Lots webpages with circuit diagrams and products.

One of those pages may put you on the necessary path.
 


What you want is a monostable 555 timer circuit. However, note that every press of the button will not reset the circuit in this design. If you wish to be able to reset or refresh the circuit, you'll need to add some additional components.
 


Switches come in three main varieties. There are maintained contact switches such as toggle switches, the switch either opens or closes the circuit and stays that way until you move it. Then there are momentary-contact switches, which either are normally open (NO) and are push-to-momentarily-close and normally closed (NC) and push-to-momentarily-open. Your best bet would be to use a momentary contact switch to trigger a timer circuit, which you have set on a 30-40 second run time. Whether you use a normally open or normally closed switch depends on what IC you use and if you need to pull a pin to VCC (use a NO switch) or ground (use an NC switch) to trigger the timer. Typically start switches are NO and the momentary closing of the circuit when you push it starts the controller.

The cheating way to do what you want to do is to get a solid-state motor controller where you can program in a run profile. If you can do so, switching your motor to a 3 phase AC induction motor and using pretty much any inverter drive would be trivially easy to accomplish your task.
 
Solution