123Views9Replies

Author Options:

I need to find a way to on/off a motor automatically after about 5-7 seconds. Is it possible to do this ? help needed ! Answered

Discussions

Do you want it to come on, then off, then on, then off continuously? If so the circuit you want to build is called an astable.<br /> <br /> If you want it to come on for 5-7 seconds when a button is pressed and then go off until it is next pressed, you need to use a monostable.<br /> <br /> Either a monostable or astable are very easy to make, you just need a 555 timer IC from somewhere like maplin or radioshack and a few resistors.<br /> <br /> The 555 timer would output the timing, you'll probably want to put a transistor on the end so you a) don't damage the 555 timer b) get enough current for the motor.<br />

The links you sent were really helpful , thank you. I'm thinking more in the way of limit switches and relays. Is it possible? Just have difficulties with the circuit diagrams though.

Agreed...One could also purchase a premade off-delay relay, if it's just a one-shot following activation.

And a protection diode in parallel with the motor to prevent feedback into the transistor.

Jayefuu's answer is exactly what I was about to write. You didn't specify the type of motor you're using. If its an AC motor you'll need to do what Jayefuu suggested but use it to drive a relay, and use the relay to control the motor.

If its a DC motor, but very large you'll need to do the same thing or use a high power switching transistor.

We are planning to use a gear down motor, to make it move till it hits a limit switch.

 I was thinking about rigging an automotive turn-signal blinker relay. As amperage crosses the device, the heat caused by resistance makes a dissimilar metal pair flex (like an old-timey thermostat.)