looking for a 3 minute cutoff circuit

[jeff262]

I need to cut power to a solenoid anywhere between 3 to 5 minutes after it receives power. the power is supplied by a switch so getting the solenoid to power up isn't a problem but getting it to turn off after 3 to 5 minutes automatically is really stumping me since i have no design ability with circuits. I can make stuff just fine if I have schematics but other then that I'm stumped. the input power will be 12v or 24v and the amps are .5 and under depending what voltage i use, i would prefer to use the 24v which gives me .2 amp draw. anyone have a suggestions on what to do? weight really isn't an issue either

thanks jeff

[vintage1]

How accurate?

Could just use a simple R/C/FET type circuit.

[slipstick]

Have look in the Free Flight forum for simple timers....it's basically the same problem.

The simplest as V1 says are a resistor, a capacitor and a FET.

Steve

[MarkusN]

Can you use a timer relay? Decidedly un-geeky, but it works.

[xorcise]

Consider a P10 or P12 PIC as your event timer, small and inexpensive. I have written precision RTC routines that can be used as event timers. The PIC can be triggered from external events and thus start the event timer, and then turn the device off.

http://www.sfcompiler.co.uk/wiki/pmwiki.php?n=SwordfishUser.SoftRTC

Another thought is let the switch power the PIC. On Power On Reset of the PIC, it outputs to turn the Solenoid. After a predetermined period, the output turns off. Simple enough.

[AndyKunz]

Are you an AMA member? If so, contact Bob Hunt (contact info in his column). I did a USB-programmable throttle manager for him that allows the changing of the throttle to any setting. This would be what you would want if using an ESC.

If you want something that simply generates an on/off signal for you after a period of time, e-mail me andy@montanadesign.com.

Andy