Hiya
I've got a scenario where I want to power-up a 12V supply for (say for ~60 seconds) based on a momentary supply of 9V current (basically I want a doorbell push to turn on a small LCD monitor)
Its been a while since I've played with breadboards, but it strikes me as something straightforward but googling for components has drawn up a blank.
Anybody got any pointers?
Cheers
Colin
RS sell a wide range of plug-in timers...
Sounds like a nice job for a 555 based monostable (single shot) application. See the ten minute timer circuit here:
A 555 timer chip plus a relay would be my option. If you pop along to the RS site you can download a PDF of the data sheet with circuit diagrams that should give what you want.
Ahh, that'd be the ticket... takes me back a few years!
However, I think I've come up with a better idea of using a PIR sensor, but I may yet choose this.
Thanks for your help guys.
If you don't want to make one,
If you do, Velleman K2579 from Maplin does up to 15 mins
Owain
Colin Chaplin presented the following explanation :
A 555 timer IC will do that, combined with a small relay.
On Tue, 8 May 2007 10:47:15 +0100, "Colin Chaplin" mused:
Why not just use a relay with a delay timer built in?
Did something similar for my brother and his outdoor model railway to light track lights.
Basically just use a diode and capacitor (+small value resistor to limit capacitor current) and connect low current relay across capacitor. Applying
9V to diode charges the capacitor instantly'ish, relay closes. With 9V removed capacitor holds charge and relay remains closed. Relay discharges capacitor and after say 60s relay opens. Choose as low current relay as possible and vary capacitor value to get required hold time. He got all the bits from Maplin.Have something to add? Share your thoughts — no account required.
Ask the community — no account required