Any EE can help with simple circuit plan?

[JasonP]

I need a circuit that will trip a relay momentarily, say 200-400ms, once after mains voltage (110V) is applied. I mean I switch the device on, and it will trip this relay once and that is all. I feel this is an elementary design question, but I'm no EE. Ideas?

[Sydney]

There are adjustable time delay relays sold.
( Most time delay circuits I've used have a longer delay time - usually seconds not milliseconds ).

http://www.bowdenshobbycircuits.info/page2.htm
Delay time in theses circuits is set by a combination of Capacitor and resistor values to set a common emitter.

[craigk]

I need a circuit that will trip a relay momentarily, say 200-400ms, once after mains voltage (110V) is applied. I mean I switch the device on, and it will trip this relay once and that is all. I feel this is an elementary design question, but I'm no EE. Ideas?

What exactly are you trying to accomplish ? Sent from my SCH-S968C using Tapatalk

[Sydney]

What exactly are you trying to accomplish ?

That would speed things along to define the circuit requirements.

[JasonP]

When I turn on the power to several boards, I also need to trip the power switch on a motherboard.

[ngjockey]

Used a pair of DPDT relays in series for something like this once. First relay feeds the the coil of the second and "signal" goes through the NO of the first and NC contacts of the second. The second coil takes time to react but not sure how much. Enough in my case.

[Sydney]

Sounds like for $6 a ICM102 Delay-on-Make Timer with .03-10 minute adjustable delay, universal 18-240 VAC might* do it.
* Load current?

[wogg]

When I turn on the power to several boards, I also need to trip the power switch on a motherboard.

Are you talking about a computer motherboard? Those use a momentary contact on the front panel header to send turn on signal to the power supply. That's an important distinction since most delay relays are intended to turn on and stay on.

[Sydney]

Perhaps using Wake-On-LAN setting in BIOS?.

[JasonP]

Are you talking about a computer motherboard? Those use a momentary contact on the front panel header to send turn on signal to the power supply. That's an important distinction since most delay relays are intended to turn on and stay on.

Yes, which is why I need a momentary click from the relay setup.

[JasonP]

Perhaps using Wake-On-LAN setting in BIOS?.

I considered the "restore to on" setting in BIOS to tell the board to start when power is connected but I worry what would happen if the bios was reset somehow and I wasn't the one using it to reconfigure the board.

[wogg]

A good old 555 timer one shot perhaps. You could drive a small SPST relay to hit the MB header. Sent from my SM-G920P using Tapatalk

[Sydney]

RE 555 circuits:
http://www.edn.com/design/analog/432...-interruptions
http://solorb.com/elect/bootcirc/PCautoboot/

[Millstonemike]

I considered the "restore to on" setting in BIOS to tell the board to start when power is connected but I worry what would happen if the bios was reset somehow and I wasn't the one using it to reconfigure the board.

The BIOS has to be specifically programmed to change its parameters. The parameters are stored in non-volatile ram. I've never had an instance of the BIOS being "reset" without human intervention in the 30 years since PCs came out.

Perhaps others have had a different experience.

[craigk]

The BIOS has to be specifically programmed to change its parameters. The parameters are stored in non-volatile ram. I've never had an instance of the BIOS being "reset" without human intervention in the 30 years since PCs came out. Perhaps others have had a different experience.

Right. It would be next to impossible, if not impossible without human tinkering. Sent from my SCH-S968C using Tapatalk