Need to create a momentary contact 6 seconds after power applied

Thread Starter

dablitz

Joined Sep 17, 2019
5
I have a LattePanda Delta I am using in a project. I have a 12vdc 5a power source through a switch. I am looking for help in creating a momentary contact closure to trigger the power on of the LattePanda 6 seconds after power is applied. I have tried varied attempts with a relay to momentary combined with an ne555 timer and am not have any luck. can anyone give me a hand?
 

schmitt trigger

Joined Jul 12, 2010
246
A 1Meg resistor, tied to +12v on one side charging a 4.7 uF capacitor. Low leakage type.
The junction of those two components, feed to the input of a CMOS schmitt trigger like the CD4584.

Since the output will be inverted, use a second gate in series (there are six per IC package) to have a positive-true output.

Buffer the output with any general purpose NPN transistor, like the ubiquitous 2N2222.

Ah! almost forgot......put an antiparallel diode with the 1 Meg resistor, such that when the power is removed, the capacitor voltage is rapidly discharged.
 

MisterBill2

Joined Jan 23, 2018
6,103
Two small time delay relays, the first provides the six second delay, powering the second relay that delivers that start pulse until it opens a second or so later. Then both relays stay energized until the 12 volt power switches off. Use the small "half ice cube" sized time delay relays made by P&B, as well as others. No complex electronics to build and house, and they will last for 20 years.
 

crutschow

Joined Mar 14, 2008
24,996
I am looking for help in creating a momentary contact closure to trigger the power on of the LattePanda 6 seconds after power is applied
Is momentary just a second or so?
What's the maximum closure time?
Is the closure to ground?

Below is the LTspice simulation of a fairly simple circuit that uses CD4093 Schmitt-trigger NAND gates and a MOSFET to provide a delayed, momentary closure to ground, if that's what you need.
It provides about a 6 second delay with a 6 second closure upon power-up (I used the same RC components for both to minimize part types).
You could also use CD40106 Schmitt-trigger inverters for the circuit.

1587579208429.png
 
Last edited:

crutschow

Joined Mar 14, 2008
24,996
the momentary is about 1 second. the closure is to close a switch curcuit power on button.
Do you have a circuit diagram of exactly what the switch does?
If you don't, then M1 can drive a relay to give a contact closure.

Changing R2 to 100k will give a little over a 1 second delayed pulse.
 
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