Powering on/off after 3s

Hi,

we don´t know about
* your power supply,
* nor your device´s voltage, AC, DC, current,
* nor the signal level
* nor timing requirement....
So your question is not very precise.

Thus the answer can´t be precise either.

My first idea: use a very small microcontroller.

Klaus

Here is basic example for using an Arduino Nano board or ATTINY85.

Can use control signal to turn on/off device by driving a relay or a SSR. Or just
as a logic control signal to another board.....



The above is mBlock, takes your block design and turns that into Arduino C Code.
Used by children in school to program robots. mBlock is free.

Arduino Nano board -



Or use a Nano board to program code into an ATTINY85 -



Regards, Dana.

KlausST said:

Hi,

we don´t know about
* your power supply,
* nor your device´s voltage, AC, DC, current,
* nor the signal level
* nor timing requirement....
So your question is not very precise.

Thus the answer can´t be precise either.

My first idea: use a very small microcontroller.

Klaus

Click to expand...

I'm using a battery for devices and their voltage is DC,I don't wanna connect them directly to the battery so a circuit is needed between them to control their on/off state because there's no need for all of them to be on all the time,just when the button is pressed for 3s they're connected to the battery and devices work until we press it again for another 3s.

Hi,

* Battery: All batteries are DC. But it could be a tiny 1.5V coin cell or a huge 48V 200A solar buffer
* Device: is it a 3V 1uA SRAM backup system, or a 10 kW motor
... how can we know?

Klaus

What maximum current and voltage do you need to switch?

crutschow said:

What maximum current and voltage do you need to switch?

Click to expand...

It needs lithium polymer battery (3.7 v)

ElecP said:

It needs lithium polymer battery (3.7 v)

Click to expand...

That answers half my question.
How much current does the load take?

Hi,

This is one possible solution. VG1 represents a pushbutton connected to the battery positive (three second pulses). C1 or R1 would need to be a bit larger to get it over three seconds, this simulation shows about 2 or so seconds needed to toggle the latch on and about 2 seconds for it to toggle off (after being pressed), it seems precisely 3 seconds is not important. It's a really typical circuit that uses the CD4013 or any variant of that (presumably you might prefer a lower voltage type than 'CD' models to maximize the 3.7V and falling battery usage). Only one flip-flop needed. Supposdedly about the same timings/durations at 27ºC and at 100ºC. To carry a bigger load than a 1k resistor might require adding a pass transistor, that's why crutschow asked about current/load, and I'm sure he'll provide you with a more elegant solution than mine, especially if you fill in the gaps, so to speak. What happens if in this version the pushbutton is continually pressed for more than three seconds, no idea, caveat emptor. A latching comparator and an RC network may be another option. Load switch might be another useful term.

d123 said:

This is one possible solution

Click to expand...

The possible problem with that is, the required maximum clock rise-time for the CD4013 FF is fast (below) with is apparently not in the model, and that circuit generates a very slow clock rise (Vin1).



Thus I added a Schmidt-trigger gate to my similar circuit to provide the fast clock rise (below):

The circuit does not change states for a push-button on for less than 3 seconds, (green trace) and changes stage for anything over 3 seconds.

R1C1 determines the delay time

R4C2 provides a power-on reset to set the output off.

I added a P-MOSFET driver at the output for the load.
It can be any logic-level type with a low enough on-resistance rating for the load.