Latching switch circuit to switch on IC's

Thread Starter

christiannielsen

Joined Jun 30, 2019
330
After several months of house renovation I now have time to pursuit this hobby again.

I have this latching circuit diagram which I would like to use to switch power on and off to the rest of the circuit (a 555 and a 4017be IC.)

The latching circuit gets its 'turn on' signal from a mini switch. But where should I connect the mini switch in the latching switch circuit to make the circuit switch on?

The latching switch is suppose to power a 555 and a 4017be decade counter. Where should I connect the vcc or ground from the ICs to the latching circuit switch?

A signal from the decade counter 4017be's output 6 is suppose to turn the latching switch off after only 1 cycle. Where should I connect the output 6 to the latching circuit diagram?

So in general the mini switch turns on power to the main circuit and the 4017 turns it off. Both with help from the latching switch circuit.

Thank you so much in advance.
 

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Thread Starter

christiannielsen

Joined Jun 30, 2019
330
I have drawn this diagram in KiCad.

This returning project is controlling a servo motor in a Jumping Jack Santa.

I need a latching switch to power on U1-U3 when pushing a momentarily mini switch. And I need U2q6 to signal the latching switch to power off after only 1 cycle.

So a push on the mini switch makes the Santa jump 3 times.

The question is how do I create the latching switch?

I apologize in advance for the poor diagram.
 

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crutschow

Joined Mar 14, 2008
27,743
Here's the LTspice simulation of a CD4001 CMOS NOR gate in a cross-coupled SR latch circuit controlling a P-MOSFET high-side switch, that should do what you want.
The PB (blue trace) turns the 9V to the load on (red trace) and the simulated signal from U2q6 (yellow trace) turns it off.

How much current does the servo motor require?
The P-MOSFET can be just about any with a maximum on-resistance that causes no more than about a 0.1V drop carrying the servo motor current.

Note that you could likely get by with one 555 if you configured it as an astable oscillator.

Also you will likely need a power-on (RC circuit) reset (to all zeros) for the 4017, otherwise it will likely come up in an unknown state.



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Thread Starter

christiannielsen

Joined Jun 30, 2019
330
Thank you I will look into that. I have a cd4001b and probably also the p-mosfet.

Im not sure how much current the servo draws, but its just at small hobby servo. Maybe I can measure it.
 

Thread Starter

christiannielsen

Joined Jun 30, 2019
330
As far as I understand it must be a logic level mosfet because the circuit runs 9 volt? I have been looking through the list I linked to, and I am not good at datasheets yet, but I dont think that any of those in the list would work.

As an alternative there is also:
https://softgenie.dk/72-power-transistor

and digikey, but I still havent figured out how to even browse their site.
 

Thread Starter

christiannielsen

Joined Jun 30, 2019
330
Also you will likely need a power-on (RC circuit) reset (to all zeros) for the 4017, otherwise it will likely come up in an unknown state.
Do you mean that I would want to make U2p15 go high at some point? (I understand why)
I have actually been playing with that pin before but it seems that I cant use U2q6 to reset U2p15 because the current will flow directly to ground instead of going to switch off the SR latch. Could I put in a pull-down resistor at U2p15 and which value should it have in order to have U2q6 make both U2p15 and SR latch go high? if possible?

thanks again, I will update my diagram and post it
 
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