timed 3v circuit,,or other options

Thread Starter

kittyflin

Joined Apr 29, 2019
5
on a project im working on,converting an old animated telephone into a games console,everything is working apart from the statup sequence which just loops on forever(on the phone),The other option ive got at the minute is it does nothing unless I press a test switch on phone then it does its thing for 5 seconds and stops),on switching on console the usb port sends a stepped down 3v constant power supply to the phones animated circuitry which sets the phone off doing its thing,ideally I would like it to stop after 5 seconds and not operate again until console has been restarted,,im a total noob to this stuff at present so any ideas are welcome
 

AnalogKid

Joined Aug 1, 2013
8,468
Important stuff first - what is an animated telephone? Photos?

Your question - when a +3.3 V power source appears, produce a +3.3 V pulse that lasts 5 seconds, stops, and restarts only when the 3.3 V source tgoes away and returns again.

yes / no ?

If yes, this is a stretch version of a POR - power-on reset circuit. Lotsa ways to do this, relay, transistors, IC, home-built, ebay module, etc. Depending on what the pulse drives (input impedance / current draw), this can be only one transistor and a couple of passive parts. What does our new, friendly 3.3 V pulse drive? (What I'm after is whether the downstream circuit needs a fast, clean turn-off edge after 5 seconds or can the 3.3 V wander down to 0 V relatively slowly.)

And, what is your skill set for building a small circuit on perf board?

ak
 
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Thread Starter

kittyflin

Joined Apr 29, 2019
5
ok thx for reply,my skillset could just about build and solder a circuit,as for animated telephone see attachment,head spins and lights up whilst making the artoo beeps,,the 3v just powers this and nothing else,so yes to your question I would like it to work like this
when a +3.3 V power source appears, produce a +3.3 V pulse that lasts 5 seconds, stops, and restarts only when the 3.3 V source tgoes away and returns again.
 

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djsfantasi

Joined Apr 11, 2010
6,439
ok thx for reply,my skillset could just about build and solder a circuit,as for animated telephone see attachment,head spins and lights up whilst making the artoo beeps,,the 3v just powers this and nothing else,so yes to your question I would like it to work like this
when a +3.3 V power source appears, produce a +3.3 V pulse that lasts 5 seconds, stops, and restarts only when the 3.3 V source tgoes away and returns again.
That runs on 3.3V? I’d think that the motors would require something higher.
 

AnalogKid

Joined Aug 1, 2013
8,468
I'm not Wally by any stretch, but here is a first pass simulation of a circuit that will pass 300 mA. External power is on from 1 s to 11 s. R4 represents a 330 mA load. R5 is adds hysteresis to decrease the off-time transition.

ak

POR-5sec-3.gif
 
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djsfantasi

Joined Apr 11, 2010
6,439
Do you know how to determine the current?

This may not be sufficient, but cut the power supply line so you can put a DMM in series. Then, with the DMM in current mode, either A or mA, operate the device activating as many features as possible. Watch the DMM and note the highest value that it measures. Add a bit (10%?) and use that as your current requirement.
 
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