converting power supply signal into pulse signal

[john23]

Hello , I have a power supply which outputs +12V -12V as shown below in the CSV csources and plots.I get stable 12V -12V after a second
Is there a way to take the voltage after its being stable and make a pulse as shown below(or close to it) after 5seconds or so?(automatickly without using MCU)
Or atleast when the "device recognises we have 12V and -12V stable then it releases them at once(not like the power suplly does it)?
Thanks.

[PGPG]

I suppose it should be possible to be done with NE555.
If the pulse have to be square than next 555, if not than C+R at first 555 output will be enough.

[jwet]

"Supervisor" IC's do essentially what you want.  Their purpose is to hold reset low (usually on a micro) while Vcc is ramping and a bit after to get the logic ininitialized.  Most modern supervisors are 50 - 250 mS delay time but there are vintage parts that used a cap to set the delay.  There are some negative supervisors as well.  You could easily do similar with a comparator, reference and some R's and C's.  I'm sure you could get a 555 to do this as well, they'll do anything...

Old supervisor type circuits worth looking at include the TL7712 (set up for 12v).  There also a lot of "Ideas for Design" circuits that were variations on this voltage detect and delay theme.

Good Luck

[Ian.M]

Yes, Jwet's suggestion to use a power supervisor IC is the right way to go about it.  Masochists might build that functionality with a voltage reference,  a pair of window comparators, one for each rail and a retriggerable delay, but when you can get it all in one IC for not a lot of money that's not the smart way to do it.

If you need power rails that cleanly transition from OFF to ON, take the POWER_GOOD signal from the supervisor circuit and use it to gate a pair of MOSFETs, a NMOS in the negative rail and PMOS in the positive rail, with gate resistors chosen to keep the inrush current within the MOSFET's SOA.  An even better solution is to use automotive protected high side, and low side, switch ICs (instead of the MOSFETs) which basically give your power rails overload protection + the switching you need.

[PCB.Wiz]

Or atleast when the "device recognises we have 12V and -12V stable then it releases them at once(not like the power suplly does it)?

As above, Voltage Supervisor / Voltage monitor / Voltage detector parts can do this, and there is a subset called window detectors that have dual comparators for over and under voltage.
You can use both to confirm (say) +12 is over +10V and -12 is under -10V - all voltage driven, no time assumptions needed.

see also
https://www.analog.com/en/resources/design-notes/flexible-overvoltageundervoltage-detector-monitors-negative-and-positive-voltages.html