Looking for a Low Cost On Delay Timer

Hi Fred, a counter solution is nice. Can I ask a silly question? Where the bleep is the oscillator? The R's and C tied to the Phi inputs?

Thanks, George H.

Classic 3-inverter CMOS RC-oscillator:

Please view in a fixed-width font such as Courier.

. . . . . . . ____ . Phi1 |\ |\ Phi0 |\ Phi0 . .-| o-----| o---+---| o--+----> . | |/ |/ | |/ | . | [R] | . | | C | . '----[R']-------+---||---' . . .

Make that the classic 2-inverter CMOS RC-oscillator:

Please view in a fixed-width font such as Courier.

. . . . . . . ____ . Phi1 |\ Phi0 |\ Phi0 . .---| o---+---| o--+----> . | |/ | |/ | . [R'] [R] | . | | C | . '---------+---||---' . . .

I use this one all the time on my chip designs (without the divider needed for avoiding ESD clipping with discrete devices)...

...Jim Thompson

As in my ancient RCA data book...

...Jim Thompson

There's something about the 2-inverter that tends to hang at small time constant and squegg at large time constant. I think they discovered that after the 4060 was in production.

If you're making this with CMOS gate chips, it's a good idea to stick to the unbuffered variety. The usual (these days) buffered gates can ring on the transitions. Somtimes.

Yep. Horrendous crossover currents. On my chips I use unbuffered small inverters...

Yes that is the way I would do it I have done many many projects using a

Simple just use the Reset Pin..

When 12VDC is applied to the input, I need a 12VDC output for 5 seconds. Then output will go back off and stay off until the input goes to zero. Then cycle starts again.

Current for both legs is in the 10-50ma range.

A simple on-delay timer would work but I'm having trouble finding one with NC contacts. Tons of stuff $100+, but for this application, it has to be under $20.

===

Thanks for all the tips and good info. I had wanted to put something together from components but my brain is too far behind these days. I'm going to give this a shot and hopefully I'm not picking the wrong one. It's $5 at Frys...

Velleman MK111

On a sunny day (Sun, 25 Aug 2013 23:29:54 -0700) it happened "Guv Bob" wrote in :

The reason I did not reply with a ciruit or whatever is that your logic is false.

You say: 'until', that means the output goes active again. Then you say : 'cycle starts again', but that cycle is not the same now (starts active).

First, for yourself, work out the correct logic. Then you already have the solution, probably from stuff you have laying about.

It can be modified to do what you say you want.

seconds. Then output will go back off and stay off until the input goes to zero. Then cycle starts again.

with NC contacts. Tons of stuff $100+, but for this application, it has to be under $20.

together from components but my brain is too far behind these days. I'm going to give this a shot and hopefully I'm not picking the wrong one. It's $5 at Frys...

Hmmmm....... in that case, forget the electronics! ;O)

Thanks Fred, Jim... Sorry my bad. I don't know the 4060.. I didn't realize it had a built in oscillator.

George H.

seconds. Then output will go back off and stay off until the input goes to zero. Then cycle starts again.

with NC contacts. Tons of stuff $100+, but for this application, it has to be under $20.

together from components but my brain is too far behind these days. I'm going to give this a shot and hopefully I'm not picking the wrong one. It's $5 at Frys...

- Hmmmm....... in that case, forget the electronics! ;O)

If I disconnect pin 7, would that make it a one-shot pulse?

On a sunny day (Thu, 29 Aug 2013 10:18:17 -0700) it happened "Guv Bob" wrote in :

When power is off C1 is discharged. When power comes on the gate of MOSFET T1 is posive via C1, and C1 slowly charges via R1, R.C time, select a suitable capacitor and resistor. The gate voltage slowly drops, and then T1 stops conducting. When power goes off, then C1 is discharged again via D1.

D2 and C2 are needed to prevent transients on the drain (load line) of T1 piercing the gate electrode isolation layer.

IRLZ34 is a logic level (2 to 3 V gate on IIRC) MOSFET.

Alternative solution:

Try leaving out R2 & RV1* and D2*, and jumper the free end of R1 (R1-D2 junction) to pin 8.

If you can't quite get 5s with RV2 cranked up all the way, increase R1 to 10K or 20K.

What discharges that 1000uF (and the 1uF) when the transistor isn't turned on? Or are you assuming push-pull drive on the 12V?

Maybe replace C2 with a resistor and put 1K/12V zener before the cap.