Names can be confusing, so here's what I'm doing....
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.
-- For way under $20, this'll work, and if you need NC contacts, all you'll have to do is put either a solid state relay or a mechanical
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.
Thanks John, I'm not following you. Can you sketch the circuit?
-- Sure. View with a fixed-pitch font like Courier New:
seconds. Then output will go back off and stay off until the input goes to zero. Then cycle starts again.
one with NC contacts. Tons of stuff $100+, but for this application, it has to be under $20.
Thanks again! Would this work?
NTE955M Timer, (555 Type), 200 mA Iout, CMOS 8 DIP 1.20
-- If you can work out how to trigger it on the rising edge you said you wanted your timer to, it might, but $1.20 is a little high for a 555.
seconds. Then output will go back off and stay off until the input goes to zero. Then cycle starts again.
finding one with NC contacts. Tons of stuff $100+, but for this application, it has to be under $20.
mechanical
Vcc)
I was going to say this sounded like a perfect fit for a 555 timer. (So what's the best RC combo to get 5 seconds from a 555?)
George H.
I used to know all that stuff by heart, but I've been swapping modules too long. This not the usual rush job, so it's a nice change to be able to spend some time on it. Now I'm off to re-learn all the RC stuff.
Maybe like this:
in------+-------------+ | | | . . . .|. . . . | . VCC(8) . | . . +-----+-------RES(4) OUT(3)------ out _|_ | . 555 . D1 A [R1] +---TH(6) DIS(7)-- 'T` | | . . +-----+---+---TR(2) CV(5)-- | . . C1 ===== . GND(1) . | . . . .|. . . . | | ----+-------------+--- ground U1 LMC555 / 7555 D1 1N914 C1 10uF R1 470K
-- ?? 100% natural --- news://freenews.netfront.net/ - complaints: news@netfront.net ---
-- Yup! :-)
-- Just for grins, the device you've described is an "OFF delay" timer.
modules too long. This not the usual rush job, so it's a nice change to be able to spend some time on it. Now I'm off to re-learn all the RC stuff.
That was my 2nd guess. LOL!
In industrial relay timer parlance, we'd call that an "interval timer". An "off delay" timer would drop out a period of time after the power was removed (a more rare beast since it would have two power supplies or a big capacitor inside). An interval timer is/was just an on delay timer with logic inversion before the relay driver, so it pulled in immediately upon connection to the power source and drops out after the delay.
The terms are used differently in different domains so I wouldn't count on them being valid in any particular instance. For example, some cretinous poltroons will refer to a recycle timer as an "interval timer".
Best regards, Spehro Pefhany
These used to be called "Delay Relays" and looked like a vacuum tube. Now there are solid state models. See .
You can find these on eBay, i.e.
You should be able to figure out a way to get what you need though you may need another regular relay as a latch.
Well under $20.
Yes that is the way I would do it I have done many many projects using a
555 Time IC..
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)
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?
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