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RC Timing Circuit output into another RC circut

I have built two identical RC circuits that seem to work perfect. But I have connected the output signal from one RC circuit (A) into the voltage input of the other RC circuit (B) to try & create a timing signal with a "gate time" or delay. ie. One pulse every second from circuit B and circuit A turning circuit B on for 5 seconds then off for 5 seconds. When I check these circuits with the DMM for frequency & duty cycle they're fine until I connect them together. When connected together the DMM gives some erratic readings (during off state of circuit A I think?... not sure). I tried a diode on circuit A output incase there was some sort of signal coming back from circuit B but didn't seem to effect the readings. The voltage levels out of circuit A seem to meet the specifications for minimum voltage input for circuit B 555. Should I have a transistor after both RC circuits to boost voltage back up to

12volts? Can anyone help me with where I'm going wrong so I can get clean readings again from these circuits together? Thanks for any help :)
Reply to
Jason
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Am i going about this the right way to achieve the desired outcome? i'm open to suggestions if there's better ways :)

Reply to
Jason

Maybe the circut is working fine, just the gate time is confusing the DMM reading. I'm getting two different readings, one circuit A on & one for circut A off.

Reply to
Jason 

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Schematic?

JF
Reply to
John Fields

It's not clear what you think you're doing, but if you expect to put a nice square pulse in one end and to get a nice square pulse out the other -- it ain't going to happen.

If your DMM measures frequency and duty cycle it's making the implicit assumption that it's seeing rectangular pulses, which (in general) you're not going to get at the output of an RC circuit.

From your description of what you _really_ want, I'd consider using one

555 timer circuit that pulses at 1/10th Hz to drive another one that pulses at 1Hz.

Or I'd use an 8-pin PIC and some code...

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
Reply to
Tim Wescott

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