Circuit that sends 1 pulse when input goes high, 2 pulses when input goes low

[CDRIVE]

Hop, I hope you do because I can't bring myself to mess with multiple 555's and or a 4017 when I know I can do it with a single uC and a 12V output level interface. Besides that, he's worked with 555's before. So I'm sure he'd like to design it himself, with just guidance in the right direction.

Chris

 

[hevans1944]

Hop, I hope you do because I can't bring myself to mess with multiple 555's and or a 4017 when I know I can do it with a single uC and a 12V output level interface. Besides that, he's worked with 555's before. So I'm sure he'd like to design it himself, with just guidance in the right direction.

Chris

I don't think I am allowed by Florida law to design it for him. That would be "practicing engineering" without a license. Can maybe offer guidance and suggestions...

 

[CDRIVE]

I need a simple circuit that will output a single pulse when the input goes high, then output two pulses when the input goes low. The input will be 12 to 14 vdc, each pulse has to last about 500 ms. Can anyone offer any suggestions where I might find this?

Hop, after reading your reply in post 20 can I assume that while the output will be OR'd to a single node the input is not being sensed at a single input node? I interpreted the first post as single pin input, single pin output.

Chris

 

[AnalogKid]

I interpreted the first post as single pin input, single pin output.

I think that is correct. A 555 and either a 4017 or a 4-bit binary counter can do this, with only a small buttload of external gating, assuming that the circuit always starts in one condition. There has to be feedback, but I'm trying to do it without flipflops.

OP: Does the input stay in one state or the other while the output makes its one or two pulses, or can it change during the output pattern?

OK, I think I've got it. Differentiate both edges of the input, invert one and OR, so either edge creates a short reset pulse to the counter. The steady state of the input drives the decode gating that inhibits the counter when the cycle is finished. With a 4017, OR outputs 0 and 2 to the output stage. With a binary counter, Q0 is the output for either pattern, Q1 terminates the single pulse, Q2 terminates the double pulse. Since I'm not a 555 fan, this can be done with 1 CD4060 and 1 CD4093.

ak

 

[AnalogKid]

Something like this.

1. This circuit powers up running a full cycle, 1 or 2 pulses depending on the input state.

2. The output is delayed by one pulse time (~493 ms) after an input state change.

ak

 

[AnalogKid]

Hop, as you're probably aware I've always been a Picaxe guy but only because I simply can't or won't invest the time to learn ASM or any flavor of 'C'.

start:
like
goto start

ak

 

[Solakian]

Thanks for the details but we still need an answer to #2.

Chris

estimate less than 50mA

 

[AnalogKid]

For a 50 mA output stage that pulls a +12 V load down to GND, add a 2N7000 or 2N7002 to the output in post #25.

ak

 

[CDRIVE]

start:
like
goto start

ak

Been there. Done that. Didn't like ASM. I'm a VB6 programmer and Great Cow Basic's syntax and structure was easy for me to transition to. There is no Bootloader involved with GCB. It programs blank PICs. The GCB editor can mix and match Basic and ASM seamlessly. I'm happy as a clam with it!

Chris

 

[hevans1944]

... I'm happy as a clam with it!

I have GOT to get one of those! My beloved freshman BASIC, circa nineteen sixty-something, compiled and downloaded into a PIC with some assembly thrown in for flavor... what's not to like? It's like being back in the 1970s, but with microprocessors on steroids slimmed down to just eight pins and three bux. Oh, you do need this $24 starter kit too. But none of this external program and data memory chip crap... just one chip, one input, one output, one power supply terminal, and one ground terminal. Oops! That's four pins... maybe someone could find a use for the other two pins.

 

[Solakian]

Thank you all for your help! The circuit you provided is just what I was looking for. I really appreciate it.