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Pulse from >3 pulses in 5s?

My (infra-red) Remote Control unit, made some 25 years ago, uses this 12 button remote to control a variety of stuff in and outside the house.

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I want to add a new function: toggling a security light near my shed workshop. Although I have a couple of buttons still unused, I want to avoid the hassle of fresh wiring and holes drilled through two walls.

One of the existing devices is a 'Shed Chimer. Key #3 sends a 14V DC pulse to the shed while held (typically by my wife to get me back in the house). So my idea is to use that. Three or more input pulses within say

5 seconds would generate a brief output pulse. I would then use that as input to my light-triggering circuit. The only drilling would be through the wood side of the shed.

I'm a bit rusty so would much appreciate any circuit logic suggestions please, ideally using my old CMOS devices (4001/4011/4013/4017/4016/4066, etc).

Terry, East Grinstead, UK

Reply to
Terry Pinnell
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How about a CMOS '555? Capacitor-couple (C1) to a couple of diodes to make a charge pump, that pulls DOWN the trigger. A capacitor (C2) to ground will collect the pumped charge, a resistor to V+ will reset C2 (size the resistor for that five second time). Since the trigger operates at 1/3 of Vcc, you'd want C1 to be about one third of C2.

This is a kind of analog solution, but with most CMOS gates it'd be poor practice to let the input dawdle for five seconds at a time, so the LMC555 or a Schmitt trigger are closer to ideal.

Reply to
whit3rd

c1 in +--||---+--->|---------+----+ out | | c2 | | | +---|

Reply to
Jasen Betts

Save yourself a lot of hassle and get WAY more capability with one of these:

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Just helped a friend do a pulse width discrimination project with one of these.

His project was almost exactly what you want, generating additional functions from an existing remote. There's a bigger version should you need more pins.

Lots of potential for expansion: Add timer functions to turn it off after a delay Photocell to turn it off during the day etc.

I'm never gonna build an analog timer again.

Reply to
mike

Thanks both. I'll experiment with those circuits tomorrow. Much simpler than the logic I'd vaguely had in mind, starting with triggering a 5s monostable with first pulse.

Terry, East Grinstead, UK

Reply to
Terry Pinnell

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