Circuit design for phone strobe light alerting system

I don't know everything..so hopefully other posters can fill in the gaps...

I know a ring off a telephone line is a large voltage. But I don't know the waveform or how much it can be loaded. But I do know very bright LED's can substitute for a strobe.... But I don't know how many can be used...

D from BC

You are sitting on one of the great research tools around - did you search for it? Lot of schematics on the net.

This is Usenet, not Google Groups, before you post, you look for the information yourself, "Groper."

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I've used neon bulbs attached directly across the incoming phone line. Radio Shack or your local equivalent probably stocks them.

Bob

Not hard to make, but why do it? It will probably end up costing you more money. I would suggest buying one, take it apart, tinker with it, etc.. get the education, and then gift-wrap it?

You will solve at least the following problem issues: --which you did not mention.

1 - FCC Part-68 Registration issues (legal & technical requirement for devices intended to be connected to the public switch telephone network). I assume you are in the US, if not, other countries have similar requirements. 2 - Safety. (Think lightning strike, here.) Ring voltage (US) can be 90-volts DC nominal, sometimes much higher.

3 - Reliability. OK, this one might be a reach depending on what you might buy. I don't mean to imply your design would be inferior, but I think we can all agree it would be re-inventing the wheel. A wheel that has literally been beat to death....

That said, I don't know a single elect. hardware design engineer who hasn't taken a phone apart at some point!! Enjoy!

Neon bulb would work if you are looking directly at it, not too useful otherwise.

Ring voltage is something like 90 VAC 30 HZ. With a cap, rectifier, zener, small filter it is easy to just put the limited DC into a solid state relay or optical coupler.

Or buy one ready made phone line flasher at Electronic Goldmine for $5. receptacle switches 120 VAC lamp

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But then you use the light from the neon bulb to turn on a photelectric device, which controls the light flasher.

Or, you get a modem, and power it up (easiest if it's an external modem), and then use the ring detector circuitry from there to control a flasher.

Michael

That's doing things the hard way . . . build an optical isolator around a neon bulb (LED, cds photocell, triac and some potting resin. I used to do that before solid state relays came along) It could be done, but why would you want to?

Modem? Let me guess, you really, really, like Rube Goldberg?

You'll love this: take a laser pointer and power it from the ring voltage and use mirrors or optic fiber to send it around the house. Or how about a mechanical gate that drops a ball into a tube, the ball winds its way through the house tripping mechanical flags, and setting several wind up mechanical toys into motion, . . . .

Has a simple schematic, except U1 and everything West of it could be replaced with a single solid state relay, and eliminate the transistor and DC supply. Still cheaper to buy it ready made though . . .

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50-100V low frequency (no more than 20Hz).

sine with a 48V DC offset.

not a whole lot, but then a xenon strobe doesn't use much power,

start with a mains strobe bulb add a few Cockroft-Walton stages to rectifier.

If low-visibilty is acceptable use an off-the shelf 110V rated neon indicator.

Bye. Jasen

yeah, pin 9 (or 22 for 25 pin ports) goes to -12Vish when the phone rings.

that could switch on a p-channel mosfet, pnp transistor, or optocoupler but there's not quite enogh drive to operate a small relay.

Bye. Jasen