Electronics

domiflichi · Joined: 11 Oct 2006 Posts: 5

hello,

I'm a total newbie, so this may sound like a dumb question, but I'm a little confused on this telephone flasher circuit:

http://www.circuit-diagrams.com/dg14-Ringing-Phone-Light-Flasher.php

The circuit shows +5v going to R2 and +5v going to one of the inputs of the relay. My question is where are these 5v sources coming from?

Another question is how do you 'ground' the transistor (Q1) and the Opto Isolator (U1) ?

thanks

neon · Joined: 25 Feb 2006 Posts: 586

the gnd or the 3 bars is the return for the the +5 volts source to complete the circuit the +5v are tied together anywhere as is the gnd. whatever goes out of +5v must return to to gnd so tie the gnd together and the +5 v also. the optcoupler is another source which is isolated from the secondary circuit. the ac is just connected or disconnected by the relay contacts.

domiflichi · Joined: 11 Oct 2006 Posts: 5

Thanks for the reply...i'm starting to understand, but still a little confused. Where do the +5v come from? Do I have to hook up some batteries to supply the +5v? I didn't realize a phone flasher needed batteries if this is the case. We have a store-bought phone flasher at our shop at work and it doesn't need any batteries, so this doesn't make any sense to me.

thanks.

neon · Joined: 25 Feb 2006 Posts: 586

well 5v volts it can come from 120v ac via a diode resistor zener of 5 v or 9 volts battery 120v must know pull in current of relay to figure it out resistor value like 120*1.41/.020 ma that gets the idea don't forget to add a big cap to sustain the voltage across the zener or use 9 v batter instead of 5 v but it will not last for very long. frankly you are better off buying it.

domiflichi · Joined: 11 Oct 2006 Posts: 5

Again, thank you for the info. I would buy one, but last time I went into my local Radio Shack, they didn't have any. Also, I would like the experience and fun of actually building one myself.

Do you (or anyone else) know of any other diagrams I could use to build my own without having to use a battery?

Here's a couple images of my store-bought one:

So this is more of what I'm wanting I guess.

thanks.

neon · Joined: 25 Feb 2006 Posts: 586

yes you could get 120vac resistor cap and 5v zener and no battery or change the relay to 48 vdc like what they do. actualy i dont like to use relay there are simpler circuits for that using LEDs

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