How to lit a LED when phone rings?

Hi, I would like to know a simple way to lit a white 5mm led when the phone rings, simpler is better

Thanks!


Pablo

Perhaps gettting an old phone with a ringer and checking the voltage to the ringer, and replacing it with a resistor/regulation and LED could work.

Hi PEU,

I don't know if this is exactly what you are looking for but it seems close.

http://www.electronic-circuits-diagrams.com/telephonesimages/telephonesckt15.shtml

And this site has some other good ones.

http://www.discovercircuits.com/T/telephone.htm

Hope it helps.

**EDIT**

Also be careful about the voltage on the phone ringer, it can give a nasty zap.The voltage may be different in different locations but it is more than the standard white LED can handle. If memory serves me correctly it is only about 20-30 volts less than the standard wall outlet (in America 120V).

http://www.tech-faq.com/telephone-voltage.shtml

**EDIT**

Sincerely,

Shaman

Thanks!

from shaman's links I found this schematic:



Can it be made simpler? I mean this one flashes, and I'm happy with the led on.

Thanks


Pablo

This is good recipe for terrorist...:naughty:

Hi PEU,

In the first link, there is a schematic that doesn't require batts and I think it is on only when the ring comes. You might be able to charge a capacitor then make it light the LED until the next ring comes (thus charging the cap once again). Glad it is helping!

Sincerely,

Shaman

Shaman: the IC from the 1st link is not readily available here in Argentina.

OTOH the one I copied in my last posts uses a super common IC and I dont mind using a 3v battery I just want to make it as simple as possible.

Koala: I don't have that in mind at all

Thanks


Pablo

Hey there Pablo, nice to hear from you...


I was thinking, perhaps this...

A zener diode (maybe 50v) in series with a resistor (maybe 10k) in series with
a high brighness LED, and the LED is in antiparallel with a 1N4004 diode.
Only thing is, im not sure if your phone lines are the same as ours here in the
USA, where we have something like 40vdc on the line until it rings, then
the ring ac goes much higher. The ring ac would light the LED, not the dc.
You would have to set the resistor (10k) to a value that only allowed a small
dc current (maybe 5ma) to flow through the LED, but it would still show up good.
This would be the simplest circuit...no ic's or batteries.

If you can do this:
With the phone on the hook and no ringing, measure the line voltage dc and ac.
See how much dc you have on the line.
Next, with the phone still on the hook have someone ring you, and measure the
ac voltage that appears on the line when the phone rings.
That's two measurements:
1. dc with no ringing
2. ac with ringing.

With these two measurements we should be able to come up with
the correct resistor value, or you could experiment yourself.

If you are interested maybe i'll build one for myself too.


Another idea:
Measure the dc value and hook the LED up so it only conducts
when the ac voltage comes along. A diode in series would do it,
in series with a resistor maybe 20k. The LED should not be lit when
hooked up and no ringing, or else reverse the connections.


Take care,
Al

The peak AC Ring Voltage is 150V's, so on top of the 48V DC "battery" voltage from the CO (Central Office), you could se a 200V peak between Tip/Ring. In the schematic above (which I agree with Mr. Al in that it is overly complex!), it properly shows diodes with a 200V rating since during peaks each diode in the "active" branch will see a cool 100V across it

Will

You probably have an electronic ringer rather than bells. What's the voltage across the speaker for the ringer?

Use this simple circuit - make sure the LEDs are joined anode-cathode. It will light 2 red LEDs to maximum brightness.



More circuits here... http://quantsuff.com

i made one a while back with just a diode and LED.. stayed lit all the time, dimmed when someone was one the phone, and flashed when it rang...

nice simple circuit there!

i made one a while back with just a diode and LED.. stayed lit all the time, dimmed when someone was one the phone, and flashed when it rang...

Click to expand...

That's why there is a .22uF cap in the circuit - so that only the ring signal gets through. Actually, in a dark room, you may see some slight flickering of the LEDs during a conversation.


.

That is my kind of circuit. It might actually work even with me building it.

Builder said:

That's why there is a .22uF cap in the circuit - so that only the ring signal gets through. Actually, in a dark room, you may see some slight flickering of the LEDs during a conversation.


.

Click to expand...

ahhh... got cha..

Wow, I didn't expect the answers to be so complicated. PEU:1) There are some phone keychain thingies I've seen which lights up when the phone is ringing and during conversation. It only has to be close ehough to the phone to be activated. They are not 5mm LED but I'm sure you can do the necessary adaptations.

2) There are also phone vibrator attachments you can buy. I can't exactly see the point of them since every phone has the option of vibrate but, they attach to the phone and vibrates when the phone rings. I don't see why it can't be adapted to light up an LED instead of vibrating...

Hi again,

These circuits presented are so simple i cant see why you'd want to do anything
else. Either use the circuit with the cap in it, or the one i suggested...either way
it's cheap and simple, and very reliable too.

Take care,
Al

LOL Mr Al, simple is relative...

eebowler he is talking about a land line, house phone not a cell unless house phones vibrate now and where can I get one:naughty:

C