I am no longer maintaining the electronics sections of this site. For an explanation, see the electronics contact page. If you need help, you can ask your question in The Forum.

Ringing Phone Light Flasher


I have received several emails asking how to connect up some lights so that when the phone rings, they flash. This is very useful in a situation were there is lots of noise and it is impossable to hear the phone, such as a workshop. Here is such a device. The ring detect part of this circuit came from http://www.hut.fi/Misc/Electronics/circuits/telephone_ringer.html.

Schematic


Schematic for phone flasher

Parts:


Part
Total Qty.
Description
Substitutions
C1 1 0.47uF 250V Capacitor
R1, R2 2 10K 1/4 W Resistor
R3 1 1K 1/4W Resistor
D1, D2 2 20V 1/4W Zener Diode
D3 1 1N4148 Diode
Q1 1 2N3904 NPN Transistor 2N2222
U1 1 4N27 Opto Isolator
RELAY 1 Solid State Or Regular Relay (See Notes)
MISC 1 Case, Wire, Board

Notes:

1. You may need to use a lower voltage zener for D1 and D2.

2. You can use a regular relay instead of a solid state relay, but the arcing accross the contacts may destroy it pretty quickly.

3. Be very sure that you have not accidentally connected 120V to the phone line when building and installing this circuit.

Back To Circuits Page | Mail Me | Search