My wife has a hard time hearing so im trying to make a FRS radio that will light up a lightbulb to get her attention, when I need her. Ive tried running wires from the speaker to the light and that does nothing. The battery is a 3.7 volt in the radio. Whats the best way. Wait I should say the easiest way as im just learning this hobby. Thanks for your time, Dave.

 

Out of curiosity, have you contacted the radio's manufacturer to see if they can offer an option?

You would need to amplify the output from the speaker to drive an external light. Does it have a headset jack?

ken

 

What's an "FRS" radio?

Regardless, most radios (so to speak) don't put out enough audio power to light much of anything over a small LED - if that. As someone asked above, if there's a headphone jack (or you're willing to go inside and extend the speaker wires out) it would be easy to build a circuit that amplified it enough to trigger a larger lamp or a relay.

 

Yes the radio does have a headphone jack. And I have no problem going inside the radio. FRS- means family radio service. Could I use a SCR with this project? To switch on a 9 volt battery to power the light whenever I key the radio.

 

You would probably still need to amplify need the speaker output signal. If the output exceeds 0.6V peak you could just use a NPN common emitter amplifier. If it's lower than that, then you would need an opamp.

Ken

 

Hello,

Take a look at post 2 of this thread:
http://forum.allaboutcircuits.com/showthread.php?t=37795

Bertus

 

Thank you everyone, I'll try that today and see what comes of it.

 

One other thought would be to use the earphone jack and connect the signal to a comparator with an adjustable level set by a pot (or forget the pot and just use the volume control). Then when a signal changed the comparator's state, its output could light an LED. This might only take a comparator chip, a battery, a few resistors, and an LED. If you want to use an incandescent light instead for more visibility, then you may need to have the comparator's output drive a transistor. If you choose to go this route, the helpful folks here will no doubt post a reasonable circuit for you.

 

You'll also want a diode to remove the negative portion of the audio output waveform.

I'll assume this radio can drive a speaker to a listenable level however we've got to accept that fat that some headphone output jacks aer padded down.

Also let us know what kind of light you're wanting this to illuminate - does it need to be a simple indicator similar to a pilot lamp or are you wanting to turn something like a table lamp on?