Lowering hi frequency alarm beeps

[Tom Frank]

Both my Futaba 7C TX and Duratrax ICE charger have built-in alarm beepers, both of which oscillate at something around 5000 hz (guessing, because I can't hear much above 3000 hz.

Does anyone on this forum have the savvy to know a way to replace piezo device or lower the frequency to less than 2000 hz (1000 hz would be even better). Can another device be wired in parallel with the stock one? The ICE charger can generate different frequency tones, so it doesn't use a fixed frequency piezo device. The 7C TX just generates single frequency beeps.

I guess the specifics of each device would need to be know for a definitive solution... I was hoping someone here might have done this already or has similar equipment to figure it out.

[MatC]

The piezo is probably the simple flat type, with the freq set totally by the driving circuit (maybe even the microprocessor directly). No easy fix: other stuff in parallel won't work, and no easy way to divide down the freq. (If you do, you'll need to amplify up the signal again anyway).

A couple of suggestions:

1. Wire a LED+resistor in parallel with the piezo. You still won't hear it, but you might see it. If it's like my FF7, the pulsing happens at a frequency that would make the LED flash nicely.

2. Detect the existing output, and drive your own custom (low freq) unit. You can get small/cheap ready made pizeo blasting units, the detector should be easy enough (resistor/diode/transistor).

Good luck.

[Acetronics]

Hi, Tom

You can find two freqs groups on the market ( same size ): ~ 2-3 kHz and ~4-6 Khz. a search by electronic components shops for Hobbyists can make you find the good one.

Sorry for the links ... but I live in Europe !!!

ex : http://www.selectronic.fr/article.asp?article_ref_entier=60.9143-9999

Alain

[MatC]

That's the self-contained with own-oscillator type. Chances are the actual unit is a bare piezo, but worth checking.