Non-Automotive Electronics Question

addo · Unread post by **addo** » 01 Oct 2011, 12:59

I'm trying to help my father who is quite hard of hearing.

He has a little piezo beeper timer that he uses for cooking - carries it in his hand or pocket while it's counting - however the range/volume are slowly slipping out of audible for him. That's even with a hearing aid factored in.

Wondering if I can drop the frequency of a piezo timer in any easy way, like by soldering a cap or resistor in? I can't afford to lose volume, though.

TIA for any suggestions.

OwenP · Unread post by **OwenP** » 01 Oct 2011, 15:45

From what I can see after a little digging on the net, the frequency of sound produced is a function of the frequency of power supplied, i.e. how rapidly the power supply to the piezo material is switched on and off.

From this website: http://justanotherlanguage.org/content/ ... orial_pwm2

Also according to the above, the duty cycle controls the output volume, although they appear to be talking about using a particular chip for the control (and this is a little beyond me at the moment.)

It is a long time since I've studied electronics, but from what I do understand of that page it may be more complicated than adding in a resistor or capacitor. A lot may depend on the circuitry that is already there and if you can access the control chip.

Beyond that I'm not having a lot of luck digging anything up and I never covered piezoelectrics during any of my electronics courses to fall back on other knowledge, sorry.

HDI · Unread post by **HDI** » 01 Oct 2011, 18:35

Easier solution, buy him a flashing light or vibrating timer ?!

Unread post by **xantia_v6** » 01 Oct 2011, 19:36

It is a few years since I worked with this sort of stuff, but I think that piezo transducers are self-resonant, which is why they are so efficient. This means that you can't change the frequency much.

If you can find a suitable DC signal, maybe you can fit a vibrator unit from an old phone (old ones are best because they were designed to shake a phone with a lot of mass).

dnsey · Unread post by **dnsey** » 01 Oct 2011, 22:40

I think that piezo transducers are self-resonant

And usually fitted in a resonant cavity, too, in this sort of application.
Is there room for a physically larger transducer in the case?

addo · Unread post by **addo** » 02 Oct 2011, 01:41

Not really.

I may just suggest he uses the iPhone's timer - covers all requirements.