weak buzzer, now no sound

jennifer6 · Post by **jennifer6** » Fri Apr 27, 2012 6:14 am

Hello 9x enthusiasts,
I have just reworked and finalised my second 9X and all good.(er9x, hk backlight and this time hard wired usbasp instead of the smartieparts board).
However I noticed the buzzer sounded very weak compared to my other 9X and decided to remove it and try a piezo unit I extracted out of my many electronic used boards.
Well it did not work, so I put the original one back, and yes I believe in Murphy's Laws and of course that does not work now either!
I notice the original has polarity shown but not the ones I tried to replace it with. So I assume it to be a self generating buzzer not a piezo speaker?
Any help to get this going would be appreciated as I like to hear the countdown timer, and consequent alarms.

Post by **Rob Thomson** » Fri Apr 27, 2012 6:49 am

Have you followed the guides from the wiki?

I have had poor sound and tracked the issue down to a bad connection on the strip plug - the one from the power board to the main board. This plug also carries the signal for the buzzer.

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jennifer6 · Post by **jennifer6** » Fri Apr 27, 2012 8:06 am

Tnx Rob, Yes I have, and have found mods which I will try later.
Was looking for the reason the original piezo device was not operating.
The original device is driven by a transistor which appears to be a better way than the suggested mod of a high impedance piezo across the ic ouput?
Maybe I'm missing something, or are the original devices hard to obtain.
Or are the original devices just crappy.
The other radio I have sounds ok.

Post by **Rob Thomson** » Fri Apr 27, 2012 9:54 am

The main reason for the speaker mod is simply to allow variable frequency output.

This allows advanced alerts for frsky etc...

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jennifer6 · Post by **jennifer6** » Fri Apr 27, 2012 10:36 am

OK, tnx again.
I have discovered a lot in the last couple of hours.
Will modify after the weekend as I'm going away.The mods show cutting some tracks, but there is no need to. Just remove the transistor.
I assume normal beeping will be occur when firmware is set to pispk
I wonder if it sounds roughly the same beep frequency and is of sufficient audible level.

Post by **Rob Thomson** » Fri Apr 27, 2012 11:10 am

It all depends on the quality of the piezo you install.

I have found some are superb... Others just rubbish

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jennifer6 · Post by **jennifer6** » Tue May 01, 2012 1:49 am

Tried various piezo speakers today. Most have sounded very crappy.
One out of a personal alarm system at around 3cms (1.5 inches) diameter is good enough to be usable.So that is now semi permanently installed.
However when I get time if someone doesn't beat me to it, I think what is really required is a simple one or two transistor buffer/preamp circuit to drive a normal low impedance speaker of around the same size.
Any circuit(schematic) ideas welcomed.

SamoaFlyer · Post by **SamoaFlyer** » Tue May 01, 2012 3:52 am

Here;s a simple one that can run direct from the battery - no regulator needed. If the "dead bug" technique is used, it can be glued right on the back of the speaker. Plenty of audio and good sound.

Bill

: LM386 Audio Amp; LM386Amp.gif (4.39 KiB) Viewed 7928 times

gohsthb · Post by **gohsthb** » Tue May 01, 2012 1:52 pm

In the 1st general setup menu there is an option to change speaker pitch. Did you try any different values for this? Mine sounded bad too until I fiddled with this. I think it tunes the output frequencies to the piezo speaker.
-Gohst

jennifer6 · Post by **jennifer6** » Wed May 02, 2012 3:46 am

Yes, I'm playing with a number of things now.
Will report back findings later.

jennifer6 · Post by **jennifer6** » Thu May 03, 2012 5:50 am

Tried different settings in FW r760, speaker pitch. And found a slightly better tone/sound for the 3cms piezo speaker.
Then experimented firstly with a npn transistor with an 8 ohm speaker in the emitter leg, various bias resistors on the base etc, which virtually gave the same results as the piezo speaker direct from the chip.
Then tried 386 ic type amp, which just gave louder crappy sound.
So I have gone back to the non powered piezo speaker mod.It will have to do unless at some stage I come across a better sounding buzzer.
Maybe a small oscillator driving a normal speaker at a lower frequency that might be kinder on the ears.But then again all these mods use extra current.
Its a pity the micro hasn,t enough memory for wave files.Cheers, JJ.

Post by **Rob Thomson** » Thu May 03, 2012 6:37 am

Where are you in the world?

Pm me your address.

I have had some rubbish piezos.... But have a batch here that work very very well. I can send you one

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jennifer6 · Post by **jennifer6** » Thu May 03, 2012 6:55 am

Done, that would be great.
JJ

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