Speaker Mod - need Clarification

Where to find parts? Refactoring your entire transmitter, new cases? Sticks etc..
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Spainman
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Speaker Mod - need Clarification

Post by Spainman »

I want to do the speaker mod and have some questions.
From my understanding the modification as described in the wiki and in several posts includes
- bypassing the transistor that switches the stock beeper
- switching the added speaker directly by the avr with a cap for smoothing
- using a piezo speaker to keep the current low and prevent overloading the mcu

Now my question is if there is any particular reason why I can't simply replace the beeper with a speaker + cap and switch it through the transistor that is already in place just the way the beeper was switched?

Thanks in advance...

Spainman
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Re: Speaker Mod - need Clarification

Post by Spainman »

Nobody....? Really?!
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MikeB
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Re: Speaker Mod - need Clarification

Post by MikeB »

For a speaker to work properly, it needs an alternating signal that drives both ways. The transistor output only drives one way so I don't think this works.

Mike.
erskyTx/er9x developer
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ShowMaster
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Re: Speaker Mod - need Clarification

Post by ShowMaster »

The reason for the piezo speaker is to keep the impedance ( resistance) high so the CPU will not be damaged.
A normal speaker will be 4-8 ohms and requires a lot of current from the source to drive it. The m64 just can't!
The piezo doesn't require much current to make louder audio.
It my experience however, that I didn't get that much improvement in the audio level, maybe in the quality.
After several piezo conversions, I stopped and just let the FW drive the beeper. It was good enough for most to not bother. I've done maybe 10 full 9x telemetry conversions over the last 2-3 years.
The best and hands down speaker conversion is adding the megasound board. You'll be glad you did!
So...
Try the stock beeper with the latest FW before any other mods.
No, you can't add a low impedance speaker unless you add some amplifier stage that does t load down your m64.
Some I understand have tried a eBay small footprint audio amp.

But..
If you want loud, super fi, audio, add a Megasound board.
SD card for unlimited voiced and sounds, level control via the er9x or opentx menus. Full USB support for uploading new voices.
A bit of a waste if your not going to use the Frsky module and receivers that support full telemetry and tx house keeping reporting.
I hope this is of some help.



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Kilrah
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Re: Speaker Mod - need Clarification

Post by Kilrah »

In my 9x I've replaced the buzzer (leaving the regulator and transistor) by a standard coil speaker and a series resistor, 10 ohms if I remember well to limit current. Works great.

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Spainman
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Re: Speaker Mod - need Clarification

Post by Spainman »

Kilrah wrote:In my 9x I've replaced the buzzer (leaving the regulator and transistor) by a standard coil speaker and a series resistor, 10 ohms if I remember well to limit current. Works great.
Okay that makes sense and answers my question!
I have a very small nokia cell phone speaker in the parts box that fits on the board (smaller than the buzzer) but surprisingly uses a coil + neodymium magnet so it needs more juice than the io-pin provides.
I still wonder why the wiki suggests bypassing the transistor. Even when using a low amp piezo it is nice to have a transistor in between the mcu and the speaker as a protection....

Anyway - Thank you and all others!!!
msev
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Re: Speaker Mod - need Clarification

Post by msev »

Sorry to hijack this thread a bit but have a few questions for the experts.

So if I understand correctly the "PiSpkr" option can be used also with the stock tgy9x speaker, to get different beeping alarms (scifi, robot, etc.)? I've read some reports that its usable. I'd like to have a sound feedback for flight-controller mode-changes.

Some people do the piezo mod, and some people replace the stock buzzer with another one. Do you guys have some suggestions on cheap replacement options of either variety (either ebay, hobbyking or farnell)?

I've also read that people are using piezo's from greeting cards, how can I verify using a multimeter and measuring its diameter if such part is usable?
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ShowMaster
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Re: Speaker Mod - need Clarification

Post by ShowMaster »

Try it with the stock beeper first. I found the piezo mod to not be that much better and maybe lower audio. I stopped doing it and left it stock.

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