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Topic: Loud start tone signal for sports competition timer. How to connect PAM8403 amp? (Read 180 times) previous topic - next topic

Dikembe

I have built a sports competition timing system and everything works OK. System has a starting tone procedure with exact start time and duration for each tone and I've used tone() and piezo buzzer.

The only problem is that buzzer is not loud enough. I have tried several amp circuits found on the web but nothing is loud enough.

Then I've found this video:
https://www.youtube.com/watch?v=bzxQDolUcXE

And I have already ordered 89db 3W speaker and this little amp:
https://www.velleman.eu/products/view/?id=435574

Problem is, I don't know how to connect it to my Arduino MEGA. Video has no connection diagram link or comment.

Connections on amp are: RN/GND/GND/SW/+5V/GND/L+/L-/R+/R-

Any other suggestions? I am aiming for 100 ÷ 110 dB.

Maybe this: https://www.velleman.eu/products/view/?id=9181 with external power supply and 10W speaker?

Option: Is there a way of connecting computer desktop speakers to Arduino and send tone to them?

Thanks!

DVDdoug

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Problem is, I don't know how to connect it to my Arduino MEGA. Video has no connection diagram link or comment.
User Manual for the board
Datasheet for the chip

Does that help?

It's a stereo amplifier so you can connect the L & R inputs together and add a 2nd speaker for double the audio power (+3dB).  (Do NOT connect the outputs together!  There is a general rule of electronics that it's OK to connect inputs together, but not outputs.)

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Any other suggestions? I am aiming for 100 ÷ 110 dB.
The dB SPL level depends on amplifier power, the efficiency of the speaker, how close you are to the speaker, and the amount of reflected sound (it will be louder indoors with reflected sound), and the sound-direction/directionality of the speaker.

Speaker efficiency/sensitive is usually rated as xdB at 1W and 1 meter (if they give you a spec).  Horn type speakers tend to be the most efficient.

Doubling the power is +3dB, and four times the power is +6dB, etc.

Power can be calculated as V2/R.   So, double the voltage gives you 4 times the power, and halving the speaker impedance gives you double the power. 

The power calculation is based on RMS voltage.   The RMS voltage of a sine wave is 0.707 x the peak voltage.     A "normal" amplifier powered by 5V gives you 5V peak-to-peak = 2.5V peak = 1.76V RMS, minus some voltage drop across the amplifier.    So, that's about 0.8W into 4 Ohms.      But, the PAM amplifier is a bridge (push-pull) amplifier so it can put-out 10V peak-to-peak for a theoretical maximum of 3.2W.

The "real trick" to more power is more voltage...   High power car amplifiers use voltage-boosting power supplies because you can only get so-much power with 12V.     


Dikembe

Not very helpful but thanks for the electronics lesson. I'm a mech. eng. an like to stick to mechanics. I did this project for my kids, to have some fun with them.

I believe Arduino is for non-professionals, so is this forum. I've got everything working except the speaker loudness. If you have any suggestions, along with circuits, parts... I would appreciate that very much. If you just want to show your theoretical knowledge, thanks for that but it doesn't solve my problem.

Grumpy_Mike

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I believe Arduino is for non-professionals, so is this forum.
That is correct but we expect people asking for advice to actually take some responsibility themselves. Please read this:-
How to use this forum it will tell you how to ask a question and how to respond to the answers you received. Maybe you are expecting too much from us unpayed volunteers.

If you understood nothing of that answer even after googling then maybe you should "to stick to mechanics". DVDdoug was giving you a comprehensive answer to your very wooly question.

Maybe a better answer to:-
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Is there a way of connecting computer desktop speakers to Arduino and send tone to them?
Would be, yes just wire up the buzzer to the amplifier input and the ground of the amplifier input to the ground of the Arduino. That would be buzzer to L+ and R+ and ground to GND and L- and R-

However, even that might not work because you have not said what sort of buzzer you have. There are two types of buzzers, ones that need a pulsing signal to make it produce a sound and those that produce a sound from the application of a steady voltage to it. It is only the former type and not the latter type that is suitable for connecting to an amplifier.


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