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How to Make Speakers Louder with Feather RFM69
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How to Make Speakers Louder with Feather RFM69

by BethDuPlessie on Thu Jul 29, 2021 6:06 pm

Hello!
I need help making a speaker that I am using with a Feather RFM69 M0 (powered with a 3.7 V lipo battery) louder. I'm not sure if I need an amplifier or just better speakers. The current speaker I am using is a magnet speaker 2W 8 Ohm that we already owned (https://www.amazon.com/gp/product/B0177ABRQ6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1).

We are using the speaker inside a 3D printed box. We've designed holes into the box next to the speaker to help with the sound - but even when the speaker is tested outside the box, it is too quiet.

Any and all help is greatly appreciated!
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Re: How to Make Speakers Louder with Feather RFM69

by TI545 on Sat Jul 31, 2021 8:46 pm

What are you using to send sound to the speaker? A pwm pin on the feather? The speaker needs a lot of power and the pin can only provide a little power.

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Re: How to Make Speakers Louder with Feather RFM69

by TI545 on Sat Jul 31, 2021 9:00 pm

If you’re using the DAC to send sound, I noticed this hint from adafruit.

analogWrite() DAC on A0
If you are trying to use analogWrite() to control the DAC output on A0, make sure you do not have a line that sets the pin to output. Remove: pinMode(A0, OUTPUT).

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Re: How to Make Speakers Louder with Feather RFM69

by BethDuPlessie on Sun Aug 01, 2021 8:28 pm

Thanks so much for your response! We are currently using a PWM pin to power the speaker, but we would able to switch to another pin if we can get better results from there. Would using pin A0 be more powerful?

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Re: How to Make Speakers Louder with Feather RFM69

by adafruit_support_mike on Tue Aug 03, 2021 2:33 am

The DAC pin creates better audio signals, but isn’t strong enough to drive a speaker by itself.

Try using a PAM8302 power amplifier:

https://www.adafruit.com/product/2130

It’s small and inexpensive, but when driving an 8 Ohm speaker at 2W it will send about 750mA through the speaker.

Speakers are power hogs. Only about 5% of the electrical energy that goes throughthem gets turned into sound energy.

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Re: How to Make Speakers Louder with Feather RFM69

by BethDuPlessie on Tue Aug 03, 2021 9:13 am

That amplifier looks great, thank you! Does it need its own battery or can we power it from a pinout on the Feather?

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Re: How to Make Speakers Louder with Feather RFM69

by adafruit_support_mike on Tue Aug 03, 2021 4:44 pm

You can power the PAM8302 from a Feather’s LiPo. Just connect it to the BAT and GND pins.

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Re: How to Make Speakers Louder with Feather RFM69

by BethDuPlessie on Tue Aug 10, 2021 6:08 pm

Thank you so much! We'll try that amplifier!

We also have the massive arcade buttons with LEDs on our project, powered by the Feather. Do you have any advice for how to make these lights brighter? I posted to this other forum, but maybe it wasn't the proper place, we didn't get any replies = )
https://forums.adafruit.com/viewtopic.php?f=47&t=181712

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Re: How to Make Speakers Louder with Feather RFM69

by adafruit_support_mike on Wed Aug 11, 2021 12:13 pm

You'd need to take the switch apart until you find the LED and its resistor, then replace the resistor with one whose value is lower.

It's not too hard. The LED is connected to the microswitch, which snaps into the back of the button. Then the LED sits in a plastic tube that snaps onto the microswitch. Both are easy to pull apart and reassemble by hand.

To choose a new resistor value, start by connecting the LED and its existing resistor to 3.7V and measure the voltage from one end of the resistor to the other. For a white LED it should be somewhere near 0.5V. Once you know the voltage, divide that number by the amount of current you want.

Most indicator LEDs are designed for 25mA, and assuming 0.5V across the existing resistor, the resistor value for 25mA would be 0.5V/0.025A=20 Ohms.

Try a few different values while you have the LED and resistor out where you can play with them. Once you have a combination you like, put them back into the plastic tube, snap that onto the microswitch, and clip the mmicroswitch back into the button.

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Re: How to Make Speakers Louder with Feather RFM69

by BethDuPlessie on Wed Aug 11, 2021 1:03 pm

We will try this, thanks so very much!

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