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How to connect audio to baby monitor bypassing mic?

Geeman2000

Jul 22, 2015
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Jul 22, 2015
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Hi All,
I have a Raspberry Pi configured to audibly enunciate movement around my property from outputs of reed switches and ir beams. I want to use a wireless audio baby monitor as a portable speaker.

So I want to direct wire the audio output from the RPi into the listening module of the baby monitor via the microphone wires.

Should I just direct connect or is some circuitry required?
 

Harald Kapp

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Nov 17, 2011
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Should I just direct connect or is some circuitry required?
The voltage level of a mcirophone is much lower than that of a raspberyy's output. You need to attenuate the signal e.g. using a resistive voltage divider. As I don't know the mic's level, I can only giess, but an attenuation of 1/1000 or higher should be necessary.

You can achieve this by using a 100kΩ resistor and a 100Ω resistor in series, 100kΩ to the raspberyy's output, 100Ω to ground. Use a capacitor to decouple any remaining DC component. See this schematic:

untitled-png.21095


Use a potentiometer instead of the 100Ω resistor if the level is still too high and the audio is distorted. Adjust the potentimeter until the distortion is minimal.
 

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Geeman2000

Jul 22, 2015
2
Joined
Jul 22, 2015
Messages
2
The voltage level of a mcirophone is much lower than that of a raspberyy's output. You need to attenuate the signal e.g. using a resistive voltage divider. As I don't know the mic's level, I can only giess, but an attenuation of 1/1000 or higher should be necessary.

You can achieve this by using a 100kΩ resistor and a 100Ω resistor in series, 100kΩ to the raspberyy's output, 100Ω to ground. Use a capacitor to decouple any remaining DC component. See this schematic:

untitled-png.21095


Use a potentiometer instead of the 1k resistor if the level is still too high and the audio is distorted. Adjust the potentimeter until the distortion is minimal.
Thanks for the reply, I'll try it later today.
 
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