Hi,
This is my first time here, hopefully I am putting this in the right place. I am trying to get audio out of my buildings door intercom and into my raspberry pi using a USB soundcard, a cheap one from Sabrent.
The USB soundcard has a microphone in port. It is a Sabrent USB soundcard.
Measuring the voltage across the speaker it is about 6.5V, and the speaker is approximately 125 ohm. I obviously cannot simply plug this into the soundcard's mic in port. I am wondering what the easiest and simplest way to attenuate this down to a mic level would be. There's only a few small issues.
On this board there's a relay. Somehow the impedance of the speaker connected impacts the relays trigger voltage. I don't entirely understand how this works. I plugged in earbuds to the newly soldered audio jack which had a 35ohm impedance. When I used my pin to pin adapter and the lower impedance headphones, the relay stopped working as the output voltage of the relay terminals dropped to only 2V instead of the usual 7V. I don't entirely understand why.
My thoughts are to make a voltage divider to bring the line level down with a total resistance of 150ohm, but I don't know what the output voltage would/should be. I don't know if I am approaching this the right way. I have both a ton of resistors and potentiometers on hand, so I am willing to mess around with those.
Finally, I would need to do the same with the output of the soundcard back into the intercom which is expecting a mic level input, I will likely simply reverse whatever strategy I used for attenuating in one direction. I can also use the volume control to help with that.
I really appreciate anybody's thoughts on this, I can try to provide schematics, however I am a mechanical engineer, not electrical so that is not my strong side! 🙂
Thank you.
MB
This is my first time here, hopefully I am putting this in the right place. I am trying to get audio out of my buildings door intercom and into my raspberry pi using a USB soundcard, a cheap one from Sabrent.
The USB soundcard has a microphone in port. It is a Sabrent USB soundcard.
Measuring the voltage across the speaker it is about 6.5V, and the speaker is approximately 125 ohm. I obviously cannot simply plug this into the soundcard's mic in port. I am wondering what the easiest and simplest way to attenuate this down to a mic level would be. There's only a few small issues.
On this board there's a relay. Somehow the impedance of the speaker connected impacts the relays trigger voltage. I don't entirely understand how this works. I plugged in earbuds to the newly soldered audio jack which had a 35ohm impedance. When I used my pin to pin adapter and the lower impedance headphones, the relay stopped working as the output voltage of the relay terminals dropped to only 2V instead of the usual 7V. I don't entirely understand why.
My thoughts are to make a voltage divider to bring the line level down with a total resistance of 150ohm, but I don't know what the output voltage would/should be. I don't know if I am approaching this the right way. I have both a ton of resistors and potentiometers on hand, so I am willing to mess around with those.
Finally, I would need to do the same with the output of the soundcard back into the intercom which is expecting a mic level input, I will likely simply reverse whatever strategy I used for attenuating in one direction. I can also use the volume control to help with that.
I really appreciate anybody's thoughts on this, I can try to provide schematics, however I am a mechanical engineer, not electrical so that is not my strong side! 🙂
Thank you.
MB