Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Speaker OUT To MIC IN

Status
Not open for further replies.

Suraj143

Active Member
I want to use ISD1820 voice recording modules speaker output to connect to SIM800L MIC IN Pins.Can this being done? How to connect it?
In other words Instead of a MIC input on SIM800L module, I use the sound out of the ISD module.
Please see the attached file.

Thanks
 

Attachments

  • Mic IN.jpg
    Mic IN.jpg
    244.1 KB · Views: 190
A series resistor should be all you need - historically the original Philips cassette recorders used a 1.5Meg inside the DIN plug to make a mike input into a line input. The value obviously depends on the input impedance of the mike input.
 
In addition to a resistor, you'll probably also need a DC blocking capacitor as the SIM800L supplies DC to power the electret mic that it's expecting.
 
Will the fact that the ISD1820's speaker output is not ground referenced make a difference? Maybe capacitive couple both sides. Followded by a voltage divider.
 
Will the fact that the ISD1820's speaker output is not ground referenced make a difference? Maybe capacitive couple both sides. Followded by a voltage divider.

No, you only need to use one of the outputs - think how a bridged amplifier works, and you will understand why. You 'could' add a coupling capacitor, but I suspect it would make little difference - particularly with a high value series resistor rather than an actual voltage divider (the second resistor is the input impedance you're feeding).
 
OK, I can connect the two speaker wires directly to the MIC input via a single 1.5Meg resistor (It can be placed any side of these two wires).The spec sheet I posted have a MIC impedance is maximum of 27K.Is this 1.5Meg ok in that case?
 
OK, I can connect the two speaker wires directly to the MIC input via a single 1.5Meg resistor (It can be placed any side of these two wires).The spec sheet I posted have a MIC impedance is maximum of 27K.Is this 1.5Meg ok in that case?

Try it and see, adjust as required - you only use ONE of the speaker wires (for bridged outputs), the other connection is ground.
 
If you looked at the attachment on my first post it doesn't have a common ground in either MIC IN (sim 800l) or speaker out (isd1820). It shows SP+ SP- & MIC+ MIC-.
 
Did like this.Quite ok. But there is a noise coming out.Noise means a background noise (the sound like when tuning a FM radio).Any method to cancel the noise?

1593166506320.png
 
What happened to all the discussion about resistor values for attenuation?, you're sticking massive signal levels in to a mike input. R2 needs to be a great deal larger.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top