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.
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.
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?
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?
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.