How do I identify the correct power source for a circuit?

Thread Starter


Joined Nov 20, 2019
I've got hold of a Bluetooth controller module. But I do not know whether is should be supplied with A/C or D/C voltage (and if DC then what voltage). Is there a way to go about determining this?

I've got a picture of the PCB. 2 wires are the supply and the 3rd wire is a switched live activated when bluetooth remote control is pressed.



Joined Nov 29, 2011
Well, you start by getting datasheets of the devices on your board. The N52632 is a Bluetooth controller that has a DC input voltage range of 1.7 to 3.6V. The SOT89 device looks like an on-board voltage regulator, so your input at the connector has to be high enough to allow the regulator to regulate - probably 5V or so.

So, download the datasheet for the N52832, find the pinout to locate the VCC lines, then hookup a variable DC supply to the DC input line and, while monitoring the DC VCC voltage on the BT chip, slowly increase the input voltage until the VCC pin reaches a plateau. My guess is that your input DC voltage will be either 3.3V or 5V.