CJMCU-75 -- seting the I2C adress

Question

I just got embedded system CJMCU-75 which has LM75A I2C temperature sensor on top of it. I dig into the LM75A documentation and found out that it's I2C address consists of four fixed MSB and three LSB bits which can be set up externally by pulling pins A0/A1/A2 towards VCC or GND.

So I looked again at my newly bought embedded system and found that designer already took care of this on the bottom of the board where he put three pads for setting A0/A1/A2 pins:

Do you have any advice on how to solder A0/A1/A3 pads to VCC/GND in order to be able to change them easily afterwards.

Answer 1

Pick a surface mount resistor that is just the right size to go from the center pad to either GND or VCC. It should be low value resistor. If you have 0 Ohm jumpers, that would be ideal. But any low value will work fine, for example 10 or 22. Solder it in the desired location. Later it should be fairly easy to move or remove the resistor.

If you don't have any SMT resistors, cut off a small piece of copper wire or a small piece of a lead from a leaded component, and solder that in place as a jumper. Make sure it is physically short so that it does not accidentally contact both VCC and GND. That would not be good.

Good luck!

Answer 2

I just solder bridged the pads on mine. Worked like a charm.

Answer 3

Apply plenty of flux to make a clean bridge. I found a $5 flux pen works nicely for small jobs like this. Roughly the size of a permanent marker.

Apply flux to each pad, a dab of solder on each, then a little more to join them into a bridge.

To remove the bridge later, add more flux and drag your soldering iron across a few times, or use a little solder wick between the pad and your iron to suck up any remaining solder.