Thanks for all the suggestions!
Once more in life, I realize that it’s a mistake not to tell the whole story, which is:
What you see are the innards of a node inside the SAN network. The MCU is an Arduino Pro Mini 5V controlling four Neopixel LEDs and communicating on four ports simultaneously, using my library MultiTrans. Now I want to add an ADXL335 or ADXL337 accelerometer to measure the tilt angle of the node. Space is limited. Furthermore, I currently have 22 nodes, and fitting them all with an accelerometer can take a lot of time. So I want to reduce the number of connections that need to be soldered.
Arranged on a breadboard the current setup looks as follows:
Here one of the two batteries powers the Sparkfun ADXL 337 breakout board. I am now considering two alternatives:
- Use a voltage divider to power the breakout board.
- Use a breakout board that accepts 5V and regulates it down to the 1.8 to 3.6 V required by the ADXL335/7. In fact, for testing, I have a Seed Grove ADXL335 breakout board here. This board includes a voltage regulator, but it’s too big.
Concerning your responses:
DVDdoug:
a battery isn't a great reference since the voltage drops over the life of the battery.
I assume the voltage on AREF is allowed to drop over time, so that the measurement stays the same.
Wawa:
Why not use the 3.3volt pin of the Arduino to power whatever sensor you have.
The 5V Pro Mini (see above) doesn’t have a 3.3V output.
stowite:
TL431A shunt regulator/voltage
This looks like a nice suggestion, thanks! (though I think I better get a breakout board with everything integrated – already have enough to solder)