Power Board PCB

I am working on a PCB that will be used to power 3 arduinos with 3 x 4 AA Battery packs. This is the board that I have designed: Will it work? I think I have connected the batteries in series, and the Arduinos in parallel.

A 4AA pack usually has the cells in series or ~6V. Three packs in series would be 18V. Was that your intention?

good information here is http://www.zbattery.com/Connecting-Batteries-in-Series-or-Parallel

There are two ways to power an Arduino, either ~6.5V to 12V on Vin, or 5V on Vcc. The barrel jack is one way of powering Vin.

If you want to use analogRead and get accurate values the 5V on Vcc needs to be regulated (which is automatic if you power via Vin, the on-board 5V regulator does the job).

If you connect AA batteries in series to power Vcc, then you won't have the accurate 5V, so analogRead() will be uncalibrated.

More importantly its vital you don't overload the Arduino, the maximum voltage you should put on Vcc is 5.5V - never exceed this.

With a 16MHz Arduino the Vcc can go down to about 3.5 to 4V and the board will still function.

AA batteries come in several different voltages depending on their chemistry:

alkaline cells are about 1.5V so 3 in series will give 4.5V which can safely go to Vcc, but 4 in series is 6V which is unsafe for Vcc.

rechargable NiMH cells are 1.2 to 1.35V (depending on state of charge), so 4 in series will give 4.8 to 5.4V, which again is safe for Vcc. 3 NiMH's will only give 3.6 to 4V, barely enough, but should still work. Note that many sensors and other devices you might attach to an Arduino will want their Vcc to be in the 4.75 to 5.25 range.

So you can either:

use 3 alkaline AA cells in series to Vcc (analogRead inaccurate, only ~4.5V on Vcc) use 4 NiMH AA cells in series to Vcc (analogRead inaccurate, ~5V on Vcc) use 5+ alkaline AA cells in series to Vin (analogRead OK, Vcc = 5.0V) use 6+ NiMH AA cells in series to Vin (analogRead OK, Vcc = 5.0V) also use 1 LiPo cell (3.7V) to Vcc (analogRead inaccurate, only 3.7V on Vcc, many shields will fail) use 2 LiPo cells (7.4V) to Vin (analogRead OK, Vcc = 5.0V)

Further options are using a DC-DC boost/buck converter to allow a wider range of input voltages to provide 5.0V to Vcc. However these put noise on the power rail so there will then be more noise on the ADC readings.

Note that batteries output changes over time, depending on the charge state of the battery. So, you can't depend on alkaline batteries giving 1.5v for a long period of time. This is how many battery meters work, they measure the actual voltage and compare it to 1.5v.

Rechargeable batteries tend to have a stable voltage for a longer period of time, but when they are freshly recharged, their voltage is somewhat higher than their nominal voltage (1.2v for Nimh AA/AAA batteries), and when they get close to discharged, the voltage will eventually drop.

Since nobody else has directly answered your question: Yes, as described,your circuit board, when all wired up, will most definitely produce about $100.00 worth of smoke, but just once (at least until you replace the arduinos). Should that NOT be your intention, I would suggest you do some more research and go back to the drawing board.