Power one arduino from a 2nd arduino

I have done many scans of the forums here and just can't seem to find the andwer to this. Sorry if it is a dup..

Can I use one arduino board to power a second arduino board? I am thinking the answer is yes, but I would like to make sure before I damage one or both of them. If it is possible, would someone please tell me how to wire them together? If not possible, or only possible with some added circuitry, I would welcome that info as well.

Thanks
Ray
:slight_smile:

Yes, you can. On the Arduino there are a few headers for 5v, Ground, and Voltage in.

Just connect the 5v to Vin and gnd to gnd and you should be in business.

Just connect the 5v to Vin and gnd to gnd and you should be in business.

That's not the correct way as the Vin goes to the input of a 5vdc regulator chip which needs to have a higher source voltage then it's rated 5vdc output voltage, 7.5vdc minimum or so. Connecting the 5vdc pin to the other 5vdc pin and ground to ground should work OK.

Keep in mind that with this configuration the there is only one 5vdc regulator handling the current requirements for both boards. This should be no problem for just the boards needs, but you need to consider all the external loads being driven by all the output pins of both boards and keep the total current draw to that which the one regulator can handle.

Lefty

Thanks Lefty!

Based on this, is it correct to assume that I can daisy-chain several arduino's in this way as long as I keep the regulator on the first board in mind.

Can you point me to the specs on that regulator in terms of the total draw I should be able to pull for the sum of all the boards and all of the output pins?

Thanks again
Ray

Well different Arduino boards use different model regulator chips so we need to know which model is being used to power everything. Also how the first Arduion gets it's power is important. If it's being powered via the USB cable then there is a limit on how much total power you can draw from the PC's USB port. That is the USB port becomes the limiting factor rather then the first on board 5vdc regulator. If you are powering from the external power connector then the regulator chip will most likely be the limiting item. Data sheets are available for all the common regulator chips that will give their current ratings, however there are external factors that can become the limit rather then the chips maximum capacity, like voltage in Vs voltage out power dissipation rating and how large in any heat sink is mounted to the regulator. So it can get a little complex to give you a complete accurate answer.

It would be helpful if you could give us a idea of what the Arduino boards are going to be wired to, to get an idea of the total current demand.

There are several ways to power an array of Arduino boards but without an accurate picture of total current consumptions it's hard to steer you to one over the other.

Lefty

Great set of questions and I will try to answer them to the best of my newbie ability. Keep in mind, I am a software guy and I am just teaching myself electronics via the great arduino experience.

I want to daisychain a maximum 6 arduinos, 1 master and from 1 to 5 slaves. As far as I know, I will be using the exact same model of adruino for master and slave, but ideally I would want the slaves to as inexpensive as possible, so maybe a BBB or RBBB version would be enough for my needs. Still TBD on that and maybe the result of this thread will guide me in that choice.

The master is a Duimanilove (sorry if that speeling is wrong) and will be using the pins as follows (not wired or tested yet, but it will give you and idea:

7 pins to drive a LCD (ADM1602K-FSY-YBS/3.3V)
2 pins for I2C
1 pin for interrupt to know when to start sampling button pins
4 pins for sampling 4 buttons
4 pins the ethernet shield

Each slave will a Duiman (same as master) doing the same thing, but since the duino is single threaded, none of these happen at the same time:
Every so often, I will sample one of the analog pins
very rarely, I will drive a relay on one of the digital pins (200ma)
2 pins for I2C with the master

Thanks for all the advise!
Ray