S3ky
Posts: 10
Joined: Mon Sep 02, 2013 11:04 am

Powering Arduino, Rpi and DC motors from battery

Thu Oct 10, 2013 5:08 pm

Hi guys,
I bought a 12V battery 6800mAh and I want power from this battery Arduino and Raspberry Pi and possibly DC motors. I built a schematic as I show at my upload image. I know that arduino has its own regulator and 12V for it is not problem, but for Raspberry Pi I need range from 4.75 to 5.25V. When I use this regulator at ouput I show about 4.9V. But to the Rpi I have connected USB WiFi dongle, USB camera and Ethernet cable and when I use 5V 1A adapter from my HTC mobile all is OK. But when I use 4.9V it was reseting, but when I measure voltage at output of battery there was 4.7V and output of regulator 4.9V I mean it is impossible, for this reason I go to charge this battery and next I will post a reaction. But I need to know, that is possible powering Arduino and Raspberry Pi via this way. And then when all will be ok, what I need when I go to power DC motors?...Now I power it from 6.7V another battery, it only powers DC motors, but I want rebuild it only at one battery, what I need? 6V regulator or what?...but I think, that I need there something more or not?...Thanks for reply..
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uberscubajim
Posts: 162
Joined: Thu Jun 21, 2012 12:22 pm
Location: Ipswich, Suffolk. UK.

Re: Powering Arduino, Rpi and DC motors from battery

Thu Oct 10, 2013 5:29 pm

This might look like a good idea but the problem is that you're going to dissipate a lot of power in the regulator. For a Pi taking an amp it'll be dissipating 7V × 1A = 7W, which is a lot of power.

It's possible to use a switching DC to DC converter. However I'm unsure as to the quality of some of them, especially if one were foolish enough to buy a cheep, dodgy one from eBay :lol:

Finally, I'd keep motor power as far away from Pi power as is humanly possible. The nasty spikes coming from motors are likely to be very unpleasant for the poor Pi.

I'm sure other electronics fiends will be able to help out here....

Jim.

S3ky
Posts: 10
Joined: Mon Sep 02, 2013 11:04 am

Re: Powering Arduino, Rpi and DC motors from battery

Fri Oct 11, 2013 1:45 pm

So, I tested a regulator 7805 with full charged battery. Battery output shown 12.28V and stabilizator`s output with no connected Raspberry Pi 4.99V. When I connected Rpi with all devices (WiFi,camera and ethernet). It showed at multimeter about 4.98-4.97, I had regulator without heat sink it it got soo hot and after 10 sec voltage went down to 4.92 and then I switched-off my battery with switch on it. I have idea that for this high temperature 7805 cant hold a regular voltage or what?...I will mount a fan but it will help?...oder I bought DC-DC converter and all will be ok...Can I build DC-DC converter on my own? (I think it is hard?)...because it is my project to school and I want build things on my own (those that are possible).

Thanks

uberscubajim
Posts: 162
Joined: Thu Jun 21, 2012 12:22 pm
Location: Ipswich, Suffolk. UK.

Re: Powering Arduino, Rpi and DC motors from battery

Fri Oct 11, 2013 2:24 pm

I was quite expecting the overheating. Powering a Pi from 12V using a linear regulator was never going to be very efficient. You'll have a much lower battery life but a warmer room!

Getting a DC to DC converter is probably the best way to go but if you're doing this for a school project it's important to note what doesn't work and why as well as what does.

S3ky
Posts: 10
Joined: Mon Sep 02, 2013 11:04 am

Re: Powering Arduino, Rpi and DC motors from battery

Sun Oct 13, 2013 9:49 am

Yes you are right but whats up with this? http://www.eleccircuit.com/12v-to-5v-3a ... -regulator...I know that I dont create this, but at least I will build it on my own. I think it is better that linear regulator as 7805 but it is similar as http://www.ebay.co.uk/itm/Car-Power-Sup ... 20d556437b or what?

grahamed
Posts: 277
Joined: Mon Jan 30, 2012 7:01 pm

Re: Powering Arduino, Rpi and DC motors from battery

Sun Oct 13, 2013 11:35 am

Hi

Have a look at http://www.ti.com/lit/ds/snvs107c/snvs107c.pdf - 5 components. Just make sure that you keep it tidy with short, fat wires or tracks and make sure the diode is the right one. Test it well before use. Do not use your £30 Pi as a test load for a £1 regulator.

You can do it!

http://www.eleccircuit.com/12v-to-5v-3a ... regulator/ is a linear regulator.

S3ky
Posts: 10
Joined: Mon Sep 02, 2013 11:04 am

Re: Powering Arduino, Rpi and DC motors from battery

Sun Oct 13, 2013 3:41 pm

Hm, so short as possible and bold as possible lines? because inductor? I need at output 5V and Imax about 1,2V for this reason I will use LM2576-5.0, inductor L150, diode 1N5820 and capacitors as shown. Is my logic right? Thanks

grahamed
Posts: 277
Joined: Mon Jan 30, 2012 7:01 pm

Re: Powering Arduino, Rpi and DC motors from battery

Wed Oct 16, 2013 9:54 pm

hi
the 'typical circuit' on p1 is what you need. you must use short fat tracks and a tidy layout to keep impedances and cross-talk low, therefore circuit stable.

S3ky
Posts: 10
Joined: Mon Sep 02, 2013 11:04 am

Re: Powering Arduino, Rpi and DC motors from battery

Mon Oct 21, 2013 5:16 pm

I have only last question, I built a schematic http://prntscr.com/1ysqz2, but for saving a place a took a polymon to ground, so ground is the biggest area on the PCB, is this ok?

trudymiles
Posts: 2
Joined: Mon Jul 29, 2013 1:43 pm

Re: Powering Arduino, Rpi and DC motors from battery

Thu Oct 24, 2013 1:19 pm

We feeded Raspberry and Arduino both together in an interactive art installation. You can find info about sport bets in Betway in this review site.
First we made some tries and finally we went with the DC DC converter. We used just a regular one (purchased at Home Depot).
It worked ok, the only thing was that we had to get a longer cable from the battery to the devices. We were working with both robotic and interactive audio and we got some interference in the sound.
“The ability to read becomes devalued when what one has learned to read adds nothing of importance to one's life.”
Bruno Bettelheim.

gelfling6
Posts: 23
Joined: Sat Dec 01, 2012 8:39 pm
Location: Canton, Connecticut, USA, Planet Earth, SOL-3, Milkyway Galaxy, 3rd star on the left...
Contact: Website

Re: Powering Arduino, Rpi and DC motors from battery

Tue Nov 12, 2013 1:18 am

not impossible, but I would heavily suggest a LARGE heatsink and fan assembly. Since You're powering it off a 12V battery, a simple 12V cooling fan would be ideal, drawing air through the heatsink. (I never was a fan (pardon the pun) of fans blowing the air through the heatsink.. forces too much dust to accumulate, and requiring removing the fan to remove the dust.) (having just recently giving last rights to a 3Ghz P4 desktop my brother in law rarely maintained. had a solid cake of dust under the CPU cooler fan.. And he couldn't figure why the fan would speed-up, and the machine was slowing to dead stop.)
I would build a small box, with the fan, regulator and heatsink enclosed, plenty of air flow through the box, and through the heatsink, out through the fan side. Here, You'll also have ability to add a on/off switch, (on the supply side. Also add a small low-uF (1-10uF) 16WV-Minimum capacitor. across the output to the regulator.) and simply feed the regulated +5V out to a cheapy (or expendable) USB cable. (you might want to also consider adding a place to draw GND & +5V for anything else. after the regulator, but be warned, the Pi is already going to be eating a good amount of the 1-Amp already, so even consider adding a 2nd 5V regulator to the heatsink for this ONLY. (Both can use the common GND.))

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