What's the best power supply to run an Arduino and a Mini Th

by willyb on Wed Oct 16, 2013 1:59 pm

I have an Arduino Uno R3. I'm going to buy Mini Thermal Receipt Printer (http://www.adafruit.com/products/597) and control it with the Arduino.

What is the best power supply to use to power them both together (from a single power supply)? Inside the project box I can split the incoming power wires so there's one pair to the arduino and one pair to the printer. But I need a single power supply to plug into the wall and feed power to the project box.

The printer details say it needs 5v-9v with at least 1.5A and the 5v 2A power supply is recommended for the printer (https://www.adafruit.com/products/276).

The Arduino is supposed to have a 9v to 12v input (http://playground.arduino.cc/Learning/WhatAdapter). I've ordered a 9V 1A supply from adafruit (http://www.adafruit.com/products/63).

I suppose I need a 9v supply that delivers 2A right? I can't find such a thing though.

What do you recommend?

Thanks!

-WillyB
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Re: What's the best power supply to run an Arduino and a Min

by michaelmeissner on Wed Oct 16, 2013 3:15 pm

Well going on to ebay, and searching for 9v 2a power supply, selecting US seller, New, and Buy it now, I see 178 different power supplies, such as: http://www.ebay.com/itm/AC-100V-240V-Converter-Adapter-DC-9V-2A-5-5-2-1-Power-Supply-US-DC-Charger-/251203115359?pt=US_Server_Power_Supplies&hash=item3a7cdf595f

If you have a used computer store nearby, you might want to check their power supply bin, trying to find one with your voltage, amp, and connector requirements.

My favorite device is the Radio Shack 11343870, which is no longer sold. I think it was 2a, but I may be mis-remembering. It had interchangeable tips, and it combined a battery with A/C adapter. It had two outputs, one 5V USB and the other had select-able voltages (3-12v).
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Re: What's the best power supply to run an Arduino and a Min

by adafruit_support_mike on Wed Oct 16, 2013 10:48 pm

You can probably use the Internet of Things Printer project as a design reference: http://learn.adafruit.com/internet-of-things-printer

The trick there is that we bypass the regulator and feed power from a regulated 5v supply into the Arduino's 5v pin.

Do note the use of the word 'regulated' though.. you want a power supply that puts out nice smooth VCC and GND rails. There are unregulated supplies labeled '5v' that put out roughly enough current to produce 5v across a load with the correct resistance, and there are regulated switching supplies that produce an average of 5v but also include lots of switching noise. The spikes on those can be as large as a volt or two, and that won't be good for your Arduino.

The only supplies I know well enough to recommend are the ones we sell, because I know those have been tested. If you want to try other suppliers, make sure the supply is regulated, and look for information about 'load regulation' or 'ripple'. Be prepared to do some testing on your own with a new and unknown power supply and an oscilloscope to make sure it produces good output when it turns on and off, with a steady load, and when exposed to sudden changes in the load.
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Re: What's the best power supply to run an Arduino and a Min

by willyb on Thu Oct 17, 2013 12:25 am

adafruit_support_mike,

Thanks for the prompt response. I definitely want to buy an Adafruit power supply and it sounds like this is the one you're recommending: the 5v 2A (https://www.adafruit.com/products/276).

I gather from your comments below that if I take the power output from that and connect it directly to the arduino's barrel jack, that it wouldn't work. That's because the Arduino needs at least 9v right? So that's why you do the trick of feeding the 5v directly into the Arduino's 5v pin right?

-WillyB
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Re: What's the best power supply to run an Arduino and a Min

by adafruit_support_bill on Thu Oct 17, 2013 5:57 am

That's because the Arduino needs at least 9v right? So that's why you do the trick of feeding the 5v directly into the Arduino's 5v pin right?

Mostly right. :)

The Arduino processor needs 5v. But because it needs a clean, stable 'regulated' 5v, the board has it's own built-in voltage regulator. The Arduino's voltage regulator needs more than 5v input to assure a stable 5v output. You can power it with anywhere between 7 and 12v.

However, if you have a good supply of clean stable regulated 5v power, you can bypass the Arduino's regulator and feed the processor directly via the 5v pin.
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Re: What's the best power supply to run an Arduino and a Min

by unexpectedly on Tue Oct 29, 2013 7:01 pm

I have some experience with the mini thermal printer and its increased performance is worth the effort to get it 9V.

I'd suggest buying one of Adafruit's 12V power adapters and then what I did for the printer's power was convert the 12V to 9V via an eBay offering.

As far as feeding Arduinos voltage, I've played with OEM Unos & Mega, as well as off branded ones from all over. They all don't seem to care what I feed them; 5V to 12V. And when giving them 5V, there can be unexpected behavior when USB is connected or not, so I used 9V and 12V wall adapters. For playing with motors, I drive the motor controller boards with a separate supply and never from the Arduino. If you go ChipKIT, their regulators get quite warm with 9V or more.

:) Chris
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