Help with power supply. 19v 3.95amp to power Arduino via USB?

I’m powering my stepper motor driver with a 19v 3.95amp supply which is all fine and well, and the arduino with the USB from the computer. When its all done I’d quite like to have only one plug required. Can anyone recommend any plans or ways forward to take the 19v supply and split a line off to power the arduino? TIA

For a "regular" Arduino you should drop the 19V down to no more than 12V or so using a voltage regulator like a 7812, or a switching regulator module, like this.

Or you can use our Ruggeduino which takes voltages up to 24V directly.

Either way, keep the ground return paths for the Arduino separate from the motors. Connect the grounds together right at the power supply, and have one ground wire going to the motor driver and another going to the Arduino.

-- The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons

You cant power the arduino with 19V directly but you can get a lm7812 and feed that with the 19V then pump the 12V output into the arduino’s Vin which has a recommended max of 12V. An LM317 would also work, you could set the output to 5V or 12V or whatever. Check the max voltage for the voltage regulator you choose, it’s in the datasheet. Don’t forget the heatsink. You might need a big one. Heat output in watts for a Vreg is (Vin-Vout)*amps.

RuggedCircuits: Either way, keep the ground return paths for the Arduino separate from the motors. Connect the grounds together right at the power supply, and have one ground wire going to the motor driver and another going to the Arduino.

Thanks for that link, looks ideal. The power supply I'm using is identical to a laptop power supply. When you say bring the grounds together right at the power supply, do you just simply mean at the start of the cable that comes from the transformer or do you mean back at the plug? I'm a novice please forgive!

If you have a laptop power supply you have an AC input side and a DC output side. Leave the AC input side alone! Indeed, you want to connect the grounds together at the DC output of the power supply. I'm assuming you've cut off the barrel jack and just have bare leads now?

-- The Aussie Shield: breakout all 28 pins to quick-connect terminals

Thanks for that link, looks ideal. The power supply I'm using is identical to a laptop power supply. When you say bring the grounds together right at the power supply, do you just simply mean at the start of the cable that comes from the transformer or do you mean back at the plug? I'm a novice please forgive!

The word 'ground' can cause confusion and misunderstanding for many people, esp newcomers to electronics. Suffice it to say that the word 'ground' is a very overloaded term and leave it at that. ;)

In your case you are dealing with a AC powered DC power module. The output wires of your power supply will comprise of two wires, a positive wire and a negative wire. You want to make sure that you make a connection from the supplies negative wire to one of the Arduino's shield ground pins along with to whatever you are powering externally with the power supply.

Lefty

Yeah just cut the end off. I couldn't find a specific supplier easily of that one in the UK. But did find this cheap one in hong kong on ebay:

http://cgi.ebay.co.uk/AX3022-Voltage-Regulator-Adapter-Step-Down-2-5-18VDC-/350470966998?pt=UK_ConsumerElectronics_PowerAdaptors_SM&hash=item5199b28ed6

Would I need to worry about heat generated from it? And on that ebay one, what does EN stand for? Is it earth neutral or something?

EN on the output is most likely an Enable signal that you can use to switch the output on or off. See page 2 of their installation guide:

http://www.sureelectronics.net/Temp/PT-PC031_Ver1.0_EN.pdf

I doubt heat will be an issue at the low-ish currents needed to power an Arduino.

-- The Ruggeduino: compatible with Arduino UNO, 24V operation, all I/O's fused and protected

I'll give that a go, will save on a load of wires trailing about.