Rube Goldberg Bench PSU

I'm in the planning stages of making a bench power supply with a TFT, current sensors and voltage sensors using an old pc case. My question is about using a usb cable to power an Arduino Uno from the psu, breaking out just the data wires to a usb jack on the front to take care of programming. Anyone see a problem with this.

This is my first 'duino project that wasn't prepackaged, need some gentle guidance.

Crappy weather blah's have hit early, need a project. I think I have figured out the rest of the issues and will post some pics when the project gets further.

I will probably need help with the TFT also but that will be later once it is assembled.

montyst509:
I'm in the planning stages of making a bench power supply with a TFT, current sensors and voltage sensors using an old pc case. My question is about using a usb cable to power an Arduino Uno from the psu, breaking out just the data wires to a usb jack on the front to take care of programming. Anyone see a problem with this.

This is my first 'duino project that wasn't prepackaged, need some gentle guidance.

Crappy weather blah's have hit early, need a project. I think I have figured out the rest of the issues and will post some pics when the project gets further.

I will probably need help with the TFT also but that will be later once it is assembled.

There is no problem powering a Uno board via the +5vdc and ground pins of the arduino's USB connector, I have done this often, makes a quick way to turn power on and off the board. However I don't know if you could at the same time strip out the D+ and D- signals and wire them to something else at the same time. The PC USB tracks current draw of the attached device via it's USB power wires and may not connect or disconnect properly if the power on the usb cable is coming from other then the PC' usb connector. Just a thought.

Lefty

That was my thinking also, just looking to see if anybody else has done this, a search turned up nothing. Couldn't be as simple as a resistor on the power leads on the usb? (The one on the case I would be plugging into to program)

montyst509:
That was my thinking also, just looking to see if anybody else has done this, a search turned up nothing. Couldn’t be as simple as a resistor on the power leads on the usb? (The one on the case I would be plugging into to program)

Not following that last. Perhaps a drawing would help explain what you are attempting?

Why not just use a USB hub inside the old computer case, saves on a lot of cable hacking.

The computer will always supply power on the USB, and will not care less what is connected to the power as long as it does not draw more than 500mA.
How the O.S. keeps track of what is connected, is via resistors (on the peripheral) on either the D- and +V or D+ and +V to indicate a low speed or high speed device.
How the O.S. knows what is being drawn is because during the enumeration process, the peripheral reports back how much it will need/use and the O.S. simply believes it and does not actually measure it so the extra tens of mA that the Arduino will draw will not make any difference.
Just don't go powering a whole bunch of other things from the Arduino board and exceed the 500mA limit.

Just get a small 4 port hub (they cost about 5 or 6 bucks) and simply don’t use the other ports, they are cheap enough.

SmallUSBhub.jpg

Sorry I wasn't clear before but the USB hub sounds splendid, still thinking thru the project, thanks for the replies

montyst509:
I'm in the planning stages of making a bench power supply with a TFT, current sensors and voltage sensors using an old pc case. My question is about using a usb cable to power an Arduino Uno from the psu, breaking out just the data wires to a usb jack on the front to take care of programming. Anyone see a problem with this.

It's not quite clear what you're trying to achieve, but it sounds as if you want to power the Arduino from a local 0V/5V supply, and also provide a USB slave socket which could be connected to a USB host port for programming. In that case you will need to ensure that the local power ground and the USB ground are equal. How easy it is to do that would depend how your PSU output is grounded.

Going on a different track, after a good nights sleep, remembered the dc jack, I can use that and use a usb panel mount to accomplish my mission. Thanks for getting me to think of alternatives, I get single tracked.