Modern Device Forum

I am very new to building electronics so please excuse a question about what I am sure would be self evident to someone that knew more. (I built my first BB arduino last week.) I am interested in building a bank of four 8x8 LED boards. I am confused by how to power them. I looked on the websites for All Electronics and Jameco, as the PDF instructions recommended, for power supplies but it was not clear to me what would work.

I found this which looks like it would power one lcd panel by plugging it directly into the BB arduino:
http://www.powerstream.com/ac-0510-usb.htm
(It says that it is regulated power supply with stable output, 5 watts continuous - 5V 1.5A power supply with 3.5 x 1.35 mm barrel connector)

On the same site there is one that looks to me that it would power two lcd panels when plugged directly into the BB arduino (with the output adapter for a 1.35 mm barrel connector):
http://www.powerstream.com/ac-0510-usb.htm
(Again it says that it is regulated with stable output, 18 watts continuous, Output: 5 Volts DC, Output Power: 15 Watts max, 3.0 amps, 3000 mA)

But when powering four panels, it is not clear to me:
Would I get something like this and cut off the barrel connector and splice two wires each to the ground and 5v lines and run them to the first and third lcd panels? Or get two of the wall adapters above and splice them to the first and third lcd panels respectively?
http://www.powerstream.com/ac-0510-usb.htm
(regulated power supply, 30 watts continuous, Output: 5 Volts DC, Output Power: 30 Watts max, 6.0 amps, 6,000 mA)

Or would I run four panels off something like this:
http://www.allelectronics.com/make-a-st ... Y/-/1.html
Is it a problem if it puts out too many amps? Is something like this regulated? And (I am a little embarrassed to ask but) how do you a run a wall plug to this thing?

Thanks for your help!

npb,

If you really want to be able to light up all the LED's at once, and also want to run them at 20 mA, then you do really need a 5A, 30 watt supply. With high brightness LED's this will be bindingly bright and be visible from many hundreds of feet away. If you find you don't really need all the illumination then you could swap out the current setting resistors (there's only four per panel) with larger ones and use a smaller power supply.

I'd go with the powerstream power supply if you are beginner because it will avoid some potential gotcha's in the All Electronics open-frame models. The biggest problem with the All Electronics model is that sometimes switching supplies of that type won't turn on unless they see at least a 10-20% load. You can trick them by padding them down with a power resistor to draw an amp or so but the power resistor will get hot from dissipating the power, so you'll need to take that into account in your case design. Also many parts on the open-frame design may expose people to dangerous voltages so you'll need to get it into an enclosure. The power cords usually are a standard configuration, and All Electronics can probably help you with a cord.

The desktop supply is going to avoid all those issues, for a very reasonable price I thought. Do confirm that it will turn on with no external load though, but I would be surprised if that wasn't the case.

Be very careful, when hooking up the panels not to get the polarity reversed on the panels. They each have a diode for reverse polarity protection, but with a larger power supply, it may have enough current to fairly quickly smoke the diode(s) and then go on to ruin the panel(s) so double check the polarity before proceeding. Another thing that would be a good idea is to run separate power leads to every two panels, instead of daisy chaining power to all of the panels from two power lines, this will limit the current in the wires.

Good luck with the project and write back if you get stuck.

Paul

Thanks for your help!

I wasn't paying attention when I was posting yesterday: that powerstream site I was looking at for power supplies uses frames and none of the links I cut and pasted were the ones I intended to link to.

The power supply I was looking at to power one board was this little wall mount one (directly to the BB arduino):
http://www.powerstream.com/ac-0515w.htm

The power supply I was looking at to power two boards was this one desk one (with the adaptor - again directly to the arduino):
http://www.powerstream.com/ac-0530.htm

And the power supply I was looking at to power four boards was this one (running power to the first and third board):
http://www.powerstream.com/ac-0560.htm

Do those look right? I think I might only need two boards now for my project.

This 6 A model will run everything with room to spare. Very economical too!

http://www.powerstream.com/ac-0560.htm

Check to make sure they have a UL rating, but I'd be really surprised if they didn't.

Paul

This 6 A model will run everything with room to spare. Very economical too!

http://www.powerstream.com/ac-0560.htm

Check to make sure they have a UL rating, but I'd be really surprised if they didn't.

Paul

I can vouch for this adaptor. I ordered it and it came promptly, is labeled as UL Listed, and works well so far.

*I'm using it to power 4 panels running simultaneously.