Multiple wall warts providing power for electronics?

As long as the grounds of both supplies are connected together, there should be no problem. In some rare cases you could get noise spikes. I would consider transients (or undefined states) when I turn everything on. You don't want the possibility of commanding an accessory or switch in multiple ways simultaneously.  If you are really worried, you can use opto-isolators on all the signal lines.

-Lad

I'd consider some caps at the input of each board to swamp any noise coming in the 5V line.  An electrolytic with a .1 ceramic cap in parallel is a good combo.

Thanks for the input guys. Since I'm programming everything including Legacy myself, I'll proceed as is and wait and see if I have any reliability issues. I can always add caps.  My main concern was I didn't want to blow something up ;-). Thanks for the clarification. 

How you've explained things sounds just fine, though I do concur that you'll want to make sure the supply power for the Arduinos is filtered just so you don't have any problems.  Your best bet is to use optocouplers on all the I/O pins that you want to perfectly isolate them from any interference.  

As a second note, it isn't needed at all, but the Arduinos are more energy efficient if you power them with 5VDC on the header rather than using the onboard regulator.  If you are driving a lot of current you may also get better results this way as the on board regulator may not deliver enough current to all the I/O pins.  

My favorite high current, well filtered, 5VDC supply is a computer power supply.  $15 will get you a 25 Amp+ 5 volt supply.  

JGL

Thanks John.  I guess that's also an option down the line if I experience any issues --- just one huge regulated 5vdc with lines out to every digital device.

Very nice looking control panel and wiring!

JohnGaltLine posted

My favorite high current, well filtered, 5VDC supply is a computer power supply.  $15 will get you a 25 Amp+ 5 volt supply.  

John,

how do you typically modify the power supply to power the arduinos with 5 volts?

Chris

trainman129 posted:

Very nice looking control panel and wiring!

Thanks!  I will post some prettier pics when I get some code running to light up some LEDs. 

How do you like my travel poster? ;-)

crood58 posted:

how do you typically modify the power supply to power the arduinos with 5 volts?

The ATX standard computer power supply is pretty straight forward for simple +5VDC and +12VDC.  There will be one large 20 pin connector that would normally connect to a computer's mother board.  On this connector you can use a jumper wire, or cut the wires and use a toggle switch from the green wire to any black wire.  This is the power switch for the power supply.  

On all the other connectors there will typically only be 3 colors present, Black, Red, and Yellow.  Black is ground, Red is +5VDC, and Yellow is +12 VDC.  

Here is a picture of the various connectors:  for experimenting I tend to stick breadboard jumper wires into the floppy connector.  For more permeant things I cut off one of the Molex connectors and solder the wires to whatever they are powering.  

And here is the 20 Pin connector:  

This shows the other voltages available, as well as the color of their wires.  As a note negative 5 volts is no longer standard on all ATX power supplies, so if you need it for some reason, make sure the power supply you chose actually has it.  

If you want to get really fancy, the grey wire (pin 8, also called 'power good') can be used to detect that all voltages are at their proper level.  

Here are the outputs on on the cheapest ATX supply from NewEgg:  

+3.3V@28A, +5V@36A, +12V@16A, -5V@0.5A, -12V@0.8A.

Short version:  Green wire switched to Ground for power switch, Black=Ground, Red=5v, Yellow=12v.  

JGL

Hi John, I am slow when it comes to stuff like this. but I do have one question. looking at the 20 pin connector it looks like you would have 5 5vdc outputs? Is that correct? IF so I would take it that I could run 5 differant things?

You can run 50 things from the 5V, all those outputs are parallel inside the supply.  Occasionally, they will split the 12V on some supplies from two separate outputs, but that seems to have fallen out of favor.  Also, you have the +5VSB, that's a low current output that's always active. 

Note that some (but not all) ATX power supplies need a load on either the +5V or +12V outputs to properly regulate

PS: that's a 24 pin connector, which is standard on ATX power supplies for the last few years.

Thanks John.

Yep, As GRJ says, there is just one source for each voltage.  Many wires are used on the 20(+4) connector so that the current can be spread between them, and between several traces on the motherboard.  When last I shopped for a high end power supply, multiple 12v lines where still in vogue. Not sure if that has changed, but even then it was a feature found only on power supplies in the $100 range... well beyond what is needed for powering some electronics experimentation.  

GRJ, I suppose my calling it a 20 pin shows from what time period I was most into computers.  The ATX standard was fairly fresh when I was learning how to put together a computer, and I still think of it as a 20 pin and a plus 4 pin. (which I think is still the official designation, 20+4)  I also have a number of high end mother boards that had a molex connector for additional power before the 4 pin MB power was added.  It seems lately motherboards have enough power, I don't know of any using more than the standard connections now.  

Anyway, seriously digressing here... 

JGL

JohnGaltLine posted:

crood58 posted:

how do you typically modify the power supply to power the arduinos with 5 volts?

The ATX standard computer power supply is pretty straight forward for simple +5VDC and +12VDC.  There will be one large 20 pin connector that would normally connect to a computer's mother board.  On this connector you can use a jumper wire, or cut the wires and use a toggle switch from the green wire to any black wire.  This is the power switch for the power supply.  

On all the other connectors there will typically only be 3 colors present, Black, Red, and Yellow.  Black is ground, Red is +5VDC, and Yellow is +12 VDC.  

Here is a picture of the various connectors:  for experimenting I tend to stick breadboard jumper wires into the floppy connector.  For more permeant things I cut off one of the Molex connectors and solder the wires to whatever they are powering.  

And here is the 20 Pin connector:  

This shows the other voltages available, as well as the color of their wires.  As a note negative 5 volts is no longer standard on all ATX power supplies, so if you need it for some reason, make sure the power supply you chose actually has it.  

If you want to get really fancy, the grey wire (pin 8, also called 'power good') can be used to detect that all voltages are at their proper level.  

Here are the outputs on on the cheapest ATX supply from NewEgg:  

+3.3V@28A, +5V@36A, +12V@16A, -5V@0.5A, -12V@0.8A.

Short version:  Green wire switched to Ground for power switch, Black=Ground, Red=5v, Yellow=12v.  

JGL

John,

Thank you for the information. I haven't messed with one of these in awhile, probably 7 years when I bought my last computer. I like the idea of using pin 16 for a power switch. This is sure going to come in handy for the things that need 5 volts to 12 volts of DC power. Especially the 5 volts for the arduinos. 

Chris 

Randy,

Would you mind contacting me via email (in my profile)?

Thanks!

Alex (Alexander Müller)