Running PD Board from an outlet

[MAldridge]

I second the computer power supply. Ask your school's tech department if you can get a power supply out of a dead computer. Those can easily put out a huge amount of clean current (I currently use one to drive the stereo in my school's NOC).

A word of warning though, those can put out dangerous amounts of current, make sure you know what you're doing when working with it.

[andreboos]

I've used a car battery charger to power a minimal control system (digital sidecar, cRIO, camera, single motor) through a power distribution board. I'm guessing this power isn't much cleaner than that from the car adapter. Does the dirty power permanently damage parts or is it simply unreliable?

I have also used a PC power supply to power the newer cRIO directly (accepts as few as 9 volts) but have not attempted to power anything through the PDB.

[cgmv123]

Originally Posted by MAldridge

A word of warning though, those can put out dangerous amounts of current, make sure you know what you're doing when working with it.

They can also retain lethal voltages, with all their capacitors and what not, even when unplugged. Don't ever open a computer power supply!!

[FrankJ]

You do know the battery will put out a lot more current than your typical power supply? Even with big capacitors? But you point is well taken.

If you use a car charger, keep the battery connected as well. It will clean up the charger's dirty power. Just do not use a charger that has a start the car mode.

[Bill_B]

I recently measured our control board at .9A drawn during motor idle period. Aboard are the usual suspects and 6 jaguars. To this you would have to add the motor currents as noted above. Connecting some other source of 12vDC could be done, but as you can tell from the comments, this designation covers a lot of supply waveforms and reactions by the supply.

The other thing you should consider is getting some additional energy supply gear for your team. Perhaps you already have it, and were only talking about powering the board during a home-based session. We've done this too. You have to be very careful not to discharge the legal batteries too deeply. They can be damaged by it. Be sure to search CD for more discussion of battery and electrical practices.

[Al Skierkiewicz]

Everyone,
Motors can produce significant currents at start up. My 35 amp linear supply will go into over current protect on an FP motor. Not only does the supply need to be able to handle large currents, it must also be able to handle startup current and be low impedance. You might find one cheap but in general, the cost for a line operated supply is likely too costly for most teams. Most inexpensive car chargers simply put raw rectified current into a battery. This is pulsed at power line frequency and could be either halfwave or fullwave rectified power. Even a battery connected across the charger will not take care of all the transients. Bench supplies can be had to run the PD and Crio along with controllers and relays as long as there is no load on these devices. Any CB power supply available at Radio Shack will likely be able to handle the current. I have a 5 amp supply at home that we have used from time to time.
As to computer power supplies and most switchmode, line operated supplies...
These devices generally rectify the incoming line voltage giving them a ~160 volt primary power supply. It is the capacitors in this part of the supply that carry the high voltage warning. The caps across the low voltage supplies are generally small in comparison and only carry the rated voltage (+/-12, +/-5).

[FrankJ]

If you are running motors at anything besides completely unloaded, you are better off using a battery. I was thinking more of ways to power just the electronics.