Running PD Board from an outlet

Technical Technical Discussion
#1

The battery I have with me has completely died for our test programming/electrical board.

I was wondering if I could run the PD Board from power from an outlet instead? Obviously not directly connected.

I was thinking one of those AC to DC Car lighter convertors. It would still be 12 volts. Here’s an example http://www.amazon.com/Universal-Cigarette-Lighter-Socket-Adapter/dp/B001TXWNLQ/ref=pd_sxp_f_i

I have one of those around.

Has anybody tried this and been successful? Or is it just a really bad idea.

#2

I doubt that would get you enough current do run anything. You might be able to run the cRio and digital sidecar, but certainly not any motors. The CIMS (on the robot) are wired to 40 amp breakers, I doubt that even puts out 1 or 2 amps.

#3

We have no motors or Jaguars hooked up. Only the cRIO and a digital sidecar. Everything else is either not connected or already powered via a power strip on the board.

#4

Some of the switching supplies in the PDB are not very friendly to this approach. I strongly recommend staying away from it unless you really know what you’re doing.

#5

By “not friendly” you mean they are only going to work for a specific setup? If so, what is it looking for? I’ve moved on to the idea of using a laptop 12 volt power supply instead as it would probably be closer to the correct voltage and provide enough current. If I knew what they are looking for I can try a different power supply that is more appropriate easily.

#6

Could you use a desktop power supply like this to power the whole robot with motors and all? At 12V/135A, it provides more current than the main breaker can handle anyway, right?

#7

Where did your 135A stat come from?

#8

12V@135A is listed on the spec page on newegg for the linked power supply.

#9

A pc power supply like the one from newegg could run the robot.

to power it on, connect the thin green wire to ground on the motherboard connector.

#10

If you just want to program things and not make anything move, any clean 12V >30W power supply will do. The original part linked is likely to put out incredibly dirty power, I would not try it. The power supply module linked will likely work nicely.

Be sure not to use the battery charger as a make shift power adapter - they can interact poorly.

#11

If you’re making and buying things, why not just get an extra charger, it will likely have more uses to you and your team.

#12

Eric,

What power supply wattage would be needed to run motors off of?

#13

Decide how much power the motor takes. Worst case for a CIM on a 40A fuse is going to be 12V*40A = 480W coming from the power supply. Add up all the motors you want to use to get a worst-case idea.

with a 500W power supply, you can test 1-2 motors at a time under full load. If your wheels are not on the ground, they are not at full load, so maybe you can run 4 motors or so.

#14

For a full robot on the ground? Somewhere in the range of 2-6kW.

For testing subsystems while up on blocks? 1kW might do it.

Actually, a CIM can easily draw 100-130 Amps at stall depending on wiring. When a breaker has a 40 Amp rating, it means that it can sustain 40 Amps indefinitely.

EDIT to add:
Regenerative breaking can play havoc with some power supplies. Where a battery would simply accept the regenerated charge, some power supplies will go high-impedence to protect themself. The voltage can spike and destroy the supply or the robot electronics.

#15

For just powering the electronics, a small 12 volt power supply will work. I imagine you could dig one out of an old computer.

To survive a regional you are going to need lots of batteries and an extra charger. So buying that now would be a good idea. If you are not running motors or running them lightly loaded, the robot battery lasts a long time.

#16

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.

#17

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.

#18

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

#19

You do know the battery will put out a lot more current than your typical power supply? Even with big capacitors? :eek: 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.

#20

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.