Direct DC Power Supply for Cortex

Hello, I have seen a large number of stationary robots and I think it would be great to have a DC power supply from the wall outlet directly to the cortex. This allows those robots to have a constant power supply without having to worry about battery life affecting all the operations of the robot.

If this has been done before, could someone point me to it?

This would be very easy to make. Just buy a 7.2 V- 8V DC power adapter and put a tamiya plug on it. Parts would cost less than $10. (ok, maybe not $10 if you want to be running a lot of current i.e. lots of motors)

Has anyone been able to find one online? I"m going to look in my garage.

Lots to choose from. You can narrow them down by search parameters. None of them have quite as high of current as you would probably need for a full robot. But would work very nice for general testing of components/subsystems.

Here is an example: 7.5 volt 4 amp


(if you get into the 9 volt adapters you can get up to 8 amps from digikey…that would work very well if you don’t mind running 9 volts to your cortex)](

the maximum the cortex is designed for is 12 volts

For long programming and debugging sessions we found a 12 volt adapter that worked fine and used the connector off of the old battery holder that VEX used to ship in their kits.

Yes the cortex can handle it, but wouldn’t that also send 12 volts to your motor? (they receive direct battery power don’t they?) So for testing that would give you false results…?

Crank it up to 8.5 v because that’s the reading of our batteries fresh off the vines.

Be careful, you will ned a lot of instantaneous current if you want to reproduce what your batteries are capable. It might be good for general work, but when it comes time to put in control loops, or just auton in general, move back to batteries.

No, No, No…

Two 18v power supplies in parallel still gives 18v.

Old thread about this subject here.

If you are using motors I wouldn’t even try to use an external power supply unless you can source a good bench supply able to deliver perhaps 20A @ 7.5V.

My mistake…I should have thought for 2 seconds before I wrote that. I deleted the whole thing to hide my stupidity. I feel ashamed…I was just scolded by jpearman.

…walks away to hide in the darkness

Thanks for all the replies, everyone. It totally slipped my mind how high the current draw would be on the system with that many motors all trying to start up at once. Those little 393s sure do pack a wallop for LRC.

I’ll examine the situation a bit more, then. Thanks.

Like this one? 20A at 7.5v for $61 in a nice enclosure.

Looks ok, as long as an adult wires the AC power in and makes it safe for student use. It really needs to be placed in an enclosure with power switch etc.

Yeah those open terminals labeled “AC” look ominous. Bad things could happen.