Power supply keeps tripping

[watkykjy]

Hi Guys,

I finally got my AMC 1.6 to talk to my computer, and everything is coming along just beautifully. So, today I spent some time building a power supply for my sim (an old 750W server psu), and I am using the Pololu Dual VNH2SP30 driver with a HUGE heat sink to drive my motors.

Now, just connecting everything up and running the AMC turns the motors on, but the moment I run either a game and start sending data to the motors, or if I simply change the pots quick enough to change the motor direction, my power supply registers a short, and then goes dead. Luckily PC power supplies are built with quite nice protection, so nothing gets hurt, BUT the problem is that the moment this happens, I have to manually turn off the PSU, wait for the cap to drain, and then turn it back on, and within a few seconds I can sit with the same scenario again. Trust me when I say that this is not due to overloading the power supply. I have measured the current being drawn from the psu in total and at 12v the max I could get was around 9 amps, so it's less than 120W in total for both motors...

The problem still remains that the psu keeps on turning itself off all the time when the motors change direction quickly. I have tried with one or two other PC power supplies, and they all do the same...


So, I guess my question is to ask if there is a way to prevent this from happening, or a way to make the transitions in direction smoother or "less painful" on the power supply? Maybe a large cap somewhere?

Thanks so much for all your help thus far, it's been great!

Thanks

[motiondave]

Try a car battery in parallel with the PSU.

[prodigy]

Now, just connecting everything up and running the AMC turns the motors on, but the moment I run either a game and start sending data to the motors, or if I simply change the pots quick enough to change the motor direction, my power supply registers a short, and then goes dead.

This happens with ATX PSU's, I don't know for server PSU's. You can try putting a resistor on output to make it stabilized.

Here is solution for ATX, you can see if it works for you. Maybe trying only resistor first to see if it works, than adding battery if not.
http://www.dimensionengineering.com/app ... xguide.htm

Try a car battery in parallel with the PSU.

Are you using a diode in battery + PSU setup?
I've read somewhere that it is used to protect PSU, if battery discharges power back to it.

[watkykjy]

Thanks guys,

I was kinda hoping that there would be a solution without having to use a battery... I have even tried running a huge 400V 25A bridge rectifier before my H-brdige, so that no feedback can go back to the PSU, and also tried a couple of big 90A diodes, but nothing seemed to be able to absorb the feedback when the motor changes direction. Needless to say, I also tried with 5W and 10W resistors connected between ground and 5V as dummy load, but nothing seemed to help.

So, alas, I tried the battery suggestion and it did the trick, although I was really hoping to go without it. But hey, it beats paying $300 upwards for a decent power supply that can deliver 62 odd amps at 12V, and the battery absorbs those spikes coming back just fine .

Have a good one guys, I can now finally start to finish my frame which was built more than 3 years ago already, so with a bit of luck I will have it running before new year!

Cheers for now, thanks again for all the help!

[motiondave]

I have run a car battery in parallel with 2 different PC psu's and the current proper switchmode supply.
I never have had to put a diode in. I just remember to power up correctly, PSU on, then connect to battery, then connect jrks.
Power off, unplug jrks, unplug battery from psu , turn off psu.
Al works here and has been doing so for about a year *

[watkykjy]

Thanks Dave,

I am already busy building mine to power on in the same fashion. I am thinking of going for an old school look and feel where you have those big switches like in the old planes and then you turn them on one by one... lol...

Will see how it pans out when I get to the finishing stages and making every thing look nice and pretty

Have a good one mate!

[bwl265]

Hi guys,

Do you think a small battery (say 12aH) would handle the kickback from the motors? I have 2 x single rail psus that can supposedly deliver 45amps continuous, to put in parallel.

Thanks.

[bwl265]

Sorry, forgot to ask whether I will need a battery in parallel with EACH psu, so 2? I am running 38a max current when using a car battery, I'm hoping it will reduce slightly with a more stable 12v.

[motiondave]

Sorry, forgot to ask whether I will need a battery in parallel with EACH psu, so 2? I am running 38a max current when using a car battery, I'm hoping it will reduce slightly with a more stable 12v.

what motors and control boards are you running?
I run a PSU rated at 32 amps max in parallel with 330CCA car battery , with big worm gears and JRK's, no trips there. Even when I have an old 18 amp PC PSU rewired on it, no tripped power supply.
I have run my big worm gears at 34-38 amps each off that setup (12v 32 amp max psu) with no problems.
Only one car battery with one PSU should be fine.

[bwl265]

I'm running JRKs with ZYT-90 motors, similar to yours I think Dave. Cheers for the advice, I have two of the psus already, so thought I'd try and use both with smaller (cheap) batteries for kickback from the motors, but seems easier as you say, to just use one with car battery and save the other psu for my next pc build. This is the last item before the build is finally finished!