Jrk reverse voltage protection , is not correct

Well after I have been using Jrk12v12 for over 4 years in motion sim at xsimulator.net, I have discovered the reverse voltage protection in the Jrk does not even work.
The other day I was rebuilding my simulator after giving it a lick of paint, plugged all the electronics back it, though everything look correct, but failed to notice one jrk was wire backwards for power, hit the power button and no leds on both Jrks, WTF. It must of been a 2 sec power on and off. Now both jrks are dead ducks, this is bad news as we promote this driver on our website and people from our advice by heaps of them.
Now for something that advertised reverse voltage protection and doesnt deliver it , I in the future have big doubts in recommending this driver to the thousands of users we have.

Now the Jrks will power on only via power supplied in the Vin , not via usb, so it seems the usb driver has failed on the board. But once you start the motor via the your supplied app they fail and the comport drops out. Without power they come up as an unrecognised usb device. After over 4 years of using them Im gob smacked on how quick they died even thou you guys advertise they have reverse voltage protection, sorry guys they dont.

Staff at xsimulator.net.
Robbie Lindsay. :imp: :imp:

Hello, Robbie.

I am sorry you are having trouble with your jrk motor controllers. We put a lot of effort into the reverse voltage protection on the jrks, and there are components on the board specifically for that purpose. However, there is only so much that protection can do when multiple boards are part of a larger system like yours. In your specific situation, according to the email you also sent us, your two jrks were connected through a USB hub, which would give both boards a common ground. When you put the positive power supply on the ground of one board and the negative power supply on the ground of the other, you were directly shorting out your power supply through your USB hub, and that is not something reverse-voltage protection can prevent (though it probably did prevent the components on the jrks from being damaged).

I suspect the GND traces near the USB connectors on the jrks are burnt off or your USB hub/port is damaged. Could you try connecting the jrks individually to a different computer? Are there any visible signs of damage on either board? Could you post pictures of both sides of the jrks?

- Jeremy

I’m glad to see that some important information was missing from the original post. I’ve been considering buying the jrk controller and was concerned, however it did not make any sense that connecting the power backwards on one board could destroy a second board at the same time!

It is nearly impossible to failsafe a board from every conceivable improper connection, as evidently happened in this unfortunate accident. I’ll bet that the damage is repairable.

Thanks for the support JeremyT, both Jrks are dead.
I have tested them on two different pcs, and different (new) cables and both do exactly the same thing. As soon as you plug the usb cable in the red led flashes on and off once very very quickly and Usb is unrecognised by windows 8 and same on the xp laptop I use to run my old ones on, I have bought several over the years and recommend them highly, my first set from 2009 could handle the power being reverse without an issue, not sure what you guys have changed. To me the usb driver or micro controller is scrambled or something.
No visible burns or even smells on the pcb at all, I thought it might have burnt a trace inside the board, its quite easy to isolate the earth’s on the usb ports we do this with other drivers hooked to an Ard , actually quite simple. You guys advertise they are protected , well the driver might be the usb ports is not, Im just lucky my pc has usb port protection, or I would have been fuming to destroy a 1200 motherboard because of your cards not being protected properly.

Ok from further testing I can power them up only by providing 12v to the Vin and GND and they light up again but the issue comes back as soon as I click run motor in the Utility and they drop out with windows unable to recognized them again.
Both these cards are close to a year old and have never given me an issue, very pleased with them indeed. But would dearly like to replace them but feel I warrant either replacement or discount for new ones because as advertised they don’t have “FULL” reverse power protection.

I will post back photos of both sides of boards , if this can be fixed easily I will be satisfied but please beware I will be posting on our site to warn people that we have recommended the cards too, to be very careful applying power to them as the reverse protection does not seem to protect the usb port which will lead to crashing the cards and even the pc connected to them. To me you guys need to remove this from the Advert or someone may sue for misinformation when they take out their expensive pc, glad I didn’t have my expensive laptop connected to them when it happened because I know the port is not protected on it.

Again Thanks for the reply I hope I either get a hand in repairing them or help in getting a pair of new ones.
These are the preferred recommended drivers for Dc motor Motions Sims on our website and I do wish to continue to support them.

Pictures as asked for.

2nd Jrk.

Please excuse hot glue on base as trying to find small enough mounting screws is almost impossible here in Australia

Hi, Robbie.

I do not know how to prevent the kind of failure you experienced without electrical isolation of the USB ports, which is not something we claim to have on these controllers. Can you tell us more about this simple isolation technique you mentioned?

- Ben

As an uninvolved bystander who has lost many chips and boards to stupid mistakes, I suggest to eaorobbie: swallow your pride, admit to an unfortunate mistake, stop trying to blame the Pololu engineers for poor design or false advertising and move on.

Many, many hobbyists (especially Arduino enthusiasts) and even some professionals have destroyed boards and burned out laptops due to circuitry plugged into USB ports, but I have never heard of anyone even hinting at legal action before today. USB was not designed or intended to tolerate abuse or even use with noncommercial products, but we are stuck with it for the time being.

Cheers, Jim Remington


Just to clarify where we are on supporting you, we are not just saying tough luck and try again. We appreciate that you have been recommending our jrk motor controllers to others for a while, and we would like hear about the isolation technique you mentioned because we do keep trying to improve our products. (By the way, we have not changed the design of the jrks you have.) If repairing the units proves impractical, we can probably offer you a discount on replacements.

In general, there are many ways to break electronics subassemblies through inadvertent voltage misapplication, so we fully support warning people to be careful about their connections. As with airbags or anti-locking brakes on your car, safety and protection measures cannot guarantee you invulnerability. In case you feel like you have put your own reputation on the line by endorsing our products, we would be happy to help you craft a message that accurately conveys the extent of the reverse-voltage protection the jrks offer.

- Ben

Simplest solution that we have done in the past is placement of a diode to prevent power coming in the Gnd line, its not practical to isolate the usb port as you have explained and we agree but if the isolation of the gnd line with a diode will stop the possibilities of power corrupting this line and flowing through the gnd of the usb port.
Sometime the simplest solution work the best.
We are only human and prone to making errors.
Yes agree this is my error , been over it with a meter can not seem to find a trace or piece that is broken, would dearly love to replace these units so I may continue testing our software as this is my main purpose on the site, Im the first tester in most cases of modifications to our motion software and game plugin, Im the man people ask the hard questions too, can I do this, and how to do I do it.
I do still promote your products not just the Jrks , at the moment Im testing a new motion controller that we have developed and using a motor driver that I bought from you guys years ago, and all looks promising, but have to admit we will properly never better the Jrk, I do love the product.

Yes a warning is needed in the advert of the product on the potential of crossing the power lines and burning out any usb device attached this will cover yours and our issue.
If you guys word something together I will use it too. Was just going to place a simple warning of what not to do and what the result will be if you do it. With no warning yes being a commercial product liability can arise. I too have been involved in small business and know from first hand how you need to protect ya selfs.

I am keen to buy 2 new units but feel some sort of compensation is needed as you have suggested. I will continue to support the Jrks on our site as I have done for the past 4 years, when motor control with feedback support is needed , the Jrks rain king in my books.

Again thanks for the support and this powerful, brilliant product, my motion sim would not be the same without it.

Video of sims firsts tests with the new software.


Since this is a “public” forum open to customers of Pololu and all other interested parties, I’ll summarize my understanding of the situation.

  1. Robbie used two $100 jrk 12v12 controllers for four years with great satisfaction, then:
  2. recently destroyed them by accidentally connecting them incorrectly
  3. published misleading claims that the reverse voltage protection does not work
  4. published misleading claims of false advertising
  5. hinted that legal action could possibly result
  6. now admits there is no engineering solution to prevent that mistake from happening again
  7. wants compensation for the loss

It is very difficult for me, as a satisfied customer with otherwise no connection to Pololu, to be sympathetic with Robbie in this situation.

Gday Jim,

  1. No this is my 11th sim built using the Jrk12v12, I don’t normally buy direct from pololu but from my local dealer , cost me a little more but to support local businesses its worth it. These units were bought in a batch by a mate in Sydney who I helped to build sims.
    Apart from that from recommendations on several websites over the years this is the product I support openly and nearly everyday answer setup and fine tuning questions people have.

2.Yes one unit was wired incorrectly the other was wired properly, I expected to have to replace one but not two of them. That took me by surprise.

  1. Well the reverse protection does not work when usb port is attach think that quite obviously, proven.

  2. It is false advertisement to claim the device has reverse power protection as a customer I’m in my rights to publish an error and ask questions.

  3. Im in no way ever looking at legal action, Im not that kind of person at all, I advise people on how to build motion platforms and make sure that all information given is to my best abilities and any warnings of possible mistakes that they could make are forwarded to them. So to make sure I dont get a "You didnt tell me this could happen, I now have lost money, what are you going to do about it.
    Its a shame but its part of the world we live in today.

6.? Pololu have said above that this may happen, well it happened and another case too of this happening has been brought to my attention.

  1. Without a warning in advertisement or technical documentation, I think is fair.

Really just would like this to be brought to peoples attention so this will not happen to them, your entitled to your opinion and I still eagerly promote the use of their products and help new users daily with any issues that may arise with them on simulators, mainly tuning PID on different motors.
I still am a very satisfied customer of Pololu and as said above openly promote their product with no deals or kick backs for doing it, I believe in supporting people who do the right thing in life.You get back what you give out.


We will be in touch with you by email to get your order information and figure out how to handle replacements.

- Ben