Pololu Jrk 12v12 USB Motor Controller with Feedback (POLOLU-1393)

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The powerful jrk 12v12 motor controller is a highly configurable brushed DC motor controller that supports four interface modes: USB, logic-level serial, analog voltage, and hobby radio control (RC). The controller can be used as an open-loop speed control or for closed-loop speed or position control. The continuous output current is approximately 12 A (30 A max) and the operating range of 6–16 V (with transient protection up to 40 V).

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with regard Jrk12v12 motor controller. The DC motor I want to position control might draw more amps [ on rare occasions] than the limit of the controller. My question is: " what will happen if this occurs?" Is the controller protected and what is the nature of the protection. Cheers Phillip

Hi Phillip,

It’s not safe to exceed the amperage limitation of the motor controller (30A momentary). If you exceed that limit the motor controller will overheat or burn. There is no protection against this in place other than being certain that you’ve paired it with a suitable amperage motor.

I hope that answers your question!

Thanks Stephen… but surely there is some way to limit current? Firstly, obviously a fuse. The application is that an electric power steer unit which is basically a DC motor and a very efficient worm and wheel right angle drive will be position controlled[ instead of being controlled by driver input torque as conventionally occurs]. This EPS [ with the jrk controller] will " bi wire" control the position of steerable wheels on a small vehicle. I will use two pots one on the drivers control and one on the output shaft of the EPS. The current draw depends entirely on the loads applied to steer the wheels and in some isolated events [ up against a kerb etc] the motor might exceed the limit of the controller. In conventional EPS steering systems their controllers cut power when the unit detects overload but these controllers are not suitable for remote " bi wire" control. But surely the principle is identical when it comes to potential overload protection?
So 1] a fuse. But in the wide world of electronics [ of which I know little] surely there is a way to detect excessive current flow and limit it?
Sorry to cast doubts on your answer but I suspect that there will be a way.
I acknowledge that my original question may not have been put well, and I accept that IF excessive loads reach the JRK motor controller it will burn but that’s just a problem to be solved surely? Regards Phillip

Hi Phillip,

The max current can be set in the config utility, refer to the linked user guide (in the product description). Screenshot below.

The jrk range is designed to be part of a control system in which the output (usually a motor position or speed) is constantly adjusted to match a specified target value. To achieve this, it constantly measures the state of the system and responds based on the latest information. With that in mind, PID isn’t often “instant” and you really should keep within normal specs from motor to controller.

In general, don’t go beyond a constant 15 Amps for this device.

hi , yes I just found the user guide and hopefully I can limit potential problems. When steerable wheels are rolling there is very little current required to steer them. If they become locked against something and the driver continues to attempt to steer them[ say for example against a kerb when not rolling] then the driver may not be aware that he is overloading the control system. One way to avoid this would be a feedback motor attached to the drivers control to inform him of resistance to steering of the wheels.
One more question:
If I configure the controller for an artificially low current output… what would be the observable consequences ? Would the controller output oscillate as it regulates or would it simply switch off in a situation where a load was preventing the position feedback loop from being maintained [ steerable wheel stuck], Cheers Phillip

Hi Phillip,

The PID loop will do it’s best, though if control parameters (current, etc) are less than physical requirements (real world torque, etc), then the PID will simply set the max allowable settings and remain there, despite everything else.

Graham, Thanks for your further info. Sounds hopeful.
I am experimenting with various slow speed control systems for this
vehicle [ below 10kph] www.tiltingvehicle.net
As a matter of interest. I purchased G sensors and Arduino etc
from Core. These g sensors are used to compensate when driving on
extreme slopes.
They did not work at all well due to engine vibrations etc.
I now use a potentiometer and a bob weight, but the trick is that
the stiction/ friction that makes a pot " unsatisfactory" can be solved
by vibrating
the pot. For example… mount a mobile phone vibrating motor to the
pot housing. This continually breaks and re makes the stiction of the
wipers and
the result becomes remarkably stable. I know there are ways to
stabilize electronics in G sensors but sometimes its more important to
simply get
something to work before refining. [ same with the Steer by Wire problem]
Thanks again P.

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