Under review

MC4x option to disable open load detect on PWM out HS+LS

Frederick Prigge 1 year ago in IQANdesign updated by Gustav Widén (System support) 8 months ago 7

Hi, would it be possible to disable load detection on PWM OUTs. We are using extensively the MC43 and require to drive some external devices via PWM. These are digital inputs on the other devices (fan controllers, pumps, etc), so they present a very high impedance. We use the "detection disable" feature on DOUTs a lot. Can we do the same thing for PWM OUTs? If not possible, please add it to futur releases. Thanks!

For driving an external device, I think that it is only the PWM out HS+LS that could work if it was possible to switch off open load detection. (currently it isn't available as a property) .  The low-side of the output could then possibly be connected to an external device with a pull-up. 

I don't think the PWM out HS could work, the internal pull-up used for open load detection would cause too much of a leakage current. 

Hi Gustav, we are using indeed the LS of a PWM output with a crazy large resistor right now, since we can't disable the "current check". That means we have 5W pull-up resistors just dissipating power in our harnesses!

Please add a disable option on the check, like the DOUT, in the next release, it would be greatly appreciated!


Under review

We are considering doing this, but it's on the backlog. 

Converted topic from question to feature request and modified the title a little to make it easier to spot. 

I am here to up vote this. I am using a voltage PWM signal to control a heater valve actuator. The actuator gets power from a circuit that is different from the PWM, and the impedance on the actuator's PWM circuitry is very high. We added a 390 ohm pull down resistor from signal to ground to solve the problem, but I would prefer to not have to heat up the wiring harness like this.

I want to emphasize that this is an excellent product and the development environment is easy to use. I think the hardware is ideally suited for hydraulic controls, but because of the overall quality of the product, it can still be used outside of hydraulic controls. 

I am not sure this change would help in the case where the PWM controlled device is connected to the highside of the MC4x PWM out HS+LS, the external pull-down would still be needed.  

Have the same issue with COUT output. Make a system with optional equipment, and when it is not installed we get a lot of open load errors.


For an optional COUT, there is a simple solution: Place the optional function in a function group of its own, and use a Digital Parameter to enable/disable the group. The example files shows how it can be done: 

\Documents\IQAN Files\Examples\Fork lift\Fork Lift MD4-7.idsx