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PWM control

Andy Drummond

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Hi Would like to install an electric water pump into my race car. The pump speed (voltage) is proportional to the engine setpoint temperature. Specification of pump motor is 5 to 12 volts DC operating range, upto 2 amps. As the load is high, will need to install a solid-state relay. The solid-state relay will allow for PWM control. Is it possible for the Link to control the electric water pump? Need PWM control that has the following conditions, 1/ Proportional/Integral control, PI (don't need D its to hard to tune with little benefit) 6/ Time base or frequency (Hz). 3/ Selectable process variable (PV) (eg engine temp, rpm, IAT, etc). 2/ Setpoint parameter value (SP). Must be in the same units as the process variable. 5/ Control action either SP minus PV or PV minus SP. 4/ Output limit low (as %) and output limit high value (%). 7/ Enable PI control (on/off) (selectable) (eg continuous, Auxiliary output 1-11, Digital input 1-12, Internal output, etc. If the input or output is high then operate the PI/PWM (on) with the above parameters otherwise turn off PWM control (zero the PI output and disable PI equation). 8/ The control variable (CV) is the PI output as % of the time base (frequency). That is proportional PWM. All the above is generic and can be used for other devices now and in the future. Also you may consider adding some internal outputs that are used internally only (within the Links software only). These internal outputs can act like a normal general output with the standard operating conditions and then these internal outputs are selectable as part of the other outputs operating conditions. Benefit to you and the user is many different conditions can be cascaded allowing for multiple conditions without adding all the fields into one output conditions window. Regards Andy

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As you have realised, at the moment there is nothing setup to control the water pump as you require...  Sounds like you are quite on to it, maybe just build a simple analog PI controller to do the job.

I am not sure about water pump control, but I know circulating water outside a cold engine makes it take way too long to heat up.  You need to circulate the water internally until operating temperature is reached, then circulate through the cooling system.

We have thought about creating more configurable outputs that can be a function of GP inputs etc...  We cannot make it overcomplicated as a lot of people struggle to set it up as it is.  Truth is what we have covers pretty muchly all control systems on modern motors.  It is only when adding other stuff (like your water pump) that requires specialed control that is not allowed for.

Thanks for taking the time to give feedback and share your ideas...

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  • 2 weeks later...

Hi Ashley For my electric water pump control I need to move to plan “Bâ€. Using the ISC open loop control the link will give a %DC (PWM) output proportional to engine temperature. Setting other parameters steps to zero (fan step %). With base pattern table setting the % at the higher temp to 100% (opposite to rear ISC control). See example table below. Next problem, as the electric pump needs a min clamp voltage say 30% but doesn’t want to operate below engine temp of say 50 degrees (allows for engine warmup). The solution is to add a GP output that actives an external relay when ECT is above a value (50). This GP output external relay enables/disables (interrupts) the ISC PWM output. Tuning the system, need to vary the base pattern % around the engine temp setpoint required. See table below. Example base pattern values: Engine temp 40 50 60 70 80 90 100 Duty cycle 30 30 40 50 75 100 100 PS. as it is a race engine it is NOT using ISC. It would be much much better to have the generic control as previous discussed, but?? The Link’s already has all this control in it, just needs a different presentation to the user. Life is easy, yeah right. Cheers Andy

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