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Potentiometer problem

Hi everyone,

Please help me out with this electronics question for a university project.

I need to get a pump running at different speeds so I ordered an electric motor, a potentiometer and a power supply adapter. I put them all together and they worked, however the potentiometer got burnt out.

These are the items:

Electric motor: https://uk.rs-online.com/web/p/dc-geared-motors/0420631/

Potentiometer: https://uk.rs-online.com/web/p/dc-motor-controllers/7522009/

Power adapter: https://www.amazon.co.uk/JnDeeTM-ADAPTER-Transformer-Monitors-Powering/dp/B00W3S8630/ref=pd_sbs_60_3/259-9125614-7206729?_encoding=UTF8&pd_rd_i=B00W3S8630&pd_rd_r=c94db45d-e732-4094-a04e-bf491ea10498&pd_rd_w=KlZ1r&pd_rd_wg=DRo3H&pf_rd_p=7f9048ad-9bda-4493-8578-13e4eff8da65&pf_rd_r=E45DERHGHBHYBXTQ1KVA&psc=1&refRID=E45DERHGHBHYBXTQ1KVA

And this is what happened with the controller:

 

I am trying to find where the problem is. Is the power supply not giving a non-digital dc input? Is the current rating (3A) of the potentiometer being different to 6A given by the power supply?

If you could help I would really appreciate it!

Thank you.

0 Votes

Comments

August 2, 2019 14:12

Having a quick look at the specs I think the speed controller is not rated for the motor load and hence the damage observed. Looking at the datasheet on the RS site https://docs-emea.rs-online.com/webdocs/0bf3/0900766b80bf315d.pdf if you look at the "motor data" it shows 5.5A at a particular torque.
Unfortunately I could not find a low cost controller for this current.
Does the motor have to be reversable? If not there may be more options.

August 2, 2019 14:12

This may be an alternative part rated at 12A continuous https://uk.rs-online.com/web/p/dc-motors/8347584/ and it's also bidirectional. See if anyone else suggests a solution and do a detailed chec of the specs to make sure it meets your requirements. You could also try linking the motor connected to the pump to a lab power supply and check the load current at different supply voltages to check the required ratings. One point you raise is the term "non-digital" related to the power supply. I saw this on several parts I looked at and it needs clarification (any takers?). I always consider power supplies as analogue and switching so do not know if "digital" refers to "switching" or is refering to say LED supplies which are sometimes "switched or pulsed" and not smoothed, so could be considered digital. Look forward to comments on this.

August 2, 2019 14:12

@Boss would that work with the motor I have? Does it make a difference if it's a geared motor? Thank you for your reply and suggestion btw!

August 8, 2019 14:35

@RoxanaRadu Sorry have been away, the answer is yes I think so, but obviously cannot guarantee this. You could try powering the motor direct to the power supply or as said a lab supply and check the start current and running current. The worst case is a stalled motor which will be high current and may burn out, so it would be good to know what the motor load really is. The controller appears to be rated for the task, but note it does not include the thermal protection option.

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