Long time lurker and customer. First time posting:
I have a PV panel directly connected to a 40 Volt, 11 amp dc motor that drives a water gear pump. When the sun rises highenough up the 24 volt 190 watt panel starts the motor. This simple set up keeps our little farm in plenty of water.
I am concerned that the intermediate time during sun rise/set and cloud cover the panel might be causing damage, perhaps to the motor’s brushes. Its a very good motor so I would like to protect it. Am I correct about low voltage causing damage?.
Would like to put an Arduino Uno to work out there. I was thinking of using an LDR to monitor solar flux and then turning the system on or off accordingly. My question is can I use a solar phone charger like this to power up the Arduino separately from the PV system? I think the main thing is to join the grounds of the two electrical sources.
Here is Specs on the solar charger I am looking at to supply the Uno:
Specification:
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Battery Type: Li-Polymer battery
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Capacity: 5000mAh
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Solar Charging: 5V 200A(max)
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Input: Micro USB 5V / 1A
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Input: DC 5V/ 1A
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Output: DC 5V/ 2 x 1A
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Product Size: 142 x 75 x 13.6mm
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Product Weight: 140g
*Operation Temperature: 0-45 degree
If the motor stalls with high current flowing, the brushes and/or commutator might be damaged. Otherwise, “undervoltage” itself is unlikely to be a problem.
jremington:
If the motor stalls with high current flowing, the brushes and/or commutator might be damaged. Otherwise, “undervoltage” itself is unlikely to be a problem.
Well, it has been running directly supplied by the PV panel for some weeks now without a problem. The motor stays cool to touch even in full sun. Maybe this is a workable system. In case someone else is trying to move a trickle of water over a long distance here is my set up:
Panel: “24 volt, 190 watt” - note that this can go way beyond 24 volts in full sun…more like 30 volts even under load.
Load: 40 volt, 11 amp DC motor driving a bronze gearpump.
The source is a trickle feed of clean spring water, about 3 liters per min.
The head is vertical about 3 meters and horizontal about 700m. The low rate varies around 2 liters per minute.
Thanks for the reassuring answer JRem!
The voltage rating of a brushed D.C. motor is usually a maximum recommended value. The voltage controls the speed of rotation and the current controls the torque.
I did not know that. I have used this motor for years, always at about 12 volts to drive an old reciprocating “Jack” pump off my tractors battery. I always felt bad that I was abusing it by giving less than 40 volts! Now i know the rest of the story.
Thank you, this forum is really a great resource for a lot of people.