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Voltage regulator or not?

lectricboy

Apr 5, 2022
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I have a 12volt 3amp DC water pump with an ac to DC power supply rated 12volt 8amp 96watts, connected with 75 feet of 12 guage wire.
The power supply when not in use reads 12.3volt output, but when connected to pump voltage fluctuates 14-20 volts. I've tried connecting a DC to DC buck converter rated 9-36volt input and output of 12volt 5amp 60watts, but then the voltage output with pump running reads 9.xx volts and the DC male to DC female adapter after power supply started to smoke some.
Should I just not use buck converter, or what would be the proper buck converter/voltage regulator to use???
 

Bluejets

Oct 5, 2014
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Motors do not require regulated supply.

Is the 23 metre run in one direction?

If so I'm guessing you will suffer quite extreme voltage drop.

Better to place the dc power supply at the motor position.
 

kellys_eye

Jun 25, 2010
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The power supply when not in use reads 12.3volt output, but when connected to pump voltage fluctuates 14-20 volts.
The voltage INCREASES under load????

Something is wrong with your power supply!
 

ivak245

Jun 11, 2021
65
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Jun 11, 2021
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If you are just running a water pump, you could start off with a supply a couple of volts more at the supply end (I would go to 15V), with enough current capacity.
 

lectricboy

Apr 5, 2022
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Motors do not require regulated supply.

Is the 23 metre run in one direction?

If so I'm guessing you will suffer quite extreme voltage drop.

Better to place the dc power supply at the motor position.
Main reason for the 75ft 12/2 stranded wire is to have low voltage running out thru yard instead of 120volt in yard out to pump. I thought the voltage might drop across the 75 feet but strange it reads 14-20 volt fluctuations when pump running and converter not connected. It's cheap pump so may run it without converter and see how it lasts.
 

AnalogKid

Jun 10, 2015
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12 V supply:

Make
Model Number
Part Number
Photo of the nameplate / sticker/ whatever
Link to manufacturer or vendor

anything - ?

ak
 

CircutScoper

Mar 29, 2022
300
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Mar 29, 2022
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I have a 12volt 3amp DC water pump with an ac to DC power supply rated 12volt 8amp 96watts, connected with 75 feet of 12 guage wire.
The power supply when not in use reads 12.3volt output, but when connected to pump voltage fluctuates 14-20 volts. I've tried connecting a DC to DC buck converter rated 9-36volt input and output of 12volt 5amp 60watts, but then the voltage output with pump running reads 9.xx volts and the DC male to DC female adapter after power supply started to smoke some.
Should I just not use buck converter, or what would be the proper buck converter/voltage regulator to use???

I'd guess your pump motor is brushed/commutated and that's making so much electrical noise (a.k.a. arcs and sparks) when running as to discombobulate (EE technical term) the power supply. I'd try a large electrolytic capacitor (say 1000uF @ 16V) across the supply output terminals to suppress the crud. Be sure to observe the cap's polarity when connecting it.
 

CircutScoper

Mar 29, 2022
300
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Main reason for the 75ft 12/2 stranded wire is to have low voltage running out thru yard instead of 120volt in yard out to pump. I thought the voltage might drop across the 75 feet but strange it reads 14-20 volt fluctuations when pump running and converter not connected. It's cheap pump so may run it without converter and see how it lasts.

Sez here 12ga cu wire is only 1.588 ohms per 1000'. So 2x75' should impose only 0.24 ohms = less than 1V drop at 4A.
 

Bluejets

Oct 5, 2014
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Main reason for the 75ft 12/2 stranded wire is to have low voltage running out thru yard instead of 120volt in yard out to pump. I thought the voltage might drop across the 75 feet but strange it reads 14-20 volt fluctuations when pump running and converter not connected. It's cheap pump so may run it without converter and see how it lasts.

Ok, then charge a battery with your mains and run 12v dc from the battery.
As far as fluctuations, no telling how you measure the voltage or any circuit diagram /photos of what you have so no comment there.
 
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