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    Thread: Build a twin air pump for a pond with a 50W PV system

    1. #1
      kAMILLE is offline Junior Member
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      Build a twin air pump for a pond with a 50W PV system

      I am building a twin air pump for a pond, powered by a 50W PV system with charge controller connected to a DIY fused DC consumer unit. I have a project box with two switches - each switch goes to a pre-made (fan controller) LM317 linear adjustable voltage regulator, each going to a simple DC motor. The idea is to have each pump independently switched and adjustable but running off one 12V output from the consumer unit - because it will be attached to a single timer.

      When tested on separate outputs on the consumer unit, they worked fine, but when I forked them at the point of entry into the project box (before the switches of course) they worked erratically for a few seconds during adjustment. After a while the potentiometers 'died open' allowing full speed only. There was no visible sign of damage to each circuit board however.

      I've now obtained another pair of these regulator circuits - but before risking them again is there a best practice method of protection here? My initial thoughts were a diode on each (+) between where the line forks and the switch and/or diodes on the line between each regulator and motor. I have 1N4001 silicon diodes and SB560 Schottky diodes available. Are diodes enough or is there something else needed here?

      Parts used:

      • 2x Mini toggle SPST switches. Rated 5A @ 125VAC / 2A @ 250VAC.
      • 2x RF-370 Mini motor pump. Rated 12V. Suited 5V-12V. Rated current 250mA
      • 2x DC Linear Converter LM317 Down Voltage Regulator Board 'XH-M137 v5'.


      Adjustable: 3V-15V. Input: 3.25V-15V. Output: 1.25V-13V. Output current: 5-1500mA.
      This consists of the 12v +- input, 2 5-band resistors (can't read them against the blue), 1 zero ohm resistor, 2 tiny brown disc capacitors labelled '102', the LM317T chip & heatsink, a B10K pot, tiny red LED, and 2 fan outputs (1 goes to +- wires for the motor, the other is a 3 pin socket for a PC fan which is not used). Schematic is here:

      Name:  T2mq7tXkdXXXXXXXXX_!!199304554.jpg
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      My solar setup outputs around 12V and can deliver up to around 3A. The output this pump unit will be connected to is protected with a 1A blade fuse.

      My solar setup outputs around 12V and can deliver up to around 3A. The output this pump unit will be connected to is protected with a 1A blade fuse.

    2. #2
      Grumpy's Avatar
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      I wish I understood your setup, well beyond my understanding, however, is it possible your getting overvoltage to your circuits?

      powered by a 50W PV system with charge controller connected to a DIY fused DC consumer unit

      Did you have a gauge in the circuit to monitor incoming voltage?

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