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DIY power supply — Parallax Forums

DIY power supply

Brian_BBrian_B Posts: 842
edited 2012-01-01 14:45 in Robotics
Hi,
I needed a 24 volt power supply so I thought I would try and build one myself ,I machined the circuit board in my mill and assembled it. I know that the electronics guys are probally going to laugh at this, but why is my 24 volt ac transformer putting out 39 volts dc ? I'm a little worried because the cap is only rated for 35 volts.

Brian
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Comments

  • LeonLeon Posts: 7,620
    edited 2011-12-29 16:39
    A transformer will only deliver the specified output voltage with the load it has been designed for. The voltage will be much higher with smaller loads. Also, a full-wave rectifier and capacitor will produce a DC voltage 1.414 times the AC voltage.
  • Brian_BBrian_B Posts: 842
    edited 2011-12-29 17:00
    Thanks' Leon,
    Will the 35 volt capacitor (2200 uf) blow up when there is no load on the power supply ?

    Brian
  • LeonLeon Posts: 7,620
    edited 2011-12-29 17:07
    It might. I'd use a higher voltage one.
  • kwinnkwinn Posts: 8,697
    edited 2012-01-01 14:45
    Rule of thumb is to use a capacitor with a rating at least 2X the AC voltage input. In your case a 50V cap is good.
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