24 Volt Power Supply

Discussion in 'General Electronics Chat' started by Machine Gun Kelley, Jun 17, 2013.

  1. Machine Gun Kelley

    Thread Starter New Member

    Dec 13, 2012
    Good Morning
    I am a industrial construction electrician by trade with a limited understanding of electronics. I want to build a 24 volt 8 amp power supply to help with checkouts.

    I will have to buy a transformer but I have all of the other components.
    the bridge is out of a synchronous motor control and the cap is a 14000 UF @250 volt left over from a UPS upgrade.

    The transformer is rated 24volts 8.3 amps but I have no idea what the unloaded voltage is. I would think close to 30 volts and when I hang a filter cap that could put the unloaded voltage over 40 volts.

    My question is what can I do to lower the output voltage to 24 volts?
    would a regulator or a zener do the job. I want to follow the KISS principal because it has to hold up to a construction enviroment.

    Last edited: Jun 17, 2013
  2. t06afre

    AAC Fanatic!

    May 11, 2009
    Even if it is fun to build electronics. You will probably save a lot by getting a properly rated switchmode supply. As transformers that big can be expensive.
    It is also important to spec the transformer properly. Here is some papers with design thumb rules for transformers specification. I can say that a 8.3 A transformer will not give you wanted output current
    Have a look at them and we can use this for further discussion.
  3. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    Use an LM317K regulator to set the voltage and use a PNP buffer transistor for the excess current figure 43 on page 18.

    Better to use a Switchmode as its readily available.