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Basic PSU question - best option

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by Leftfield27, Dec 17, 2022.

  1. Leftfield27

    Leftfield27 New Member

    Joined:
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    My Motion Simulator:
    2DOF, DC motor, Arduino, Motion platform
    Hello, I've just received some equipment to get started and am missing the power supply.

    I have an Arduino uno and threee IBT2 boards. 5 cheap kohm pots, and just received today three second hand windscreen wiper motors.

    The plan is just to build a simple prototype for 2dof plus traction loss, just to move a wooden board, then upgrade bits once I have proven that I can do the basics. So down the line I will invest in some better motors, like the 12V crab pot pullers which seem to be around 300W typically. I would like to build a compact rig if possible.

    But now I need a power supply, to work for my windscreen wiper motors, and then later for some more powerful motors.

    Having spent a little time reading the forum, i can see three options:
    1. LED PSU (from amazon or similar)
    2. Car battery (12V) with charger
    3. Modified server PSU

    It seems to me like I'll need to supply 900W which would draw 75A at 12V.

    1: LED PSU... Can find a 1000W supply for around 90 euros, 300W around 30 euros, 600W around 50 euros.
    I guess that three 300W supplies would be the best option here, but would a single 1000W supply do the job?

    2. I can find a new car battery rated at 60Ah for 70 euros, if I drew 75A continuously this would last 48 minutes.
    If I charged it at 10A the three motors would draw only 65A and so it would last 55minutes before discharging completely. I can find a 10A charger for 30 euros, total cost 100 euros for one hours use (at maximum current draw). Then I'd have to wait 6 hours before using it again.
    A 20A charger, and I would consume 55 A, lasting 65 minutes. Cost 80 euros charger plus battery total 150eur.

    3. Modified server PSU from ebay. I have seen the instructions on the forum to adapt a server PSU for 12V motor use. The price is often around 30eur for a 350W, 40 eur for a 600W, and 150eur for a 2000W, but there are a few offers on ebay which seem cheaper if you hunt around.
    I guess that this is the same as option 1. again, would one powerful PSU run all three motors or is it better to have three PSUs.



    I know that you can also add a battery to a PSU powered setup to help deal with spikes.
    I understand that the setup will not draw 900W continuously, what is the likely average draw (just a vague idea to see if the car bettery and charger idea is any good...) an average of 300W for three 300W motors and I could get three hours of use with the battery system.
    Will a 300W motor draw more than 300W for short spikes that could trip the power supply? If so how much headroom roughly would be sensible? Three 450W PSUs? Or just add a car battery and stick to 300W supplies ?

    It seems like the easiest plan is to get three new 300W led psus on amazon for a little under 100 euros. The most economical would be to get three 575W server psus on ebay in order to have some headroom and try to find a good deal, but I would have to fiddle a bit to modify them. And I worry that they might break being second hand.
    The car battery and charger seem to be a bit limited because the charge at 10 of 20 amps doesnt give a very long play time before discharge of the battery.

    Well can anyone guide me a little bit ? Have I understood correctly ? Do I need some headroom above 900w total?

    I will start a thread with my build once it gets underway, but I just need to get a power supply to get me started (and some wire!) before I have a few days off work to start to build a prototype.

    Many thanks in advance for your pearls of wisdom and experiences,

    leftfield 27
  2. Ads Master

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  3. noorbeast

    noorbeast VR Tassie Devil Staff Member Moderator Race Director

    Joined:
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    My Motion Simulator:
    3DOF, DC motor, JRK
    A little bit of headroom is always a good idea, as there will be power spikes in fast reversals.

    If you are not going with a battery then my personal preference is 3 PSUs, those should be more resilient in power spikes than a single PSU.