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Making A rotisserie

Discussion in 'General Electronics Discussion' started by rinkrav1, Aug 8, 2012.

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  1. rinkrav1


    Aug 8, 2012
    I am new so please do patient with me. I love tinkering with stuff and I have a very simple power source problem

    I have a outdoor barbecue and am trying to add a electric rotisserie as well as some other things to it. I have some old electric motors etc that I found and am wanting to put them to use if possible. Okay so here is what I have...
    I have 2 12 volt High Torque motors that have are 10 RPM.

    I have reduction gears to reduce the RPM to 3, which is what I need.

    These motors run fine on a 12 volt car battery.

    My problem is this.

    What can I use as a power source for this motor. (Meaning I would like plug something in a wall socket and then end up with the motor running.) I cant use a car battery all the time.

    I tried using an old PC power supply. This worked for a few minutes and then it stopped)
    The motors are rated at 20 amps.

    Any ideas on what I could use or create for an external power source. I know this sound simple , but please keep in mind that I am a newbie to electronics.
    Any help greatly appreciated.

    My idea is that I switch the power on and the motor runs. I really want to keep i as simple as possible for starters.
    Once I get the basics down, i do have some other components that I can add.
    I have a remote controler circuit that operates the motors. But am still stuck on just getting a good power source.

    Any help greatly appreciated.....

  2. CocaCola


    Apr 7, 2012
    A 12 Volt 20+ Amp supply is going to be costly...

    There are some comparable units on Ebay slightly cheaper but you are pretty much looking at $100+

    In the end you might find it more economical to use a car battery that is hooked up to a small battery charger... This will keep the battery charged at all times and you have the reserve Amps to draw from the battery when in use...
  3. rinkrav1


    Aug 8, 2012
    Thanks so much,
    That is what I thought also.
    Now here is my next question.
    Will i need some sort of circuit to hook everything up. That is I am sure it would not be wise to just connect the leads straight from the battery to the motor.
    Any help greatly appreciated.
  4. CocaCola


    Apr 7, 2012
    Get an inline fuse holder, they sell them at any autoparts store, and get a 25 Amp fuse for it...

  5. rinkrav1


    Aug 8, 2012
    Great, I have one. This is perfect. Thanks so much.

    Will let you know in a few minutes how it works. Also this is just a random question.The charget is hooked to the battery terminals, and then the wires from the motor go to the same terminals, just curios on how the whole thing works. How does the motor draw powere from the battery and not the carger itself. I know its a stupid question am just curious.

  6. CocaCola


    Apr 7, 2012
    It draws from both when in use, it will draw off the charger and then tap the battery when necessary... Basically the battery is acting as a reserve to an underpowered power supply (aka your battery charger)... You won't have unlimited run unless you charger is charging in excess of 20 Amp, but you will increase the run time vs just the battery... One thing to consider without testing the 20A rating of the motor should be the max start up or full load requirement, it will actually run at much less under low loads, your battery charger might actually be able to supply enough on a 'fast' charge mode...

    BTW good luck, I just helped my brother weld and cut up an old used fuel tank to turn it into a pig roaster last week... I believe he already had a rotisserie mechanism lined up, I'll find out tomorrow...
    Last edited: Aug 8, 2012
  7. rinkrav1


    Aug 8, 2012
    Thanks so much This worked perfectly. Now I will finish the rest of the project. Thanks so much for the explanation, everything makes sense now.
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Since it sounds like this is not a rotisserie motor, I would imagine that it came from some original application where over 200W of power was required.

    Chances are that the motor draws a lot less than that when not under load, and chances are that under the load imposed by your meal it won't draw 20A either.

    In fact, at 10RPM it may have so much torque that you could damage your BBQ should anything jam your lunch.

    I would recommend measuring the current drawn under no-load conditions (freely running) and also under what you feel is a reasonable working load. It may well be that the motor doesn't draw more than (say) 5A under your load.

    This may mean that you can either use a power supply rated at lower current, (and/or) or use a lower rated fuse to protect yourself and your dinner.
  9. rinkrav1


    Aug 8, 2012
    Hi *steve* and cocacola,
    My apologies. I mixed 2 different things up.
    Teve you are absolutely correct about one of the motors. My apologies for the confusion. I wrote that both motors had the same specs. This is in correct. I am sorry. They are very different motors.

    I rechecked my specs and they are as follows.
    The first motor I have has the following specs. It was from a small robot hobby kit.
    10RPM 12V DC motors with Metal Gearbox and Metal Gears
    18000 RPM base motor
    6mm Dia shaft with M3 thread hole
    Gearbox diameter 37 mm.
    Motor Diameter 28.5 mm
    Length 63 mm without shaft
    Shaft length 15mm
    180gm weight
    42kgcm torque
    No-load current = 800 mA, Load current = upto 7.5 A(Max)
    I am using this motor to circulate air through a small metal oven that is placed on a fire place. It works okay with an old pc power supply that I have. Iam still open to any suggestions as this may not be ideal. Also if there is a way to join it to the bigger motor(used for the rotisserie) and have them work together through some simple circuit would be great.
    Now to come to the second motor(the one for the rotisserie), which is where i am having the problem I really do not have too many specs.
    It is an old motor that was rusted and came from a revolving statue that weighed about 5 to 7 pounds. It looks like something from some heavy machinery or a car or something like that. Not sure what it was originally used for. I got the statue at the flea market and the motor was attached to it but had no power source.
    I had a friend test it and he says that it runs at 40 rpm
    it needs 15 amps to start according to him. But I am not sure.
    How this was tested I am not sure.
    Also he was not able to simplify the entire process. Thanks to info on this forum I have understood a few things and love the posts.
    I do have a multimeter and if you could point me in the correct direction I am sre I will be able to find the correct amps. I just need to know what to do.

    Thanks so much for all your help.
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