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Chopped up RC ESC, does this work like I think? — Parallax Forums

Chopped up RC ESC, does this work like I think?

rwgast_logicdesignrwgast_logicdesign Posts: 1,464
edited 2012-12-23 11:52 in General Discussion
Someone gave me an ESC today looking at the specs it seems pretty medicore but I dont know alot about these things and was hoping someone could help me understand how it works a bit.

Im thinking basically I can hook the cut input wires up like a servo and then pulse the thing when its connected to a motor? Is this correct?

What im wondering is why it has 8 mosfets on it, can this thing drive one or two motors?? Im thinking the 8 transistors represent two hbridge circuits, but im probably wrong. The second question is the thing is rated at 7 to 8v input, is it usually safe to ramp up to 9.6? I have a perfect 9.6v drill motor i could use with this. Lastly what in the heck is a 12T motor? Even the rc shop couldnt really tell me anything technical about the T rating in RC.

Comments

  • CircuitsoftCircuitsoft Posts: 1,166
    edited 2012-12-21 23:35
    12T is 12 turns per phase of a brushless 3-phase synchronous motor. You probably don't want to run it beyond 8.4v ( 2 Lithium cells in series).

    It won't drive your drill motor. Luckily, 3-phase motors are very cheap. Check out HobbyKing.com
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2012-12-21 23:38
    "What im wondering is why it has 8 mosfets on it" ... can you provide a picture? Most likely the mosftes are paired together, so essentially it is a 4 transistor H-Bridge with the transistors doubled.

    "Lastly what in the heck is a 12T motor?" ... This indicates the number of turns of wire on each leg of the motor armature ... 12T = 12 turns

    As far as voltage, I would stay within the specifications.
  • Mark_TMark_T Posts: 1,981
    edited 2012-12-22 05:37
    rwgast_logicdesign wrote: »
    Im thinking the 8 transistors represent two hbridge circuits, but im probably wrong.

    If its a brushless ESC then there are 6 FETs arranged in a 3-phase bridge and the other 2 packages are likely 5V voltage regulators in parallel(!) providing 2A BEC.

    I had an one ESC from a set of 4 sort of explode, so took it apart - that had 15 FETs, 2 n-channel's in parallel and 3 p-channels in parallel in each arm of the
    3-phase bridge.

    RC ESCs are designed for very low resistance motor windings, 0.5 down to 0.05 ohms sort of range. RC motors can generate about 200W mechanical power per cubic
    inch, very specialist really.
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-12-22 12:39
    Oh wow I totally didnt post the link!!!0 How do you guys know its for a three phase??

    http://www.ecxrc.com/Products/Default.aspx?ProdID=ECX1070

    So mines a bit chopped up, apparently there are 4 16 guage wires going to the motor(s)... I only have two I see where the other ones got hacked off though. Then I have three wires leading in red white black.

    So will this thing controll a 2 phase brushless DC motor? Will it controll 2, is that why theres 4 wires out?
    Next if I hook the black and read wires up to motor voltage, then the white to a bs2 pin, can I just pulse it like a CR Servo? If this can do 2 motors it would be great for a bs2 bot. If not I may use it to drive the my robots rotating body, im not sure though a 1khz pwm is gonna be noisy.
  • Mark_TMark_T Posts: 1,981
    edited 2012-12-22 12:53
    Ah, its a brushed motor ESC - an H-bridge with PWM. Very high current H-bridge of course, 80A (I'd take that pulse rating of 240A with a BIG pinch of salt, the wires will
    burst into flames at that current leve!). 4 wires for a 4-brush motor I suspect, high power motors usually have 4.

    In RC models brushed motors have to be used for land vehicles as sensorless brushless motors can't go really slow or reverse under load.
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-12-22 13:22
    Nope just found this

    http://www.ultimaterc.com/forums/showthread.php?t=167454

    the wires on the outside are to connect the battery, what happens if I connect this to a brush less motor? I dont think I own a single brushed motor... how exactly will something like this not work with a brushless motor?? I mean your sending a pulsed frequency down two wires and amplifying the current using transistors, it seems like any two lead motor would work just fine as long as it is within the current specs.
  • CircuitsoftCircuitsoft Posts: 1,166
    edited 2012-12-22 15:13
    Any two-lead motor is a brushed motor. A brushless motor would have three leads.
  • Mark_TMark_T Posts: 1,981
    edited 2012-12-23 11:52
    Circuitsoft wrote: »
    Any two-lead motor is a brushed motor. A brushless motor would have three leads.

    Well we have to be careful with language here, an AC induction motor has no brushes, two leads (no counting earthing)... Any _DC_ two-lead motor
    is a brushed motor would be more accurate (someone probably has an exception to this rule, but it must be exotic device!).

    Occasionally a brushless motor has 4 leads - for instance some hard-drive spindle motors bring out the common lead (middle of the Y). I've seen DC brushed
    motors with 6 leads (4 brushes, red/black/red/black and 2 thinner wires to a brake-release solenoid). A little time with a multimeter will verify / disprove any
    theory about a particular motor.

    In the RC world brushless motors often have yellow/red/black phases (a little unfortunate as red/black is standard colour coding for brushed motors!).
    Having said that I have some cheap ESCs with 3 blue leads - actually less confusing because you know the order doesn't matter (modulo getting it
    going in the direction you want).
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