4 wire dc motor?

15 years 7 months ago #3428938 by bebel
4 wire dc motor? was created by bebel
Hello,

I am trying to use 2550 in the position mode with a dc motor.

The motor has 4 leads, it says to turn clockways, hook two leads to + voltage and two to common ground. To turn counterclockways, swap one pair, such as take one wire from + and hook to ground, and vice versa.

The motor works when I connect leads direct to power and ground. I figure that I hook one wire to power, one to ground, one wire to white on roboteq, one wire to green on roboteq. This turns motor constantly until pot end but only in one direction, if I swap green wire lead with white wire, it turns in opposite direction until pot end. Roborun reports good batt voltage but 0 amps through MOSFET.

What am I doing wrong? Any advice anyone?

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15 years 7 months ago #3429420 by cosma
Replied by cosma on topic Re:4 wire dc motor?
I am not familiar with your motor but you should wire nothing directly to battery or ground.

Try wiring the two + leads to the white wire and the two common to the green wire (as in for turning clockwise). Depending on the polarity on the white and green wire during operation, this will most likely make your motor turn one way or the other, even though this is not specified in your motor's documentation. (unless your motor has built-in active devices such as diodes or transistors that would be affected by reversed polarity)


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15 years 7 months ago #3429508 by bebel
Replied by bebel on topic Re:4 wire dc motor?
Thanks, I will try that

If that doesn't work I will try leaving two wires floating, which will be interesting to see as it seems that one pair(the pair through the controller) does not need to be current carrying. I will investigate though.

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15 years 6 months ago #3450681 by bebel
Replied by bebel on topic Re:4 wire dc motor?
Hello,

I just thought I would reply over how it worked in case other people have the same problem.

First I connected one pair of wires to the green wire on the roboteq and the other pair to the white. The motor became very hot and began smoking(I believe the lubrication oil) until the fuse blew. No damage to roboteq, motor or anything else but I quickly detached that configuration.

I eventually got it to work, because one _specific_ pair must be connected to the roboteq and one to power/gnd. My theory is that one pair is the shaft coil and the other is the field coil(taking place of permanent magnet).

I believe one is field because it is 10 times the impedance of the other, indicating more turns of wire, so more magnetic field at less current. The pairs are also at high impedance from each other.

So to recap, I connected the field wires to roboteq and shaft wires to power/gnd (polarity matters in both). The motor still gets very hot but works just fine(I believe the motor is very low efficiency anyway; it's industrial surplus custom gearmotor)

I am amazed at the quality and precision of the roboteq, I do not work with motors typically which is why I had trouble, but I have seen high-torque professionally-built servo systems before and this is quite comparable.

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