I'm wondering if it's possible to take readings on the tabs of the ribbon cables from the windings of the yaw, roll, and pitch motors to see if those are good or bad. I can't seem to find any consistency in reading resistance on them now.
Can windings on yaw, roll and pitch motors be measured?
- Thread starter Monkeyleg
- Start date
I just want to be able to figure out if a problem is in a gimbal motor or in a motor board without having to take it apart multiple times. Now that I figured out which leads on the copper ribbon cable go to the windings and to the different posts on the hall sensors, I should be able to make a simple tester.
I removed the ribbon connector from the bottom of a defective pitch board. On the copper ribbon cable from the motor, the three thickest tabs on the right side are for the windings. The next tab is ground for the hall sensor. The next three tabs are for the inputs for each of the three hall sensors. The last tab is for the output from the three sensors. I may have that reversed, as it would make more sense to have three different output leads and a single one for input. I'll find out which is which once I get the wires soldered.
So, I'll solder 30 gauge wires (that's as big as will fit) to each of the pins on the connector. I'll have four slightly worn AAA batteries going to the three sensor inputs to give about 5 to 5.5 volts. Then I'll have the ground lead going to the ground end of the batteries. For the sensor output lead, I may solder it to a 3 to 6 volt light bulb if I can find one. Otherwise I'll just use a voltmeter on them. For testing, once it's hooked up, I'll rotate the magnet on the motor. There should be voltage coming from the sensor three times per turn.
For the windings, the resistance is too low for a regular multimeter to measure. So I ordered a cheap ($18) LC meter to measure inductance between the three sets of windings. If any of the three measure significantly different than the others, then the winding is bad.
It's a lot of dinking around for just one or two gimbals, but if I have problems in the future, it will make testing easier.
So, I'll solder 30 gauge wires (that's as big as will fit) to each of the pins on the connector. I'll have four slightly worn AAA batteries going to the three sensor inputs to give about 5 to 5.5 volts. Then I'll have the ground lead going to the ground end of the batteries. For the sensor output lead, I may solder it to a 3 to 6 volt light bulb if I can find one. Otherwise I'll just use a voltmeter on them. For testing, once it's hooked up, I'll rotate the magnet on the motor. There should be voltage coming from the sensor three times per turn.
For the windings, the resistance is too low for a regular multimeter to measure. So I ordered a cheap ($18) LC meter to measure inductance between the three sets of windings. If any of the three measure significantly different than the others, then the winding is bad.
It's a lot of dinking around for just one or two gimbals, but if I have problems in the future, it will make testing easier.
ur right on using L for winding tests since R is too low; I do that on 20-200 hp ac motors to test for shorted windings.
rather than bulb use led with 1k or 2k resistor in series for each hall output tester; they are probably hall transistors rated about 10ma load - we do that on linear motors today too
Know that you will get more than 1 on/off per mechanical rev of motor: u will get 1 on/off per pole pair; min is of course 2 poles, so min will be 2 on/off per mech rev. those motors are likely more like 6 pole so be ready for more cycles.
rather than bulb use led with 1k or 2k resistor in series for each hall output tester; they are probably hall transistors rated about 10ma load - we do that on linear motors today too
Know that you will get more than 1 on/off per mechanical rev of motor: u will get 1 on/off per pole pair; min is of course 2 poles, so min will be 2 on/off per mech rev. those motors are likely more like 6 pole so be ready for more cycles.ya, I once used those a1326 to make a patentable sin encoder for a custom linear motor we built for Navy to make a moving floor! But anyway, think for sec WHERE those 3 halls would have to be to give you 120 mechanical degree on/off outputs: yep, equally spaced around the whole 360 mech degrees of the motor. but you saw them - they are all close together in one spot... cuz they are 120 ELECTRICAL degrees apart for ONE motor POLE.... You will see, no biggie.
Wow then! a two pole motor! wonder why they would do that when it wouldn't really cost anymore to make it a bunch more poles and get a bunch more torque at a bunch lower speed - not like it needs to run 10,000rpm. Very interesting.
Here's two photos of the roll motor. You can see the hall sensors at 120 degrees.
http://www.phantompilots.com/threads/gimbal-motor-failure.47610/#post-445318
http://www.phantompilots.com/threads/gimbal-motor-failure.47610/#post-445318
Last edited:
Just confirmed the pinout:
1. V_a (bigger pad)
2. V_b (bigger pad)
3. V_c (bigger pad)
4. GND (conveniently provides a little noise isolation)
5. V_hall_1
5. V_hall_2
6. V_hall_3
7. PWR (e.g. 5V)
The hall sensor is from TI on this motor, not Allegro. The markings read +NLAG: http://www.ti.com/lit/ds/symlink/drv5013.pdf
The sensor latches on polarity changes, that is, it toggles from 0 to 1 or 1 to 0 when the rotor magnet moves across it and then persists that value until the other magnet crosses it. These are NOT analog sensors. These sensors are open-drain so they REQUIRE the pull-up resistors on the other PCB.
There are four pole-pairs on that motor (4 cogs), so the 8 unique bit combos that can be sensed give an absolute mechanical position resolution down to 45 degrees.
1. V_a (bigger pad)
2. V_b (bigger pad)
3. V_c (bigger pad)
4. GND (conveniently provides a little noise isolation)
5. V_hall_1
5. V_hall_2
6. V_hall_3
7. PWR (e.g. 5V)
The hall sensor is from TI on this motor, not Allegro. The markings read +NLAG: http://www.ti.com/lit/ds/symlink/drv5013.pdf
The sensor latches on polarity changes, that is, it toggles from 0 to 1 or 1 to 0 when the rotor magnet moves across it and then persists that value until the other magnet crosses it. These are NOT analog sensors. These sensors are open-drain so they REQUIRE the pull-up resistors on the other PCB.
There are four pole-pairs on that motor (4 cogs), so the 8 unique bit combos that can be sensed give an absolute mechanical position resolution down to 45 degrees.
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