Vesc motor temperature issue

Joined
Mar 2, 2021
Messages
11
Location
Daytona Beach, FL
Ok so I have a fs75100 vesc and I'm trying to add a temperature sensor to my dd hub motor so when I start pushing it far beyond its sold rating my esc can stop me before I go to far as it were. The problem I'm running I to here is when I connect the ntc 10k at 25c thermistor my motor readings go from -70 were they normally would be with nothing connected to 1c when its like 40c lol. The b value in the vesc has been updated to the correct value... or at least the one stated on the package. I've had the same result with 3 diffrent thermistors and am getting tiered of opening this motor... any ideas?
 
What happens when you use a thermistor not mounted in the motor, but still wired to the motor wiring harness just like the one inside the motor?

What happens if you use an independently-wired thermistor not mounted in the motor?
 
Your motor *has* had one mounted, by you, according to your previous post, three times, unless you meant something completely differently by this statement:
I've had the same result with 3 diffrent thermistors and am getting tiered of opening this motor... any ideas?
If you did mean something different, please clearly and completely describe exactly what has already been done, so I can suggest tests that will help you find a solution.


Otherwise, I am asking you to try the thermistors you already have (that are not presently mounted in the motor) on the VESC, while the VESC is connected to the rest of the system just like you already have it, but with the thermistor external to the motor, just measuring air temperature, not touching the motor at all.

First wire it using the wires that go to the thermistor in your motor now, in place of that in-motor thermistor, and note it's readings.

Then test it just directly connected to the VESC, without using the wires that go to the presently in-motor thermistor, and note it's readings.

These tests will eliminate the possibility that something within the motor or motor wiring is interfering with the reading.

If the results are exactly the same with both of these tests as with the in-motor thermistor, then either the thermistors are not what they say they are, or the VESC is not setup correctly to read them.

You can test the thermistors directly with an ohmmeter, at various temperatures (measured with anohter thermometer that you know is accurate at that temperature, with it's sensor right at the same place the thermistor-under-test is at), to determine the beta.
https://www.ametherm.com/thermistor/ntc-thermistor-beta
You'll need to measure at (at least) two temperatures.

Just testing the base resistance at room temperature doesn't give you the data needed to determine the response curve (which is what you're have a problem with--the response is not what the VESC expects, and/or the VESC isn't reading them right for some reason).
 
I'm sorry I wasn't clear but I have already ran through these tests and with 2 of the sensors even tried to test and calibrate the b value using two points myself. This resulted in a temperature being correctly measured at ambient with the motor not ran at all but after putting it under load the temperature did not move from that point from what I believe was a b value that was way out of spec. I.e. when calculated it was around 15000.0k this have me the correct ambient temperature before the motor was run. But after a moderate load over 30 min the temperature did not change at all up or down
 
So the tests with the thermistors notthe motor at all work exactly the same as with them inside the motor, regardless of wiring?

I'm re-asking because you haven't yet stated that you tested them outside the motor, and only reference results about motor temperature.


If testing outside the motor is exactly the same as inside, then either:

--the sensors are not working correctly (which is verifiable with simple resistance tests--if the resistance measures as expected, the sensors are working correctly; if the resistance does not measure as expected, the sensors are not working correctly).

--the VESC is not reading the sensors correctly (which is verifiable using a potentiometer of the same resistance range as a thermistor; you can then adjust the pot to a specific resistance that a thermistor would read at a certain temperature, and then see what the VESC reads. If it reads correctly in all cases, it is working; if not, it isn't).
 
And again I state I did testing inside and out side of the motor same result. I have already as stated tested the resistance of the sensors and that came back fine. The vesc is reading them there is change just not at the expected temperatures. I unfortunately do not have a pot to test the vesc that way. It looks to me like with the correct b value it's working its just showing a temperature that's impossibility low. When I ran it with the sensor and given b value the temperature rose as expected but was just unpossably low
 
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