Motor temperature sensor?

[fechter]

The magnets and magnet glue are not going to get as hot as the windings in most cases. The hall sensors, however, are generally placed right between the windings or attached to the stator core, which will be exposed to the highest temperatures. The popular SS41 hall sensor is rated for 150C, so I would take that as the absolute upper limit. I've seen several reports where the halls failed due to heat. Personally, I would not want to run past 100C.

 

[tostino]

The magnets and magnet glue are not going to get as hot as the windings in most cases. The hall sensors, however, are generally placed right between the windings or attached to the stator core, which will be exposed to the highest temperatures. The popular SS41 hall sensor is rated for 150C, so I would take that as the absolute upper limit. I've seen several reports where the halls failed due to heat. Personally, I would not want to run past 100C.

I'd much rather my halls go than my windings, so i'd hope they would fail first. Just got done two days ago replacing them in my motor because I broke off the leads coming out of them accidentally.

 

[dnmun]

the heating is from the eddy currents in the steel laminations of the stator i thought. the magnet glue on DD motor is actually the coolest since it is between the magnets and the outside hub body exposed to the wind.

i agree with richard the hall sensors can fry but even they are isolated from the windings somewhat by an insulating fabric patch on my goldenmotor and so should not get as hot as the windings. plus the side covers will swirl air past them too.

i still think my idea of using a thermistor attached to the stator is the solution. the problem is getting an extra wire into the hub through the axle and if you use the hall sensor ground then you only need the one small wire to the thermistor.

the controller can provide a fixed voltage from the hall sensor power rail or the throttle rail, both regulated by zeners. using a voltage/temp chart one could determine where to set a comparator voltage using a high resistance divider off the regulated voltage rail of the hall or throttle , use controller current to drive the op amp, add it inside the case and then bring out an led which would toggle on when you reached the temp set point. a high temp idiot light for cheapsters.

maybe we can work out the circuit here, gotta find a source for thermistors and get the chart to make the selections of resistors for the divider. should work well permanently.

guess i will google up thermistors. or digikey or mouser or newark. found this on digikey, 50 ohm at 100oC: http://search.digikey.com/scripts/dksearch/dksus.dll?Detail&name=235-1127-ND

also 3369 matches at mouser: http://mouser.com/Search/Refine.aspx?N=254137&Keyword=thermistor&FS=True

this one is 50 cents and has insulated leads: http://www.mouser.com/catalog/specsheets/64090059.pdf

 

[Link]

In my browsing of the internet for PC stuff, I came across this. I originally got it to replace one of the temperature probes on my case's built-in thermometer, but realized it would be perfect for my bike, since its already got long leads, is backlit, and I'm already going to need a 12V supply for the pump and fans, anyway.

Might take a bit of work to figure out how to mount it (and you're going to want to spray something on the back to insulate the PCB), but might be worth a look...