Motor Temp Monitor

[LipoShirly]

Killing time, thinking out loud, waiting for the ice age to end, hopefully outside temps will rise above "plastic turns to glass" thresholds here pretty soon. Just got my first real RC a few months ago, the times I did get to run it outdoors have always been cool enough that motor temps have not been a problem. Its a Typhon 3S but I've been running on 2S until I get my feet wet, still managed to break a chassis. Anyway. making plans for this summer I'm concerned with keeping an eye on motor temps as I plan on more use on 3S lipo, with hopefully extended runtimes (not having to worry about frostbite) and I also added one of those hairnet covers to keep the gravel out of the Typhon. Anyway I'd thought I'd tap into the knowledgebase and hear from the experienced. I've read of many users having one of the handheld IR sensors (FLIR) , and that sounds like a good way to go for ESC, Batts and motor. This also sounds good if you have multiple cars. (Hmmm, may have answered my own question....). For fun I started looking into adding real-time temperature measurement with telemetry. Adding up what it would cost with a new Spektrum radio and receiver capable of telemetry, and adding sensors got expensive pretty quick, easily surpassing half the cost of an entirely new Arrma 3S rig, couldn't justify it unless I was running a much more costly unit. Started looking into a homegrown version, and here is where I actually ask for your advice. I have couple of options to choose from. Let me know if the path is a waste of energy, or if I'm re-inventing the wheel.

1) Simple on-board sensor with an LED to notify user of an OT situation. This could easily be done with a couple of stick on TC's , a cheap Arduino (microcontroller) and a bright red led mounted under the rear wing for about $20. Actually would be cheaper with discrete hardware, but not as flexible. Motor gets hot, LED comes on.

2) BlueTooth. I've seen these on Amazon for GPS and temp data (I think TRAXXAS has a system as well), they get a little pricey, reviews seem mixed, range is limited. I'm thinking of using the previous LED method and upgrading to a blue tooth capable version of the Arduino ($35) . Advantage over the LED is that I can now actually see the temp rise. Disadvantage is the limited range, meaning I would probably still have to bring the car to me and wait for the connection (might as well use handheld IR)

3) Packet Radio. Buy Arduino available with packet radio, but now you would need 2 (transmit and receive) and would require a home grown display unit. Range would easily equal any control radio, but price tag and dev time just increased substantially, now looking in the $80-$100 range. But..... this would also allow other real time measurements, like GPS ground speed ( I don't really need but sounds cool)

4) Buy spare motors from JennysRC and don't worry about it.....

Anytime I get the car out in public the conversation goes like this:
Bystander: Is that your RC ?
Me: Yep
Bystander: How fast is it going?
Me: Not fast enough....

Again, this is my fight against going stir crazy, sorry for the length.....

LS

 

[SrC]

I sometimes use an LCD temp display that has a wired Thermistor to wrap around the center of the motor. I use this when I have a hot setup that pesters me trying taller gearing and all. Using/ Buying a cheap temp gun is advisable. It is just a required tool box item. ESC, motor, Lipo, and wire/connectors all should be monitored for temps. Even a ST servo gets super hot btw.(can be 120F+) Usually when running a higher BEC voltage. Higher than 6v. Cant just focus on Motor temps.
Rebuilding the motor, cleaning and relubing the bearings and never getting it wet makes for longer life when it comes to motors. Needs to be done every 10-15 runs at least. More so if you run in very dusty and wet areas. If it gets fairly wet, the motor needs an immediate rebuild after.
A Temp gun is more practical and usually more accurate. Ambient air temps always impact electrical temps. I take air temps first for reference when out bashing.
After a while when you are comfortable with running temps being fine, There is usually not much of a need to constantly monitor it. But many guys like to run large capacity packs (8-9k mah) in high traction terrain for 40+ minutes and even more. Temps can shoot up when bashing long like this. Good to bring in the rig for periodic temp checks anyway.
Running 3s over 2s wont necessarily give you MORE run time. The Lipo's capacity in Mah determines that. Regardless of cell count.
Yes 3s will run hotter. Motor will spin at roughly 1/3 more higher RPM's.. And will draw more amps from the Lipo through the ESC. All will run hotter. Normally. Expect this.

 

[LipoShirly]

Thanks Src, good advice. What I'm hearing is unless I start to push the limits I should be fine. Your comment about Temp gun being more practical is sorta what got me started down this path to begin with, practical is usually not fun. And my bad with the 2S vs 3S, didn't express that very well. What I meant to say was that soon I will be moving up to 3S batts, and as warmer weather arrives I expect longer run times..... I could see myself running continuous for hours if I acquire enough batteries....