EagleTree E-Logger RPM sensor accuracy - RC-Monster Forums

tom255 · **EagleTree E-Logger RPM sensor accuracy -** 04.11.2008, 11:18 AM

OK today finaly I got my e-logger and tried out in LIVE mode in car without wheels on half empty battery, just to learn.
So choosed there E-logger and on RPM sensor i marked that its brushless and motor is 2pole.
All seems fine but I noticed that RPM sensor clock 34722RPM on 13,8V its 2516KV (no load)
My motor is Feigao 9XL (which is about 1800KV)
My setup is:
Feigao 540C-9XL
TrueRC 8000mah 4S2P battery
LSP with 46/18 gearing
Question how accurate RPM sensor is on E-logger V3?
Anybody have similar issue?
I am confused what to think...

Motor was bought from Mike maybe year ago on box was marked 9XL

BrianG · 04.11.2008, 11:38 AM

Well, you can run the vehicle and clock it with radar/GPS. Working backwards, calculate the motor rpm based on measured speed. Compare that with what the ET says the motor rpm is. You can then calculate kv by using the calculated motor rpm and the ET measured voltage.

tom255 · 04.11.2008, 11:50 AM

Unfortunatly I dont have radar and GPS I hoped that RPM sensor is accurate.
so Brian as I understand I need calibrate it?
I try figure out proper RPM using Prop Tacho, My friend have it...
Buy now I charging my battery and will try out it on load. Lets look what amps is going through maybe i will figure out why my 9XL run so hot? Outside is now perfect day for test Dry and Cold :) only 43F

speedracer1129 · 04.11.2008, 04:25 PM

Quote:

Originally Posted by tom255

Unfortunatly I dont have radar and GPS I hoped that RPM sensor is accurate.
so Brian as I understand I need calibrate it?
I try figure out proper RPM using Prop Tacho, My friend have it...
Buy now I charging my battery and will try out it on load. Lets look what amps is going through maybe i will figure out why my 9XL run so hot? Outside is now perfect day for test Dry and Cold :) only 43F

tom,

the car profile is a little screwy! i have been working with Don at ET on this. Make sure you go online and download the latest software and firmware. Also, use the airplane profile as it seems to be more accurate at this time.

rabosi · 04.11.2008, 04:46 PM

Where and/or how does the eagle tree measure rpm anyway?

speedracer1129 · 04.11.2008, 04:56 PM

It uses 2 wires that splice into 2 of the motor wires. I just capture them between the bullets.

rabosi · 04.11.2008, 05:07 PM

Ahh, ok. I would like to get that system eventually but did a quick look and couldn't find info on the rpm sensor. Would number of motor poles make a difference monitoring that way?

speedracer1129 · 04.11.2008, 05:32 PM

Yes. that is why the # of poles must be entered when programming the V3.

rabosi · 04.11.2008, 05:36 PM

An optical sensor for the wheel probably would've been more accurate for speed

speedracer1129 · 04.11.2008, 05:46 PM

Quote:

Originally Posted by rabosi

An optical sensor for the wheel probably would've been more accurate for speed

This is to measure motor RPM, not speed! It can't get more accurate...

rabosi · 04.11.2008, 06:03 PM

I did read that but had speed on the brain. Must be all the benadryl I'm on.

Actually I was hoping it did speed also.

tom255 · 04.15.2008, 05:48 AM

OK i made software and firmware update to my eagletree and still RPM's is way high. And one issue more i see 65K RPM spikes, is this normal?

I changed gearing to 46/14 on HB LSP and car still pretty fast and i start to think maybe i have wrong motor :) not 9XL maybe 6XL

Any way to detect it?
Maybe measure no load current? but on what voltage?

speedracer1129 · 04.16.2008, 07:26 AM

Quote:

Originally Posted by tom255

OK i made software and firmware update to my eagletree and still RPM's is way high. And one issue more i see 65K RPM spikes, is this normal?

I changed gearing to 46/14 on HB LSP and car still pretty fast and i start to think maybe i have wrong motor :) not 9XL maybe 6XL

Any way to detect it?
Maybe measure no load current? but on what voltage?

The spikes at the beginning of the session is normal. Yoy have to graph the run and read the info within the run to see actual info.

tom255 · 04.16.2008, 07:34 AM

OK I see, Thanks

But any advice about motor? Can I measure some parameters to detect motor turns?
Lets say, no load current on some volts?

MTBikerTim · 04.16.2008, 09:03 AM

I just bought one of these today. I will post the results when I get it. Sadly I won't be able to test it on a fiegao cause i don't have an esc yet. I suppose I could test it on a mates truck.