headspeed measurement using Eagle Tree

[shauntot]

chaps, just picked up an Eagle Tree FDR. Don't know which logger to choose for measuring the headspeed for my 600. Keen to measure it as I've just picked up a Z30A-1110kv for it today turning a 16t pinion.

Which one is more accurate?

The Brushless Motor RPM Sensor or the Optical RPM Sensor?

http://www.eagletreesystems.com/MicroPower/micro.htm

thanks in advance!

[cbdane]

chaps, just picked up an Eagle Tree FDR. Don't know which logger to choose for measuring the headspeed for my 600. Keen to measure it as I've just picked up a Z30A-1110kv for it today turning a 16t pinion.

Which one is more accurate?

The Brushless Motor RPM Sensor or the Optical RPM Sensor?

http://www.eagletreesystems.com/MicroPower/micro.htm

thanks in advance!

I use the brushless sensor. Very easy to install. Works great.

[Mercuriell]

I've also been very pleased with the brushless sensor (hot glued direct onto the datalogger and shortened its lead) and have no worries about its accuracy

[cudaboy_71]

they're both equally accurate. the brushless motor sensor is a LOT easier to set up. in fact you can just push a straight pin through the wire on the sensor and through a wire on the motor and you're done.

the optical one needs a black/white reference on a spinning part. so, you'll end up either painting one of your rotating parts or fabbing up a colored ring to mount somewhere on a spinning shaft..then mounting the sensor so it can read it.

[bullaculla]

I still haven't mounted my optical sensor...
what a pain!

[shauntot]

ok then..brushless sensor it is! :)

thanks guys!

[th3tick]

I tried all three on my 600 ;)

The optical sensor didn't like my sharpie on the main gear idea. For the Hall effects sensor, I couldn't find a good spot for the sensor itself, but the magnet glued into the gear just fine. I later found the magnet stuck to my battery box. I wonder when that came loose!

The brushless sensor is simple to install, but I hated resoldering it when I changed ESCs or motors. I ended up taking a pair of connectors, soldered a piece of bare wire in between, then the wire from the brushless sensor to it. I formed it bent at 60 degrees, which made heatshrinking it a pain, but it worked out Now it's just an inline plug between the ESC and the motor. Let me know if want to see a picture of what I came up with.

John

[cudaboy_71]

The brushless sensor is simple to install, but I hated resoldering it when I changed ESCs or motors.

no need for any of that. just take a straight pin and stick it through the red lead from the sensor and through one of the 3 motor wires from your motor or esc. not very clean. but, i don't run the eagle tree all the time. i'm usually just after a quick reading after a change....a flight or two max. so, a temporary install is perfect...especially with 4 electrics i want to monitor.

[th3tick]

no need for any of that. just take a straight pin and stick it through the red lead from the sensor and through one of the 3 motor wires from your motor or esc. not very clean. but, i don't run the eagle tree all the time. i'm usually just after a quick reading after a change....a flight or two max. so, a temporary install is perfect...especially with 4 electrics i want to monitor.

Two electrics, two Micro Power recorders here. I want to be able to check after each flight, so mine are semi-permanently installed.

John

[cudaboy_71]

i'm just saying i can check after every flight, too. moving it from one heli to the other takes less time than plugging in another lipo.

but, there's nothing wrong with running multiple loggers. i just need one. thought i'd point out the reasoning. that's all.

[shauntot]

any pics guys? :)

[bullaculla]

I think i'm gonna buy the skytach. I used a friends at the field the other day and it was awesome. but hard to do it solo :mrgreen:

[shauntot]

agree, skytach is still the best, but you have a point, it'd be impossible to use alone :) anyway i think the best would be to have a skytach and someone tach the heli, and run a FDR along with the flight to verify :)

[Tasteless]

For a single person job.
I used a 1/2-1 degree pitch down on a throttle curve end point to end point.
The negative is to make sure it does not take off and provides a little load, and I don't ever do this in any sort of wind.
This gives a reasonable speed indication under a little load.
Much easier to do this properly with a second person doing the tach.

Regards
T

[n55w131]

The brushless motor sensor is not as accurate (You can ask eagletree why and they can explain it to you, it is a result of resolution/time) as the optical or hall effect rpm sensor for measuring rotor head speed. The brushless sensor uses a derived head speed, calculated from motor rpm / gear ratio. The optical or magnetic (hall effect) are a more accurate reading as they are mounted directly on the main gear / shaft and are reading true head speed.

I have all three, I can show the differences. The optical and the magnetics are within 2% of each other. At the same time the brushless can be more than 10% off.

[thefig781]

The brushless motor sensor is not as accurate (You can ask eagletree why and they can explain it to you, it is a result of resolution/time) as the optical or hall effect rpm sensor for measuring rotor head speed. The brushless sensor uses a derived head speed, calculated from motor rpm / gear ratio. The optical or magnetic (hall effect) are a more accurate reading as they are mounted directly on the main gear / shaft and are reading true head speed.

I have all three, I can show the differences. The optical and the magnetics are within 2% of each other. At the same time the brushless can be more than 10% off.


...my eagle tree using a brushless rpm sensor was spot on with the reading from a sky-tach. So I guess
that is close enough for me.

Jim

[philo]

Ive had the FDR for over a year on my Eraptor and av tried all 3 methods. The only one i had that worked for me was the brushless sensor. As for the acuracy ive found that if you program in the correct gearing ratio it is suprisingly accurate i tached my head speed 6 months ago and set my TC at 1800 RPM suprised to see that the headspeed displayed was 1802 on the FDR. Bear in mind that the resolution on the optical tach is + - 100 rpm on the display (please confirm if im wrong) dats my 2 cent hope it helps

[Sandy]

I too have had to change the gear ratio to match the tacked HS, but once that is set it is consistenly accurate..