MicroPower E-Logger (Optical RPM Sensor)

[W4DJW]

Has anyone setup the T-Rex 500 with the EagleTree Optical RPM sensor? I was wondering where would one mount the sensor to get best the results from the onboard tachometer. Photos would be nice.

Thanks in advance for any assistance.

[skeppley]

Is there a reason you went for the optical instead of the very easily setup, 1 wire brushless sensor?

[W4DJW]

Yes, it was a lack of experience on my part. As it is turning out so far, its not so bad. I mounted it under the main gear so that it senses the 10 holes in the main gear. The programming allows you to compensate for more than one alternate light/dark period per revolution. It appears to be working fine so far. The live mode in the computer software appear to be giving correct information on the bench. I'll have to wait until the back ordered helicopter tachometer arrives to validate it is sensing correctly.

[whaleboy]

Yes, it was a lack of experience on my part. As it is turning out so far, its not so bad. I mounted it under the main gear so that it senses the 10 holes in the main gear. The programming allows you to compensate for more than one alternate light/dark period per revolution. It appears to be working fine so far. The live mode in the computer software appear to be giving correct information on the bench. I'll have to wait until the back ordered helicopter tachometer arrives to validate it is sensing correctly.

I'm in the same boat (um... aircraft?). I just hooked up the optical. Why optical... it just seemed easier to me at the time, I'd be putting it on my 450 also, and didn't want to be changing the setup (gear ratio and motor info) every time I switched. I started to mount it under the gear (where the screw goes in). I wrapped it with white tape then covered half in flat black tape. Before hooking it up I realized that was not the best place as I'd likely have to remove/redo the tape quite often.

So... I just did the same thing on the locking collar above the top shaft bearing. Easier to get to, and I won't have to change it much, as I can get the head off without messing with it. Seemed to work great on the bench and for the first few minutes in a test hover, but then completely stopped working, just reading a HS of 0 (reading it with the LCD panel). Everything seems ok, but 0 headspeed. I'm just now starting to troubleshoot the thing. I have a feeling I may pick up a brushless sensor anyway... might be better in the long run.

-David

[whaleboy]

well, after more testing the optical is pretty hit and miss. Works fine inside when I take the blades off. Outside in the sun it won't work most of the time. In the shade it starts but cuts in and out. Right now the shaft collar is marked with flat black and flat white tape. I wonder if the white should be glossy instead. I'll give that a shot but if that doesn't work, I'll just get the motor sensor.

I also had an issue with the LCD not coming on. It would just display vertical lines moving around right to left. I have to unplug and replug the lcd in several times to get it to display properly. Today it seemed ok, but I don't know if the issue is in the LCD end or the Logger end?

BTW, when the RPM sensor did work it read a max 2560 rpm, 100% throttle 12t pinion. Sound about right?

-David

[W4DJW]

Well, you have had better luck than me. I got mine mounted under the main gear and like you said, inside on the bench it was working fine. Got the elogger LCD display mounted on the side so I could peak at it when in a hover (too close I know) and noticed while in the hover I had 0 head speed. Hummm... Couldn't wait for the ten minute flight to end so that I could rush right in the house and see the current draw, voltage drop, mAh used up and RPM!

Got inside and plugged in the USB cable and downloaded the data and everything was there except the RPM. I had 3 spikes of some RPM during the whole flight. The highest spike was between 1,600 and 1,800 RPM and didn't last long.

It was cool to see what is happening with the current draw in a graph but I'm thinking... back to the web stores to find the 1 wire brush-less sensor. In the mean time I'll do the same thing, and play around with flat black and non glossy white perhaps inside the cage just below the main gear where there will be less ambient light to effect the infra red light.

I'm using the 4000mAh pack and a 15 tooth pinion and that works much better than the 13 tooth pinion that came with the 500 for the heavy battery pack. I'm shooting for longer flight time rather than the hard core 3D stuff. I pulled 3400mAh out of the pack in 10 minutes according to the logger and put back 3777mAh according to the TP1010C so that appears to be working within design parameters. :thumbup:

[skeppley]

BTW, when the RPM sensor did work it read a max 2560 rpm, 100% throttle 12t pinion. Sound about right?

-David

That sounds about right with a 12 tooth.
I had heard the optical took a lot more fiddling around with to get up and running, now I'm pretty sure of it.
The brushless is definitely the way to go.
Good luck.

[W4DJW]

Is there a reason you went for the optical instead of the very easily setup, 1 wire brushless sensor?


Got the Brushless Sensor in today and the results are a lot better. Thanks for the tip skeppley!

Looks like it got some false spikes, I'll look into that but during the 10 minute flight it recorded just fine.

[skeppley]

Sweet. You can also change the settings from RPM to Prop RPM to get the head speed instead of the motor speed in your graph.
Not sure about those spikes, maybe a loose wire from the sensor?

[W4DJW]

Thats probably it. In the instructions they suggest sticking a pin in one of the motor wires so thats what I did. I guess its not making good solid contact. I'll have to redo it.