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Dark Helmet · 04-04-2015, 10:47 AM

So I recently bought a T-Rex 800E DFC. This is my first time building a helicopter, so far I've had only BTF and RTF models. Getting the mechanical parts together was fairly easy, but now I'm stuck at the electronics (looks like this time I got a WTF model

). I do have an idea how the stuff generally works, but there are some details that are confusing me.

What I have is:

Futaba T10J radio,
Futaba R3008SB receiver,
Futaba CGY750 flybarless control gyro,
Phoenix Edge HV160
2x 6s 5000 mAh LiPo
1x 2s 2200 mAh LiPo (receiver battery)

Connecting the batteries to the ESC is simple, I just need an EC5 connector for the ESC and an EC5 battery series harness. Connecting the motor also is a no-brainer although the cable colors of the ESC and the motor don't match. I'll see which way the motor turns and adjust as necessary.

I have also connected the receiver with the CGY750 via the S.Bus cable. Now, I understand that the ESC needs to be connected to the "TH/E2" connector of the CGY750, but unlike the S.Bus connectors, this one is not coded AND the cable colors differ from the S.Bus cable. Looking at the orientation of the servo connectors (luckily their colors match with the S-Bus cable) I would assume that the correct orientation of the ESC connector should be orange/red/brown (top to bottom). Can anyone confirm this? I couldn't find any information about the pin assignment.

My next question is: how does the CGY750 get powered? From the little information I found in the manuals, it appears that I'm supposed to connect the receiver battery to the #7 connector on the receiver which will in turn provide power to the CGY750 via the S.Bus cable. Is that right? And is there any good reason why I should use the "Extra voltage" input on the receiver? And yet another question: can I simply connect the receiver battery to the receiver or do I have to use a regulator? I believe the receiver, the CGY750 and the stock servos (3x BL800H for cyclic control and 1x BL850H for the "rudder") should all be able to handle the voltage coming from a 2s LiPo.

Another thing that is still a mystery to me is the governor mode. I understand that it keeps the rotor rpm constant at up to three selectable speeds. So far, so good. But which unit actually controls the speed? In order to keep the rotor speed constant, we first need to know what the rotor speed is. But there is no rpm sensor. The only way of knowing is to either install one OR to know what the main gear/pinion size are and calculate the corresponding motor speed which should be known to the ESC. BTW, if someone could enlighten me what kind of motor the 850MX actually is that would be great. Looking at the cables it seems that it's a synchronous motor. I read all the fancy marketing blahblah, but there is never a technical description of the underlying principle.
Anyhow, I'm assuming that the ESC provides feedback about the motor speed to the CGY750 which then adjusts the power as necessary. The remote doesn't actually select the rotor speed but selects the presets stored in the CGY750, is that right?

Sorry if this is obvious to everyone here, but I've never actually built a helicopter and the information I have found on the internet hasn't always been helpful. It would be great if someone could shed some light on my noob questions.

Heli biggie · 04-04-2015, 11:52 AM

I was where you are a year ago. It will be all good. I cant answer all your questions because I use dx8 spectrum 2 satellite setup. But I do know it is a good idea to use both power inputs on your gyro or rx to have a back up. With this big bird you can just run straight 2s lipo to you rx or gyro. These servos can take it.
About the gov feature. You will need to get a castle link to hook up your ESC to pc and setup everything. You may have got coupon with esc. You will have to enter pole counts and main gear teeth count into castle calculator. Then pick rpms. It's a learning curve but with the help of the awesome people here and video on YouTube I'm loving my 800. You really learn a lot when you build it yourSelf. Then if you do everything correct it actually flys. I hope this gets you started.

Dark Helmet · 04-06-2015, 07:53 PM

Thanks for the response. I wasn't aware that ESCs can do so much more than just run a motor. You are right, there was a coupon in the box. I ordered the USB adapter now. The Castle link software runs even without the USB adapter which helped me understand what else the ESC can do.

04-04-2015, 10:47 AM	#1 (permalink)
Dark Helmet Registered Users My HF Map location Join Date: Jan 2015	wiring / governor questions So I recently bought a T-Rex 800E DFC. This is my first time building a helicopter, so far I've had only BTF and RTF models. Getting the mechanical parts together was fairly easy, but now I'm stuck at the electronics (looks like this time I got a WTF model ). I do have an idea how the stuff generally works, but there are some details that are confusing me. What I have is: Futaba T10J radio, Futaba R3008SB receiver, Futaba CGY750 flybarless control gyro, Phoenix Edge HV160 2x 6s 5000 mAh LiPo 1x 2s 2200 mAh LiPo (receiver battery) Connecting the batteries to the ESC is simple, I just need an EC5 connector for the ESC and an EC5 battery series harness. Connecting the motor also is a no-brainer although the cable colors of the ESC and the motor don't match. I'll see which way the motor turns and adjust as necessary. I have also connected the receiver with the CGY750 via the S.Bus cable. Now, I understand that the ESC needs to be connected to the "TH/E2" connector of the CGY750, but unlike the S.Bus connectors, this one is not coded AND the cable colors differ from the S.Bus cable. Looking at the orientation of the servo connectors (luckily their colors match with the S-Bus cable) I would assume that the correct orientation of the ESC connector should be orange/red/brown (top to bottom). Can anyone confirm this? I couldn't find any information about the pin assignment. My next question is: how does the CGY750 get powered? From the little information I found in the manuals, it appears that I'm supposed to connect the receiver battery to the #7 connector on the receiver which will in turn provide power to the CGY750 via the S.Bus cable. Is that right? And is there any good reason why I should use the "Extra voltage" input on the receiver? And yet another question: can I simply connect the receiver battery to the receiver or do I have to use a regulator? I believe the receiver, the CGY750 and the stock servos (3x BL800H for cyclic control and 1x BL850H for the "rudder") should all be able to handle the voltage coming from a 2s LiPo. Another thing that is still a mystery to me is the governor mode. I understand that it keeps the rotor rpm constant at up to three selectable speeds. So far, so good. But which unit actually controls the speed? In order to keep the rotor speed constant, we first need to know what the rotor speed is. But there is no rpm sensor. The only way of knowing is to either install one OR to know what the main gear/pinion size are and calculate the corresponding motor speed which should be known to the ESC. BTW, if someone could enlighten me what kind of motor the 850MX actually is that would be great. Looking at the cables it seems that it's a synchronous motor. I read all the fancy marketing blahblah, but there is never a technical description of the underlying principle. Anyhow, I'm assuming that the ESC provides feedback about the motor speed to the CGY750 which then adjusts the power as necessary. The remote doesn't actually select the rotor speed but selects the presets stored in the CGY750, is that right? Sorry if this is obvious to everyone here, but I've never actually built a helicopter and the information I have found on the internet hasn't always been helpful. It would be great if someone could shed some light on my noob questions.

04-04-2015, 11:52 AM	#2 (permalink)
Heli biggie Registered Users My HF Map location Join Date: Jul 2011	I was where you are a year ago. It will be all good. I cant answer all your questions because I use dx8 spectrum 2 satellite setup. But I do know it is a good idea to use both power inputs on your gyro or rx to have a back up. With this big bird you can just run straight 2s lipo to you rx or gyro. These servos can take it. About the gov feature. You will need to get a castle link to hook up your ESC to pc and setup everything. You may have got coupon with esc. You will have to enter pole counts and main gear teeth count into castle calculator. Then pick rpms. It's a learning curve but with the help of the awesome people here and video on YouTube I'm loving my 800. You really learn a lot when you build it yourSelf. Then if you do everything correct it actually flys. I hope this gets you started. __________________ TREX 800 DFC PRO HV , TREXIKON 600 EFL PRO , LEAP 3D QUADCOPTER

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04-06-2015, 07:53 PM	#3 (permalink)
Dark Helmet Registered Users Thread Starter My HF Map location Join Date: Jan 2015	Thanks for the response. I wasn't aware that ESCs can do so much more than just run a motor. You are right, there was a coupon in the box. I ordered the USB adapter now. The Castle link software runs even without the USB adapter which helped me understand what else the ESC can do.

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