Bunnygirl's : DesireRC Alexmos and RCTimer Gimbal

[bunnygirl80]

Hi guys,

Well DesireRC have amazed us again with this superb Alexmos board (manufactured in the UK under license). It can be used with a number of different gimbals, but for mine I';ve used the recommended $99 RCTimer gimbal.

http://www.rctimer.com/index.php?gOo=goods_details.dwt&goodsid=872&productname=

I must say I am very impressed! The entire installation exercise took 3 hours. There was no tuning, it truly is plug and play and the only reason you have to use the computer GUI program is to calibrate the device.

DesireRC have their own set of instructions which can be found here. But, here';s my attempt at some step by step instructions...

http://desirerc.co.uk/controllers.html

STEP 1 - Assemble your RCTimer Gimbal

The first thing to do is assemble your RCTimer gimbal and solder the wires to the motors. Don';t forget to put some thread lock on those little screws and you might want to swap out the little locking allen nuts (not sure of the size). As far as your motors are concerned, it doesn';t matter which wires go where. The standard wires that come with the gimbal will work, but DesireRC do have some of the proper cables on the accessories page of their website. Alternatively you can order some from eBay for a few pennies. For now, I';ve used the RCTimer ones and my new ones will arrive on Tuesday! 

http://www.ebay.co.uk/itm/Lipo-Balance-Lead-for-repairing-battery-packs-2s-JST-XH-male-2-cell-7-4V-22AWG-/230897695578?pt=UK_ToysGames_RadioControlled_JN&hash=item35c2933b5a

http://desirerc.co.uk/accessories.html

STEP 2 - Power Up your Alexmos to make sure its working

The next thing to do is to connect the wire between your IMU and the Alexmos board. Mine were already connected, but you can';t really go wrong with this. You should get a red, blue and green lights. As long as they all power on, you know your board is working and you can mount in your aircraft or rig. I used an old motor rig to make things easier!

STEP 3 - Attach the Alexmos to your MultiRotor frame

Attach your gimbal and your alexmos board to your frame and make sure your IMU board is level and mounted onto the gimbal, just above your GoPro. The larger Alexmos board can be mounted anywhere and in any orientation. There is a X and Y on the IMU. The Y needs to point forward and the X to the right as you look from behind. It is also important that your GoPro is in the gimbal as the weight is critical. I had to add 10g of counterbalance to the right of the gimbal to make it balance on the CG. I';ve also centered the lens of the gopro in line with the axis points of the gimbal. This gives for better performance.

STEP 4 - Get your Bluetooth working on your PC

Then power up your Alexmos without the motors connected. Then I went to my Windows 7 PC and turned Bluetooth on. You might need to get a bluetooth adaptor if your PC doesn';t support bluetooth. Then add new device from control panel bluetooth devices. You should be able to search and find your Alexmos board. Mine was found and bound to COM40. You need to remember this COM port.

STEP 5 - Download the GUI program to Calibrate the IMU

The next thing is to download the GUI program. You can get this from the http://desirerc.co.uk/down-load-files.html website. Make sure you have the latest Java installed otherwise it wont work.

Next thing to do is to launch the GUI program and connect to the COM40 port. Mine defaulted to the 15600 speed. Now make sure the quad and gimbal is level. Power on the Alexmos and press the connect button on the GUI in the first 10 seconds or so, before the Alexmos tries to correct itself. Then press the calibrate button on the Basic page.

STEP 6 - Tap yourself on your back for a job well done! TEST

That';s it job done. Now move the frame and you should see your alexmos correcting.

TROUBLESHOOTING

If it is not correcting then you probably have your motors wires the wrong way round, so simply flip the cable 180 degrees. Also, make sure you have the correct roll and pitch motors connected to the correct sockets.

When you power off your gimball it should stay level if you';ve balanced it properly! This also puts less strain on the motors and makes it work better.

NOTE: The board doesn';t fit on the rctimer standoffs, but you can buy loads of those plastic standoffs from maplins. Personally, I have positioned my board vertically onto a home made mount which im testing and seems to work well.

If the weather is good tomorrow, I will take out to test and make a movie.

http://youtu.be/1zzSvowcsuI

The gimbal is still wobbling a bit and I need to make it a little more sturdy. I also need to make a rear battery mount for the alexmos 500ma 3s battery.

[Balders]

nice guide Stef, good job.

[Tango21Delta]

Looking good, I found a cheap and easy way of taking most of the wobble out of the mount was to get some of the cheap yellow foam ear plugs from Screwfix, cut them in half with a craft knife, compress them and then insert them into  each of the hollow rubber anti vibration mounting balls. Once they reassert themselves inside the mounts they firm up the rubber and take up the slack.

[Riggsbie]

Good comprehensive guide....

Be good to see the results from a test flight, damn might have to get a Gimbal....

[Gaza07]

Nice job 

[bunnygirl80]

Looking good, I found a cheap and easy way of taking most of the wobble out of the mount was to get some of the cheap yellow foam ear plugs from Screwfix, cut them in half with a craft knife, compress them and then insert them into  each of the hollow rubber anti vibration mounting balls. Once they reassert themselves inside the mounts they firm up the rubber and take up the slack.

Hi TD,

Oh! Many thanks for that useful tip! I was a little worried about the firmness of those shocks and I';m sure your tip will work superbly. All I need to do now is get in touch with my friendly neighborhood fork lift truck driver! lol. I';ll try with and without so we have a comparative.

Thanxx.

[Rafter]

Brilliant guide Stef, wish you';d put this up before I spent hours grafting....

Those plugs you';ve ordered from Ebay, are they not 4 pin, as the motor sockets are 3 pin, or am I missing something else !!!?

Peter

[bunnygirl80]

Brilliant guide Stef, wish you';d put this up before I spent hours grafting....

Those plugs you';ve ordered from Ebay, are they not 4 pin, as the motor sockets are 3 pin, or am I missing something else !!!?

Peter

Hi Peter,

Yup, my cables arrived today and silly me assumed that DesireRC had used the same cable for the motors as the main power cable! Doh! So now I have another 2 day wait until I can change my servo cables to proper ones! LOL. Well spotted! 8 Gold Stars to you! )

Stef

[RS]

Hmm   it wobbles quite a lot..   
but those earplugs  might really help.
Otherwise I would mount  it without  those rubber shocks  and  see  if  there are  any vibrations.

P.S .  the gimbal in  this  video isnt perfectly leveled  I  think.
The IMU needs to be  re calibrated on a  perfectly level surface

Looking forward to see some  video :)

[bunnygirl80]

Hi RS,

Yes, that was the first power up with no proper calibration. Last night, I spent some time cutting up some earplugs and stuffing them into the little shock absorbers and everything is a little more rigid now. The AUW including the camera is 2.2KG which is really light, so plenty of room to improve. I';m also going to add some stand offs on the gimbal support frame to make it more rigid. Hopefully weather permitting I will be testing today.

Thxx.

[Rafter]

Over on FPVHub, Simon says there is an update. All the first boards had v.2.0b3.
I asked him for a step by step and he sent this via pm.

"OK - there appears to be a bit of an issue updating from the b3 firmware, it will not recognise the bluetooth connection (well actually it will not allow it to be torn down and then re-connected). We have discussed this with Alex in Russia at length and he also recognises the interface issue. We no longer have this problem with the latest v2.1 firmware.

The firmware that you have (as you have found) works really well, but IF you want to upgrade it then I';m afraid it';s going to be a pain for you to do, so you would need to return the board to me (just the board, not the IMU) and we will carry out the firmware upgrade for you - any further upgrades can be done by you.

I';m really sorry about this but I just can';t get the original firmware to allow the firmware interface via bluetooth (although everything else is fine - go figure eh)"

My original board is working OK and I don';t know what the upgrade does, but thought you might be interested.  I';ll ask him what the upgrade does and if it';s worth it.
Peter

[bunnygirl80]

Over on FPVHub, Simon says there is an update. All the first boards had v.2.0b3.
I asked him for a step by step and he sent this via pm.

"OK - there appears to be a bit of an issue updating from the b3 firmware, it will not recognise the bluetooth connection (well actually it will not allow it to be torn down and then re-connected). We have discussed this with Alex in Russia at length and he also recognises the interface issue. We no longer have this problem with the latest v2.1 firmware.

The firmware that you have (as you have found) works really well, but IF you want to upgrade it then I';m afraid it';s going to be a pain for you to do, so you would need to return the board to me (just the board, not the IMU) and we will carry out the firmware upgrade for you - any further upgrades can be done by you.

I';m really sorry about this but I just can';t get the original firmware to allow the firmware interface via bluetooth (although everything else is fine - go figure eh)"

My original board is working OK and I don';t know what the upgrade does, but thought you might be interested.  I';ll ask him what the upgrade does and if it';s worth it.
Peter

Hi Peter,

Yes, I have two of these boards and I spoke with Simon a few weeks ago. He said, use the boards all summer and send them back when the weather worsens and he can upgrade. I';ve spent a lot of time playing with both the alexmos';s I have and comparing results and I';ve learnt a lot about setup. Mine are both working lovely now and I';m not sure if there is anything major to be gained from the upgrade (maybe the ability to change profile by switch, but noy a must).

Thanks,

Stef