ZMR250¶
While building up my first multirotor (a DJI F450) I learned a lot about quadcopters. I was making a list of the various components and was planning on buying all the parts individually when a ZMR250 came up for sale from an aquantence from the local FPV community. I jumped at the chance to grab it; it was just the kind of vehicle that I needed as a total FPV noob. It was also significantly built up already. I just needed to get batteries, a FPV camera and a video transmitter.
The flight controller is a Naze32 Rev5 clone flashed with the latest Cleanflight firmware. The ESC’s are Afro 12A flashed with BLHeli firmware. The motors are Dys BE1806-2300KV with Gemfan 5030 propellors.
The ZMR uses an X configuration and when combined with the Naze32 software the motor numbering is as follows:
4 2
\ /
X
/ \
3 1
| Motor | Direction |
|---|---|
| 1 | CW |
| 2 | CCW |
| 3 | CCW |
| 4 | CW |
Adjust sub-trim in Transmitter so that Roll, Pitch and Yaw are centered around 1500.
Reverse Aileron and Rudder in Transmitter so that right on transmitter moves the channel slider right.
I had a problem arming motors with the initial configuration. This was because the lowest that the trottle would go was still above the lowest motor value configured in the Cleanflight config app.
I used sub-trim on the throttle to bring the lowest value under the value set in the Cleanflight config app (i.e. to about 1030 which is below the 1060) minimum set in Cleanflight.
Arm: min throttle and yaw right. Disarm: min throttle and yaw left.
Receiver¶
I am using a S603 Receiver
Video Transmitter¶
I am using the ImmersionRC 5.8GHz 200mW Video Transmitter.
FPV Goggles¶
I am using the FatShark Attitude V3 FPV Goggles.
Problems¶
This quad was really problematic. After lots of investigation I finally determined that the cause was the 5V BEC unit soldered to the ZMR V2 PDB.
After some period of normal (beginner) flight time the quad would keel over as if the motor 1 had stopped. At the time I thought there was something wrong with the quad but I was also pretty new to flying them so it might have just been my noob skillz.
This resulted in two 2 Naze32 boards were destroyed. It was a weird problem. After the crashes the Flight Controller board would not power up at all. Then by the time I walked home to investigate further it would power up.
However, while I could arm and disarm the quad, the throttle would not work. Also, when I tried to plug it into Cleanflight I found that the USB interface was not functional. This exact same sequence happended to two Naze32’s.
While flying Line of sight with a third Naze32 I observed it keel over and fall to the ground again. This time the flight controller was never able to be powered up even after waiting a while. However this board could still communicate with Cleanflight when I plugged it in.
Pulling the quad apart I finally found that the 5V BEC was not functioning anymore. Perhaps it was getting hot after a length of flight. Perhaps it was just flaky right from the start. At this point I am assuming that as it was degrading it probably fed 12V to the 5V output intermittantly, which consequently damaged the first two flight controllers.
I am going to replace the integrated PDB with a very simple stackable unit.
Rebuild¶
I sourced a stackable PDB from a fellow quad flyer and commenced the rebuild. It took a solid weekend. The motor connections to the ESC’s remained the same but everything from the other side of the ESC needed to be re-wired.
Once the rebuild was complete I attempted to connect it to Cleanflight but could not for some reason. I assumed that maybe there was nothing loaded on the Naze32 by default so I attempted to flash a new version of betaflight
I went to the Silabs.com site the to their Interface and Drivers page to find the CP21XX driver package for OSX. This was called CP210x USB to UART Bridge Drivers. Silicon Labs >> Products >> MCUs >> USB to UART Bridge VCP Drivers. Once I had updated the driver I was able to successfully flash the Naze with both Cleanflight and Betaflight. I left the Naze with Betaflight.
Use transmitter sub-trim to adjust mid-point of roll, pitch and yaw to around 1500. Then use travel adjust to attempt to get range from 1000 to 2000. Typically I can get it to about 1030 - 2000.
For some reason I was having trouble disarming. This was because I could only get the yaw down to about 1055 but the min_check was set to 1040.
To fix this I used the CLI to set the following:
set min_check = 1065
I originally had wired the power input for the video transmitter to the 12V BEC output. However, the power demands from the video transmitter must have been to much for the BEC to handle. Without the video transmitter connected the 12V output was just over 12V but when I connected the vide transitter it went down to 5V. I’m guessing that the video transmitter draws a lot of current that in turn drops the voltage.
I have since connected the video transmitter directly to the battery power input on the power distribution board.
After a crash I broke one of the arms on the ZMR. After replacing the arm I found that the motor on that arm no longer worked. I first spent some time replacing the ESC thinking that the problem was in the ESC but after swapping in a good ESC the motor still would not spin properly. I’m guessing that one of the phases on the motor was burnt out.
I didn’t have a spare 1806 2300KV so I order some DYS 2205 2100 thinking that they should be fine on the ZMR. I’ll replace the Afro 12A ESC’s with FVT 20A eventually.
After fixing all these problems the ZMR still intermittently keels over just like it used to before. I’ve got new motors, new flight controller, new power distribution board which leaves just the ESC as the culprit. I am guessing that they fail when they get hot. It is very hard to replicate.