Cheerson CX20 testing and modding

Our long term testing of the CX20 continues.

This entry, we have had some very good flights.... and one scary moment. The CX20 is very responsive. Many have found that gently taking off can often lead to a 'tip over'. Most suggest giving it a leap into the sky and throttling back to where you want. This sounds far more dramatic than it really is. That being said, if you pay attention, you can readily take off gently, just pay attention if it starts leaning.
Flying the CX 20 in the different modes is interesting, The 'headless' mode (it will go away from you or directly to you. Based on where the motors were armed. regardless of which way it is pointing). It can be easier, but if you are trying to fly by what way it's pointing, you can get messed up. Altitude hold means it will try and keep the same altitude while you fly whatever direction you like. I tried hover which is a position lock, It is supposed to stay exactly where it was when you engaged that mode. If you are moving or not completely still, it can go awry.
Just to see how responsive the CX 20 is, I got it in a comfy hover, then slammed the throttle to full. It rocketed straight up at an astounding rate.
We have also started testing flight times.
With the stock battery (2700Mah), and no accessories attached, Flight time was a solid 15 minutes.
With the 3200Mah battery, we measured a 17 and half minute flight.

With the SJ4000 Camera attached using the fixed base, we only lost 3 minutes of flight time off of each battery. That's not bad. It still rockets upward when told to but slightly slower. When we use the gimbal mount, it should give us a good idea what you can expect.

When choosing a gimbal, weight is a huge factor. These craft literally hang on the propellers. More weight cuts into handling and endurance far more quickly than on a fixed wing aircraft. And when the battery gets low LAND, don't push for that extra minute of flight time of you are just setting yourself up for some repairs at the very least. One Youtube video showed a pilot with hiw quad up about 80 metres (around 250 feet). He kept flying and flying after the low battery warning came on. Finally it just dropped like a stone. The damage looked like a complete write off. 


As we add accessories, flight times will continue to be checked to compare how much these items affect duration. 




NOTE: there is a big update to this. Skip to the end of this article to see details.

Of the accessories we are adding, a 433Mhz telemetry module is the first added. Most people run the wires through one of the holes in the hull and attach the telemetry transmitter to the outside of the craft. We opted for an internal mount. It looks cleaner and compared to the usual external mount, it's not harder to do.



First off. look at the space inside. To help minimize the chance of interference with the radio control, the opposite side from the antennas was chosen. You can see how small the transmitter is on the desk to the right.

 

There is plenty of space here and it does not interfere with any of the electronics. 

Triple check, the antenna is in a good place and doesn't interfere with the landing skid.

The size of the antenna base is carefully measured.  15/64th of an inch makes for a tight fit. Drill the hole from the inside to out. That way when the bit penetrates,  it will not damage internal components.

The location works great. The antenna is oriented to swing back. A bit of hot glue around the transmitter inside gives a little more strength. Probably not needed but a little strength isn't a bad thing if it doesn't add much weight.

Now it's time to get to the surgical part of this exercise. Snip the Zip tie that secures the cap of the FC.

The lid snaps off with little effort. Don't lose the foam underneath. It moderates the air to the barometer/altimeter.

To avoid removing (and possibly mis locating) the wires into the FC, a clamp holds the circuit board at a better angle to work on it.

for this part, you have to make sure you are connecting the correct wires to the right points on the board. This is some delicate soldering. If you don't have the skills or the right tools, it's worth it to find and pay someone who is good with this fine work.

put the board back to the position it was in before. Make sure the foam is covering the barometer again before you close the case. I used side cutters to nibble off a small section of the case right below where the USB connecter plugs in to allow for the wires.

I bared a section of the output signal wire and spliced in an extra wire (white) for later. Don't forget to put a new Zapstrap on the case for the FC.

Everything looks neat and in place.

The antenna fits perfectly and doesn't get in the way.
Close her up and you are set.

STOP THE PRESSES !!!!!!

There are several series of the CX20 (And Quantum Nova), and many of them use slightly different hardware. Getting the telemetry to work on our testbed didn't work, (there have been a few things that stubbornly defied us) but Jordan Worley in one of the Quadcopter groups on Facebook dug in deep and got to the heart of the matter. There have been a few well intentioned articles on getting telemetry installed on the CX20/Quantum Nova series and he uncovered some things that explain a lot. Many of the previous articles are incorrect or incomplete. Here is his revised version that is making it work for people 

Telemetry mod

And if you haven't joined already, this Facebook group is a great and fun loving bunch that freely share knowledge and tips to grow this hobby.
Facebook Link








Do you remember that white wire We spliced in?
In an upcoming entry we will be adding 2 video systems. One will be a gimbal mounted camera and that will stream video to our groundstation. Our setup will be a laptop computer. The Telemetry transmitter sends it's signal to a USB receiver so that it can display the information (if desired) on any video transmitted and recorded.
A second, lightweight fixed FPV camera will be mounted and the white wire will give the same data to the flight display.
When doing camera work, the operator can get disoriented with the camera tilting and moving. The fixed camera makes sure you have a fixed point or reference while angling the filming camera.