Thursday, January 15, 2015

Nova Rebuild - APM Internal Component Placement (Winter 2015)

Methodically going thru aircraft to try to cure WobbleOfDeath. Here are some pics of my work. I think this series of posts will also be a good example of setting up a Nova/CX20 from scratch.

Removed everything from PowerBoard plate and cleaned away old foam-tape.

Since the FC boards are not actually screwed down inside white plastic case, there is some movement. I'm not sure, but I think the PCBs (and attached sensors) can vibrate inside case. I added 2 small pieces of gyro (single-sided and plush) foam-tape to inside of case bottom (not on top where barometer-foam piece is). Seems to work fine.
Zeal gel-tape is highly recommended to mount FC and isolate it from aircraft vibrations. It's not that costly when you consider how far it goes. It seems that while the cheaper alternative "plush gyro mounting tape" also isolates FC from vibrations, it allows the FC to micro-rock-and-sway, which ends up making it an inferior solution ... the Zeal is confirmed to be much better suited for this task. I used 4 cubed 11mm x 11mm pieces as recommended (one in each corner).

FC is again perpendicular to front of aircraft, but now mounted with gyro in exact middle of aircraft (distance between motor shafts). I am mounting in the Default Flight-Controller Orientation (aka AHRS_ORIENTATION,0 ). The RX radio now (foam taped) on it's side, in only other place it will fit.


 Accelerometer/Gyro chip (on top PCB, inside FC) should be right under edge of red "O" in NOVA label, specifically market by dot on nylon tie-strap. Another way to measure is ... between Pins 2 & 3, and just past the middle (going in other direction).  

Final placement. Nothing touches each other or any Power-Board component. Everything is loosely tied-down to deter any un-wanted vibrations. Power-Board layout and USB cable further limit possible GPS-Module locations. Specially-cut a gray hard-foam piece to extend platform for GPS-Module, and wedged and foam-tapped in place level. No more RX antenna on outside but one is close to it's old location (but now inside and on opposite side). Near front area is left for FC-RX wiring, and any future upgrades like maybe a SBUS-CPPM converter. Re-mounted 915mhz Telemetry radio back underneath quad where it was before.

Re-mounted Compass/ Magnetometer in a new way with black foam tape and nylon tie-strap (but no hot-glue). Minimum metal screws, and use non-magnetic screw-driver. Simple is good. Red wire is Positive (VCC +3.0v - 3.3v) and Black is GND - verified with meter.

Flight Controller and Radio Wiring

Still using connection method #2 from HobbyKing PnF Setup Video (fairly standard but connecting "Signal Only" as allowed by bridged power rails).

RC Cable 1CH-1 VerticalCH-1 Vertical
RC Cable 2CH 2-4 Horizontal (signals only)CH 2-4 Horizontal (signals only)
RC Cable 3CH 5-7 Horizontal (signals only)CH 5-7 (FC Aux 1-3) Horiz
A-JumperCH 8CH 8 (FC Aux 4)

  • Power from 5v-BEC (on PDB) goes to RX first, and then to Flight Controller. FC really gets its 5volts from CH-1 (3-wire RC-DuPont) cable.
  • Vertical connections are the standard way, with standard RC-Cable radio plug (Gnd, Power, and Signal).
  • I used "black to the right" when plugging in horizontal "servo-like" RC Cables.
  • A-Jumper is a standard (single-pin) 3inch Arduino Jumper cable
  • While Channel-Signal-Rail is on FC bottom, it's on X8R's top (opposite).
  • By using previously unused SBUS socket for power, frees a standard channel. It shares the same power-rails.
  • At this point, I can't even see a reason to need BEC-5v routed to quad's under-carriage connection panel. If need arises in the future, I can just use a RC Y-cable.
  • This simple wiring works fine again (for now). When and if I get my gimbal, I will switch over to a FrSky SBUS-to-CPPM Converter wiring setup.
Good pic that someone made.
The white boxes are where you connect Dupont (servo like) RC-Cables. Mine is mostly like this pic. Only difference is that I went ahead and connected CH-6 also to RX (in case needed later). Red VCC and Black GND drawn boxes are just informational.

Another good pic someone drew
This is post 1 of 3 for the rebuild. See next post for APM and radio setup and programming.


  1. Hi, great page, I have the same problems, and even tought I don't have the same knowledge you hage(it's is my first quad) I will try to redo your work and cross my fingers to get the same results. I wonder if I can make you some question?

  2. Thanks for publishing this. It has helped to clarify my lack of understanding.
    I have the gimbal so want to connect that. I believe that power is provided to the S1 and S2 from the PCB. I guess I can snip the wires that are on pins 6 and 7 of the FC and connect S1 and S2 so they are going into the Rx.

    1. You are welcome. I'm still waiting on my gimbal so I haven't examined it real close myself yet. (double-check yourself and with meter) . If you are talking about the ports on bottom of quad ... I think the 12v ones are hard-wired to battery while the 5v ones have Dupont plugs (that can be connected to RX or FC as needed. You can also Dremel a small hole and run your own.

  3. I really hope you can help me. I'm at donation time. lol I've about had it with this thing. Long story short, I had a BIG crash. Got it all back together the way I thought it should be with two new ESCs and two new motors, but kept getting acceleromenter and gyro errors and compass and GPS errors as well. I assumed the crash ruined them. I ordered a new neo M8 gps and the wiring was all weird, found the comments from users on Banggood and they had a pic of of how it was supposed to be wired for the CX 20. NOPE. Wiring turned out to be right for APM 2.6 but not the CX20 which appears to have the grounds all opposite of where they are on the APM 2.6
    So I have the good GPS and the old good compass and separate slots for them for the APM 2.6 so I figured that would work. SO I put it all together with the new APM 2.6 and got nothing but consistent beeping when I put it on battery. Plugged just into USB, all seemed to work fine I was able to calibrate the compass and transmitter but the motor test would fail.
    Well, come to find out...this FC doesn't have marking on it for which is the ground, signal, and power so I had it wired like the cheerson...upside down. No telling what I screwed up. Then I read that the old hookup worked by channeling the 3 pin molex from the board to the RX and then the RX powered the FC. SO I took the power module out, hooked it up as the cheerson originally was, and immediately the RX and FX smoked. SO they're screwed. Ordered a new FC tonight and a new RX.
    WHat I don't know is if there is a way to test these ESCs before I get the new RX and FC. I'd hate to have something wrong with them now and have them screw up yet another FC and RX. Also, I'm still trying to figure out how the CX-20 actually got its power to the FC. If that 3 pin from the back of the board didn't go to the B slot in the FC and power though to the FC, then I have to assume the power comes TO the RX from the FX. But how? And where does the damned 3 pin go?
    I'm about to chuck the whole thing off a bridge as I drive across with the top down but I'm too stubborn to let it go. I HAVE to not only fix it, but understand what went wrong. I've poured about 20-30 hours into reading online and I find so much contradictory information it's making me crazy. Your site seems to be the most accurate so I'm hoping you can help. Heading to make a donation now in advance.... :-)

    1. So, what exact components are you going to try to connect together this time?
      Are you going to use Cheerson PowerDistributionBoard or generic APM PowerModule for 5volt power?
      Do you have a voltmeter and know how to use it? You always check power before connecting. If +5 and GND aren't correct on final connect, something will fry and the magic smoke escapes.
      FC gets it's 5volt power from RX (as shown above).
      If you want to post pics as you go, we might have to move this to RCGroups.
      and if still using stock radio

  4. Well, next time around it will be a new APM 2.6 that's already on order, and I'm looking to see if I can find an RX that's compatibly with my TX so I don't have to buy another of those as well. I'd like to use CPPM if possible. I plan to power it with my PowerModule. I took it out of the loop to eliminate a possible point of failure that may have caused the endless beeping from the ESCs.

    I do have a good voltmeter and know how to use it......but I don't know what I'm looking for. I don't know what voltages should be where. I was really thrown of by the ESCs having red wires that fed back into the outputs of the original controller because it seemed to me that since that was on the output side, it would have been voltage going from the FC to the ESCs. But then I see the ESCs getting power from the board and the red wires were clipped from the factory. Then I read elsewhere that those were power coming OUT of the ESCs which made no sense to me if they were going to the output side of the FC.

    What I REALLY should have done is taken it apart before flying it, took pics, measurements, meter readings, and figured out how it worked while it was in working condition. But I just didn't expect this to be a project. I just expected to fly it.

    Which is fine of course. But now I'm putting a puzzle back together without a picture of what it's supposed to look like and then supplemented with the occasional person that says "it's a picture of a cat" when it's really a mountain scene.

    So I need to order a new RX. Do you know of an upgraded one that is compatible with the native TX I can get in the states that won't take 10 weeks to ship from China?

    Also, do you know of a way to test the ESCs without a receiver? I tried putting a 3.7 volt battery on the + and - terminals but that probably wasn't enough voltage and I didn't want to create more magic smoke. I Have no idea what the hell to put on the signal wire to make them spin. So I'm stumped. I did some of this robot building back in 1988 in my electronics class but it's been so long and things are much more complex and I've found a new hobby with a lot to learn that's just as complex as photography and designing wide area networks. lol

    Moving it to post pics sounds fun. I'll be taking care of your coffee for a while I think.

    1. Yes, remove the PM and try to get make it as stock as possible.

      Connect LiPo battery and see if you have +5v volts at BEC on PDB

      New ESCs must be connected to PDB like the old ones. Beware, newer revision Cheerson ESCs might have the the 3 heavy gauge input wires in a different orientation, but as long as you note that, you can reported-ly, mix different revision ESCs.

      Best way to test ESC's is with APM FC. It's normal for ESC/Motors to pulse and beep if they are not getting a (digital control) PMW signal from APM-FC.

      Only a stock RX will work with stock-white transmitter. You can get one at BangGood (CX-20) or HobbyKing (Nova).

    2. Typo correction: Best way to test ESC's is with APM FC. It's normal for ESC/Motors to pulse and beep if they are not getting a (digital control) PWM signal from APM-FC.

    3. I did hook it all back up stock and other than my RX starting to stink after being fried last night, it sounded perfectly normal beep beep beep beep........b -b- beeeep" But then the smoke came before I could test at the BEC. So I disconnected it fearing some kind of fire. I'm sure testing at the BEC is pointless if the FC doesn't have power, right? Power comes right off the PDB onto the ESCs, but I'm assuming that with the wires running back ti the FC, they won't be functioning properly if the FC doesnt work. I am right in assuming that the red wire coming off the ESC that is cut is the BEC, right?

    4. No reason for RX to fry if BEC outputting +5 volts and connected properly. I added some "stock radio" notes to this page for you:
      BEC is on PowerBoard ... not ESCs. ESC do not have BECs. LEDs get their voltage and control from PDB. Read carefully, don't quickly scan.
      Yes, ESCs need FC for control.
      No, cut red wire is just because PWM is only 2 wires ... signal and ground.

  5. do these things have fuses built onto the boards?

  6. Also, if you have any idea where I can get this receiver in the US and get it here in a few days instead of weeks, I would appreciate it.

    1. Check BuddyRC or HobbyQuad (both good companies). Maybe Amazon or Ebay vendor. Are you sure neither HK or BG ship from USA warehouse?

  7. Nobody had one that could get it to me in a reasonable timeframe. So I ended up buying an actual APM 2.6 FC, a new receiver and transmitter pair with CPPM, and a new neo M8N GPS. But the new GPS came in DOA. I'm starting to think that maybe I was never meant to have one of these that actually flies. lol

  8. Hello,

    Can I control AUX1 or AUX2 with the FC via Mission planner?
    I want to operate a single Servo within a waypoint mission.
    Thx and BR


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