Wednesday, October 15, 2014

Nova ESC and body Repairs

Repaired (red led) ESC and it tests good. Saved some down time and $35. I am using (normal) leaded solder and have iron set to 360c.

Notice PWM signal from chip, thru resistor and then to top of board where it uses PCB Via to jump to other side.

I verified that the 5v trace (with usable solder-pad) is indeed not connected to anything else (notice a 5v component is intentionally not soldered in). All the Vias are the same size and very tiny. As other blog pics show ... the only PCB traces (on this side) that still carry the PWM signal is the PWM's Via's circle. So that it will accept solder, I used finger-nail buffing-pad to carefully buff-away the green paint from the Via circle pad AND a 2mm section on adjacent 5v trace. After fluxing this small area, created a solder bridge between the two. The tiny blob of solder pictured here (where "W" used to be) is covering the whole via top surface as well as the whole 5v trace cross-section. Checked work with ohm-meter.
So, now the previously un-used 5v pad becomes the PWM pad. Since we now have a solder-pad large and sturdy enough to handle a 26awg wire, soldered the PWM wire to it.
The "PWM detection for LowVoltageAlarm & LED control circuit" wire gets a proper connector (so whole ESC can be installed or removed without soldering). Soldered it to it's own pad further along this new hi-jacked trace. I suppose it should be noted that it was this short red hard-soldered wire (with no slack) that lead to the pad being ripped from the board in the first place.
The repaired version was tested in the quad with a battery and works fine.
Three strips of Plastruct (added in a second phase) 
A new frame/body/shell is about $40 (shipped) but currently Back-Ordered at HK. Repaired cracked styrene body with Plastruct Plastic Weld Solvent-Cement and then some thin strips of Plastruct (# 90739), were layered inside for reinforcement (on side-edges and middle). They also sell "dowel-shaped" pieces that might work. Over the years, I have gained experience with various glues and materials. I know that using the right glue for each material is important. The Plastruct Solvent "wicks-into cracks" and melts the plastic back together. It the end, the cracked pieces (and any reinforcement pieces you add) all become very close to "one piece" again. I was impressed how well it worked.

Basic Testing
IIRC, you can test motors and ESCs via MissionPlanner option and/or Terminal without arming motors (or pre-arm checks). Be sure props are removed first.

Troubleshooting "All ESCs are beeping"
  • ESCs are getting main (hard-wired) run voltage from main LiPo battery, but ESCs can tell they have no PWM control (control signal that tells them to stay Off or stop, Arm motors and start them, speed-control, etc.)
    • Check in this order
    • This can be caused by no BEC (+5v) voltage being connected to RX radio (and therefore, also no power being passed to FlightController).
    • FC might not be getting power (usually via CH-1 Aileron connection) 
    • FC might be damaged or malfunctioning
      • FC might have a corrupted firmware and needs to be reset and Firmware re-loaded with MissionPlanner.
        • Followed by loading of Default params & complete calibration.

Trouble-Shooting visibly fried or damaged PowerBoard, Motors, or ESC after a crash or LiPo battery problem.
I've never had to do this, but I have wrote this procedure to help a forum member. I think it might come in handy in the future. Seems to fit on this post.
  • Unplug all ESCs and RX.
  • Connect LiPo and check PowerBoard for BEC +5
  • Check PowerBoard for +11v output at each corner (ESC Input motor-run voltage)
  • Connect one (non-fried) ESC
  • Connect one (non-fried) Motor
    • You can test the motor's 3 phases with a LCR or LC meter. It measures the inductance of the coil-sets. All 3 should be similar. The motor should not be connected to ESC or anything else during test.
  • Use MissionPlanner Motor Test and try to get this set working.
  • Keep testing at this location the rest of motors and/or ESCs.
    • Remember that testing a fried motor might destroy a previously good ESC and vice-versa. I would just write-off any obviously blown parts and try to check and/or save the rest.
ESC Replacement Notes:

I've never had to do it, but according to forum reports, different version ESCs can be mixed. Be warned that the orientation of the solder-pads is reversed on some models. If in doubt, use a meter to check volts and/or ohms before connecting. As I stated before, there doesn't appear to be a 5v generation circuit (aka +5_BEC) on these ESCs.

There are 3 heavy-gauge (thick) Power-Input wires:
Red - 12v +
Black - GND
White - 5v+ (for LEDs)

There are 2 thin PWM motor-control wires (black Dupont/RC-Type plug):
White - Signal
Black - GND

There are 3 wires for brushless motor connection:
Red, Black, and Yellow

The PWM signal only needs White (Signal) and Black (GND) wires ... for each ESC. If there is also a red wire in that set, it should not even be there. But, it seems that at the Cheerson plant, pre-made 3-wire Dupont cables (RC servo type) are plentiful. So if it is there, either heat-shrink it or leave it soldered down to the ESC with the other two (actually used) wires. If you trace the ESC's PWM red-wire solder pad, you will see it actually goes no-where. You can also just remove it (back-out pin, etc.) on each end.

The 5-volt power for the LEDs comes from the PowerBoard, but is only sent to the LEDs when the quad wants each of them to light up. If you think about it, it must be this way. Otherwise, you would have separate control lines going to each ESCs ... to control the LED lighting.

There is one other thin (usually red) wire, but only on the Forward-Port ESC. That is something different.

Motor Troubleshooting:

Haven't done much with Nova motors, so no dedicated page yet. Seems to fit here for now. You can easily open motors and check inside (glued-on magnets, etc). If you ever mounted motors with wrong screw (too long) windings are likely permanently damaged underneath (just takes a scratch). Electrically, they can be checked with LCR Meter (aka LC or Inductance Meter). A basic Volt/Ohm meter is usually not sensitive enough.
Stock Radio Notes:

Since I purchased a PnF Nova (without radio), I have never owned the stock white radio set transmitter or receiver (TX or RX). However, I know many of you visiting this Blog might have them, so here are some notes from the RCGroups forums.
Here is the basic wiring, showing where the Ground, Positive-5v, and Signal rails are located on RX. In a stock config, power comes from BEC on PDB to Battery (B) socket on RX. Then (since all the "power-rails" are connected) the power gets to FC through standard 3-wire Dupont (servo-like) cable connected to Aileron (A) channel.

Please note that (like any electronic machine or vehicle) through-out the whole aircraft ... proper power polarity must be followed (for all standard voltages ... like +5, +12, etc.). If any component's power is connected with reversed polarity, it will short-out when power is applied. It might destroy several components when the "magic smoke" escapes (as components fry and burn-up). If unsure of voltage or polarity of a "power supply point", check first with voltmeter before connecting. Verify plug and socket polarity (with docs or pics), and power requirements before connecting anything.
The stock white RX/TX radios work as a matched set. Only this Cheerson RX model will work with this TX model. It might be FlySky protocol (not to be confused with FrSky) but I don't know it's ever been proven. If you need a new one of either, you can get them at HobbyKing (for Nova) or BangGood (for CX-20) ... or if serious about hobby ... use a better, more hobby-grade radio.

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