Quad Build Group
The Introductory session
Maker's Asylum arranged an introductory session for the Maker community to understand what a drone is, what it can do, what components go into it and how it is constructed.
The session was also aimed at getting members interested to participate in the Build group that starts next Saturday.
Rupin went over the details of each component in detail, these were:
Motors, ESC's, Battery, Frame, Radio controls, Propellers and their types
The community was pretty interested and started to pitch ideas and contributions towards the build.
Collaboratively, the group started to set goals for the build. These were:
- Minimum 20 minute flying time
- Ability to generate a total lifting strength of upto 3 kg, including the drone weight.
- Be possible to do GPS waypoint navigation, and have the ability to be available as a platform for the build contributors to experiment.
In the middle of the week 1, mechanical parts were ordered for the drone. These included:
- Frame from eBay.
- Motors (935KV EMax Motors)
- 30A Simonk ESC's
- 2200mAh 20C 3S1P Li-poly battery
All the associated hardware like nuts, connectors etc. came bundled with the respective parts. Parts arrived on Friday.
Build Group Day 1
It was decided to meet at 2PM on a Saturday and start building the mechanical parts of the drone, calibrate the motors, and do a speed test on all four motors.
Rupin explained the parts to the participants, and guided them to start building the frame. We had handy instructions on how to assemble the frame, so this was a moderately difficult task. Participants learnt what an allen bolt and screw is ( as opposed to a philips screw), learnt about how to figure out over tightened vs adequately tightened nuts.
The team also installed the landing gear making a mechanically stable quad frame.
Once the frame was built, we started of to mount the motors to the frame. Each participant started to mount the motor, and with a few minutes the motors were mounted.
The 3.5mm gold bullet connectors were next in line to be soldered on the ESC terminals. Participants used the two iron's available at the Asylum to solder those. They were covered with heat shrink to prevent accidental shorting.
Once the terminals were ready, it was time for ESC calibration. ESC calibrations a process of telling the ESC what the range of throttle is for best performance.
The process is (without props attached)
- Connect the ESC to the throttle terminals on the radio RX, with throttle at max position on the Tx
- Wait for first two beeps from the motor
- Immediately move the stick to a min position, and wait for confirmation tones. (3 beeps)
- The ESC has been calibrated Provide a slight input to the throttle to spin the motor and verify there is no deadband.
Once all four ESC's were calibrated, it was time to call it a day.
Electronics for the quad were ordered. this included
- APM 2.6 flight controller board
- 433 Mhz Telemetry Radio set
- APM Power module
- Servo connectors
- Neo GPS Module and Compass set
Parts arrived in time for the Build Group Day 2.
Build Group Day 2
This was an electronics assembly day. Since this was the last step, we asked the build group participants to arrive at 11:30 AM, just so that we have sufficient light by the time we were ready to test a flight.
A quick 15 minute session about all the parts was conducted so everyone was at speed. Downloads of the APM Mission Planner also was initiated.
Once APM Mission Planner was installed, we started to configure the board using the APM planner wizard. These were the steps we followed
- Configure frame type. Ours was a quad with a X configuration
- Configure Compass. This involves moving the board in a random orientation and the software logs compass values from the APM board. We capture 1000 samples, and was sufficient to capture the true orientation of the compass.
- Calibrating the Accelerometer and Gyro. The wizard asked to orient the board forward, left, right, front, back, down and up. We placed the board on a flat surface during these and calibrated the two sensors.
- Radio Callibration- This step is done with the radio RX connected to the board according to pin mappings between the APM and Radio Rx. Once connected, the radio was bound to the Tx and the control sticks were moved in all four orientations so that the APM firmware knew exactly the limits of each channel/stick.
- Aux Channel configuration- This is the 5th channel on the Tx, and controls what mode the quad is flying in. We set one of the positions as stabilize, because it is the safest mode to arm the quad to fly. The second was RTL (Return to Launch) and was a failsafe mode to switch to in the event the battery goes weak.
Once we had done the calibration, we placed the board, radios and all electronics safely on the quad. The APM board was mounted using double-sided 3M tape to dampen vibrations from the motors reaching the APM board.
Next was orienting the props. The APM website has clear instructions on what prop (CW or CCW) should be placed on what motor and this is in respect to the forward marked on the board. Members were now instructed that the quad poses a hazard because the props were mounted, and to be safely away from it, until the basics of arming, and flying were figured out. A loose wire could make the prop run in absence of any throttle input.
It was now time to fly! But, the quad wouldn't arm at all.
We connected the quad to the mission planner diagnostics and figured out the radio calibration was unsuccessful. We recalibrated the radio a couple more times but the quad would not arm and there was no error message on the APM console.
We then went back to basics and figure out that our arming sequence ( sequence of stick positions on Tx) was wrong, once we keyed in the quad flew.
We crashed a couple of times, before the battery ran out, and so we called it a day.