An inexpensive current limiter for flashing and initial testing of ESCs – Mk II

There is a risk of damage when flashing ESCs. It accrues from the fact that ESCs have a three-legged H bridge and if a high and low FET are turned on simultaneously, damaging currents may flow. In fact, this can be an issue if the FETs are on together for just microseconds on each PWM cycle. Loading the wrong hex module is a recipe for disaster, it may turn on FETs in an unexpected way.

So, for safety, the ESC should be powered from a current limited power supply during flashing and initial motor testing.

In a process of continuing development, this article describes a variation on the inexpensive current limiter for flashing and initial testing of ESCs – Mk I.

Continue reading An inexpensive current limiter for flashing and initial testing of ESCs – Mk II

BLHeli v11.0 on APM X450 quad

I had some Skywalker 40A with BLHeli v11 spare from the tricopter project, so I have put them on the APM X450 quad for a trial.

SW-prog

The BLHeli beacon is really annoying, so I turned it off. Otherwise it is a pretty basic Multi BLHeli configuration.

The ESCs were throttle calibrated using APM’s all at once procedure… but it didn’t work as expected, the motors remained stopped when armed. A lot of fiddling around to find some parameter changes did not work until power was cycled. Set MOT_SPIN_ARMED=200, THR_MIN=220.

Initial tests in stable, alt hold and loiter modes have been good.

 

Tricopter build – 20140204

The 1245SF props arrived and replacement HK922 servo, both were fitted.

The tricopter is very hard to fly with 1245SF despite lots of time tuning pitch and roll, and level PID parameters. It appears that the propellers are just too much and that control loop stability is hard to achieve at lower motor speed.

So, the 1145 propellers were refitted and fine tuning of the saved PID parameters commenced.

The replacement servo works fine, stable stand alone with and without load, and mechanically smooth through its entire range (no sign of any stiff spots in the gears as in the previous one).

The project is coming to an end, the tail mechanism is an obvious vulnerability in this implementation though it seems to work quite well… more in the final report.

SimonK ESC FW – test of commit 8873df24 – #3

F330-01

SimonK commit 8873df24: (20140119) with COMP_PWM was loaded on the F-30A ESCs on this F330 quad with Multiwii 2.3 FC, 3S, Hobbyking┬áD2830-11 motors and 8×4.5 SF propellers.

Performed rapid acceleration under WOT, motor idle, recovery, maneuvers and no issues, no hint of sync problems, works fine.

SimonK ESC FW – test of commit 8873df24 – #2

X450

SimonK commit 8873df24: (20140119) with COMP_PWM was loaded on the F-30A ESCs on this X450 quad with APM FC, 3S, Hobbyking D3530-14 motors and 11×4.5 SF propellers.

Performed rapid acceleration under WOT, motor idle, recovery, maneuvers and no issues, no hint of sync problems, works fine.

Tricopter build – 20140201

Tests on the tricopter using a data logger to capture motor speed, current and pack voltage gives an insight into platform operation.

CropEagle005

Above, data capture from the tricopter on 3S. The datalogger adds 50g mass.

The plot shows the device hovering at about 5000rpm and 10.8A at 11V. Two WOT ascents were made to check acceleration and motor recovery during closed throttle descents. From idle, it takes about 500ms to accelerate to hover rpm. This test was repeated and the motor reliably restarted every time and the tumbling craft stabilised quickly. A set of 12×4.7SF props has been ordered to try at 3S to more fully load the motors.

Similar tests were conducted also on 4S, and peak current on WOT was 80A on 15.5V for 8500rpm. Operation on 4S would provide sufficient lift to carry a camera payload, but WOT operation exceeds the motor’s continuous current rating.

 

 

An inexpensive current limiter for flashing and initial testing of ESCs – Mk I

There is a risk of damage when flashing ESCs. It accrues from the fact that ESCs have a three legged H bridge and if a high and low FET are turned on simultaneously, damaging currents may flow. In fact, this can be an issue if the FETs are on together for just microseconds on each PWM cycle. Loading the wrong hex module is a recipe for disaster, it may turn on FETs in an unexpected way.

Continue reading An inexpensive current limiter for flashing and initial testing of ESCs – Mk I