Reduce steering when AP not active

[It Paradyske]

I know it doesn't work without IMU, I hope it will be delivered soon... :-)
In the mean time I am trying to get it up and running as far as possible.
I connected a Nokia 5110 LCD on the spi interface, the LCD is hardly readable due to a bad connection by the way, so I ordered an other one.
The actuator is an old Raymarine ST2000+, the compass of the thing is defect so I was able to purchase it for little money.
It is driven by an H-bridge, with IRF540/9540, and a couple of transistors (bc547 and bc557), I designed myself.
I use an arduino red board (equal to uno, still waiting for the nano to come in) with your code to drive the H-bridge, the only modification I made was the polarity of the driving pins to the H-bridge. To activate a MOSFET in the bridge, a positive signal is needed.

Could you please post your source code changes or make a pull request?

The irf540 and 9540 has high on resistance.  These may work for a few amps but are still less efficient.

The mosfets I am using are 1-2 milliohm, all n channel giving less than 1% losses in the mosfets at 12 volts 10 amps.

RDS on is indeed a bit high, 117 mOhm and 44mOhm (I must admit I only saw the 44mOhm when I selected them)
150 mOhm on 10A gives 15W dissipation ...
I use a ST1000+ currently I have limited the current to 5 A.

I didn't know you were pulsing the MOSFETs, I expected a static steering voltage, so the H bridge would be activated continuously when the motor has to turn.
What driver are you using for the MOSFETs? One that shifts the power up, to be able to use N-channels for high and low?


My code for the Arduino:


// run at 4mhz instead of 16mhz to save power,
// and to be able to measure lower current from the shunt
#define DIV_CLOCK

//#define HIGH_CURRENT   // high current uses 300uohm resistor and 50x amplifier
//#define HIGH_CURRENT_OLD   // high current uses 500uohm resistor and 50x amplifier
// otherwise using shunt without amplification

#define rc_pwm_pin 6 // todo: use this pin to detect rc pwm
#define RC_PWM  // remote control style servo

#ifndef RC_PWM
// for direct mosfet mode, define how to turn on/off mosfets
// do not use digitalWrite!
#define a_top_on  PORTB |= _BV(PB1)
#define a_top_off PORTB &= ~_BV(PB1)
#define a_bottom_on PORTD |= _BV(PD2)
#define a_bottom_off PORTD &= ~_BV(PD2)
#define b_top_on  PORTB |= _BV(PB2)
#define b_top_off PORTB &= ~_BV(PB2)
#define b_bottom_on PORTD |= _BV(PD3)
#define b_bottom_off PORTD &= ~_BV(PD3)

Yes I mixed up the outputs a little bit, and changed the levels.

And I use a lower PWM frequency:
#ifdef DIV_CLOCK
    ICR1=4000;  //fPWM=1khz
#else
    ICR1=16000;  //fPWM=1khz
#endif

I'm not so familiar with creating pull requests, so I have to study on that.


Could you please explain how I make my changes persistent?

regards
Hans