How to set pixhawk

MMMMK · September 26, 2018, 1:43pm

Hello,
I want use another type light to change the BR light to get more lumen,
The light controller is like this
It supports 0-5v control or PWM(which not suitable normal pixhawk PWM).
How can I set pixhawk to change the frequency and duty. or control pixhawk to out 0-5V
or I should use other transform board

patrickelectric · September 28, 2018, 2:51pm

Hi,

You can use a transistor to convert the signal from 3.3V to 5V, to change the pwm frequency you can use SERVO_RATE and if you don’t want to use pwm, check the RELAY_PIN* parameter (works like a digital signal ON-OFF).

Ben · January 31, 2020, 1:37pm

I want to adjust the PWM frequency, but I don’t see SERVO_RATE in the parameters list. Has something changed or am I missing something?

jwalser · January 31, 2020, 10:04pm

What you likely need is to control the pwm duty, not the pwm frequency. I don’t think there is an option to make a single output 0-100 duty based, you will need to add some software support to use the light.

Ben · February 2, 2020, 5:04pm

No, I have a different issue and do want to increase the frequency. I have your Lumen lights connected to the auxiliary channels on the PixHawk. I’m measuring a 50 Hz PWM signal from the autopilot which is creating a strobing effect with my third-party low-light camera. I’ve read the PixHawk should be capable of up to 400 Hz PWM, but I don’t see how to change it.

patrickelectric · February 2, 2020, 6:36pm

The frequency is controlled by the Lumens firmware, you can check it here:

github.com

bluerobotics/lumen/blob/master/Lumen-Arduino/Lumen-Arduino.h#L52


      
          #define NTC_R0          10000.0f            // NTC resistance at ref. temp, ohms
          #define NTC_B           3350.0f             // NTC equation B parameter, Kelvin
          #define T_MAX           75.0f               // 80 C abs. max board temperature
          #define T_CONTROL       60.0f               // dimming start temp
          #define T_KP            ((N_STEPS-1)/(T_MAX-T_CONTROL))
          
          
// OUTPUT LIMIT
          #define OUTPUT_MAX      230                 // 0-255 - 230 for about 15W max
          
          
// SIGNAL CHARACTERISTICS
          #define PULSE_FREQ      50                  // Hz
          #define PULSE_PERIOD    1000000L/PULSE_FREQ // microseconds
          #define PULSE_CUTOFF    500                 // microseconds
          #define PULSE_MIN       1120                // microseconds
          #define PULSE_MAX       1880                // microseconds
          #define INPUT_TIMEOUT   0.050               // seconds
          
          
// INPUT FILTER CHARACTERISTICS
          #define FILTER_DT       0.010f              // seconds
          #define FILTER_TAU      0.100f              // seconds
          #define N_STEPS         128                 // # of discrete outputs

It’s not possible to change it from the autopilot firmware, but you could change the code frequency and flash a new firmware.

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How to set pixhawk

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