# How to set PWM range

**URL:** <https://discuss.px4.io/t/how-to-set-pwm-range/42434>\
**Category:** PX4 Autopilot\
**Created:** [November 15, 2024, 8:38am UTC](https://discuss.px4.io/t/how-to-set-pwm-range/42434 "2024-11-15T08:38:52Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![JaimeParker](https://discuss.px4.io/user_avatar/discuss.px4.io/jaimeparker/32/10003_2.png) [@JaimeParker](https://discuss.px4.io/u/JaimeParker)\
**Post date:** [November 15, 2024, 8:38am UTC](https://discuss.px4.io/t/how-to-set-pwm-range/42434/1 "2024-11-15T08:38:52Z")

</div>

PX4 version: release/1.13  
gazebo 11, ubuntu 20.04

for `iris_ctrlalloc.sdf`, it load the default params in [rc.mc\_defaults](https://github.com/PX4/PX4-Autopilot/blob/release/1.13/ROMFS/px4fmu_common/init.d/rc.mc_defaults):

```auto
set VEHICLE_TYPE mc

# MAV_TYPE_QUADROTOR 2
param set-default MAV_TYPE 2

if param compare IMU_GYRO_RATEMAX 400
then
	param set-default IMU_GYRO_RATEMAX 800
fi

param set-default NAV_ACC_RAD 2

param set-default RTL_RETURN_ALT 30
param set-default RTL_DESCEND_ALT 10

param set-default PWM_MAIN_MAX 1950
param set-default PWM_MAIN_MIN 1075
param set-default PWM_MAIN_RATE 400

param set-default GPS_UBX_DYNMODEL 6

#
# This is the gimbal pass mixer.
#
set MIXER_AUX pass

set MIXER quad_x

set PWM_OUT 1234

set PWM_AUX_OUT 1234

```

and in [10017 iris\_ctrlalloc](https://github.com/PX4/PX4-Autopilot/blob/release/1.13/ROMFS/px4fmu_common/init.d-posix/airframes/10017_iris_ctrlalloc),

```auto
. ${R}etc/init.d/rc.mc_defaults

param set-default SYS_CTRL_ALLOC 1

param set-default CA_AIRFRAME 0

param set-default CA_ROTOR_COUNT 4
param set-default CA_ROTOR0_PX 0.1515
param set-default CA_ROTOR0_PY 0.245
param set-default CA_ROTOR0_KM 0.05
param set-default CA_ROTOR1_PX -0.1515
param set-default CA_ROTOR1_PY -0.1875
param set-default CA_ROTOR1_KM 0.05
param set-default CA_ROTOR2_PX 0.1515
param set-default CA_ROTOR2_PY -0.245
param set-default CA_ROTOR2_KM -0.05
param set-default CA_ROTOR3_PX -0.1515
param set-default CA_ROTOR3_PY 0.1875
param set-default CA_ROTOR3_KM -0.05

param set-default PWM_MAIN_FUNC1 101
param set-default PWM_MAIN_FUNC2 102
param set-default PWM_MAIN_FUNC3 103
param set-default PWM_MAIN_FUNC4 104

set MIXER skip
set MIXER_AUX none

```

then I revised vehicle in `mavros_posix_sitl.launch`, and launch ,but got this:

 ![image](https://discuss.px4.io/uploads/default/original/3X/7/1/71e26dc3b06da3cf04727d22bb3073e2ed96570f.png)

then I tried iris.sdf without control allocator:

 ![image](https://discuss.px4.io/uploads/default/original/3X/8/c/8c86b9cded97470cbe58deba500835eb0e5087e8.jpeg)  
weirder.

so how to make `PWM_MAIN_MIN` and MAX effective?

thanks for any advice and suggestion.

---

<div class="post-metadata">

**Author:** ![JaimeParker](https://discuss.px4.io/user_avatar/discuss.px4.io/jaimeparker/32/10003_2.png) [@JaimeParker](https://discuss.px4.io/u/JaimeParker)\
**Post date:** [November 15, 2024, 8:40am UTC](https://discuss.px4.io/t/how-to-set-pwm-range/42434/2 "2024-11-15T08:40:25Z")

</div>

also there is a chat in [dronecode discord](https://discord.com/channels/1022170275984457759/1306872366080593950)

---

<div class="post-metadata">

**Author:** ![sfuhrer](https://discuss.px4.io/user_avatar/discuss.px4.io/sfuhrer/32/3931_2.png) [@sfuhrer](https://discuss.px4.io/u/sfuhrer)\
**Post date:** [November 18, 2024, 8:15am UTC](https://discuss.px4.io/t/how-to-set-pwm-range/42434/3 "2024-11-18T08:15:55Z")

</div>

I recommend you use a newer PX4 release, a lot has changed in how we do control allocation/mixing and PWM configuration since 1.13.