PWM Priority Circuit

Discussion in 'The Projects Forum' started by xz4chx, Feb 15, 2015.

  1. xz4chx

    Thread Starter Member

    Sep 17, 2012
    I have a quad copter I am building. I want my RF signals from my controller to be separate to from the micro-controller controls.

    The PWM goes from 5% duty cycle to 10% duty cycle. When the AUX port moves to 10% of the duty cycle, I want the controls from the quad-copter to be taken over by the controller.

    The radio controller has priority controls of the quad copter, then a certain state causes the micro-controller to take over and fly on its own.

    I want to have a safety switch that allows me to over ride this command. Because it is a PWM change for the AUX instead of a 0 to 1 change, I'm not sure how to go about doing this.

    What kind of circuit can I use to switch which part of the quad copter is doing the controls?

    Also I hope this is the right section for this question.
    Thanks for the help
  2. Shagas

    Active Member

    May 13, 2013
    On my quad I use a dedicated microcontroller that does this job. It looks for the PWM input of the AUX port and routes all the inputs to the outputs accordingly. So basically it takes 4inputs from
    the controller and 4 inputs + 1 AUX from the Receiver and routes them to the 4 outputs according to the AUX. The reason I use a dedicated controller is so I know that it works all the time and nothing can
    go wrong if I make a mistake in my main system.
  3. xz4chx

    Thread Starter Member

    Sep 17, 2012
    That makes sense. I was just trying to make a circuit to make less of a foot print, also to be a little cheaper as well.
    I have a Hoverfly system that takes in the inputs of my system, then helps with the controls.

    So I wanted to have a switch that allows either the MCU to take over or the receiver but I want to have the receiver to have priority. But again the AUX uses PWM, so I can't use a MUX or anything like that.

    Is there a circuit to do this or do I have to go with the separate microcontroller?

    If I put a low pass filter, I can make them different amplitude sin waves with the same frequencies if that would help.

    If using a separate microcontroller is my only option then I will use that or I'll just use a dedicated pin that isn't used anywhere else in my program for this.