Lowering the voltage ripple on Power 1 (Pixhawk 2.1)?


Is there any way to lower the voltage ripple on Power 1 on the Pixhawk 2.1? It differs from 5,24 to 5,31 using Mauch BECs. Like with capacitors or any filter? Also, shouldnt it be around 5,35V? Maybe its normal when using 8 motors?


You can use a small ferrite choke on your power leads.

A ferrite choke does more less nothing with a voltage ripple in small voltage DC environment.
Mauch BECs are quite well designed and have very low ripple. It could be a measurement noise (you can check it by powering up from USB and check voltage).
If it is indeed a power ripple, if could be coming from the motor/esc line feeded back to the main power. In this case you need a proper filter. Recommend checking Dave’s excelent video on the topic : https://www.youtube.com/watch?v=wopmEyZKnYo

That is not true that ferrite choke will not suppress ESC generated EMI noise due to brushless motors.

The EMI noise on DC voltage is due to brushless motors otherwise the entire pixhawk power design is running of pure DC battery power source (There is no AC to DC conversion going here) then how you can have ripple on such a system besides brushless motors are the main culprits here.

Mauch power system never touches the ESC wires (signal and BEC out put voltage) connecting back to the FC. even though you are powering the motors via Mauch but that doesn’t solve the problem of feedback from motors.

I always use chokes on ESC leads prior to connecting them to the FC. they suppress EMI noise both on signal wires as well as DC if used to power anything off using the built in BEC.

If one really wants to get rid off all the noise, we’ll there are many ways that can be accomplished using filters but then the UAV weight will increase significantly.

The main thing to monitor in a UAV design is that does the noise generated by the motors causing an other devices to malfunction? This is a whole different discussion altogether.

  1. There are DC/DC converters in the power train and they are generating EMI noise and that noise can bee feed back to the power system
  2. Common ground and conducted EMI is a real bitch and can travel enywhere. And from that perspective the Mauch dc/dc converter and the ESC’s are one electical system.
  3. Chokes are effective in case of high frequency conducted EMI >100Khz. But ESC’s are generating EMI on the lower frquency range, where chokes are not effective. So choke on the ESC pwm wire is a snake oil. (if it is there it is for filtering EMI from the shitty dc/dc converter in the ESC) -(Fun fact, a choke on a PWM ESC signal wires does nothing, but put the same choke on a DSHOT1200 ESC’s signal wire and it will stop working.)
  4. ESC not only generate EMI but also generate current ripples on the main power bus due the switching which also generate voltage ripples.
  5. And there is regenerative breaking that also generates significant voltage changes in the main power line which can cause voltage ripple in the DC/DC converter’s output.

So this it why I said that chokes are not effective for power ripples in UAV.

  1. Agree, but I thought the use of MOSFETS and onboard power train filters pretty much almost eliminate any noise ( or brings it down at acceptable levels). I guess depends on the design.
  2. Agree, however Mauch is not addressing Brushless motor generated noise feedback which is fed back into the FC.
  3. I was not aware that ferrite chokes are only effective for frequencies higher than >100 kHz. Which raises the question what frequency Brushless motors really generate. I am going to measure it as now I am curious to know more.
  4. Agree, and most ESC,s are horribly designed unless you buy fairly expensive and high quality products.
  5. Agree.

Have you seen this system? Human carring UAV.

Some company in Ukraine design these ESC for large T motors.

Not Ukrainian but Czech

Any experience with these products. I saw them at the Boeing human UAV flying contest in CA earlier this year.