Sonar Quick Connector and Power Filter


I thought I would share a couple of photos of the quick connector I soldered on to my arducopter Sonar which incorporates the power filter I posted a while ago (Link).   I started experimenting with different sonars from MaxBotix and wanted a way to incorporate the passive filter and connector together.  Over time having everything wired up including the resistor in the +5v line seemed to eventually break with the cable moving / being unplugged from the APM.  If you look closely you can see I have the 10 ohm resistor going into the +5v on the Sonar board and the other end connects to the appropriate edge connector pin.  I find this setup very reliable when swapping out parts for testing.

Here are some other photos:


The above photo shows the 100uF Electrolytic mounted across the +5v and gnd.


E-mail me when people leave their comments –

You need to be a member of diydrones to add comments!

Join diydrones


  • Wow, thanks Greg, I have been playing around with simple electronics during my hexa build.  This will be the perfect addition to my knowlage base.  Thanks,


  • Rick the resistor and capacitor together make up the passive filter for the +5v power to the sonar. The resistor value effects the discharge and charge time of the capacitor known as the time constant. I think if memory serves this is denoted by the formula T=RC. Here is a nice article / tutorial on low pass filters and how to calculate the low pass cutoff frequency. It explains everything better than I could.
  • What purpose does the resistor serve?


  • Moderator

    Great tip... and thanks for the hi-res pic that makes it easy to see what you're talking about!

  • Admin

    @Jack Crossfire,

    The "giant trimpot" looks more like a tunable inductor for the sonar's oscillator's tank circuit maybe?



  • Haven't seen one of those giant trimpots in decades.  That thing must allow it to communicate with Michael Jackson in the afterlife.

  • Thank you for the positive feedback. I should have mentioned I still have a twisted pair shielded cable with a matching connector on it. Yes I agree, MaxBotix could offer something like this. Adding some surface mount versions of the componnents for the filter would make the design neater. I will drop them a line and make the suggestion. Perhaps this is something 3DR could offer when they sell the sonars, given the sonar application in the arducopter?
  • I also use the rat-tail method, and I hotglue the resistor, cap, and the beginning of the rat-tail to the board, for strain relief.

  • Developer


    I have also used the power filter approach above, but not the connector. Instead mine has a long rat-tail cable hanging off the sonar. 

    Despite the long cable, I dont seem to be getting interference and I'm getting superb sonar results. 

    thanks for the power filter tips!

  • Distributor

    very nice and clean! wish these sonars came like that from factory! 

    good work! 

This reply was deleted.