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.

Views: 1539

Tags: Sonar

Comment by Dany Thivierge on June 7, 2012 at 8:20am

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

good work! 

Comment by Andreas M. Antonopoulos on June 7, 2012 at 9:29am


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!

Comment by Rob_Lefebvre on June 7, 2012 at 9:35am

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.

Comment by Greg on June 7, 2012 at 1:22pm
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?
Comment by Jack Crossfire on June 7, 2012 at 6:57pm

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

Comment by Thomas J Coyle III on June 7, 2012 at 7:32pm

@Jack Crossfire,

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



Comment by Mark Harrison on June 7, 2012 at 9:58pm

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

Comment by Rick Stewart on June 15, 2012 at 2:44pm

What purpose does the resistor serve?


Comment by Greg on June 15, 2012 at 4:16pm
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.
Comment by Rick Stewart on June 15, 2012 at 5:03pm

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,



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