Shielding your sonar cable.

We all want an excelent sonar ALT-hold so we do everything to get the most acurate reading from our sonar. Move it away from the ESC's and shield your sonar cable. But how to shield?

First of all: find a 3 core shielded cable ( i sacrificed a mobile (gsm) handsfree set.

On one end make your oilpan connection, be sure you connect the shielding in the cable to 0v (the black)

I have an jst male on the oilpan side, but you can see the connection between the black and the shielding.

Next, connect your sonar the right way, and do not connect the shielding at this end, do not connect, do not connect ( did i say do not connect )

Connecting the shielding at the sonar end would cause unwanted problems and the signal quality could even be worse. Why not connect the shielding at both ends? We want to shield, and not conduct. If we had te 0v conected at both sides it is possible the shielding would act like an antenna for spikes and show-up in your signal. So if using shielded cables only connect the shielding at the end closest to te main 0v and never at the far end.

2cents from Pieter

I will likely get some flack for this one but since it is working very well for me, I thought I would post and perhaps I will get some new ideas out of it that may make everything work even better.

First things first, I'm working with a DJI F550 with a shiny new Spektrum DX8 with AR8000 receiver and TM1000 telemetry module (this was included since the whole reason I bought this radio was my old DX7 browned out and with the floating inputs the mode got switched out of loiter...translation - motors shut off at 150ft+ and couldn't break the freefall) which currently feeds my flight pack voltage, receiver voltage, and control link quality to my transmitters display.I also have the 3dr telemetry radios for monitoring and mavlink, as well as the uBlox gps(recently flashed with the GLONASS capable firmware and prepped for a test flight now)

In mounting my gps I didn't want to ziptie it to an ESC, and had some aluminum laying around so I cut off two pieces of L the same length, put them together to make a T, drilled a hole and rivetted them together, little bit of trimming to the downward side to make it flat rather than a T, and it got bolted on between the top right arm(first one during the motor test command) and the second arm.I then put the gps up on about 4cm brass standoffs so it is even above the props. Then once my sonar arrived and I did a lot of reading, I ended up with the sonar mounted to the bottom of that T using a couple of 3cm brass standoffs to stradle the T, I found that the sensor fits perfectly like this, and has about 4mm of clearance from the ground without modifying the legs.

For my cable I dug around for several hours before I found one I liked, ended up being an old school USB cable from when USB2 was brand now...so the cable is about 5mm across, and shielded. I then soldered pins to the sonar, and the smallest 10v 100uf cap directly to the back of the pins(ie put the right angle pins in, solder them in place and before you do anything else, add the cap to the + and -) I then crimped the proper pins to the + and - wires, then combined the remaining two wires in one pin, did the same on the other side leaving the cable a little(ok WAYYYYY too) long so that if I had any issues, I could easily relocate things without ruining the cable, and I can obviously always cut it to length and re-crimp...This is the first thing that could have made it end badly, my cable measures 3ft long...

Second possible mistake that I see now is what I did with the extra cable...around around it goes along the outside hex pathway 1.5 revolutions.

For this end I crimped the two data lines together, put in the - and crimped a pin directly to a rresistor then soldered the + wire to that, added a little heatshrink then crimped the shielding to it's own pin and plugged it in to a spare server outputs ground connector.

The result is working quite nicely dispite the two snafu's mentioned. At some point here I will remove the extra cable, but I definately think shielding is needed. I am very seriuosly considetring putting in your library and moving the sonar to pwm, I tried to program that myself but couldn't manage to find the right code so I abandoned trying to do that part myself. Thanks for posting your code and all the testing.

Comments? thoughts?

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Nathan Asdourian April 26, 2013 at 9:56am

I will likely get some flack for this one but since it is working very well for me, I thought I would post and perhaps I will get some new ideas out of it that may make everything work even better.

First things first, I'm working with a DJI F550 with a shiny new Spektrum DX8 with AR8000 receiver and TM1000 telemetry module (this was included since the whole reason I bought this radio was my old DX7 browned out and with the floating inputs the mode got switched out of loiter...translation - motors shut off at 150ft+ and couldn't break the freefall) which currently feeds my flight pack voltage, receiver voltage, and control link quality to my transmitters display.I also have the 3dr telemetry radios for monitoring and mavlink, as well as the uBlox gps(recently flashed with the GLONASS capable firmware and prepped for a test flight now)

In mounting my gps I didn't want to ziptie it to an ESC, and had some aluminum laying around so I cut off two pieces of L the same length, put them together to make a T, drilled a hole and rivetted them together, little bit of trimming to the downward side to make it flat rather than a T, and it got bolted on between the top right arm(first one during the motor test command) and the second arm.I then put the gps up on about 4cm brass standoffs so it is even above the props. Then once my sonar arrived and I did a lot of reading, I ended up with the sonar mounted to the bottom of that T using a couple of 3cm brass standoffs to stradle the T, I found that the sensor fits perfectly like this, and has about 4mm of clearance from the ground without modifying the legs.

For my cable I dug around for several hours before I found one I liked, ended up being an old school USB cable from when USB2 was brand now...so the cable is about 5mm across, and shielded. I then soldered pins to the sonar, and the smallest 10v 100uf cap directly to the back of the pins(ie put the right angle pins in, solder them in place and before you do anything else, add the cap to the + and -) I then crimped the proper pins to the + and - wires, then combined the remaining two wires in one pin, did the same on the other side leaving the cable a little(ok WAYYYYY too) long so that if I had any issues, I could easily relocate things without ruining the cable, and I can obviously always cut it to length and re-crimp...This is the first thing that could have made it end badly, my cable measures 3ft long...

Second possible mistake that I see now is what I did with the extra cable...around around it goes along the outside hex pathway 1.5 revolutions.

For this end I crimped the two data lines together, put in the - and crimped a pin directly to a rresistor then soldered the + wire to that, added a little heatshrink then crimped the shielding to it's own pin and plugged it in to a spare server outputs ground connector.

The result is working quite nicely dispite the two snafu's mentioned. At some point here I will remove the extra cable, but I definately think shielding is needed. I am very seriuosly considetring putting in your library and moving the sonar to pwm, I tried to program that myself but couldn't manage to find the right code so I abandoned trying to do that part myself. Thanks for posting your code and all the testing.

Comments? thoughts?
Dani Saez August 4, 2011 at 10:18am

Hi Peter,

I used an audio cable from an old DVD unit. Just soldered and I'm amazed of the results, at least in the test.

Using the CLI sonar test, data is rock solid!!! :-D

Thanks for the great tip.

As soon as I can try it in flight, I'll post the results.

Dani
Dani Saez July 30, 2011 at 3:51pm

Nice tip!!

Have you tested how much it improves the signal??

Dani

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Shielding your sonar cable.

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