Let's Make Robots!

360 Degree sonar. Proof of concept.

Uses 3,5mm jack to transfer signals on a rotating axis.

First thing first.
This is just a quick and dirty attempt to improve the 360 degree sonar idea. I have seen some of the designs at LMR with a 3,5mm jack plug and wires that goes around the servo and enters the sonar at the top. This is a good idea, but there are at least two things that can be improved.

1. The wires to the sonar will obstruckt the sonars view.

2. It takes a lot of space on top of the sonar to fit the plug and route the wires.

Now, what do you need?
- 1 continues rotation servo or motor.
- 1 Jack plug.
- 1 Jack socket.
- 2 Gears that fits the bill.
- Some superglue and tape
- Maybe a drill.

What i did:
-Glued one of the gears to the top of the servo output shaft (The small gear)
-Drilled (Thats a lie.) a hole so the jack-plug could be placed in the middle of the large gear and secured it with a drop of superglue.
-Fittet the gear and plug into the jack-socket.
-Placed the socket so that the gears fitted together and the socket was flush with the servo.
-Secured the socket to servo using superglue.
-Soldered on two led`s with common ground and the two V+ on the other "pins"
Connected wires to the socket.
-Made a smal PicAxe program that runs the servo and flashes the leds.

You wil see in the first video that there are some minior glitches in the blinking. Found out that its beacase the plug had some uneven parts but it fixed it self after running for five min. when the socket had filed away those inpurities.

Photos:




Socket

Gears
Gear+Jack
Finished
Finished2
Finished3
Finished4
Finished5

Videos:
Video1
Video2

Other ideas:
-Use a regular servo and gear it up like ignoblegnome suggested here.
-Use a ordinary motor or stepper with encoders so you can get position reference as well.

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Hi! First of all , congratulations for this excellent site that is , at the same time, a guiding light for those who are robots experts and those willing to go  in this direction ( me ) .

I really liked this aproach using plug/jack and as soon as possible, I´ll complete my project that is a 360 degree Sharp IR detector  capable of writing the enviroment pattern inside  32K Ram Memory pages , comparing then to define a difference ( movement , maybe turtles !)  and further , using this information as a guide to navigate thru the enviroment predicting the next enviroment picture ( I swear I´ll try).

But  called my attention the fact that using this type of slipring ( plug/jack) , some inevitable noise will ocurr and since we depend upon voltage level coming from the Sharp sensor to determine the exact distance, this will be compromised.

One thing is to filter the VCC that goes to the platform that holds the sensor ( just use a good capacitor ) the other is to try to avoid the glitches that can occur ( low current ) from the sensor side, there will never be a good filter for this ( I think)

Being so, I´ll try to place a Xbee and some micro processor onto the rotating platform to send the data digitalized  without loss to an external system.  

Maybe this is a fix for the problem I think can ocurr.

This is the primary concern I would have depending on the type of sensor that you're using. Ping sensors would be more susceptible to nice as it can cause a premature trigger. This is one reason why I would hesitate to use this method for something that would need a high degree of accuracy. I would imagine that it could also be used with the analog sensors, but again, these would also be susceptible to noise issues which you could use oddbots solution. Third issue would be the wear on the plug itself. Since it's a slow speed this shouldn't be an issue, but still something of a concern. some rotations have grease for this purpose...it might be something to consider.

You can also use one of the telephone handset cord "untanglers" that let the phone cord rotate 360 degrees. That gives you 4 gold plated contacts and is actually designed to rotate. Around here, you can find them at the $.99 cent stores.

Make sure you add a 100uF and a 100nF capacitor directly to the sensors power pins to ensure reliable sensor opperation. In some cases a 220uF capacitor may be required.

You might find you get noise from the jack if you try to read the sonar while the jack is rotating. It will work best if the servo is stationary when readings are taken.

If you really need to read a sensor on the move then a small noise filtering capacitor might need to be added to the signal wire. Be careful here if you are using serial data as a capacitor that is too big can filter your data as well. Try a 10nF capacitor to begin with.

That is a smart idea!

I was thinking lately how to build a cable pass through for a rotating object. This seems to be a good idea for that.

Jack does not cause much friction and, on the other side, garantees a solid connection.

 

Edit: the videos work fine.

Cool idea. I can't seem to access the videos, though. Can you upload them to a major video provider (Youtube, Vimeo, etc.) and then post the links?

I`m a little bussy the coming days but i will see what i can do. The video files are .avi and you should be asked if you want to download it when you press them.