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One Pot For Two Devices For Feedback?

What do you all think? Is it possable to use one pot for two devices for feedback? I have one motor I have one pot attached to it so I can send position feedback to one of EZB'S ADC ports. I'm hoping I can just tap off the sensor lug and run that to another device. That device is already attached to EZB and shares a common ground. It's' a Kangaroo x2.


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The resistance value will be identical on both ADC ports.


Thanks doc, however I won't be using two ADC ports on the EZB, just one. I want to run the other lead from the pot to the kangaroo. This way I would have one cable going from the pot to the king rule and another going from the pots to the ADC of EZB. Very sorry if I wasn't clear about that.


@Dave ....I thinking it should work and of course coinciding the ADC read with one of the two devices. I am presuming the devices are not on at the same time! Also paying attention to the input voltage for the ADC port not exceeding maximum. Perhaps a quick breadboard setup running the devices on at a time and measuring the output voltage would ease any anxiety:)


That's just it, they will both be on at the same time performing their own things. I like the breadboard idea I was going to get the multi meter out tonight anyway.


OK, the answer is YES! As Doc said the resistance value was identical on the signal pin of both device's ADC ports. Here's the way I wired it;

I needed to give the pot a 5vdc and a ground on the two outside of three lugs. The center lug is the connection that reads the difference in voltage as the pot's knob is turned. I got the 5vdc and Ground from the ADC port of the Kangaroo X2. So, I have: 1). 5vdc output wire (red) from Kangaroo directly to one outside lug of the pot 2).Ground output wire (Black) from Kangaroo directly to other outside lug of the pot (Kangaroo & EZB have a common Ground also) 3).Signal wire (White) from Kangaroo to the middle lug of the pot and I've spliced a second white wire mid way that runs over and connects to one of the Signal pins of a ADC port on EZB.

When in install a ADC Value Monitor in ARC I can see the value go up and down as the Kangaroo X2 controls the position and speed of my motor from the same pot.

Now, ya may wonder "what's the big deal"? Well, The way I control my B9 waist movement is I send commands from EZB to the Kangaroo X2 with Serial Commands. The problem is that the V3 EZB only has one way serial commutation. The Kangaroo cant send back info to ARC for Speed or position. Once the command goes out EZB is blind and doesn't know anything. I want EZB to be able to send a serial command to the Kangaroo X2 at a certain point of the rotation of the Waist motor to start slowing down to a stop. Till now I've been relaying on manual timing with the Sleep() function in a ramping script to ramp down. That wasn't always working well on mutable moves. This will aid me in speed ramping down to zero easily and at the exact and proper time. Using the ADC value that EZB is reading from the same pot the Kangaroo is using for speed and position I can now start that ramp down script just at the proper moment. Using Variables and a little math in that script I can have my B9 waist move to any point at any speed at any time and always speed ramp up and down smoothly at the proper time. Yaaaaah!:D

Now I need to get the script working properly. Shouldn't be much of a problem as I've already got most of the code written for other motors in the B9. Thanks for letting me bounce this off you guys. I hope this will help others that need to do something like this and need this type of feed back with no two way serial commutation on the V3 EZB. I understand the V4 will have this feature and that will be great. However there will be lots of classic V3 EZB's still out there.

Sorry Glen, Gotta give this one to Robot Doc. He got my head gears turning first. However you helped a lot;)


No worries Dave!:) I am happy to help in any way and this is ALL good for others as well:) I luv it when satisfaction is realized!:D and of course a big thank you to Robot-Doc !


Dave, I didn't want to start a new thread since I have a question relating to the same topic. I'd like to know what encoder/potentiometer you used with your kangaroo set up? Am I correct in understanding you are using it to turn your robot's (awesome robot by the way, my wife and I were laughing at your videos the other night) waste but not movement, is that correct? I think I would have to have some sort of encoder instead of a potentiometer since my application is drive wheels but would like any input you could provide. Regards Matt De,ing


Hi @Mat,

Glad you are enjoying my vids. I'm a true armature and just muck through them.

The pot I'm using is just a cheap multi turn from The Robot Shop. I have one installed for waist rotation positioning and one for Radar positioning. They sell a real expensive one and a real inexpensive one:

I see you've been struggling with the Kangaroo X2. Have you read through my other threads where I've been working through a few issues I had? If not take a look:


Hi Dave Thanks, I'm struggling with everything right now! I made some major changes to my frame because my drive wheels were way bigger than I had wanted them to be and it has created some havoc, hence my being up at all hours night and day trying to make a simple frame square. Now I'm trying to find a hub to put in a cheap lawn wheel that will fit my jazzy motor. I've read all of your kangaroo posts and plan to make the power off circuit in the next day or two. I went ahead and ponied up for the v4 today. As much as I've really hit the wall on my budget (especially repeated frame mods) I want full functionality of the kangaroo and I think the v4 will do this well. I also am not keen on send serial commands so far, it just seems the forward commands were so much easier to understand. I also heard from the guy at roborealm for his avm software and hope that functionality will be available soon. I'll look on robot shop. Will potentiometers work for drive wheels or will I need encoders? I think encoders but my thinking can get me into trouble...


Optical wheel encoders would be a better solution for detecting wheel movement than resistive measurements provided by a potentiometer. Over time the resistive measurements would be inaccurate due to wear of the resistive surface used for reporting the position.


@mdeming1 Do you need a Kangaroo X2 still? I have a brand new one I won't be using... I'll sell it to you for $24 shipped (which is what I paid but without shipping which was on top of the $24)...


Hi all, Richard R: I have the Kangaroo already but thank you Richard, I think with the new V4 (I purchased online yesterday, not sure when I would get it) I'll get the functionality I need. Aren't you getting the V4? Don't you think it's functionality will be quite useful? Just curious as i've not played with mine.

Robot Doc, re: encoders, I have two signal wires under the large cap on my jazzy motor so there is plenty of space. I've seen varying encoders out there. I have no personal experience with them yet. I read that the optical ones weren't very accurate vs. a quadrature or magnetic encoder, is that so or is it six of one/half dozen the other?

I'm uploading a photo below, it is someone else's motor but essentially the same (I've replace the rectangular connectors on mine) This is where I want to place whatever encoder I get. I just don't want to run into the same problem I have with the wheels, i.e. finding a 17mm bore encoder or whatever. Am I thinking about this right? Does the ez-b v3 0r v4 care if I'm using a quadrature, optical or magnetic encoder?

These encoders were the right price, do you think they would work with the ez-b?

Again, i could be way off on all of my assumptions so please let me know what you think. Again, really appreciated. Matt

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PS: If this re-opening of the thread is not good forum etiquette please advise. Some forums frown on this but to me it makes sense to do so especially as a new user it makes it quite a bit easier to search for the exact information and query on that conversation rather than start an entirely new thread and clutter the forum or be told to look it up which inevitably most have. Hope that makes sense.


Yes, I have a few V4s on order... The not sure if the Kangaroo will work any different with the V4 as compared to the V3... I found the Kangaroo to be overly complex and needlessly at that... I was not able to get the results that some have had on here with the kangaroo/EZB combo... Like Dave I simply went back to using pots for precision control over motors... The Kangaroo was meant to give feedback and position to geared motors... In a sense making them kinda' act like servos... However, I couldn't get mine to work so it was just far simpler to go back to using pots for position control over my motors...


encoders will not work with the version 3 EZB. I'm pretty sure they won't work with the V 4 either. If you go with encoders then you should try to stay with the Kangaroo. I'm still not decided if I am going 2 Scrap mykangaroo set up The advantage we're going to have with the V4 is two way serial communication. This will let EZB know speed and position directly from the Kangaroo. Remember, the feedback device is attached to the kangaroo. I was able to get this setup working nicely with simple serial commands. My complaint is I'm having trouble getting a smooth speed ramp in position mode. You'll be using speed control mode and I got ramping to work just fine in that mode. Beware though, you'll have to do some coding and use their setup program to change some settings to your likening.


encoders will not work with the version 3 EZB. I'm pretty sure they won't work with the V 4 either. If you go with encoders then you should try to stay with the Kangaroo. I'm still not decided if I am going 2 Scrap mykangaroo set up The advantage we're going to have with the V4 is two way serial communication. This will let EZB know speed and position directly from the Kangaroo. Remember, the feedback device is attached to the kangaroo.

Thank you all. Just to be clear. Assuming the encoders are attached to the K-R00 and the K-R00 is powered by V4 with two way communication, wouldn't the encoders be working for all intents and purposes? Or are you saying that regardless of two way communication it's going to be simple serial still?


I haven't got anything setup presently to evaluate encoder sensors but from my experience with iRobot and NeatoRobotics it would seem that magnetic encoders would be best from both a financial as well as a longevity standpoint. It seems that the output of the mag sensor could be sent to a digital port on a V3 or V4 without the need of two way serial messages.


As far as I know you'll need to use the UART port on the V4 for 2 way communication between the V4 and the Kangaroo...


All I know is that Dj has always steered us away from encoders. I don't think he ever said that EZB did or did not support encoders. Any time the topic of encoders comes up it's the consensus that they cant be used with EZB. It would be great is someone would give them a try. I think optical encoders are different then the mag sensor Robo Doc mentions. I've been wanting to give the magnetic sensors a try. We had a forum member on here last year (Robotmaker) that brought these sensors up saying they acted and read the same a a potentiometer but could turn around an unlimited amount of times. A regular common multi turn pot usually only lets you have 10 rotations as far as I've found.

And yes, The Kangaroo will accept either a pot or an encoder and I've confirmed that it will work with the V3 EZB. You send a serial command to the Kangaroo / Sabertooth combo board and to will move in the way (Speed, position) your command is written. OR you can put it into RC mode and run it through a Radio Controller ( I haven't tried this though).


Well with big wheelchair motors I figure it can't hurt to give it a try, ample room under the cap and two unused signal wires. Those $9 ones I linked to above are what I plan to buy, I like the magnet idea because, unlike the wheels, I don't have to search kingdom come for something that fits a 17mm shaft. Would be pretty awesome if it would work on the digital port, then maybe I could use the forward commands. I just would like to be more accurate than timing a move with a clock as Richard suggested, for sure I'll do it but hope to eventually use forward. Now that I'm thinking about it though, how is an encoder on my motor different than any 360 servo in my ez robot kit? Surely it's a motor with some sort of sensor to tell its position right? Seems mine coupled with the encoder is just a larger version of the small servos I have. The ez-b reads those signals ok. I'm sure I'm not thinking about something.


In the previous page Dave linked to pots not encoders... as mentioned you can't use pots for your purpose due to most having a limited # of rotating(s). You need wheel encoders...