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Moti, a smart servo

Moti is a smart servo that simplifies the design of intricate robots.

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This project was created on 03/01/2014 and last updated a year ago.

Moti is a smart servo motor that makes it easier to build robots. Picture building a humanoid with lots of moving parts. You'd need a motor and a few sensors in each joint. You need additional circuitry to control everything, and you'd have a mess of cabling connecting it all together.

Moti makes it easier to build such systems by providing requisite features within the motor. There's a programmable microcontroller, breakout pins for attaching sensors, daisychain networking, and a continous rotation servo, with 360º position sensing inside each Moti. It eliminates the need for external circuitry.

We also want Moti to play well with the web and mobile devices, so there's a RESTful API for developing apps. And we've built the first one that gives you immediate control of your Moti-enabled robot.

There's more to do. Check out

Video overview of Moti:

The video is quite long as it is, so I'll discuss the server and app layer in a future video.

What the system diagram illustrates is that you can use our prebuilt web app to recognize, monitor, remote control & program your robot. Alternatively, you can build your own app (or use someone else's) that is customized for your application. Thirdly, you can program the motis directly to create an autonomous system.

  • 1 × ATmega328p Main Microcontroller
  • 1 × 16MHZ Crystal
  • 1 × MCP1703 250mA 5V Voltage Regulator
  • 1 × AON4420L N-Channel Mosfet for Reverse Polarity Protection
  • 1 × ISL81487IBZ RS-485 Driver
  • 2 × 1x6 0.1" smd female header for breakout pins, including GPIO, A2D, I2C,
  • 1 × 2x4 0.1" smd male header to attach 2x RS-485 cables
  • 1 × 2x12 0.05" smd female header connects processor board to driver board, plus ISP header
  • 1 × VNH5180A Interface and IO ICs / Peripheral Drivers and Actuators
  • 1 × 10k thermistor

See all components

  • Working through some basic motor movements

    12/23/2014 at 04:08 0 comments

    Recently, I've been working on basic motions with Moti; things like shooting over distances, stepping, and braking. This started with comparing different types of braking: regenerative, dynamic, locked anti-phase, and even coasting to see which would stop the motor faster. Regenerative and dynamic braking were pretty much the same, and the best performing. When initiated at full speed, it takes about 15º to come to a stop. Locked anti-phase braking didn't perform well, though I'm sure it could be done better. However it generates an audible buzz at the 500Hz PWM frequency I'm using, and I couldn't stand I quickly moved on. And of course coasting was the worst and was used as a control. So for the moment I'm using dynamic and regenerative braking. This website was helpful for understanding the differences between each.

    Before jumping into stepping, I wanted to see how an RC servo controls it's motor, and here I'm talking specifically about the output from the H-Bridge, so I spent some time probing it with my scope. I've uploaded a playlist of these explorations. The TL;DR of the matter is that this was highly useful. Not only did I learn how an RC servo steps, but also how it shoots and decelerates when approaching its destination. I was then able to whip up a step function that produces what appears to be both finely grained, and repeatable steps. I dabbled with shooting, but don't have anything conclusive to report about that yet.

  • Back to Work

    11/30/2014 at 19:49 4 comments

    There hasn't been much progress on Moti for a couple of months now as I was busy with teaching and another project. Now that those things are wrapping up, I'm looking forward to getting back to it.

    A couple of questions for you. If you had to choose, would you prefer:

    1) a few breakout pins and a smaller servo,

    2) more breakout pins and a larger servo,

    3) more breakout pins that are smaller-pitch (eg. 1.27mm or 2mm instead of the commonly used 2.54mm)?

    Lastly, congrats to SatNOGS on winning the Hackaday Prize. It's an awesome project, as were all the finalists.

  • Moti v0.3 Bring-Up

    10/14/2014 at 04:28 0 comments

    I spent much of the day getting the driver-level facilities working at their most basic. I've heard this described as bring-up, though it's the first time I've used the term, so I could be misusing it. Anyways, it was a great day, as a number of features were tested, and all worked. Thank god for using monolithic ICs instead of custom designed circuitry. It works just as specified in the documentation. Here's a playlist of a bunch of videos showing what was done.

View all 13 project logs

Enjoy this project?

Petr Švarc wrote 01/02/2016 at 11:22 point

Where can I buy ? :-) It is perfect for robots...

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nsted wrote 01/02/2016 at 17:05 point

Hi Petr,

Not ready yet. I'll let you know as soon as it is.

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Petr Švarc wrote 01/03/2016 at 16:55 point

I'll be patient :-).

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Mike Maluk wrote 10/28/2015 at 00:37 point

Very awesome project! I haven't read too in depth, so I may have missed it, but any plans to add battery power to each servo? This would allow the servo to be completely independent of any wiring, and make it really simple. I'd love to have something like this on R/C aircraft, would really ease setup!

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nsted wrote 11/02/2015 at 15:33 point

Thanks Mike. I haven't planned for a battery pack, but it wouldn't be too difficult (famous last words) to make a 3d printed battery pack that could be mounted to the back of the servo supplying power through the power pins. For now though, I am just trying to get it done!

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Whjas Huanh wrote 05/12/2015 at 11:12 point

Nice project ! If you have any PCB manufacture need, please visit PCBWay, free universal boards as gift.

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VPugliese323 wrote 09/29/2014 at 03:07 point
I have one question not addressed by your project logs. Are you planning on addressing security concerns; as a networked device, do you have any plans to make your device more secure that I gather it presently is? To be specific, after reading your project logs, it seems as if anyone could (in theory) SSH over to the server controlling the motors and control them. For an industrial robotics project, that would be extremely dangerous. I realize that you cannot have perfect security with this (or any connected) technology, however I did not see any mention of how the connections are secured. I may have missed something because I was reading quickly, if so then my apologies. This is an interesting project, I like it.

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nsted wrote 09/29/2014 at 05:39 point
Thanks for the question. The short answer is that we haven't built any security features at this stage, but aim to as the project develops. We'll need help in that area. Do you have any suggestions?

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VPugliese323 wrote 09/29/2014 at 11:10 point
For these kinds of things, I must admit I default to two good books on the matter that I have. and

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PointyOintment wrote 08/11/2014 at 18:44 point
You might find this interesting:

Be sure to check out the link in the description.

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nsted wrote 08/11/2014 at 19:50 point
Very very Cool, but the links redirect, or 404.

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Jasmine wrote 08/06/2014 at 21:20 point
Hello nsted, now is the time to add a few more details to your project to give it the best chance of going through to the next round of The Hackaday Prize.

By August 20th you must have the following:
- A video. It should be less than 2 minutes long describing your project. Put it on YouTube (or Youku), and add a link to it on your project page. This is done by editing your project (edit link is at the top of your project page) and adding it as an "External Link"
- At least 4 Project Logs
- A system design document
- Links to code repositories, and remember to mention any licenses or permissions needed for your project. For example, if you are using software libraries you need to document that information.

You should also try to highlight how your project is 'Connected' and 'Open' in the details and video.

There are a couple of tutorial video's with more info here:

Good luck!

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flaco wrote 07/13/2014 at 12:36 point
Here's something really interesting ! :D

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Robot wrote 07/10/2014 at 23:51 point
Wow. Such a worthy product; I'm sad to see that the kickstarter failed.

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crener wrote 07/10/2014 at 19:02 point
Hmm, i wonder if i could put one of these in place get all the settings/timings that i need (e.g. for a hex) and then replace with a normal servo?

It should work as long as i don't use any sensors that are attached to it. I just "learn" a pattern with the smart servo and then swap it with a normal one one i have its positional informaltion captured.

Anybody think this could work?

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nsted wrote 07/10/2014 at 21:09 point
That's an awesome idea that hasn't come up before. It should work as long as moti exceeds your max requirements in speed and torque.

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Tiago wrote 07/06/2014 at 16:27 point
I really like this project, might buy a bunch if they are not too expensive. Already got a bunch of ideas in mind for them. When you say full rotation position tracking do you mean it has a range of 360 degrees, or continuous rotation with an encoder? If it is an encoder, then am I correct in assuming that they do not know their position on startup, only relative positions?

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nsted wrote 07/06/2014 at 21:33 point
Thank you. A new development is that Moti has a 10-bit magnetic encoder with a 360º range, so the absolute position is always known. There are no mechanical obstructions limiting rotations, so it can continue rotating as long as needed, and every 360º/0º rollover is logged in a register, which you can clear when you like.

This can be used in several ways. For example, you could have it turn precisely 1001º. Or you could remote control it to go some distance, and then read back how many degrees/rotations were required to get there. You could even manually turn the motor, record the positions, and then replay the patterns.

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Tiago wrote 07/06/2014 at 22:34 point
That's really cool, would be so helpful for a project I am working on at the moment :) How much will they cost, aproximately, and when will they be available?

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nsted wrote 07/08/2014 at 16:38 point
It's still going to be a while before Moti is released. We'll probably start beta-testing the new design this fall, and hopefully have a release (at least of the boards) later this year. As for price, I'd like to keep it below $55 for a preassembled servo (and cheaper of course for just the assembled boards). I know that sounds expensive but the driver, encoder, Arduino and motor end up costing a fair bit. Actually, I'd love to hear reactions to that price?

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Tiago wrote 07/08/2014 at 16:40 point
Sounds pretty cheap, actually. A 1.5 turn servo with position control will be much costier.

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mandoline wrote 06/28/2014 at 13:56 point
Nice idea. Can these be RF controlled, because that would indeed be handy.
Also for robotics use a regular servo could be used as the backplate and its existing controller chip grafted onto the new board with the magnetic rotation sensor to add longevity.

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nsted wrote 07/02/2014 at 18:31 point
We've got bluetooth and xbee already, but for other RF one could design a new shield.

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regiscruzbr wrote 06/27/2014 at 01:21 point
Kick ass project...
I have an application for it on my home automation.

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pajolegault wrote 06/24/2014 at 23:17 point
This is a great example of a project that makes the stuff to make the stuff.
Some development variations I could see working with this. Add a hall effect sensor and accessible positional PID so that the motor can monitor and report on its loading, be tuned, and work with a wider range of voltages.

A pickle adaptor for use as a remote and for training the embedded micro.

Slaving for systematic control. You control one servo and it can control at least three other servos. For example you could have the fast servo, have it control the ratchet directional- position locker toggle servo, and the slow geared ratchet drive high torque servo, and a weighted spring, hammer drive loading servo. Or simply use a push me pull you control between two servos so that when one servo winds in, it tells another servo to wind out.

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nsted wrote 06/25/2014 at 00:04 point
Thanks for the feedback. Are you thinking hall effect for position, or current sensing, or something else? We've switched to a magnetic encoder for position, and current sensing is provided by the h-bridge. PID settings are open as you suggest. I hope to add more detail soon, and update the pics.

I have no idea what a pickle adapter is?! But it sounds like something awesome.

We're also switching from i2c to rs485 because of the extra distance it affords, with up to 128 nodes (at least in theory). You can customize the addressing, and program the nodes to achieve the desired network topology.

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pajolegault wrote 06/25/2014 at 00:58 point
A pickle is just controls on a cable, so a wired remote. You can plug in a joystick for example. It might be jargon specific to some industries. I should have just said a wired remote.

Bluetooth would also work and no socket needed.

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pajolegault wrote 06/25/2014 at 01:03 point
I was thinking of the Hall effect sensor for the motor current.

Current sensing is provided by the H-bridge or current limiting?

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nsted wrote 06/25/2014 at 01:21 point
We're trying out the VNH5180a with built-in current sensing
Will post how it works out.

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samern wrote 06/16/2014 at 17:23 point
I have some many projects for this thing, the mind boggles. I wish I knew, I would've contributed to the Kickstarter.

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technolomaniac wrote 05/02/2014 at 06:57 point
Awesome concept! Very cool to see and super interesting!

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dave.m.mcdonough wrote 04/29/2014 at 15:47 point
Is this just a servo piggyback board or the complete package? Because I'm curious about the servo torque specs, or if I want to use a bigger motor..

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nsted wrote 05/13/2014 at 18:16 point
The plan is to offer both a preassembled servo, as well as make the boards available so you can put them inside the servo motor of your choice (though they may not fit inside every case).

I don't have final specs on the on the torque of the preassembled servo, but conservatively it will be at least 11 kg*cm with metal gears. And one thing I'm looking forward to is the ability to use it with gearboxes to up the torque without having to hack the servo. (eg.

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zack wrote 04/16/2014 at 02:24 point
This is great, the added accessibility is really cool! My personal need is something with the specs of a Dynamixel AX-12, but with continuous rotation sensing. It'd be nice to see more than just Robotis serving the "smart servo" market.

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mbasecnc wrote 04/09/2014 at 16:57 point
Very very nice, I saw your Kickstarter campaign, to bad you didn't make it.
The world needs a good open source servo board!
As in open source, where is the source?
Keep it cheap and you will be succesfull!

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nsted wrote 05/13/2014 at 18:33 point
Thanks...the Kickstarter campaign was a disappointment, but we learned a lot from it. We haven't released the source yet, but we will once the first version of the servo is finalized and made available for sale.

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Eric Evenchick wrote 03/11/2014 at 19:29 point
Hey, just wondering about latency on these. It looks like you're using the HC-05 modules, or something similar. I've had some issues with latency over Bluetooth in the past, so I'm just curious what your thoughts are on it.

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nsted wrote 03/11/2014 at 20:55 point
Yes, the motor on the left shows a Bluetooth shield with HC-05. There's a bit of latency, which is on the list of todos. See for yourself:

The middle motor shows the pins that shields plug into. So you can connect your preferred serial module and set your own baud. For example, right now I'm using an FTDI cable while developing...I'll upload a pic.

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assadollahi wrote 03/09/2014 at 21:47 point
isn't that a bit similar to the dynamixel servos (position aware, daisy-chainable)? except for the web-interface?

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nsted wrote 03/09/2014 at 23:15 point
It’s more like an arduino and dynamixel combined. You can program moti directly, or add sensors, and so you don’t need an external microcontroller. Also, the 330º angle sensing limits of most dynamixels really bothered me…so we gave moti full-turn position tracking.

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