This instructable was created to be entered in the Robot Challenge. If I win, the parts will of course, go into robots like this one. Notes on how to include some of the very components in the prize packages are given in the last step. I am 28, so of course, I'm not going for the student prizes.

I created this as a simple project for those just starting out in robotics. It is relatively inexpensive, requires minimal tools and is easy to build. Once finished you have an expandable robotic platform that fits in the palm of your hand and can be easily programmed in the Arduino environment.

Here is is driving in a triangle, without any special add ons

In the instructions I'll walk you through how to:
  1. Modify the servos for continuous rotation
  2. Fit the track hubs on to the servos
  3. Make a custom battery pack
  4. Wire it with a few connections
  5. Assemble it
  6. Program it
  7. Customize
These and other additions can be mixed to make your own custom micro robot

For the basic platform the following supplies are needed:
an Arduino nano
a small rechargeable battery
a pair of 9 g servos, modified for continuous rotation
part of a Tamiya track set
a 40 pin dip socket
a rubber eraser
some zip ties

Step 1: Construction: Modify the servos

Micro servos modified for continuous rotation are the heart of this design. They give you so much of the hardware; the motors, the gearbox, the driver and control circuitry, all in a tiny cheap package, and in this implementation they also act as the frame of the robot (seen in the next step). There are many instructables on modifying servos for continuous rotation. But here is how I did it for the micro 9g servos I am using.

  1. Remove the tiny screws and open the case
  2. Cut the potentiometer wires, these are where you will attach the resistors
  3. If you have surface mount resistors, place a 5k (1k to 10k should work) on the pad from each of the side pads to the middle pad, if you don't twist a pair of through hole resistors like this
  4. Break out the stop on the potentiometer with some small pliers, you need the pot for its use as a rotational bearing
  5. solder on the resistors, if you used the pair of through hole ones, I recommend bundling them in electrical tape like so. For the servo that will go on the front, cut a notch for the wire to exit through the side so it doesn't come from under the robot.
  6. (not shown) Before you close up, put a hole in the back part of the case opposite the spline to mount the idler (wheel with no teeth).
  7. Use some angle cutters or pliers to remove any mounting flanges from the cases and file or sand down the ridges they leave, these can get in the way later.

<br> Really, really neat!<br> It's hard to make a narrow robot when you're using continuous rotation servos because of the gearbox height, but you've overcome this with the tracks and the asymmetric mounting method.<br> Just to clarify, you've drilled a hole for the idler pinion in the servo bottom cover in line with the spindle?&nbsp; Must have been pretty tight in there - the boards in those 9g servos don't leave a lot of room.
To mount the idler I did it just as you said, its screwed into a hole drilled on the back cover opposite the spindle. I had to be sure not to put the screw in too deep so it wouldn't hit the board, but in the ones I was using the board was slanted so it wasn't too near the back wall at that point. I've noticed with these cheap ones it isn't always the same slant, but on the ones where they installed it so that the near side is on the end I want to mount the wheel to I just tilt it the other way before I put it back in when I do the modification.
<p>What is the total cost of this project, I dont have any of the pieces that I need.</p>
<p>Thanks a ton, this Instructable gave me a great idea for our Cub Scout group.</p><p>I just posted my Instructable &quot;Arduino Robot for Under $5&quot; based what I learned here.</p>
<p>Awesome job! here is another type of microbot, do check it out: http://www.instructables.com/id/Arduino-Nano-Segway/</p>
<p>how did you attach two wheels to one servo in step:2</p>
<p>can we use gear box instead of servos</p>
<p>what is the hypothesis of this robot</p>
<p>how do you wire the battery to the circuit?</p>
<p>Nice cool lil robot... im gonna build one.. need to order the wheels </p>
This is awesome mini tank. What I would do when making this is add a claw and a lazer
it's awesome. but can I use a keyboard to provide the input to this minute Robo?
<p>I'm thinking of things I could add on to this. So I'd like some feedback from anyone interested. What kind of wireless would you most like to see? WiFi, Bluetooth, simple radio such as a OOK transmitter?</p><p>Any other uodates? Maybe a different miniature electro-mechanical part like a claw/grabber.</p><p>Also, changes to make it more usable. Let me know, no matter how simple or complex.</p><p>Thanks</p>
<p>thank you is very good too</p>
<p>I'm looking at some potential li-ion batteries and was wondering what you would recommend? I found a 250mAh 3.7V battery on eBay, do you think that would cause any issues with a 5V arduino nano?</p>
<p>I considered this too. I've found that in my case at least the Nano will not turn on at 3.7V. However, the chip onboard is an ATmega328, rated for 1.8 to 5.5V. The reason it won't run at 3.7V is the 5V regulator on the board. Bypass that and it will run down to 1.8V, though depending on your servos you will need more than that, 3.7V seems to be enough for the 9g servos I've been using.</p>
How much does this cost in total
<p>If you get cheapo parts on ebay*. about $30</p><p> *I haven't used these particular parts, they may be crappy</p><p>$5.50 for the micro servos [<a href="http://www.ebay.com/itm/2x-SG90-Micro-9g-Servo-For-RC-Helicopter-Hitec-JR-Futaba-Align-Trex-US-Sel-/191402239783?pt=Radio_Control_Parts_Accessories&hash=item2c90766727" rel="nofollow">for example</a> ]</p><p>$5 for the nano [<a href="http://www.ebay.com/itm/Arduino-compatible-Nano-V3-0-ATmega328-Mini-USB-Microcontroller-Board-Cable-HIYP-/221608533427?pt=LH_DefaultDomain_0&hash=item3398e5ddb3" rel="nofollow">ebay</a>]</p><p>$10 for the tracks [<a href="http://www.ebay.com/itm/NEW-Tamiya-Track-Wheel-Set-70100-NIB-/390914477064?pt=Educational_Toys_US&hash=item5b04518c08" rel="nofollow">ebay</a>] though I would reccomend making your own, since you don't need the whole kit, and I just had the small wheels left over. For example you could use plastic bottle caps and silicon bracelets.</p><p>I salvaged the battery, but if you can't find an old cell phone battery something like this would do: $2 [<a rel="nofollow">USB li-po charger</a>] $6 [<a rel="nofollow">tiny single cell li-po battery</a>] convieniently, this is already the right voltage to run the arduino nano. One could easily add jumpers to make it charge while hooked up to program.</p>
<p>Hey, I've been meaning to purchase some threads for my RC projects and on your link for the tracks[ebay] they cost 7.59+12.75 shipping when on ebay app or pc, but i check your link when on mobile it's 7.59+2 dollar shipping? I'm confused. Did you buy them with shipping for 10 dollar? are they based near you,thus shipping was lower?</p>
<p>Hi, this is great project. I'm little confused about communication between the Arduino Nano and the Andorid app.</p>
<p>I have followed the instructions on how to make the servo have continuous rotation, but as it doesn't have the potentiometer connected, the servo doesn't realize that he finished turning and it never stops. Please, someone help.</p>
<p>That is what is supposed to happen. The servo is supposed to turn continuously (around and around without a limit) rather than just moving to a position. To allow this, rather than the signal giving you a particular position, it will give you a particular speed.</p><p>So to stop, you must send the signal for zero, which is usually a 1.5 ms pulse, on a normal servo this would be the middle position. Likewise 2 ms is full forward speed for as long as the signal is applied, where on a normal servo it is full forward position for as long as the signal is applied. Likewise 1 ms will run full reverse, while on a normal signal it would hold in the full reverse position.</p><p>note: some servos vary in exactly where their forward, 0 and reverse limits are. IE they may stop at 1.3 or 1.7 ms pulse.</p>
Thanks, I discovered the numbers for my servo. <br>Full forward:180<br>Full backward:0<br>Stop:85<br>For a strange reason, the stop is not in the middle.
<p>Hello! I saw it and I wanted to help. I believe it is a problem caused from the potentiometer inside of the micro servo. But, when you &quot;hack&quot; the servo for full rotation, potentiometer will not matter and it should work just fine. For hacking the video, you can find bunch of videos online.</p>
<p>Can you do it with the raspberry pi?</p>
It could certainly handle the calculations, being way more powerful by orders of magnitude than a nano. It might be a bit big.
<p>Do you think you can try to do it?</p>
<p>I might, but I don't actually have a pi to work with. I mostly use microcontrollers on my own boards rather than dev boards. I do have a few, some arduinos, a cypress pioneer kit, some beagle bones, but no pi.</p>
This looks awesome! I plan on making a pair of these rc controlled with laser and light meter modules on these and having them be mini battle tanks :)
how i can make a nano tank controlled by bluetooth with this? (sorry for my bad english)
No worries, your English is good. This is easily acomplished. For an adapter use an hc-06 module, you can get them for $7 or so on evay and they use rs 232 serial, which the nano supports. I refer you to this other instructable : http://m.instructables.com/id/Bluetooth-Controlled-Arduino-RC-Car/all/<br>You would have to replace the motor commands with the kind i used with the servo library. Also there are free apps with blutooth rc controllers which may work better for you since that instructable doesnt detail the app very well.
<p>Great project!</p><p>Having a hard time finding genuine Arduino Nano's and I'm Leary about 'compatibles'.</p><p>Can I use an Arduino Micro instead?</p>
Yes, that certainly would work. In fact any chip or board that can generate a PWM signal at 500 Hz can do it, though some require an external programmer. It looks like the Micro does have a USB connection of it's own so you should be all set.<br><br>On another note, I haven't had much trouble with 3rd party arduino based boards, but the genuine ones are of better quality, and it is good to support the people who create the IP.
Hi, I tried making the robot but I'm trying to find out what's the battery is for. I'm new at this so some things are confusing.
<p>I didn't see this comment. It got buried. According to the arduino Nano datasheet it prefers 7 to 12 volts. So if you can't find the type of battery I used a 9V should do it, or an 11.1 lithium battery (which would need a special charger), or any other battery pack that will get you a voltage in that range.</p>
It's my dream to learn this sort of stuff. Where did you learn programming language? What's this things top speed?
<p>That's it's top speed in the video. Maybe 1/2 m/s, I would guess. That depends on the servos and drive wheels you use.</p>
<p>That is one sleek-lookin' robot! Great job.</p>
is there a way to do this with arduino uno<br>
<p>The robot could certainly carry one, and the servo library works on uno as well (it was actually on uno first) so if you wire the power and servo signals to an uno there is no reason it shouldn't work.</p>
<p>Great! Congratulations!</p>
<p>Hi Paul,</p><p>I found myself with a lot of bits and pieces lying around and like you decided to make something out of them. It turns out I have an Arduino Nano, a Tank Gearbox from Tamiya (the sort that takes 2 ordinary motors to allow for tank type driving), a PING sensor and some tracks and wheels. So I cobbled together a bot using this gearbox and it actually looks great. My question is about controlling the motors using the Nano vs a pair of servos. As I understand it, I would need a NPN Transistor, a resistor and a diode for each motor (say one hooked up to D9 and one to D10 on the Nano as you have). Would you say that this is a viable approach (I'm more ME than EE so I have to ask)? I can then connect the PING to D11 or any other PWM pin and change the code to interrogate the sensor every few rotations.</p><p>Does that sound about right?</p><p>Thanks,</p><p>Samer</p>
<p>use an H-bridge motor driver<br>it ll wrk fine</p>
<p>That approach would work, but you could only turn in one direction. If that is ok then yes. For a simpler approach, check out the L293D, it contains 2 H-bridges and can drive two motors both directions . It can be gotten for 1.25+$5 S&amp;H at sites such as this (<a rel="nofollow">https://www.taydaelectronics.com/catalogsearch/res...</a></p><p>And if you search on google for Arduino L293 you will find a wide array of diagrams on how to connect it, and code examples of how to use it, because it is a very common chip.</p><p>It handles about 0.6A per channel, and comes in a DIP package. If you need more there are several other &quot;Push pull&quot; or two channel H bridge chips, including the L298n.</p><p>If there is any confusion about how to use it just ask. Like I said theres a ton of example code and diagrams out there.</p>
Excellent, thank you!
Couldn't you just use a regular motor instead of a servo. It might bring the price down. And the code<br>Would just change a little bit
Yes that would work, if you want to get one with a tiny gearbox and add a little motor driver circuit, which wouldn't be too difficult. I haven't found tiny gear motors with enough reduction and motor drivers that can be gotten for less than $2 a set.
<p>May i ask you where i can find these wheels and belts ? :)</p>

About This Instructable




Bio: I am a robotic engineer, and I like to make things and teach others.
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