Introduction: Robo-Mobile - a Homemade Bluetooth Robot


This robot is one I built to learn. Before this project I did get my feet wet with a few small scale Arduino projects like an ultrasonic robot, (that would move backwards until it was a certain distance away from the wall,) and I did get to play with a few of the shields designed for the Arduino, but I had never built a full scale project with this microchip, or really, any microchip. I knew if I was going to continue on this journey of being a hobbyist I would have to fully understand the Arduino inside out. I wanted a project that would accomplish my goal, (or just get closer to my goal of fully understanding the Arduino,) and one that would be useful or fun to play with after completion! The project that would help me do just that was the Robo-Mobile.


The Robo-Mobile consists of two parts: a chassis and a robotic arm. The arm was designed to be able to pick up items, move them, and drop them in specific places. It was also designed to have a solid range of motion and should be able to move objects with reasonable weight. This arm would then be mounted on a chassis that can then move around like a car. Since the chassis was easier to make, I will be starting this Instructable with the chassis, and I will move to the robotic arm afterwards. This robot was built purely from scratch. (Okay, maybe not the motors, or the Arduino, or the wheels, etc. But no kits or pre-built robot arms or chassis are used in this robot.)


There are many contests that I have entered this Instructable in. One contest I really have hopes up for is the Full Spectrum Laser Contest. I know that there are over 1000 entries and that I am really late, but if you like my Instructable please give me a vote. If I were to win the 3d printer or laser cutter I could greatly improve my robots and other projects.Thanks in advance!

Step 1: Choices

There were many choices I made throughout the process of building this robot. But in this Instructable I am going to put the bigger and more important choices I made together, right here at the beginning.

Remote vs. AI

Every robot has to have some way it is controlled, the robot can be computer controlled through some kind of AI loop program, or the robot can be remote controlled, making movements based on user inputs! While making the Ultrasonic robot, (the other project I made with Arduino,) I chose to make an AI loop robot. I knew this time I would have to explore the realm of the remote control to improve my Arduino skills further. (AI loop robots are in fact harder to perfect because they need the ability to react to the outside without a user telling them what to do at every given time. But because I hadn't already made a remote controlled robot I thought it be interesting if I tried something new. Plus remote controlled robots are more fun to play with after the completion of the project!)


After deciding that this was going to be a remote controlled robot I needed a way to tell it what to do. I needed a way of communication. For communication, there were a few options. The first one being the old school wired communication. This would have been the easiest method to implement, but wired communication is "Old School," technology is moving forward and wireless has become a must have for new devices. (Ex. Wireless charging, Cell Phones, Wireless Keyboards and Mice, etc.) Wired communication would also constrain the robot's range, not allowing it to move without a wire "tail". The method I chose to use was the well known wireless communication called Bluetooth. I know that remote controlled cars usually use radio frequency and now that I'm looking back at this project I think using radio frequency instead of Bluetooth might have been a better idea for this specific project. But going back to the goal I had in mind, I went with Bluetooth for experience! I felt that other projects I would make in the future with an Arduino would be controlled using smartphones and other Bluetooth devices so I chose to use Bluetooth for this project! (The downside is lag. If I ever made a v2 I would explore with radio signals instead.)


Now for the controller. I knew I was going with Bluetooth. But making a controller work was a entire different story. Since my robot is really two parts, the chassis and the arm, I chose to split up my controllers too. For the chassis, I used a simple android app to control the movement of the robot. The android app was written by myself using MIT's App Inventor. (I will go into more detail in one of the next steps.) For the arm, I used a dummy robot arm that the real arm would mimic. When I move one of the joints on the dummy arm, the real arm on the robot would mimic the same position. This method has many benefits which include, ease of implementation and ease of use. If the controller was also a button based android app that moved a single motor one at a time, moving the arm to a specific posture would have been a pain. The only downside of this method was the need to build a 2nd arm which isn't really that bad considering after building one all you need to do is build a copy.


Before I cut the first piece of my chassis. I had to choose the material my robot would be made out of. As you may have seen from the pictures above that I chose to make mine out of plywood! I know that there are other materials out there that may suit this project much better, but I chose to use wood because I was confident working in wood! I knew how to operate wood fairly well being able to use the basic power tools suiting my needs. (Basic power tools I use include a Drill Press, a Miter Saw, a Jigsaw and a Dremel rotary tool. These tools were the tools I used to make my project but substituting the drill press out for a drill or a hand saw for the other power saws are perfectly reasonable.)

Time to start building!

Step 2: BOM (Bill of Materials)

There were many components in this robot, much more than my old ultrasonic robot had. The list I have is here:


  • 3x Arduino Unos - one is used to control the arm, one is used to control the car, one used as the dummy arm control board sending signal to the Arduino controlling the arm. (Had one and picked up two more from my local electronics store.)
  • 1x Bluefruit EZ-Link Shield - Buying a specific Bluetooth shield wasn't really necessary but to ease into the Bluetooth I bought this for ease of use. Using breakouts like HC-05 is perfectly fine. (You will see that I did buy HC-05s for the arm and dummy arm because this shield can't run as master and only as slave. Needs soldering.)
  • 1x Adafruit Motor/Stepper/Servo Shield for Arduino v2 - Be sure to get the v2 edition because this shield can run motors up at 1.2 A each. (This is a great shield for the Arduino, needs soldering though.)
  • 1x Adafruit 16-Channel 12-bit PWM/Servo Shield - This kit wasn't really necessary it just made life a little bit easier. Driving the servos for the arm could have worked with just the Arduino. (Needs soldering.)
  • 2x ProtoScrewShields - They are both used to make my own shield for the HC-05 and other circuits that weren't included in the other shields. (Picked up from my local electronics store. This shield isn't made for Arduino Uno R3 but instead an older model, even though it is missing a few pins it worked in this project.)
  • 4x Header Kits - Used to stack shields, I personally used 4 sets because the Adafruit shield kits didn't come with stackable headers. (1 set for Bluefruit, 1 set for Motor, 1 set for 16 channel, 1 set for spacing out shields to plug servos in.)
  • 8x Flip switches - Used to turn on and off the different electronics. (I used 8 of them but it depends on the wiring.)
  • 2x HC-05 - A Bluetooth breakout I used to connect my dummy arm with the arm.
  • 4x Solar Servos - I bought two D772, one D227, and D653. These had the most torque I could find at a reasonable price.
  • 1x Electro-Holding Magnet - This is used as the "Picker" in this project.
  • 4x Feedback Servos - I bought three standard sized feedback servos and one mini servo but they essentially do the same thing.
  • Wire - A various different kinds of wires were used in this project. Some wires used were specific servo extension wires for organization purposes, but most wires were just "Regular Wire."
  • 4x Battery Packs - I used two 4 AA battery packs, one 6 AA battery pack, and one 8 AA battery pack.
  • Batteries - There were many batteries used in this build. I specifically used 22 AA batteries and three 3 9v batteries. The 9vs were used to power my Arduinos when the AAs were used to power the motors and Electro-Holding Magnet.
  • 4x Pololu 298:1 Micro Metal Gearmotor MP - These are the main motors for the chassis.
  • 7x 9v Battery Snaps - These are used to connect the battery packs I bought to the circuits.
  • 3x Arduino DC plugs - These are the basic power connectors for the Arduino.
  • Male and Female Headers - Different from the kits these are used to connect breakouts to my self designed circuits.
  • Resistors - There are a few different resistors used in this project, they are all used in the self designed circuits.
  • 1x TIP Darlington Transistor - This is used to control the only "High Powered" component in this build, the holding magnet. (The model # might not be the same. I used a NTE 261 which is essentially the same.)
  • 1x Rectifier Diode 1N4001 - Also used to control the holding magnet. (Model # of the equivalent diode I picked up from local electronic store was the NTE116.)

Other Parts

  • 2x Pololu Micro Metal Gearmotor Bracket Pair - These are used to mount the motors onto the chassis.
  • 2x Pololu Wheel 60x8mm Pair - These are the wheels of the chassis. These wheels are small but fit the robot well. Larger wheels could also work.
  • WOOD - If the body is made out of wood. I used some scraps I had laying around but basically they wood I used were about 1/4 inch plywood and 1 inch plywood.
  • Electrical tape - This is a must have to keep the electronics insulated.
  • Double sided tape - Used only to tape a box to raise the dummy arm platform.
  • Box - Not entirely needed, but it is a simple way to raise the dummy arm platform for easier use.
  • Fender Washers/Ball bearings - These were only used as my counter weight for the robot arm. Something had to be used here so I used ball bearings and fender washers from a previous project.
  • Variety of different screws, bolts, nuts, and washers - These are used to connect one of the parts of the robot to another.
  • 9x Ball Caster Wheels - These are used to make a smooth base for the robot arms. I picked these up from my local hardware store and they were a perfect height for my motor. If they aren't the right height using washers to raise them works too. (More info in the step.) I used 5/8'' Roller Ball Bearings.

Step 3: The Chassis


When I started this project I knew I wanted a small but stable robot. My criteria was pretty straight forward, it should be a large enough to fit my electronics, but not too big and heavy that my micro gearmotors wouldn't have enough torque to drive it. I decided to go with a 20 cm x 20 cm platform.

Once I finished cutting out the piece of plywood, I marked holes for the brackets and drilled them out. After a little toying around with a screwdriver and the nuts, I mounted my gearmotors onto the chassis. I wasn't able to hold back the temptation of attaching the wheels so I put them on to get a look for the robot!


As I said before, the chassis of the robot is the easiest part of the project, so after mounting on the motors, there was nothing left to do but to mount the electronics and get this robot moving! I pulled out my dusty Arduino (which hasn't been touched since the last project) and the new Adafruit Motor Shield v2 which was still just a bag of parts. Adafruit Arduino shields are great! They are easy to use and little to no troubleshooting required. The only downside of Adafruit shields is the need to solder them. I can say that I am proficient at soldering and this really wasn't a problem for me. The only tricky part were the pins/headers that were a little closer together, but I got pretty good at this after soldering four of these Adafruit shields. (Note: Adafruit shields don't come with stackable headers. These are bought separately.) I am not going to show each and ever step of the Adafruit shield assembling since they have a great step by step guide on their website doing just that.


Once the shield is finished it is time to put it to use. I drilled in some holes in the front and the back of the chassis to bring the wires from the motors to the shield. I then hooked up my motors, each to a port on the terminal blocks using some wire I had lying around. (Sorry I don't have the gauge of the wire I used.) Once the motors were hooked up, I hooked up the battery pack using a 9v battery snap. Once the wiring was ready, I plugged my Arduino into my computer and uploaded a slightly modified example sketch that came with the v2 shield. I modified it to drive 4 motors and adjusted the pattern of the automated loop to test kind of movement. (Forwards: All motors driving forward. Backwards: All motors driving backwards. Turn/rotate right: right side motors move backwards as the left side motors move forward. Turn/rotate left: left side motors move backwards as right side motors move forward.)


Once the sketch finishes uploading it is time to power up the Arduino's power supply, and let the chassis run. During the forward section of the loop make sure that all motors are moving in the same direction. It is always good to elevate the chassis off the ground or hold it up in the air during first run since if the leads of the motors are backwards/flipped, the motor will spin the other way making the chassis lock up when motors move in all different directions. As I mentioned above, if motors are backwards just flip the leads on one of the motors or on the motor shield. After making sure the forward function works properly make sure you mark the direction forward is since the chassis is square and we have no way of identification. Also, don't forget to check the direction of left and right turn, make sure they are doing the correct action.


After being able to move the robot autonomously, it was time to hook up my communication method. I knew it was Bluetooth because of the choices I made in the beginning, so I bought an Arduino Bluetooth shield. The shield I used for Bluetooth was the Adafruit Bluefruit Shield. This shield was by far the simplest Bluetooth solutions for Arduino. Even though the shield comes as a kit like the motor shield, it doesn't need any AT commands or any of the hard calibrating to use this shield. All you need to do is just boot it up and connect with a Bluetooth device. (Later on, for the robot arm, I will be using the HC-05 because this shield wasn't able to be use as a master, the controller.) So after the soldering and assembling was finished, I plugged my shield right on top of my motor shield which was on my Arduino, I am really starting to stack shields. Finally, I plug my Arduino back into the computer to upload a new sketch, one that includes the Bluetooth shield's set up code found from the Adafruit resources. Now it is time to make this chassis - remote controlled.

Step 4: App Inventor: Intro

How Bluetooth works with Arduino

Bluetooth for the Arduino is basically a wireless serial port. If you don't know what a serial port is, it's basically a place where commands can be sent through to control your Arduino if it is programmed for the commands you give it. Usually this is achieved by connecting the USB to the computer and sending the data from a window on the screen to the Arduino. But now that the Bluetooth shield is connected, there isn't a need for the USB cable. Commands can now be sent from a connected Bluetooth device to the Arduino. This is exactly the function we will use to make our remote.

For us, we are first going to make it so that the android phone can be "paired" or connected with the Bluefruit. After pairing it is then connected and able to send commands through the serial port. This is going to be useful because our app is going to send the Arduino a command or in this case an easy # or value when a button is pressed in the app. Once sent to the Arduino, the Arduino takes the value and matches it with a command, once it knows its command it executes it. This is how the app will control the Arduino and therefore the chassis.

To make programming this app as easy as possible to make I used a tool called App Inventor. This tool now owned by MIT, originally owned by Google, was the easiest way to make a quick android app for my robot. App Inventor is a tool that uses blocks as its programming language. (A lot like Scratch.) You drag blocks and connect them to make a logic chunk that is the programming of the app. I will quickly go over the layout of App Inventor. App Inventor consist of two different kinds of views, block view, and the designer view. The block view shows the logic and programming. The designer view shows the look and feel of the app. App Inventor isn't very up to date on designer and has the old Android 2.x look, and not all the functionalities are available, but for our purpose it is a quick and dirty solution.

The way I made my app starts with the designer blocks. There are three essential blocks for this app: a Listpicker, a Button, and a BluetoothClient. These are the essential blocks of the app and are a must have to insure app works. Each of the blocks are explained below.

Listpicker - On the designer screen the listpicker will look exactly like a button but this button is different. This block allows you to pick a choice from a list. In the app this component/block will be assigned the list of all the Bluetooth addresses know to the phone and will be used to pair the phone with the Arduino. To ensure connection, every time the app is opened the Bluetooth address should be connected again.

Button - This component is the main input of the android app. It is the way the app knows when to send a signal/value to the Arduino and which signal to send. If a button is labeled "Forward," the button should send a value to the Arduino through Bluetooth that the Arduino will interpret as a forward command. The app should have many buttons, each one sending a different value to the Arduino, and the Arduino will interpret the commands differently based on the value received.

BluetoothClient - This is the main component that will make the app "Bluetoothed." It will give many functions/blocks that can then be connected to other blocks like the button and the listpicker to make the app work.

Other useful designer blocks:

Labels - These are pretty self explanatory. They can be dynamic and change, or just stay as a static label on the screen.

Arrangements - These are basically the dividers. Without the arrangements, the components are all organized one underneath the other. With arrangements, components can be arranged almost any way.

Step 5: App Inventor: Designer View

Designer View

The first thing to do is to is to get the designer components all laid out onto the screen. There are five buttons that are needed. Forward, Backwards, Right Turn, Left Turn, and Stop. Since the app I designed was really not going to be used on a phone but instead a 7 inch tablet. I wanted to be able to stop the robot with both my right and left hands, so I put two stop buttons one on each side to come to a total of 6 buttons. I then put my ListPicker or really the going to be Pair button right in the center with a dynamic label that would signify that the device was connected. (The label doesn't check if the device got disconnected though.) I did use the arrangements to make my screen as pretty as possible. After dropping the buttons on screen, I used the toolbar on the right side to configure the text displayed on the button. I made all the buttons' labels the function they are used for. (Ex. Forward Button labeled Forward; Backwards Button labeled Backwards; Listpicker labeled Pair etc) There were two more non visible components that I added to the app one of them was obviously the BluetoothClient but the other one I added was the Notifier. The notifier allows you to display messages. I added this component because I wanted to be able to display a message telling the user to turn on Bluetooth on their device. These are the components that I used to make this app. Now time for the Block view programming.

Step 6: App Inventor: Block View "BeforePicking"

Block View

Near the top right corner of the screen you will find two buttons one that says "Designer" one that says "Blocks." Click on the "Blocks" button to move to the block screen. On the blocks screen you will have a left toolbar, and a blank screen. The left toolbar will be the place where you drag blocks out of, the right blank side allows you to place your blocks and build. To build our app we need at least three "chunks." The first chunk is the the before the listpicking, the second is after the listpicking, and the third is the button that will send signal to the robot. Since I had 6 buttons I will have 8 chunks. If you don't care about the logic behind the app you can just skip the the pictures and copy what I did. For people that want the explanation for each and every block here it is:

Explanation for: "BeforePicking"

First you have to drag out the "when ____. BeforePicking" block from the listpicker. This block allows the app to initiate what list the listpicker will pick from. In the "do" part of the block drag in "set____.Elements to" block. This is the block that will assign the list the picking will be chosen from. Notice how there is a small notch at the end of this block, this is the place where the list will be put in. Without anything in the notch basically nothing will be assigned to the elements and it will be empty. But we want something assigned to the listpicker. Specifically we want the list of Bluetooth addresses. To do this go into your Bluetooth_Client and drag out the ''___.AdressAndNames" block. As I said before, this is the list the listpicker will be assigned. This is the end of the necessary parts of the app, but to make the app work. The next few blocks I use will be to remind the user to turn on Bluetooth if they haven't already. This is just made by putting an "If, then" block after the setting of the listpicker. In the "if" notch I will put a "Not" block from the logic part of the toolbar and in that notch I will place the block "__.Enabled" from the Bluetooth client. This part of the code basically states: If Bluetooth isn't enabled. The next part in the then section we put the "call___.ShowAlert notice" from the Notice block and in the notice notch I will place a text block stating "Please enable your Bluetooth in settings." The translation of the blocks to plain English is here: When the listpicker is initiated, set the list of Bluetooth addresses to be the list the picker chooses from; also if Bluetooth isn't enabled show a message stating so. You can see exactly what this chunk does.

Step 7: App Inventor: Block View "AfterPicking"

Explanation for: "AfterPicking"

First you have to drag out the "when ____.AfterPicking" from the listpicker. This block will do whatever is is in the "do" section after picking an address from the listpicker. Next we drag in "call ____.Disconnect" from the Bluetooth client. This will make sure the Bluetooth isn't connected to another device. Next we use the "evaluate but ignore result" block from the control section. This block allows us to connect notched blocks into the "do" section of the chunk. We connected "call __.Connect address" from the Bluetooth client. We then connect the address we just picked from the listpicker by putting in the block "___.selection" from the listpicker section. Like again, this ends the essential part of the chunk but to get some indicators that the app was correctly connected, I am going to check the connection and change the text if it is connected. Because I did put text in the designer view I now have a label I can change around. I use the "if then else" block to first check the connection and change the text to connected and green if it is connected and I set the text to Not Connected and red if it isn't. Like before I put the "____.IsConnected" block from the Bluetooth client into the notch in the "if." I then placed the "set______.Textcolor to" and "set ______.Text to" blocks into the then and the else and set color to green and text to connected in then and set color to red and text to Not Connected in else. The translation of the blocks to plain English is here: After the listpicker has picked its choices disconnect all Bluetooth and connect the Bluetooth address that was picked; also check if the Bluetooth is really connected, if it is then set the label to connected and green and if it isn't set it to not connected to red.

Step 8: App Inventor: Block View "Button Click"

Explanation for: Button Click

This is the main component of the app but it is also really simple. First drag in the "when" from the button you want. Then in the do section drag in the "call ___.send1byteNumber number" block from the Bluetooth client. This will send one byte of data or really a number. The number I assigned to this button was 1. The highest number this block can send is 255 so if you have more than 256 buttons (don't forget 0) then you will have to use a different block. The translation of the blocks to plain English is here: when button a is clicked send a byte data, in this case 1 to the connected Bluetooth device. These are basically the chunks you need for the app. You will have to duplicate the button chunk and change the variables to send different values when different buttons are clicked. That basically finish up our app.

Step 9: The Arm: the Base

The robot arm was much more difficult to make then the chassis was. One of the greatest problems I had with the robot arm was a problem with toque. The arm I designed had three parts just like how a real arm. It has a base which can turn the arm 80 degrees left and right (~160 degrees range). The second part is the the up and down motion which allows the arm to move up and down. (Lowest point is little more than parallel to the ground and goes back 60 degrees up from there.) The third part of the arm is the part that is attached to the second part and can also move up and down. (This part can almost fold into the 2nd part or fully straighten out.) There is a 4th part to the arm, the head of the arm and the little wrist that allows it to always be able to touch the ground perpendicular to it. These were the 4 parts to the arm. When building though I found that most servos were too weak to do anything on this project so I was able to find specially high torque servos.

The Base

The first problem I faced was making the base. I wanted to have a servo upright with shaft pointing up. This would allow it to turn a platform. But if I were to mount a platform directly onto the shaft, the shaft might not and probably not be able hold and balance the amount of weight, and will put on a lot of strain on such a small motor/shaft. If I were building a smaller and lighter robot arm, just mounting the base platform onto the servo might work. But since the arm was going to carry a considerable about of weight I decided to build a "Lazy Susan" like base for my arm to rotate on. To make this "Lazy Susan" I used six pre-housed marble omni-wheels. They were a dollar each at the hardware store. To build this base, I took a piece a wood and cut a hole into it to fit my servo. This hole should be as snug as possible but still able to fit the servo in. The after fitting in the servo I marked the 4 holes that could be then used to screw and secure my motor. Once secure I had to layout my 6 omni-wheels to form a circle around the motor shaft, notice how I said specifically the shaft. This is because when the base rotates on the servo the center of the circle is the shaft and not the middle of the servo. So arrange the omni-wheels, so they are equal distance away from the shaft and as close together as possible. This is to make sure the base is small so the arm is lightweight enough for the chassis to drive it around. After marking the holes for the marbles, I drilled them so that screws could be used to fasten them. (I always drill a pilot hole for the screws to lower to possibility of splitting the wood.) Once fastened down I mounted the shaft adapter to a circular cut piece of wood. This piece of wood was going to be for the platform of the arm. I put my little platform with an adapter on to the servo. I then examined the base, looking from the sides, depending on the servo and wheel dimensions, the servo could be taller not allowing the marbles to hold the weight of the arm. The servo could also be too low, this will result in not being able to reach the platform and therefore not be able to exert the servo's rotation onto the platform. If you have one of these cases, all you need is to raise the wheels or the motor with some washers or even nuts. After alignment, the wheels should just barely be touching the platform. After finishing the alignment, screw the adapter that is attached to the base into the servo and you are finished with the base.

Step 10: The Arm: the First Joint

The First Joint

The next part was the first joint of the arm. The way I designed my arm was to have the joint servo is mounted on the base platform and have the extension sticking out. After many versions of servo mounting, I found that just putting bolts through the 4 servo holes and connecting them to a piece of plywood at the back was the easiest and most effective way to mount the servo! So after gluing on a block of wood to raise the fulcrum a little so the arm could move, I attached the servo with as small piece of wood. I was only planning on using one servo for this joint but to connect two parts of the arm, the shaft would have to stick out from the other side. I decided that I would mount a bolt on the other side. This allows me to stabilize the two pieces of the the extension without using two servos. Now it is time to connect the extension of the arm. I knew the robot arm was going to have some pretty heavy weights in the front, because the weight is far away from the fulcrum the servo would have to lift more weight then if the weight was just close to the fulcrum. My servos even though they have high torque can't lift my arm up without help. This is why I added a counterweight on the back of this first length. I extended the extension a little bit towards the back so my counterweights had space to be mounted on. For counterweights, I used a bunch of washers and skateboard bearings that I had laying around, I then put them through a spare bolt and mounted that on the back. I like to call it the "Cylindrical Heatsink" because of the awesome look it gives to the robot, but really it is just extra weight. Another part of the I did to remove weight so my motors could lift the arm was to drill out wood in the extension. The holes in the extension wasn't made for looks but it was to remove some of the weight from the arm. You might ask if it really weighs that much, really it is only a few grams but because of the distance away from the fulcrum ever little ounce counts!

Step 11: The Arm: the Rest

The Second Joint

Next up the second joint of the arm was a little different then the first one was, this time instead of mounting the servo on the pre-built extension of the first part of the arm, I mounted my servos on the extension of the second joint and connected it to the extension of the first joint. I knew that my arm had to be able to touch the ground in more than one place so I made my extension a reasonable length. Again the weight would be a problem for the servo so again I drilled out wood from the extension too. When I was testing an earlier version of the arm without the wood drilled out from the extensions, the torque of the servo at the bottom was getting strained. It did work, but the motor was on the verge of dropping the arm. After drilling out the wood, the motor easily picket up the arm. This meant that the motor was just on the borderline, with the few grams of wood lost it was able to move the arm without difficulty.

The Attachment

After installing the second joint and extension of the arm it was time for the final part, the main attachment. A robot arm needs to be able to pick up objects. The choice I had was what attachment I would use. This was one of the smaller choices that I had to make so I included it here. The most common attachment was some kind of claw that allowed it to pick up what it desired. But I had a better idea, using an electo-magnet I could pick up any item that could be picked up by a magnet, it allows for easy pick up and release. With an electro-magnet, I had everything I wanted, excluding picking up non magnetic objects. But what if I made an attachment for all objects? That is just what I did! Took a fender washer and glued it to a block of wood. On this piece of wood I would stick duct tape facing outwards. This means that I could used the electro magnet to pick up the washer on the attachment then I could use the duct tape to pick up items. To drop items I would have to drop both the duct tape and the object. This was the easiest method I could find it still isn't perfect but it was the best I could get it. Before I mount the electo magnet I had to mount a small servo. This servo would allow for fine adjustment to the angle the tape would touch the item. This time I used a different approach the mount the servo yet again. I decided that I would make the servo attachment consent and have the servo move. After mounting the servo I glued together a piece of wood and drilled a hole into it. The hole then allowed me to stick a bolt in a therefore mount the electro magnet.

Step 12: Dummy Arm: the Base

This arm is the controller of the other arm. The controller doesn't have to be able to move so I don't have to worry about toque issues. Since this was the second arm I made it was much easier. Note: Steps taken here are basically the exact same I took for my real arm so it won't be that descriptive. Like the arm before, I took the same steps to make this arm. The first one being the base.

The Base

Even though it wasn't necessary to have a stable base (since the arm didn't have to support itself) but having a stable base would only produce benefits. To make this base I used the same method as before. Since the base I had on the real arm was the second one I made (the first one was for a different motor that didn't work) I tried to savage my base to see if it would fit my new feedback motors, they did. Since this base didn't have to support as much weight as the other base did I only used three marble rollers. Three of these were enough to stabilize the base. The First Joint Like the other arm, to make the first joint glued a block of wood to the base. On the block of wood I placed my servo and secured them with my bolts and back bracket. Counterweights weren't necessary because the torque wasn't going to be a problem. After mounting the servo I attached my extension without counterweights and finished the first part of the arm.

Step 13: Dummy Arm: the Rest

The Second Joint

The second joint was no different from the first join. In this joint I used the same mounting as the first arm. Since this arm was going to be the controller and the real arm would mimic this arm, I had to make them as similar as possible so electronics were easy. The way I made my second joint was no different from the first one. Just the same drilling four holes into the plywood and just mounting the servo back onto it.

The Attachment

This was the only part of the dummy arm that was going to be different. On the real arm this part is an electo magnet and a micro servo. I also have the micro servo mounted but because I don't need to mount a dummy electromagnet but instead a switch to control the on and off of the magnet. I decided to just place the switch elsewhere on the controller and just mount the servo to the extension with two screws.

The Switch Box

This is where I put all my switches for the controller. I had 2 different power source switches and a switch for my electo magnet mounted here. I made sure that my electo magnet switch wasn't near the other two switches to avoid the accident of turning off the power source switches. That basically concludes the mechanic build of the dummy arm.

Step 14: Wiring: the Arm

This is the part where I will go over the ways I connect everything together. As you already know I have split the wiring into three Arduinos. In the chassis step I already went through the wiring for that. But because of the length of steps I decided to split the build of the arms and their wiring. I will go over them starting from the arm then the dummy arm. Sorry no schematics.

The Arm

To wire the arm I used two shields, the protoshield and the 16 PWM servo shield. As stated before, the Adafruit shields are all kits so I had to solder the PWM shield. Once I finished that, I just plugged in my servos in each of the spaces made especially for servos. Some of the servos would have been far away so using a extension of the wire could help add the length needed to reach the Arduino. Once my servos were wired all I had left was the hard part. Bluetooth and the electromagnet controller. Bluetooth wiring was done on the protoshield, I used this shield to make life easier for myself and not having to make my own pin to component wiring I would have to do on a blank pcb. The Bluetooth module I used was the HC-05. This module was a really flexible breakout and let me do everything I needed. I didn't use another Bluefruit shield because they didn't have master capabilities. Master and slave is basically who is hosting the connection. The Bluefruit shield could only connect to a master. With the HC-05 I could easily make a breakout master and the other slave. No matter which one was slave I still had to wire the breakout. The breakout came with 6 pins, the Key, 5v, Ground, TXD, RXD, and Sate. The Key pin is used to change the settings like role, frequency etc. The 5v pin was used to power on the board and reset the board. The TXD and RXD pins are used to send and receive data from the connected device. The final Sate pin is to check the state of the the Bluetooth breakout. I didn't use the Sate pin in this project. To wire the breakout I decided to solder a row of 6 headers (the Sate pin didn't get connected, but I still plugged it into the headers) I assigned the Key pin to be wired to pin 9, the 5v to pin 8, the Ground pin to the ground on the Arduino, TXD pin to pin 10, and the RXD pin to pin 11. These pins will later be assigned a role in the program and coding.

For the electro magnet, I wanted to be able to control it through the Arduino but because it used 12v I knew it would easily burn it to crisps. The solution I used was the Darlignton Transistor. This transistor is basically an advance switch, I made it so that if the base received a voltage from the Arduino the electricity that powered the magnet was allowed to pass. Essentially it was an electronic switch. This way my switch could be controlled with the Bluetooth. and the Arduino.

Step 15: Wiring: the Dummy Arm

The Dummy Arm

The dummy arm only had one shield and that was the protoshield. The servos I used for this were the feedback servos. Feedback servos didn't have to be able to move but had to send data back to the Arduino stating its angle, I had to connect all the feedback wires to the analog pins so they could decipher the angles, the voltage and ground pins on the servos also had to be connected to power the servos to determine the angle. The Bluetooth breakout was again connected to the Arduino using the same wiring as the other one. Finally I made a physical switch connection to the Arduino. I wanted to have a physical flip switch that would then be sent to the Arduino if it turned off or on.

Step 16: Final Thoughts/Tips and Downloads

I really thought that my robot was pretty awesome once finished. It had everything I wanted and I learned a lot throughout the process. I think my Arduino skills have risen up a level but I'm no where near to uncovering all the secrets stored inside. Hopefully I will start my next project soon. (With an extra 3d printer or Laser cutter under my belt... :-)) Please Vote for my project if you liked it and leave comments. Here are a few tips:

  • Use electrical tape on all exposed wire, even on the back of the Arduinos if you don't have 3 cases.
  • Measure twice, cut once. Just like all projects check what you do before you do it.
  • Explore! You don't have to go on the path I went on. You could even take my build and improve on it to make it your own.
  • I might not have included everything and I know I didn't explain the coding, but the Instructable was about the awesome mechanical and physical item. The code and other links will be included below! (Yes the robot works!)

Robot Contest

Second Prize in the
Robot Contest

Arduino Contest

Participated in the
Arduino Contest

Full Spectrum Laser Contest

Participated in the
Full Spectrum Laser Contest