Actobotics Custom Robotic Arm

Hello everybody.

The purpose of this project is to build a custom robotic arm with parts from Servocity / Actobotics. I know there are a lot of robotic arm tutorials up there, but my purpose is to built a heavy duty arm that can be used for various purposes daily, in your home or in garden or wherever. As always i will use an arduino as the brain and heart of the arm.

Lets start step by step building it.

The arm consist of the below parts:

1. The base
2. The arm
3. The gripper
4. The brain

Base: For the base i used a Servocity DDP155 Pan base with a Hitec HS-5485HB standard digital servo, with 180 degrees rotation. You can also use a common 90 degrees standard servo for the base. Also 2 x Actobotics Aluminum Channels, 2 x ServoBlocks with Hub Shaft and 2 x Hitec HS-311 standard servos for the movement.

Arm: For the arm i used an Actobotics Aluminum Channel & a couple of round plates from old hard disks.

Gripper: For the gripper i used an Actobotics Aluminum Channel & Actobotics Standard gripper kit A also with a Hitec HS-311 standard servo.

Brain: Brain and heart of our robotic arm is an arduino Yun.

Lets continue now analyzing the above parts and building them.

Lets start building the base for the arm.

We will need:

1. The DDP-155 Pan base kit Pan base DDP-155
2. A standard servo (i used the HS-5485HB Digital 180 rotation standard servo)
3. A star screwdriver
4. A couple of screws from old pcs, hard drives etc.

We must first follow the Servocity Pan base DDP-155 assembly full instructions in order to assembly the Pan base The video is very helpful and it will not take more than 10 minutes. Dont attach the round plate to the top of the base because we must build the Aluminum channels for the arm first. Also dont close the bottom of the base because we have to add some weight

Take the screws and 2 or 3 little plastic bags (depend on how many screws you have) and inserted them to the base. Close the base with the bottom round plate and we are ready.

Now we have finished with the base of our robotic arm. Lets continue to the next step.

Lets start building the base channels which they'll hold the arm.

We will need:

1. The round plate from the pan base.
2. 10 x 6-32 Phillips head screws (You will need different sizes)
3. A star screwdriver
4. 2 x 90 Degree Dual Side Mount E hub mount
5. 1 x 9" & 1 x 12" Actobotics aluminum channels

First attach the 90 degrees dual side mount E hub mount with 2 screws to the end of the channel. Because the holes of the round plate don't match with the width of the channel we will connect them with only one hub mount. Repeat this step for the other channel.

Second take the round plate and with 2 screws connect the channels to the outer holes. One screw per channel. Don't worry if they are a bit loose, because when we will attach the arm they will be ok.

Third take the last 4 screws and connect the round plate to the pan base.

Take a look at the pictures above to understand better the hole structure. Lets continue to the next step.

But someone will ask what is a Servoblock?. According to Servocity web page a Servoblock is "an aluminum framework that acts as a servo exoskeleton, greatly enhancing the mechanical loads the servo can withstand". Take a few minutes and visit the official product page for more info Standard Hitec Servoblocks .

We will need:

1. 2 x Servoblocks
2. 2 x Standard size HS-311 Hitec servo motors
3. A star screwdriver

Every Servoblock kit contains the below:

1 x Servo Plate, 1 x Ball Bearing Plate, 1 x Servo Spline Shaft Hub, 2 x Hub Plates & 12 x 6-32 Screws

The fully instructions how to build the Servoblocks can be found here in this video: Building the Servoblocks. You wont need any additional screws because they are all inside the kit. Take a cup of coffee and within 20 minutes you are ready.

In this step we will built the main structure of our robotic arm.

We will need:

1. 4 x Zinc plated socket head machine screws
2. 8 x 6-32 Phillips head screws (You will need different sizes)
3. The pan base
4. The 2 Servoblocks
5. A hex key and a star screwdriver
6. A 90 Degree Quad Hub Mount C

7. A 15" Actobotics Aluminum channel

The first step is to attach the quad hub mount C to one Servoblock with 2 Phillips head screws. Then attach the Servoblock to the 9" channel of the base with 2 Phillips head screws.

The second step is to attach the 15" Aluminum channel to the second Servoblock with 2 Phillips head screws. Then attach the Servoblock to the 12" channel of the base also with 2 Phillips head screws.

Last step is to screw the quad hub mount C of the Servoblock that is connected to the 9"channel, to the 15" channel with 4 plated screws.

Take a look at the pictures above to understand better the hole structure. Lets continue to the next step.

In this step we must add extra weight to the back of the arm and also add the mount that the gripper will be placed

We will need:

1. A couple of plates from old hard disks.
2. 8 x Zinc plated socket head machine screws
3. 4 x 6-32 Phillips head screws
4. A hex key & a star screwdriver
5. 2 x 90 Degree Quad Hub Mount C
6. 2 x 90 Degree Quad Hub Mount D

The arm should be balanced so we must add some weight at the back of it. For that we use plates from old hard disk that we mount them with the 90 degree quad hub mount D with 2 Phillips head screws for one side. For the other side,the open part of the channel, we should use the 90 degree quad hub mount C with 4 head screws, as base for the 90 degree quad hub mount D.

Now move to the front of the channel and at the 4th hole add the second 90 degree quad hub mount C with 4 head screws. That mount will be the base to add the gripper.

The balance of the arm is very important. We may have to add more weight later, when we will add the gripper.

Lets continue with the building of our gripper

We will need:

1. A standard gripper kit A from Actobotics Gripper kit A
2. A star screwdriver
3. A standard servo HS-311 from Hitec

The fully instructions of the gripper can be found here instructions. The video is very helpful as always and if you follow the instructions you will have a fully functional gripper in 5-7 minutes.

Lets continue to the next step.

Lets connect the gripper to the arm main body.

We will need:

1. The gripper
2. 8 x zinc plated socket head machine screws
3. A hex key
4. A 90 Degree Quad Hub Mount C
5. An Actobotics large square screw plate
6. An Actobotics 6" Aluminum channel

First you must connect the quad hub mount C to the other hub mount of the 15" channel. This can be done with 2 head machine screws. Don't forget to connect them in angle.

Second take the 6" channel, the gripper, the square screw plate and 4 head machine screws. Put the plate inside the channel and from the outside put the gripper. Connect them with the 4 screws.

Last but not least, attach the 6" channel of the gripper to the quad hub mount C of the 15" channel with 4 head machine screws.

Perfect!!! Our robotic arm is now finished and ready to work. Lets continue with the last steps.

Cables, cables, cables

It is very important to have your cables in order. They look better & is safer for your arm. We will use 4 mounts to make 2 holders for the gripper servo cables.

We will need:

1. 2 x Actobotics 90 Degree Dual side mount E
2. 2 x Actobotics 90 Degree Dual side mount A
3. 4 x zinc plated socket head machine screws
4. A hex key
5. 2 x 12" Standard duty Servo extensions (I had only 2, you can use 4 to extend all 4 servo cables)
6. A couple of jumper wires male-to-male

Take the dual side mount A and from inside the channel with 2 head machine screws, connect them to the dual side mount E from outside the channel. Repeat that step for both the channels.

Next we have to extend the gripper cable. Very easy, connect the extension to the servo cable (be sure not to confuse the colors) and take it through the 15" channel way to the end where the hard disk plates are.

The cables from the other servos can be extended with the male-to-male jumper cables.

It is very important to know the purpose of every cable of your servos. I use standard Hitec and as all servos, they have 3 different color cables. Black for GND, Red for POWER and Yellow for SIGNAL.

Lets see now the electronic part of our project

We will need:

1. An arduino (I used my Yun)
2. A breadboard
3. A black & a red jumper male-to-male cables.

The only cables from the servos that will go straight to the Yun are only the Yellow/Signal cables. In the below order connect your yellow cables to Yun.

• 9" channel servo --> pin 10
• 12" channel servo --> pin 9
• Pan base servo --> pin 6
• Gripper servo --> pin 5

Now all the Red/Power cables of the servo to the same line of the breadboard and then a new single red cable to pin 5V of the arduino. All the Black/Gnd cables of the servos to the same line of the breadboard and then a new single black cable to pin GND of the arduino.

The arduino code is very simple and we accomplish simple moves.

First we must define the servos. We give simple names that can identified inside the sketch.

1. basechannel1 for the servo at the 9" channel
2. basechannel2 for the servo at the 12" channel
3. panbase for the servo at the base
4. gripper for the servo of the gripper

Second we must set each servo to a digital pin.

1. basechannel1 to digital pin 10
2. basechannel2 to digital pin 9
3. panbase to digital pin 6
4. gripper to digital pin 5

The delay in our code means that we stop the code for some seconds. delay(3000) means that the code stops for 3 seconds etc.

Sketch servo arm2: The code is very simple. We start by moving the arm up, then the gripper opens. Delay for 3 seconds to load the object then the gripper closes. We turn the base and all the structure, then the arm goes down, unload the object by opening the gripper and turn again the base at the starting position.

The sketch servo arm is for a different movement of the arm.

So this is the end of my robotic arm. I am very satisfied with the result and i wanted to make something useful in my daily life. A few thoughts about it:

1. Always keep notes about your project. What goes where. What kind of screws you need here or there.
2. Have a lot of screws flat head, star head and hex screws. At the end of the project i noticed that i used a lot of different sizes of screws.
3. Balance your arm. It is very important to balance the main body front and back.
4. Make a lot of tests with different setups. Also hardware and software.
5. Use 2 joysticks for arduino so you can control live the arm.
6. If you want to lift heavy objects you have to use better servos that can handle more torque.

Have fun!!!!