Robotic Hand

This is a stem related project which includes servos and geometry. This is a deep explanation and tutorial on how to build this Styrofoam hand; this hand will be doing some gestures that will be programmed by two python codes which will calculate the volume and waste.

The materials that are used for this hand are

• Styrofoam block
• paper clips
• exacto knife
• rubber bands
• sharpie/pencil
• fishing line
• sanding block
• needle
• hand model
• hot glue sticks/gun
• pliers

optional

• skewer stick
• tape

materials for tech

• USB
• Arduino Nano
• 2 servos
• Arduino software on laptop/pc
• Tinkercad

• First you start off with a Styrofoam block and you cut out a rectangular prism.
• Measure each one of your fingers and mark the lengths on the block.
• On the remaining Styrofoam trace the models wrist and hand and cut them out using an exacto knife, Make sure the wrist and hand are together.

• Trace your finger on the respective rectangular block and then cut it out with an exacto knife.(Make sure to label all fingers)
• Repeat with all fingers.
• Make sure all fingers are labelled.

Start off with a finger, Now using the sanding block you are going to want to slowly sand down the edges and smoothen the finger, Now you are going to want to cut the fingers into three pieces depending on what finger you are doing. Afterward you want to shave each piece of the finger into a 45 degree angle so that it looks like your models finger when bending. (Fingers should still be labelled for no confusion)

Each finger should now have 3 sections besides the thumb, the thumb should have 2 sections.

Now you are going to want to use the needle and fishing line to sow through each section of the finger so they are more stable and not loose.

Make sure to tie a knot at the end of each finger to ensure stability

Now you can sow your fingers to your hand and wrist

Make sure there is enough fishing line at the end of the wrist ( At least 3 inches)

Now you are going to want to tie the fishing line to the needle and poke the needle through the hand and pull it down the wrist (Make sure 3 inches at the end also repeat for all fingers)

• This step involves paper clips and your pliers

• Now you are going to cut the paper clips so it makes a U shape so that you can secure the fishing line and so it can move and go all over the place. Do this to all five fishing lines with about 4 paper clips for each line.

For this step you will need a hot glue gun and rubber bands

• You are going to need to cut the rubber bands into small pieces so that you can connect and secure your sections so they are able to bend. ( The pieces should go from section to section approx.. 0.5 cm - 1)

• Now you are going to want to use a little bit of hot glue to secure your rubber band down to the Styrofoam.

• Do this twice to each rubber band and on each finger (You will need at least 4 cut up pieces of rubber band for each finger and 2 pieces for your thumb).

The movement A finger can bend 90 degrees between each section, a half bend is 45 degrees the servos will control the degrees of the bend from the root of the fingers to create the pinch.

• Now you want to get a servo motor that works
• Next you are going to want to grab your fishing line at the bottom of your hand and put it through the hole on the knob.
• At this step pull the fishing line at the top so your sections are separated and not together and then turn the knob to see if it goes back to its normal formation.
• if that happens it works, now repeat it with the thumb

1. Attach the servo with tape any empty space on the wrist
2. The pinch will happen when the servos make the two fingers attract each other
3. if this does not happen make sure the fishing line is tight the direction of the sections are respective and the sections are pulled apart slightly

Code understanding For this code you will need the Arduino on your pc/laptop and the Arduino Nano to complete the pinch gesture, practice codes will be written on Tinkercad.

• Once your in Tinkercad instead of making your code out of blocks turn it into text
• Now introduce the servo library and void setup
• Introduce "servo thumb" and "servo pointer" for the thumb and index finger so the variables are acknowledged
• insert a void setup and serial. that is for the respective servo on both fingers to notice itself in the Arduino on your laptop/pc
• the code would be

thumb.attach() ; pointer.attach()

Between those two brackets you want to insert whatever pin number the wire of your servo has went into for example thumb.attach(8)

Put in a void loop

In that loop, reset variables and pinch variables will be introduced. this will make sure that the pinch happens and the action variables are acknowledged, these variables can include : Resetfinger() ; delay() ; pinch() and whatever hand gestures you would like, these are your activity variables

In the brackets of the delay it should be the amount of milliseconds you want it to be delayed for example 1000 milliseconds is 1 second. this means it will hold that hand gesture for 1 second until it goes back to normal.

Now if you want a pinch the code has to be. Reset, delay, pinch, delay,

That means that the code now realizes that those movements have to be done and looped.

• Now enter a void for the pinch and reset it as those are the only codes that were made, this means that the code now knows to operate. For example thumb.write() index.write()

1. "Write" circulates the variable "Thumb" and "Index"
2. Insert a degree from 0 - 180 that you want your finger to bend
3.  All degrees of finger are 0 for reset.

Now you are going to want to test your codes on Tinkercad, Now run the code to see if the fingers move the amount of degrees you put in.

From now you want to upload your code onto your Arduino, plug the USB in the laptop and the Arduino, connect your Arduino and wire to the servos, Now check to see if your code makes the finger move.

Now since you have finished with your Styrofoam hand you can finally test it out. This is what the final product should end up looking like.