This is a variation of one of the projects on the Microsoft Hacking STEM Library. There they show you how to build a robotic hand out of cardboard, straws, and servo motors. They also show how to build a glove to control the robotic hand. They use the combination of Excel® software and an Arduino to make it all work together. The Microsoft project is great, but if you have some of our Vernier products, this version is simpler.
We have three different versions of this project, each one more complex and allowing more finger control, but requiring more hardware.
This version of the project requires all the following Vernier products:
This version of the project allows you to move a complete robotic hand, with the thumb controlled separately from the other four fingers.
It requires the following additional hardware (in addition to the equipment used for the single-finger version):
You need to complete the robotic hand, with four fingers and a thumb controlled by five servo motors. This is explained in the Microsoft instructions Part 4 in the section Complete Robotic Hand. You do not need to make the controlling glove or any of the wiring shown with in this section. You do not need a breadboard. Instead, follow these instructions:
Load the sketch VernierHandControl2 and try it out. Hold the two accelerometer with the arrows pointed upward. Press the D12 button on the shield. Now try leaning the thumb-control accelerometer so that the arrow is pointed at about 45 degrees from the vertical. The thumb servo motor should rotate as you change the angle of the accelerometer. If you have made the connection of the string to the “horn” on the servo motor properly, the thumb should articulate. Remember that the accelerometers we are using measure their orientation with respect to the vertical. Make sure that when you move your thumb the accelerometer moves so it is pointing somewhat downward.
Now, try leaning the finger-control accelerometer so that the arrow is now pointed at about 45 degrees from the vertical. All four finger servo motors should rotate as you change the angle of the accelerometer. If you have made the connection of the string to the “horn” on the servo motors, the fingers should articulate.
There are two ways to tune the finger motions. Easiest is to pull the servo horns off and change their orientation to adjust the amount of pull on the strings. More complicated is changing the values of the following constants in the sketch: thumbStart, fingerStart, thumbStop, fingerStop. These numbers can be changed to correct for minor differences in the reading from individual accelerometers. They are used in the map statements. Here is what they represent:
Once you have the fingers and thumb moving nicely, mount the accelerometers on the back of a glove so the project is ready to demonstrate.
Power supply connected to each DCU.
This version of the project allows you to move a complete robotic hand, with the fingers controlled more individually.
It requires the following additional hardware (in addition to the equipment used for the Five-Finger Version Controlled by Two Accelerometers project):
For this project, the servo motors are connected to the DCUs the same way they were in the Five-Finger Version Controlled by Two Accelerometers project. This time, the second DCU is connected to and controlled by a second Arduino. Two additional accelerometers are used with this Arduino to control the index and middle finger.
Assuming you have already built the hand with five servo motors connected as explained in the Five-Finger Version Controlled by Two Accelerometers project, here are the changes you need to do for this version of the project:
You can tune the finger motions by repositioning the servo horns or by changing “start” and “stop” constants in the code.
If this is all working, try out the other Arduino. It should control the index and middle fingers.
Once you have the fingers and thumb moving nicely, mount the accelerometers on the back of a glove so the project is ready to demonstrate. Remember that the accelerometers we are using measure their orientation with respect to the vertical. Make sure that when you move a finger of your hand the accelerometer moves so it is pointing somewhat downward.
Arduino, DCU, and accelerometer connections
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