Step 1: Equipment
- HP Scanjet 200 Flatbed Scanner
- Orby Switch
- Arduino Uno
- Arduino 1.6.6 IDE
- Servo - Hitec HS-805BB with a Four Point Mega Horn attached
- Computer with scanner application
- MDF, Plexiglass
- Wires, breadboard, screws, wood glue, etc.
Step 2: Plan. Consulting with a mechanics engineer, the author decided to base the solution on the way a seesaw works. It was decided to extend the scanner lid and attach a weight to it to create a lever so that the center of balance (the fulcrum) would be right behind the scanner hinge. Then a servo engine would easily be able to tip the lid open and close.
Step 3: Extending the Scanner Lid
- Cut a sheet of plexiglass to fit the scanner lid and extend it by 8 cm at the back
- Attach it to the original scanner lid. As a temporary solution we used simple office clips to attach it. There are much nicer fasteners you can use.
- We then added a metal cylinder at the end of plexiglass. You can calculate the exact weigh you need or you can just trial and error with different scrap metal to find the right one. It should be heavy enough to tip the lid open when you touch the plexiglass lid around 2 cm in from the back and light enough to tip the lid close when you touch the plexiglass lid around 6 cm in (counting from the end of the scanner in the direction of the front of the scanner).
Step 4: Electronics. The author used an Arduino Uno to get an input from the foot switch, trigger the servo motor and when the lid is closed, activate the scanner application. Using an Uno and not a Leonardo meant we weren’t able to activate a mouse click or a enter event on the computer with the scanner application. For more information on the hacking needed: NicoHood/HoodLoader2. Make arduino uno work like leonardo
Step 5: 3D Printing the Rod Component. The final component we needed was the rod that actually pushed the lid back and forth. The team 3D printed a component that fits on the servo engine’s ‘four point mega horn’ attachment with a rod connected to one point. The original Solidworks file can be found of the author’s website.
Step 6: Housing the Scanner. In this solution, the scanner needed to be placed 6 cm higher than the table so we build a simple case with MDF spray-painted white. Inside the case we left room for the electronics to fit in. In addition, you need to build an MDF structure to hold the engine and keep it from moving around.
Step 7: Putting it all together.
- The motor with the rod component sits on the left side of the scanner, adjacent to the case. The exact y position of the motor can be calculated or as we did, you can just move it back and forth a few millimeters each time, activate the engine and tweak it so that the rod reaches the right point at the back to make the lid open and then the right place somewhere in the middle of the lid to make it close.
- Attach the engine housing including the engine without the rod component to the side of the scanner case.
- Place the rest of the electronics within the case and secure them in place with screws or hot glue.
- Put in the scanner with the extended lid and weight.
- Screw back the rod component on to the servo.
- Activate the scanner application on the computer
- Attach the foot switch.
Step 8: Summary. The foot switch was attached to the wheelchair to allow the user to easily press and open and close the lid and see the scanner working.