I have bought 2 joysticks from ebay and tried to think what can I do. Then I came up with idea to make a small robot arm. What I needed was:
1x Arduino Nano
3x MG996R servos (I used one Futaba, because I had only two MG996R and it was not necessary to have much torque for turning)
1x Micro servo
2x Two axis joysticks
1x 6V voltage regulator
Other items: double sided PCB covered with photoresist, diode, capacitor, switch, socket for Arduino Nano, strip cable with connectors, PCB stands, screws, bike spokes for pushrods, linkage stoppers.
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Step 1: Sketching and Modelling
I borrowed the frame from backhoe and made some sketches. Then using AutoCAD I made a 3D model. It was one of the longest step during production. I attach AutoCAD and .stl files if you want to see or take some ideas. Also I drew an outline for control joystick.
Step 2: Production
As you probably saw, the 3D parts are made of rectangle pipes. The reason of this is that I wanted to make the robot of aluminium pipes, but when I started, I realised that it is too big challenge. The bending places breaks, so it has to be hot, but I don't have equipment for that, so I jumped to 3D printing technology.
I brought 3D model to local company and it printed the parts for $25. That wasn't the best quality, but acceptable for this robot.
Step 3: Assembly
The best part of production was assembly. All I needed to do was to insert servos, make hinges of spokes, bend and connect spokes for pushrods.
Step 4: Programming and PCB Production
First I have made testing circuit on breadboard and wrote a program with Arduino software. I attach the code here. Then I drew tested circuit with Eagle software and printed it on transparent paper, which you can buy in almost any office. After that I peeled of the cover film from PCB, put on circuit scheme and using energy saving lamp exposured the board. I have made 2 boards, one for robot and one for control joystick. Following step was to clean left photoresistor in alkali bath and after that etching. After etching I drilled the holes and PCBs were ready to solder.
Step 5: Base and Joystick Assembly, Soldering
I used plywood to make base and joystick. When PCBs were soldered, I attached them to plywood. And here it comes two errors of designing PCB:
- Lower holes of control joystick PCB are partly covered by connector sockets, so it's not possible to screw the board through them;
- Connector socket, which goes to robot is placed incorrectly. I messed up with pins, so I had to solder it upside down.
Last two things was to connect all wires and calibrate the movements.
And that's it, here is finished Robot Arm.
Step 6: Presentation
In this video you can go through again all these steps and check how the Robot Arm works. By the way, control is based on the ISO pattern.
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