4DoF Robot Arm

grabcad

This right here, is a Robot arm made for my college robotics assignment. It´s specially designed for serving cake (That was the assignment, yes, weirdly specific). But essentially it's a regular robot arm with a gripper designed to pick some cooking tools.Since I was the only one in the group qith experience in 3d modelling, I was assigned the job of designing the robot. It´s not a pretty design, I know. It has some flaws that I didn´t correct because of time. But I'm still happy about it, and it should really work.The design is meant for 3d printing. It was design with a 25-50% infill in mind, in PLA so it's both light and food friendly. This would mean that you should print it with a tough pattern.The only part not meant for 3d printing is the base. This should be a little heavier. I would recommend mecanizing wood for it.Now, onto the electronics.This is designed to hold pololu micro metal motors. Specifically micrometal HP 6V 994,2218 or similar, since lower power motors won't be able to lift the arm. https://www.pololu.com/file/0J1487/pololu-micro-metal-gearmotors-rev-4-2.pdfFor position control we have two components.The first is a digital incremental encoder PEC11R-4220F-S0024. Tis is quite a typical encoder, don't let the name scare you.https://www.bourns.com/docs/product-datasheets/pec11r.pdf?sfvrsn=bb617cbf_7The second is a switch from omron. This is of course to know the zero position.https://www.mouser.es/datasheet/2/307/en-d3c-1221417.pdfTo make sure the motors can lift both the weight of the robot and the thing the gripper grabs I used gears with a 1:2 ratio.Of course, this would mean that the arm woun´t be very fast. But that shouldn´t be much of a problem. Specially knowing that the encoders can´t go higher than 60RPM.To move the motors an H bridge should work, and for the control an Arduino Mega, since it was both enough pwm pins, as well as interruption supporting pins.For power me and my team suggest a 7.4 V battery with 5000mAh (In the diagram it´s a 3.7 V / 2000mAh battery because I couldn´t fid the right one on fritzing. Sorry).That would be connected to a step down converter. https://es.aliexpress.com/item/32651786894.html?spm=a219c.12010612.8148356.10.72f4407e9Dd40G.As you can see in the diagram, the switches need to be connected to the switch pins on the encoders and the ground. This is meant to set the zero position.This would be all you need to know to make the arm yourself.I must say this arm coul