Category Archives: Mechanics

Robot Arm Servo Controller

My son and I thought it would be fun project to build a meArm robot arm. If you haven’t heard of the meArm, go check out their website, or download the files to make your own over on thigiverse.

The brains board that meArm sells for controlling the thing is pretty pricey, so we thought we would just design our own.  The setup is actually two boards. The larger board is processor board, and the smaller one is the joystick board.

The processor board will attach to the meArm base, and uses a cheap Arduino Pro Mini clone that you can get off ebay for around $3, to controll the servos. The processor board also has a few extra IO pins that could be used for extra servos (I’m thinking of a base with two continuous rotation servos driving wheels) or other sensors, and a IR receiver so that it can be controlled with a IR remote such as your TV remote, or the LEGO power function remote.

The small board is the joystick board. It accommodates 2 analog joysticks and 3 push buttons. The joystick board is connected to the processor board with a ribbon cable.

Processor board on left, and joystick board on right
The processor board will connect to the joystick board with a ribbon cable

I designed the boards up in Altium, and I’m in the process of converting the files over to CircuitWorks so that I can release them, so stay tuned if you are interested in using the design.

Vacuum Pump System

Most of my projects last for months, so the other day was a bit different when I managed to start and finish a project all in one in one day.  I built a vacuum pump system based on the free plans for the EVS vacuum system found on

Vacuum Pump System

I’ll be using it for vacuum clamping on my milling machine as well as for the vacuum pickup nozzle on my pick and place machine.

It isn’t a complicated system, but still, everything went together very easy. The nice thing about the plans are that they are proven, and there are lots of examples of custom systems that Joe has put up on his website. I made a few changes to the plans to meet my needs. The first was to move the filter to the system input instead of putting it on the pump input as in the plans. I forgot to order the high flow filter from so I’m stuck using a cheap filter from Princess Auto for now. It probably has a higher resistance, but for now that should be ok since my application doesn’t need a high flow rate.  The filter will protect the vacuum switch and Mac valve better in this position. Second was to mount my pump up on the tank with some big hose clamps. My piping worked out a bit different than in the plans, but my system takes up about half the floor space.

One problem I have is that the hysteresis of the vacuum switch is not adjustable. There is only one adjustment screw to set the point at which the pump turns off. When the vacuum drops to about 4inHg below this point the pump turns back on. I would like to either find a pressure switch that has adjustable hysteresis, or come up with a simple way of doing it by adding another pressure switch.