- PP4 - 
External Unit 

An external unit is build into a simple 19 inch case. It houses the following components (from left to right):

• A pressure regulator that reduces the pressure from an external air compressor to 50 mBar. It is build from a pressure regulator used for propane gas bottles. When placing the component, the pressure is switched on for a short time to compensate the vacuum in the tube that leads to the nozzle and also to blow the component from the nozzle onto the PCB.
• A vacuum-reservoir made from a 10cm sewage tube coupling and two end-caps.
• A vacuum pump made from an aquarium pump (in the front).
• A 5V power supply to supply the logic (at rear). A separate supply turned out to be neccessary because the buck-switching-converter on the controller board could not deliver a reliable supply to the logic. 
• 24V 320W switching power supply for the motors.
• A relay board for the vacuum pump with an external snubber circuit (between 24V power supply and the right side wall).