Week 5, 11 Feb

This week I have researched on some valves which has a sufficiently low operating voltage. The one which is being shortlisted is from Peterpaul.

A valve is needed in the output circuit for better control system response. As mentioned last time, the air pump motor used now does not have a valve at the vacuum side. When the air pressure builds up in the air pouch, air will constantly leaks out from the vacuum side and presents a steady state error. This is illustrated in the diagram below.

air_leak

Thus I would propose to add a 3-way multi-purpose valve manually into the circuit, controlled by the PIC. Whenever the circuit is pumping or extracting air, only one connection will be enable so that no air will leak out from the other side.

valve

The common side will be connected to the air pouch, and the other two will be connected to both air pump and vacuum. At de-energized state, the air pump will be connected since it has a built-in in the motor itself.

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