The electronics drawer distributes the analog and binary, input and output signals of the ADIO board. A five volt power supply provides D.C. power to the sparge water level indicator, the mash float switch, the boil wort level indicator (pressure transducer, op-amp, …) and other components within the electronics drawer. A 60-conductor ribbon cable from the ADIO board is connected to a 2x30 connector mounted on a circuit board towards the back of the electronics drawer. Individual lines are wired to dual-row barrier strips. Ring tongues are used to attach the individual wires to the barrier strips.
The ADIO board controls the electric heater elements, solenoid valves and pumps through SSRs (Solid State Relay). The brewing system utilizes two different SSRs,
The Potter-Brumfield IO modules are mounted on a Potter-Brumfield 2IO-4B circuit board ($24). The circuit board accepts up to four IO modules.
I tried to use a Potter-Brumfield IO module to control the solenoid valves, but the inrush current was too large and blew a fuse (fortunately) on the Potter-Brumfield circuit board. The Potter-Brumfield IO modules are used to control the sparge and mash pumps. There are two spare Potter-Brumfield IO modules mounted on the Potter-Brumfield circuit board.
The Crydom EZ accepts an input voltage in the range of 4 - 15 volts D.C. and controls an output voltage between 24 - 280 volts A.C. The Crydom EZ is rated to 18 amps. The Crydom SSRs are used to control the solenoid valves and the electric heater elements.
The four solenoid valve SSRs are mounted on a pair of 3.5" x 5.9" heatsinks rated up to 25 amps ($20). Each heater element SSR is mounted on its own 4.1" x 3.4" heatsink ($17). Neither heatsink was designed to work with the Crydom EZ. I cut a pair of fins off the top of each 3.5" x 5.9" heatsink and drilled (and threaded) three pair of mounting holes. I was able to mount up to three Crydom EZs on each heatsink. I also drilled (and threaded) a pair of mounting holes on each 4.1" x 3.4" heatsink. There is one spare Crydom SSR.
The binary output lines of the DACA are connected directly to the Potter-Brumfield IO modules, however, the binary output lines of the ADIO board had trouble driving the Crydom EZs directly. I used a pair of 7406 hex inverters to drive the SSRs.
The electronics drawer uses a pair of 3" 120 volt A.C. fans for cooling. One fan "blows" and the other "sucks". A heavy-duty rocker switch mounted on the face plate of the electronics drawer controls 120 volt A.C. to the SSRs.