First a little background info and sneak peek of my control scheme (skip if you are only interested in my selector wiring). I am going for overkill here not because it is necessary but because I am enjoying every minute of the design process. My system is going to be a 4 vessel HERMS system that is all electric powered and at some point in the distant future most system aspects will have at least some level of automation to them.
A simple PC will be running the main system control routines which will interface to a 32bit micro board I am developing. The 32bit MCU will be providing all of the low level interfacing to switches, sensors, elements, valves etc. My control system is going to be separated into two enclosures. The first is the Human Machine Interface (HMI) and will contain the PC, touchscreen LCD, switches, indicators, 32bit mcu, low voltage power supplies, and other odds and ends. The second is the Interface Control Unit (ICU) which will house all of the 240VAC components such as the contactor, SSRs, power relays. The split design will allow me to tuck the ICU out of the way and enable the main 50A service to the brewery to be segregated from the control electronics in case of system failure.
Below are the beginning schematics of my HMI and ICU boxes (there are many components missing from these high level designs).
The first image shows the start/emergency stop circuit which has ties to the 3-way selectors for 3 heating elements and two pumps. Each element and pump will have auto-off-hand control (1). All control signals are actually input into the MCU and it directly controls the SSRs and pump motor drivers (not yet finalized and not shown). My 3-way selector switches are stacked with a pair of NO and two pairs of NC blocks. The HLT element implementation for example will provide a +5VDC signal to two MCU input pins when the switch is in the off position (SW will know off is selected). When in Auto mode the left NO is now closed and Din1 is grounded while Din2 is +5 so the SW will know auto is commanded (2). In addition either auto or hand will open either the left or right NC switches which in turn removes the ground input to a power relay (3) so that AC can flow from the SSR to the element. Din2 is grounded and Din1 is high when in manual. Manual mode will not necessarily mean 100% on as I cant have all elements on at once or I would use more than 50A. The MCU will control the load to keep it at safe levels in this condition.
The start/stop circuit is similar to others that are floating around this board. All switches must be in the off position to complete the circuit when the NO momentarily closed start key is operated in order to energize the starter relay (4). The relay load output will be tied back into its coil input (5) through NC stop button. The relay output then powers a contactor (6) in the ICU which energizes the 50A service.
So at first glance, anything I messed up or am I missing something? This is still a work in progress and I am sorry for the length of this post. Part numbers are listed near the components if I have made a selection. Full quality schematics are in this
pdf.