The Controller

This is the controller panel. I drew it in CorelDraw, printed it on paper, then placed it onto a metal panel. I covered it with clear Lexan to protect it and finish it off. The border is made from black masking tape which holds it all together. The panel screws onto a closed metal waterproof box.

I thought the panel had a nice old world brewery look; actually it is a clip art diploma! I added the dials and text. If I ever come up with a name for the brewery, it can go in the top center spot.

The circuit board with the components and header connector can be seen. The ribbon cable is fanned out and connected to the two potentiometers. The remaining wires are for switches, SSR connections, and power. I am using several conductors in parallel for the power connection. The other end of the cable has the IDC connector already attached.

Most RIMS use some sort of PID (Proportional Integral Derivative) controller. This is alright if you have the money, but these things are expensive and in my opinion are overkill. I have built my own controller circuitry using easily available parts, and it works well for my type of manual operation.

Because the heating elements use 240 volts at 20 amps, this is a lot of power to be controlling, and resistors or variacs will not work well, because the cost and size would be enormous. You need to rapidly switch the power on and off to adjust the heating of the elements. If you tried to do this with a mechanical relay, it would work for a while, but it would soon wear out and burn up the contacts because you need to switch about once or twice a second.

With technology comes the SSR (Solid State Relay), which will do the job with ease, and not wear out! What is needed is to supply a low voltage control to the relay to make it operate. I designed my circuit using integrated chips, a few other parts, and it performs flawlessly. Here is a schematic diagram of my controller which controls two heaters. I only have one 240 volt electric dryer outlet available, so I am using gating to share power to the HLT and the Kettle. Gating means that only one heater can receive power and never both at the same instant of time. You can share power during the off time of the other heater. This can be done because I never really need full power to both elements at the same time. By using gating, I can keep the HLT temperature at a holding point while the kettle is beginning to heat up the first runnings. By not dialing full power to the HLT, the unused portion of the time period can be sent to the kettle.

When building any type of electronic equipment, you can spend a lot of money on mundane things like connectors. I have found that by using ribbon cable and connectors, the cost can be reduced to almost nil. When ribbon cable and mating PC board header connectors first appeared, they were very expensive. Now, they are dirt cheap, in fact, most computer technicians have them lying around, nearly tripping on them! The ribbon cable and connector used for 3.5 inch floppy drives etc. work very well. You can purchase mating header connectors from Radio Shack, etc. Using connectors to the PC card makes building and testing much easier, and the whole project much nicer. I usually fan out and strip the ribbon cable on one end and hard wire to pots, switches, etc, and use the connector end and mating header at the circuit board..