Five Senses Coffee Blog

A PID, SSRs and lots of Wire.

Cutting holes in the front panel of a stainless steel coffee machine is always a bit nerve wracking. I  hardly slipped at all in the end.  About 2 hours with a flat file and I had a nice rectangular hole of the correct size for my PID controller.

I had considered locating the PID out of sight underneath the machine and facing rearward or even under the drip tray. My thinking was that this would, with one obvious exception, preserve the standard look of the Isomac La Mondiale. (one of my stated aims) In the end though, its got to be all about the coffee and when it comes to coffee, temperature is king. We must have easy access to the brew boiler temperature display so, in front it is.

The PID and the Steam boiler pressure-stat will both drive its own heavy duty Solid State relay (SSR). The SSRs will in turn will switch the higher current to the elements themselves. I have bolted the SSRs to the underside of the base plate of the machine which will act as a heat sink of sorts though these SSRs will be operating at about 25% of their capacity so I’m not imagining they will get very hot.

The boiler level is contoled by the original Isomac Auto Filling controller. I actually had it all connected up as a test and I got some great steam happening last week.

The brew pump will be controlled by a small relay also bolted to the bottom of the base panel.  Since the steam boiler will fill under mains pressure, you may be wondering why the machines pump could not just have been switched by the Synesso Cyncra brew group switches. The reason is…… I am going to integrate a pre-infusion timer as found in the latest Synesso Hydra (as an option). The timer will take over control of the brew pump via the relay.

The current job is just wiring everything up. It looks like a birds nest at the moment but it will tidy up nicely. I’ve used color coding of the different funtions etc.  All wire is heat resistant of course.

`richard