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caffeinegeek

I added pre-Infusion to my old Comtempo 1E

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This may be of interest to those who are into modding and technically challenged! Like most things on the internet, you need to know what you are doing with mains electricity and be technically competent to try this out. These old Fracino machines aren't wrapped up in microprocessor control and I love what you can do with them. I decided after some intial experiments to add pre-infusion to the shot. Pre-infusion stops the sudden spurt you get when the 9 Bar pump kicks in. I suspected this initial pressure hit was causing channelling and not giving full shot extraction from my filter basket load? I had started with the 'standard' 7gm load but found nearer 8-9 was needed, despite doing a lot with the grind. Pre-infusion seems to expand and consolidate the grind in the basket, hence some experimenting with grind fineness and overall shot time is needed. More efficient extraction is probably not a commercial factor in a busy coffee shop, but if you are going the extra mile sourcing green beans and home roasting small amounts it should be.

 

Your machine may not work like mine, so you have to do some checks first to see if it is suitable. If you can disconnect the pump connector, hit a shot selection on the front panel and brew without error alerts, then a mod, like mine is possible.The Contempo 1E only has 2 sensing functions and neither relate to pump operation, pressure, or current draw. So you can confidently change what the pump does during a shot. In the ideal world you would have a vane type pump which could be controlled to ramp up its pressure for 'X' seconds when you call the shot. Unfortunately, the Fracino uses a rotary pump capacitor start motor and it is either on or off. - but it is a very strong reliable pump!

 

My mains water inlet pressure is 4 Bar. The object of my schematic design is to hold off starting the pump for 'X'seconds after the shot is called to wet the dose at 4psi. The Fracino flow meter is still active throughout, but you do have to re-calibrate the shot time and grind. Setting the 'X' off time needs some experimenting but I'm starting with 5 seconds. The schematic allows 'X' to be adjusted from 1-15 seconds. 4-5 seconds is about the time it takes after calling the shot for the first drip to appear from the porta filter.

 

Why did I build my own timer rather than use something off an auction site? My schematic is universal and accurate for different types of mains timing application and I know it works because I've used it for controlling bathroom fans. It has a very small profile, doesn't use a relay or need a low voltage power supply and doesn't have components that could overheat inside the Fracino cabinet. Also the pump is switched 'zero crossing' which is a lot softer starting than using a relay and better for the and capacitor pump life.

 

With 5 second pre-infusion my filter basket load has gone down from 8-9gm to 7gm for the same flavor intensity. I'm using less ground coffee and that can only be good. With such a simple addon controller for the pump I am unable to vary the pre-infusion timing for double shots etc, maybe I have to find a 'one setting fits all' compromise? In software it would be easy to change the pre-infusion time according to the shot duration. Newer Fracinos offer the pre-infusion option, but mine didn't.

 

I'll post some photos here but as I said, you need to be comfortable building live mains circuits safely and be technically challenged. I'm just about done on this mod. now and moving on to the home bean roaster project.

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Pre-infuser 1-15 Sec.jpg

pre-infuser schematic.jpg

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