Hi,

I have just ordered an air popper, since I actually roast on a pan. I already have a PID kit that's not being used and would like to know if it can be useful in the popper.

Is it more useful controlling the roast degree than a thermometer? Is there any relevant benefit in putting a SSR to control the popper heating element?

Thanks for helping.

Leonardo

I modified my iRoast2 by removing all electrical controls and controlling the fan with a dimmer and the heater with a PID/SSR. It works fantastically.

However, many PID units are designed to hold a constant variable (temperature in this application) and while this is fine for an espresso machine boiler, for roasting you really want a PID that will run a program of temperature ramps over time.

The unit I have is an Omron E5CK-T. The plain old E5CK doesn't have the programability of the -T.

Which PID unit do you have? It's an easy project and amazingly versatile.

Allon,

I have a Sestos PID, don't remember the model, but considering how much it costed I believe that it doesn't have any ramp function.

Is there an intelligent way to use it, even without ramp function?

Well,

Since my controller doesn't have ramp function I thought that I could put the termopar in a spot where the temperature doesn't change much, so I would be able to control the amount of heat delivered to the beans mass.

So...will it work?

I used a PIDed airroasters for eight years. It does not matter whether you measure the bean mass or the inflowing air, you will need to ramp up the temperature for either to get a good roast. This means you either need to change the temperature manually or use a ramp soak PID unit. The simplest approach with a single setting PID is to have it control the inflowing air temperature. Let it run at 300F to 325F for about 4 minutes, then set it up to 375 to 400 for two minutes, then up to 450 to 500 till the end of the roast. The range of temperatures is because the precise levels will depend on the position of the sensor and the insulation level of the roaster.

Is that really much different than using a variac or solid state power control to run at a percentage of output?

Sounds like how the stock iRoast works - it only measures the air temp between the heater and the beans and the results are....disappointing.

The iRoast is a poorly designed roaster or hot air blower for that matter; the P1 is a well designed one. Fancy controls cannot make a purse out of a sows ear.

I used a variac on the heater prior to doing a PID; the PID is far more automatic.

Why do you feel the iRoast is a lousy roasting platform?
The P1 is great hacking platform, but really, it was overdesigned for its purpose.
The iRoast was designed for 150g and does great in that range, though it is hampered by a crappy control system. Replace the crappy controls and you can do pretty well, while being able to catch the chaff and see the roast. Pity you can't hear it (or much of anything else) though.

So Jim,

Explanations given, I should conclude that my PID model is pretty useless for this task...

Anyway, if I want to perform (a little) better than with the stock popper I can use this PID and build my roast profiles by changing the target temperature manually. Is it?

Leonardo

This is roughly what should be going on inside any kind of air roaster.



If the PID doesn;t do ramp soak, doing the supply air (red line) manually is a lot easier than the bean temp (blue line). All you need to do is push the setting from 300 to 450 after 3 minute, since it will take two to three minutes for the actual temperature to climb to the new setting in any case. To do bean temperature properly, you would need to manually adjust the set point every 30 seconds or so.