I'm going to do it. Just ordered the parts I need. The reasoning is I'm tired of temperature surfing (Gaggia Classic) while steaming. I will be replacing the 145 degree steam sensor with an RTD and wiring in a dedicated PID controller that will activate when the machine is placed in steam mode. Now that I've settled in to roasting, I'm back to modding my super customized Classic.
Of course now Auber offers a PID kit with steam control, but this is much cheaper than replacing my existing kit and in my opinion cooler. The funny thing is I asked them about it when I bought mine, and they said they decided not to include it in the kit because of problems burning the temperature fuze on top of the boiler. I'll post up pictures when I get it installed. Anyone else have two PID's?
Two separate PIDs????? There are dual setpoint PIDs that allow a second setpoint to be selected using an external switch. You would just need to disconnect the machine's steam switch and wire it into the terminals in the PID. Flip the normal steam switch and the setpoint for steaming is selected. I had one like that on a Silvia.
I am not sure by having a Stream Temp PID will eliminate temp surfing!!
A separate PID for stream is unnecessary. You can control the stream temp with the same PID used for brewing temp. Use the alarm function like auber did. Much simpler
To get rid of the Temp surfing you need a PID that cools the boiler and bring down the boiler temp to the brew temperature. To cool either use a fan which is very simple or use a water jacket around the boiler and circulate water to cool etc
I'll have to take another look at the manual for my existing PID just in case. But I don't believe it can run two set points easily. The kit I originally bought did not come set up for it and it would be using the brew sensor If I did. I figure this would allow me to run a new sensor in the steam location just for steaming. If anyone has links to wiring and setting up a single PID for brew and steam let me know. I'd like to do a little research.
adan0327 Senior Member Joined: 6 Sep 2011 Posts: 45 Location: Toronto Expertise: I love coffee
Espresso: la cimbali m32 dosatron 3... Grinder: Astoria Super Jolly Vac Pot: hario tc2 Drip: chemex, v60,kalitta... Roaster: Lol.... Pan :D
Posted Sat Oct 1, 2011, 5:30pm Subject: Re: Dual PID Controllers
Since you are a gaggia user. I suggest you join the gaggia yahoo usergroup (google it). There are some great mods and guides the specifically cater to people who have gaggias. Also you don't need two PIDs. PIDs have a built in alarm function that can be used to also control the steam temperature. Example. My PIDs high alarm is set to 143 degrees C. At 143 my PID turns off the heating element. To activate and alarm all you need is a low voltage power source that is DC. You can use a battery or a crappy wall plug to power the alarm contacts on the PID alarm terminals. Alarm is basically a additional setting on the PID to control a secondary set point.
Posted Sat Oct 1, 2011, 7:17pm Subject: Re: Dual PID Controllers
Thanks for the info. I've been reviewing the diagram for the machine above and the wiring diagram for the Gaggia Classic. It makes sense how to take advantage of the alarm function to cut power to the element when the steam temp. is reached. I'm going to hook up the second PID to my machine anyways for a few tests. Then I will decide if I want to use it for steam control, or cheat it with just one PID. If I don't end up using it on the espresso machine, It'll be perfect for modding my roaster.
My plan right now is to power up the second PID just to read the temp at the steam sensor port on the boiler. Then I will do some temp-surfing and a variety of steaming tests. I want to see if there is much of a difference at steaming temperatures between the two sensor locations. That will tell me if I should have an RTD sensor in both locations. It will also give me an idea of the best temperature to set either setup for steaming. Since there is such a problem getting good steam from this machine, the more I play with different options, the more likely I am to arrive at the most efficient setup. I'll post up a video of the initial results when things are up and running.
OK, so PID #2 is up and running. I still need to clean up the wiring and finish fabricating the new housing for the controllers. I'm also adding some 120v neon bulbs to display my switchable settings. I'm finding that there is a bit of a delay in the temperature rise from the brew-stat to the steam-stat. Obviously because the brew-stat is right next to the heating element. Also, the temp of the steam stat drops immediately when I release steam as opposed to the brew-stat. This is something I can take advantage of for faster recovery of the steam temperature and pressure when I start steaming.
It's interesting being able to see the temperature of both locations on the boiler simultaneously while working the machine. Hopefully when I finish testing and playing, I will have the steaming power I've always wanted out of this machine. I'm going to shoot a video of the temperatures during normal operations here when everything is buttoned-up so people who don't have an RTD sensor in the steam-stat location can benefit from seeing what happens while the machine heats up and operates. Could help in proper setting of a single PID with steam control. I realize this is all overkill, but those who have seen all of the other things I've done to this Classic machine won't be surprised. Here's a picture of the mess in my kitchen. I'm putting the machine into steam function with alligator-clips right now, kinda makes me feel like a mad-scientist. Actually that's what my wife calls me every time she sees me working on it...
Posted Sat Oct 8, 2011, 1:51pm Subject: Re: Dual PID Controllers
Here's the latest. I've been playing with the steam RTD sensor and controller in both PID and On/Off function. What I've found is that PID works very well to raise the temperature, while On/Off works the best for recovery once steaming milk. In addition I've discovered something that negates this info. The factory location of the steam-sensor is a poor one. It explains why the Classic is not good at steaming. In my opinion if the steam sensor was placed near the heating element, like the brew-sensor, it would hold a much tighter window where temperature is concerned.
In other words, I'm realizing that the best location for sensing temperature for steam control is the same as the brew-sensor. I don't think it's the range of the steam sensor as much as it is the delay from the heating element to the sensor.
My next step is to control the steam mode from the brew RTD while observing the steam RTD.
Posted Sat Oct 8, 2011, 4:35pm Subject: Re: Dual PID Controllers
I was going to wait until the caffeine wore off to do some more experimenting, but my wife wanted a milk drink. So I made another change before firing up the boiler. I'm now running the steam controller as an On/Off in series with the High Limit of the original PID. It works a lot better than the last couple of setups. When I leave it alone for a while, it will hold at around 300 degrees. With heavy steam use, it will not go below 278 degrees. The highest it will hit is 311 degrees and at that point the second controller interrupts power to the SSR as a backup in case the other controller gets set too high.
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