@narwal, more information on how you analyzed the video and produced the rolling graphs please...

And thank you. Great to see this hard data!
Brad

Just think - and all just for a good cup of coffee.

Davi-L wrote:Greetings,
That variable time base causes the lights in the old house to dim slightly with each rapid pulse. Rather annoying. At one secornd, it is less noticeable. In my new home the 200 amp service seems to absorb most of this pulsation. No electrician has explained it to me yet.
Dave

Hi Dave,
Let me take a shot (haha - coffee humor) at explaining the lights dimming in your old house. The short answer is that somewhere, some wires were likely too small for the amount of current being pulled by the Carola. There is something we call "I squared R losses" in electronics. The current in Amps, squared, times the resistance in ohms of the wire gives you the voltage drop across any given piece of wire.

I hope I can do a decent job of explaining this.

Lets assume you have a power source, 40 feet of wire, and at the end of the wire you attach a volt meter (in this case a light bulb) and a device drawing a lot of current (insert Carola here). Imagine that the wire is the diameter of a set of car jumper cables. You turn on the Carola and the voltage at the machine hardly even budges; it changes from 110 volts to 109.8 volts. You can't even see the light blink.

Now imagine that the wire is the diameter of a human hair. You turn on the Carola and the voltage goes from 110v to zero 'cause the wire instantly vaporizes. After the smoke clears, we try again.

For a third case imagine that our wire is thinner than a jumper cable, but thicker than a human hair. You turn on the Carola, and the voltage goes from 110v to 100v. The temperature of the wire starts to climb. Not so much as to burn out the wire, but enough so you can feel the wire getting warm. That is where the missing 10 volts is going - it is going into heating up the wire. And that is 10 volts that is NOT going to the volt meter (or the light bulb, or the Carola). Substitute a light bulb for the volt meter and you get blinking lights when the Carola cycles.

Hope this makes sense.
Brad

Thanks for all the input everybody! I am just now catching up.

As a general update, I am still happy with the Carola EVO. Now that I am dialed in with a proper grinder and process, my wife (originally an espresso skeptic) and I are pulling very consistent/delicious shots with very little effort. This is really what it's all about. The only problem is that I now can't stand the coffee at work!

In the end, I agree with the comments about the E61 grouphead's thermal mass dominating the system's behavior and that the Carola's "fancy thermostat" is plenty for consistent results in home-use. Although I am still curious what the temperature fluctuations are during the "maintaining set temperature" phase. And, while it wouldn't have changed my buying decision, I wish I didn't think I was getting a true PID when I spent my money.

As for your question Brad,

ChileBean wrote:@narwal, more information on how you analyzed the video and produced the rolling graphs please...

My process was this:
1. Shoot video with iphone. I turned it down to 720p, 30fps to save space.
2. Use adobe premiere to crop and save the video as a bitmap sequence.
3. Import each image into matlab and analyze the average brightness value of the red channel for a box of pixels around the heater light. [Geek detail: it tooks about 204 seconds to analyze all 130,568 video frames, which was a rate of analyzing 640 images per second. crazy!].
4. Convert the brightness data (which had an arbitrary magnitude) to simpler 1 or 0 binary data, using a threshold of brightness to mean on or off.
5. Find an interesting snippet of the video and plot a graph of the data next to the corresponding bitmap image and save out a new image file, one by one (coded in a loop). [Geek detail: You mention the rolling graph... The graph is "rolling" because at each step, I set the x axis to extend from t-10 to t+2, with t being the current instant in time.]
6. Use adobe premiere to turn the new image sequence back into a video.

It's not the most elegant way to get these numbers, but it plays off of my existing skills and gives results that are a bit more visual for the casual observer.

Thanks narwal. Good to know how this was done. I really like the result.

Also, if anyone at Chris' Coffee or QM is reading this thread, I felt the same way about the temp control. I was disappointed to find out that it had a digital thermostat rather than a PID, but in the end, my measurements and my taste buds say it does not make any difference actually.

If anyone does want to add a PID controller, you can get the controller and solid state relay on Amazon for $50. Not sure if the machine has the extra power needed to run it and the boiler effectively but just wanted to share that there are affordable options out there.

Thanks for this information. FWIW, the PID is a very low-power device itself. I suspect that the digital thermostat and the PID probably draw the same amount - basically nothing compared to the heating element in the boiler. I can't imagine any reason why you couldn't swap the thermostat for a PID if you wanted to.

ELECTRICAL SCHEMATIC-

If you are interested, I have posted an electrical schematic of the original QM Carola in post #27 here:

Quick Mill Carola - Review

I suspect that the original Carola and the Carola EVO are very close from an electrical standpoint. If someone notes differences between the diagram below and the EVO, please let me know. If I can find the time to make the changes, I will do so.

Brad

ChileBean wrote:Below please find an electrical schematic I made of my QM Carola.

Wow awesome! Thanks Brad. Super interesting.

Hey, somewhere in your old thread, somebody had the idea to replace the buzzer with a matching blue light on the front panel. Do you have any idea how difficult this would be electrically (I'm guessing the voltages are likely different)? I'm having trouble finding that style of light anyways, so maybe a better mod would be to put a blue LED on the panel under the cup warmer panel slots or somewhere more discrete. No need for you to put too much thought into this, since I'd probably wait until my warranty is up anyways, but I thought I'd ask while it's fresh in your mind. Thanks

Hi Narwal,

I remember that comment on my review thread. I just looked at the pictures of my machine, and I can just about guarantee that adding an LED somewhere is a very simple job. But rather than make a guess, I will take my machine apart and make a quick voltage measurement. It will be next week before I can do this, but I will get back to you.

In the mean time, can you post a picture similar to the one below from my machine? It shows the "controller" portion of the low water alarm middle-right, and the irritatingly loud buzzer as a round black piece with one red wire and one black wire coming out of it hanging down on the left.



Brad

Thanks Brad! No rush. I'm at least a year out from doing anything that would affect the warranty. I'm guessing others would appreciate the info as well though.