"RL-HT-CTRL" Review
8/29/2013
by Randy Glass - Copyright 2013 - All rights reserved


      As has been widely discussed, Jim G. of MLG Prperties is not currently able to supply us with his HTC+TC4C circuit boards which act as an interface between Hottop coffee roasters, and a computer running a control and logging application, which in my case was RoastLogger by GreenBean (aka Tom). Jim has stated that he would likely be able to supply his boards again in about 4 months or so (Jim's estimate if I correctly recall), so Tom, the author of RoastLogger as well as having been a key member in the development of the HTC board, stepped in and designed his own board to fill the need for now.

photo Courtesy of "GreenBean"

      Tom calls his solution the RL-HT-CTRL (RoastLogger Hottop Control). Among its benefits are:
- Logging of two separate thermocoule inputs (in this case, bean temperature and environmental temperature).
- Provides the option of communicating with the RoastLogger via USB HID instead of RS232 serial.
- Smaller footprint
- Faster recognition by the computer with no need to select serial ports or load drivers ("true" USB)
- Allows the user to load precompiled sketches without needing to download and install the Arduino IDE or know anything about programming or compiling sketches
      Having the ability to log temperatures of a roast is one thing. There are various methods to do that which can be as simple as using an economical data-logging, hand-held meter and feeding a thermocouple through the bean loading chute. You could even just use RoastLoggers OCR function with a webcam to see and record the data. I've done that, and while it has its place for folks who cannot add thermocouples or wish not to modify their equipment, it seems quite archaic now.
      The real value of Tom's system begins with using RoastLogger and the RL-HT-CTRL together to actually control the Hottop from the computer. And having control is just part of it. The simple programming available from within RoastLogger automates the roast and gives excellent consistency from one batch to another while still allowing manual control at any time.

      Above you see one of the Action panels. This one is "Action at T1." Simply, the first line there tells RoastLogger that when the T1 temperature reaches 248 (Fahrenheit in this case) to set the heater element to 90% power and the fan speed to 30%. They do not have to be entered in order and you can enter up to ten, although I have found that three do an excellent job. You can even save various "Actions" in a file so that you could create any number of them for different roasts; for different origins, for different brewing methods, for decaf, etc.
      Let's take a look at that consistency:

      Here is a portion of a graph of two roasts. Both were done using the same set of "actions." The data in the inset box shows the First Crack Start (FCs), First Crack End (FCe) Second Crack Start (SCs) and the End of roast. These points are marked during the roast by the user by pressing an on-screen button. In each cell of data you have the time (number of minutes and seconds since beans were added) and the "T1" temperature which it from the bean sensor. Roast Logger allows you to load a previous roast as a "template" onto the graph before beginning the roast. That is shown by the thinner, lighter-colored blue and red lines. The current roast, logged onto the same graph in real time, is represented by the thicker darker lines (the thickness of the current roast's lines can be modified as an option). It is plain to see that with no input from the user, these two roasts progressed so identically that differences are difficult to find. If nothing else, this graph shows the remarkable potential in the Hottop Roaster which RoastLogger unlocks.


      The chart above was done using the last roast's log from the chart above and making just one change to one parameter in the "Actions" file. One of the "Action" choices you can enter is to set the heater power and fan speed at any given "T1" temperature. I have used three of the ten available "Actions at T1" programmed. For the template above it was "at 350F set the heat to 55%, and set the fan to 50%. I changed that by lowering the temperature for that Action to 340. This left the 2:00 "dwell" between the end of first and the beginning of second unchanged, but it delayed the onset of first by one minute. That was my goal for this roast; to lengthen the total time just a bit.
      We can debate my profile ad nauseum, but that is not the point of this portion of my review. The two graphs presented above were placed for two reasons:
1- To show the consistency that the Hottop is capable of producing
2- To show that with the proper interface and control system, it is possible to get very precise control over this roaster, and do so with a repeatability that would be difficult, if not impossible manually.
      A big part of that comes from Roastlogger being able to control both the fan and heating element in 5% steps (the factory Hottop control is heat in 10% increments and the fan in 25% increments).


      The control of teh Hottop as mentioned above is available using RoastLogger and either the RL-HT-CTRL board or the HTC+TC4C. Tom is willing to build a small number of RL-HT-CTRL boards to fill the gap until the HTC and TC4C are back in production and hopes to convince JimG to move the development of the TC4C towards true USB communication in future.
      The rest of what you need to know is available HERE on the RoastLogger website. These boards will be available in short supply unless things change in the future.