by Paksong » Fri Jul 09, 2010 9:37 pm
[quote="GreenBean"]The version I am using with computer control requires knowledge of electronics to connect the Arduino and thermocouples (which are built into the Hottop) and requires breaking into the control signals in the Hottop. I do not expect many people would want to do this. If anyone does they are welcome to a copy of the software.[/quote]
Hello GreenBean,
It would be wonderful if you could let me have a copy of your firmware/software, and more information about how you interface the Arduino. Do you use the Hottop control panel at all (i.e. shared control), or do you control the hottop 100% from the computer?
On my KN8828 (as you probably know) there is a cable from the control panel to the main board with what seem to be mostly TTL signals at about 5V, which determine whether to turn the heater, drum motor, cooling motor and solenoid on or off. These should be very straightforward to connect to the Arduino. The fifth signal for the fan is a little more complicated, as it has 4 different voltage levels for different fan speeds; maybe the darlington array just creates different drive voltages for the fan from the different input voltages, but I am not quite sure. On your P it is probably quite similar, is it? What is the sixth signal on the signal cable?
What I was thinking of doing as a first step is simply to put the Arduino inline in the signal cable with controller outputs as inputs and with the Arduino outputs controlling the mainboard. Then I can get the Arduino to show when the built-in controller is switching things on and off, and at the same time allow a manual override at any point, and send all the results to a computer for recording. That is just the first step, later I want to take over complete control. I was also thinking of doing a completely new ventilation system, eventually. Is your setup doing anything similar?
[quote="GreenBean"]... connect the Arduino and thermocouples (which are built into the Hottop) ... .[/quote]
By the thermocouples I assume you mean (1) the built-in sensor, which appears to be an NTC thermistor isn't it? and (2) a thermocouple which you have added yourself to get a better measure of bean mass temperature. Like the KN8828, the P only comes with the one sensor, doesn't it? When you mentioned environmental temperature above were you referring to the Hottop's built-in sensor on the end wall of the roasting chamber, or have you added another thermocouple somewhere? Do you have meaningful readings from the original hottop sensor? By that I mean calibrated temperature readings that are comparable to the bean mass temperature. Do you find it useful to have both?
Paksong