roaster control widget

[Tex]

Thanks for the tip Tex

That's avatar material, for sure!

[cfsheridan]

Larry, what I generally do with the Hottop fan is to bring it on 50% power for about 30 seconds between 3-4 minutes into the roast (suck out the moisture).  I then leave it off until about 6-8 minutes in, when I set to 25%.  About 10-12 minutes in (right before first crack), I push the fan to 50%.  It generally stays there, unless I need to quickly slow things down--that is, the temp ramp gets too steep after first.

I don't do that much, and I don't do that during 1st crack, as you can easily stall things out as the beans through the end of 1st crack.

I've got some graphical software coming that I'm going to use to build some HMIs--one of the displays I REALLY want with the hottop is bean mass temperature rate of change.  That's the main thing I am calculating in my head as the roast progresses.

[milowebailey]

So today I was thinking about the interface board to the Hottop and decided to open it up and see how they did it... as I looked at the design and thought of their website I guessed that they used a 2 board design where all the control was on the keypad board and all the switching was in the other board... I did some measurements and I was correct... the cool part is they use 5 v dc to control the high voltage board... so I connected the milowidget, wrote a little test script and it will control my hottop with no additional circuitry...  All I need to do is build a cable to connect the milowidget to the hottop and install a thermocouple or two and bam....

oh crap... forgot about the thermocouple circuit... but that's no big deal at all even for the novice...

Next step is to do the mods and I'll start roasting 

photo for those who can't read...

[milowebailey]

Oh... forgot to mention here is the pin-out:  for model # KN8828

1 - ground
2 - 5 volts (do not connect this to the milowidget)
3 - fan
4 - bean dump
5 - cooling motor
6 - drive motor
7 - heating element

Note that the drive motor must be on for the heating element to turn on...

[cfsheridan]

Oh... forgot to mention here is the pin-out:  for model # KN8828

1 - ground
2 - 5 volts (do not connect this to the milowidget)
3 - fan
4 - bean dump
5 - cooling motor
6 - drive motor
7 - heating element

Note that the drive motor must be on for the heating element to turn on...

Dude!  You're spot on to where I wanted to go--use the link to the control board and keep all the board circuitry within the machine intact.  Thing is, I think the newer models have a different interface...

Where'd you get the pin-out information--by testing?

[milowebailey]

Dude!  You're spot on to where I wanted to go--use the link to the control board and keep all the board circuitry within the machine intact.  Thing is, I think the newer models have a different interface...

Where'd you get the pin-out information--by testing?

Ground and 5 volts from looking at the board, but the rest by testing.

I suspect the other boards follow a similar pin-out... but maybe different.   What is your old board set?  I'm sure you could use that for your widget...

[milowebailey]

Good news... looks like the newer boards follow the same control wiring... except they add another pin.  INT

I haven't figured out what that would be for yet....

[cfsheridan]

Plus there's an additional wire for the chaff tray protection circuit (Three wires leading to the panel)

[milowebailey]

Plus there's an additional wire for the chaff tray protection circuit (Three wires leading to the panel)

Is the chaff tray wire on the older boards?

[MMW]

Oh... forgot to mention here is the pin-out:  for model # KN8828

1 - ground
2 - 5 volts (do not connect this to the milowidget)
3 - fan
4 - bean dump
5 - cooling motor
6 - drive motor
7 - heating element

Note that the drive motor must be on for the heating element to turn on...

That's fantastic info, thank you! Does the HT just use PWM to set the level of the heater?  1 10% duty cycle for lowes, 20% for next up etc.?  I would assume the fan is the same way.  Is that correct?

I've been meaning to dig into mine to take a look see but haven't really had the time.  I'm wondering if the 'INT' pin has something to do with the chaff tray switch...

[milowebailey]

Oh... forgot to mention here is the pin-out:  for model # KN8828

1 - ground
2 - 5 volts (do not connect this to the milowidget)
3 - fan
4 - bean dump
5 - cooling motor
6 - drive motor
7 - heating element

Note that the drive motor must be on for the heating element to turn on...

That's fantastic info, thank you! Does the HT just use PWM to set the level of the heater?  1 10% duty cycle for lowes, 20% for next up etc.?  I would assume the fan is the same way.  Is that correct?

I've been meaning to dig into mine to take a look see but haven't really had the time.  I'm wondering if the 'INT' pin has something to do with the chaff tray switch...

Mine is an older model so I can only be sure how it works.  My plan is to do exactly that set the duty cycle for the fan and heater.

I'm not sure how the B and P do it... If I had one in my grubby little hands I could figure it out... but I don't think I'm going to dish out the $220 for the parts when I can control it with the milowidet using the old "interface board".

If you have a B or a P let me know how they do it. 

[cfsheridan]

Here's a good thread on the subject.  In theory, the P adjusts power as it gets close to the target temperature--I've never seen it shown on the killawatt.

[milowebailey]

From the oscilloscope plots I see how Hottop does it... the area under the curve is the power going to the heating element.  You can't just drop the voltage easily to reduce to power so you switch the Triac on and off to clip the waveform and reduce the area under the curve.  With a Triac it's simple to do... think of a light dimmer.... works the same way except manually with a potentiometer.

The PID should have much better control.  The key is learning what the heating element is capable of... (how quickly it can heat the bean mass at 100% and how quickly it changes so you don't overshoot too much or stall.

Should be fun!!

[milowebailey]

Good news... looks like the newer boards follow the same control wiring... except they add another pin.  INT

I haven't figured out what that would be for yet....

I think the INT is an interrupt they are using to detect the zero-crossing of the AC signal.  I believe this is used to fire the Triac, to control the heater (basically it is an input used to trigger the triac so it turns on and off at the right time), which is needed if you want to turn the heater or fan on to 50% or anything other than on or off.

[milowebailey]

I did the thermocouple modification that cfsheridan did on his hottop yesterday and did a 12 minute test run (no beans) with the milowidget and hottop to make sure I didn't catch the house on fire... Seems to follow the linear curve just fine.

I plan to roast a batch this afternoon on the hottop... I'm going to see if I can hold the temp at 400 for 2 minutes... just for fun.

I also think I've figured out a simple inexpensive interface that will hold the thermocouple amplifier and make the modification on a hottop very simple.  It will also allow for the newer models and the interrupt pin (zero crossing detection).

After today's roast (If all goes well) I plan to work the PID code into the Milowidget and then start working on the users interface.

Should I add an annoying beeper like the hottop has now???