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Some questions to start right to mod a roaster with TC4


renatoa wrote:

If not fused against unauthorized reprogramming... it could.

The general schematic you described, sounds logical, is the typical way how these things works.
That's why I asked at the beginning of thread about such details, to suggest attaching an existing solution to the main entry points of such electronics: temperature and power control.

I want to try and get some better photo's of the boards with better lighting, and i'll upload pics.

the controller board has additional IO's that should be connected to the STM32 IC ready to solder some headers on for use. there is a write protect jumper already populated, so possibly will allow re-flashing (though without the source code it would need to be written from scratch).

In the minimum, the LCD could be reused and the main driver board could be controlled off an ESP32 if the main controller board was not able to be reflashed (or code written to suit).
Re-writing from scratch would be a too long job for the average free time programmer.
Has no sense to try this just to reuse a processor, imo
Better try to identify the LCD type, and thermocouple chip, to check if there are libraries available for existing open source world.
The LCD Touch Controller is a XPT2046
The LCD looks to be controlled directly via 16 IO pins, though I can not find any examples on the web using more than 8.
The TC chip on the main driver board is a MAX6675
The Triac driving the heater is a JST41Z-800BW
There is an Arduino library for a SPI version of this display:

The MAX chip is already supported by TC4ESP, even if not yet published.

The triac should be connected to the CPU by an optocoupler, please check how is the gate connected in the triac neighborhood.
If heater is manually controlled by a pot/knob, then optocoupler is a must to add.
Triac is good, it's connected via a MOC3052M optocoupler
You have there all you need for a roaster Grin
Below some close pictures of every boards.
The thermocouple driver is a MAX6675
My heater resistance is 16 ohm so 3300W as indicated on the label.

I don't think to spend time on the original hardware, to use this roaster in standalone the original hardware/software does the job quite well.

To monitor the roast with Artisan I added an ambient sensor below the beans bed (ET), a second BT sensor and use a Mastech6514 (works really well on my Macbook, no issue).

To use it with TC4 PID and Artisan, my external TC4 cabinet is almost finished, first test soon.
I chose an external cabinet, for the access (it's not easy in the roaster box), and first need to learn to discover about TC4 solution, then later I could make a choice.

Edited by iPa on 01/30/2022 8:30 PM
This morning first blank test with the new TC4 cabinet:
- Blower all ok, min, max and cool values adjusted.
- Heater output tested with a 1600W stove, all ok, and really very low heating of the ssr.
Not enough time for more today.

Edited by iPa on 01/30/2022 10:33 PM
First roast !
I think the beginning was promising, but then 2 weird behaviors.
What can explains 1 (and how to improve), change grain behavior, when they becomes exothermic, no because it’s the heater increasing suddenly, so ?
For the second, heater seems to heat again after a while. At the drop event I send a PID OFF, maybe I should send a « heater 0 » too, isn’t it ?

At the beginning of tests, I noticed the blower was not smooth, some heretics speed changes, probably wrong trig from the zero detector, here in Thailand the powerline are very dirty and unstable, so I gave up and keep only the original fan dimmer on the roaster, in fact it’s ok like this.

Edited by iPa on 02/01/2022 1:51 AM
Both PID;OFF and PID;STOP cut the heater, I would rather consider that glitch a reading issue.

To attenuate the BT bump at first crack, stop increasing power after minute 8.
When you learn how to "read" the approach of the FC, you could even step down 1% in the minute before FC, but be prepared to increase back immediately, to avoid the crash.
Edited by renatoa on 02/01/2022 2:20 AM


renatoa wrote:

Both PID;OFF and PID;STOP cut the heater, I would rather consider that glitch a reading issue.

Asap I understood that the heater was heating again, I pressed my “heater off” button then ET was immediately falling again (the glitch).
I will try another roast soon.
How to send more than one serial command ?
Which separator to use ?
Thank you
No need to send both commands, PID;STOP is enough, it covers all actions of PID;OFF, plus the fan related actions.
Edited by renatoa on 02/01/2022 5:51 AM
I spend time to read the graph and with the simulator.
I think these two issue have the same origin.
Maybe something wrong with the ssr, so I added a ssr heatsink fan, a heater voltmeter (like the one for the fan) to keep an eye on it on the next roast.
Heater SSR replaced, this time no weird behavior.
Added a SSR sensor.

Edited by iPa on 02/05/2022 7:49 AM
I've seen a video of another person who has 'extended' their glass chamber, I'm curious, what are the dimensions of the 300g glass chamber ?
my 150g model is (roughly) 85mm OD, 75mm ID and 130mm tall


Adam_M@au wrote:
what are the dimensions of the 300g glass chamber ?
my 150g model is (roughly) 85mm OD, 75mm ID and 130mm tall

96mm ID
106mm OD
220mm length
I've ordered one of these to extend (replace) the chamber in mine:

will definitely be tall, but there is plenty of power in the fan to move the beans, should help prevent the beans from escaping. I keep ending up with too many beans in the chaff through different stages of the roast.

It would be interesting to setup a top that if you turn the dial to 11 it will blow the roasted beans out of the chamber into a container.
Edited by renatoa on 02/18/2022 6:48 AM
I have these issue too especially during the cooling stage.
Last roaster version they add a deflector (picture 1) I am trying with stainless ball, it’s not perfect but better than without (75% less). I will try to add a fan grid too.

A new deflector, I have not tested yet.
2 stainless funnel mounted top-top, some TIG welding points.
This one not fit the hole so need to be mounted inside, looking for an idea, maybe with a grid fan, water drainage grid, …

First test with the new beans deflector, failed with the not modified fan grid, was fully obstructed before the end of the drying phase, the complete head was floating on a bed of air and the kitchen was filling up with chaffs. Roflmao
Success with the modified fan grid.
For the cooling phase I have used more fan power than ever before, and no beans was ejected in the chaff colector.


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