Roaster

Introduction

In late 2022, after about a 10 year hiatus, I decided to start roasting coffee again.

Looking at what I had kept, and what parts I had around, eventually decided to use a popcorn popper.  I had good roasts from it in the past.  

But I was used to having full PID control of the roast, so I had to make sure I had that now.

This project includes a Popcorn pumper with separate AC cords for heating and fan power, and  a large case to house outlets, switches, ESP32 with LCD and push buttons.

The ESP32 has a bluetooth interface to a PC/Macbook running Artisan.  So no wires needed between PC and the ESP32.  The ESP32 also has thermocouple inputs to read roaster temps, and an interface to a Solid State Relay for controlling heater power with a Pulse Width Modulated (PWM) output to control heater power.  PMW frequency is 1 hertz. 

I decided to use the PID function in Artisan, so there is no PID in the ESP32.

What follows is a description of my project.

Hardware

The main piece of the roasting hardware is an old Popcorn Pumper.

All the other hardware is installed in a Nabu chassis I built years ago, per this old blog.

But I changed a lot since that old blog, so keep reading for the latest configuration.   

Main pieces of the hardware are the Pumper, a macbook running Artisan, and a ESP32 connected through bluetooth to the macbook.  The ESP32 reads Bean and Environmental Temperature, and controls the SSR for the pumper's heater power.  I used Artisan's PID to set the percentage for the SSR power.  ESP32 also has a small 16x2 display and 5 buttons for a simple user interface.

Also bought a hurricane style glass chimney from Sweet Marias so its easier to see beans while roasting.  Had to move the bean temp probe lower to accommodate new chimney.

Parts

Nabu case (top of page)

2 115V outlets (one for heating element and one for fan power)

1 Fan Dimmer switch (to lower fan power as beans get lighter during the roast when using manual fan control)

Crydom D2450 Solid State Relay (controls power to heating element)

5 push buttons

2 x 16 I2C LCD (generic one from ebay)

8 VAC transformer 

rectifier bridge,

capacitor, 2200uf 35V.   You don't need this much capacitance or voltage, but I had it and used it.  I'd use at least 1000 uf and 15V

7805 5VDC regulator (1 amp, 5VDC out regulator)

164G12 Hammond transformer to boost fan voltage

Other parts used are listed in this link:

ESP32 and a TC4 thermocouple input module

Hand drawn kind of a schematic to show how I wired up the AC high voltage parts.

At the bottom, I generate 5 VDC to power the ESP32 and its associated circuits.

See the ESP32 page for the wiring info for the ESP32 related circuits.

In the following diagram, L = AC Line, N = AC Neutral, g = earth ground

                     View of the back of my case, from the inside. 

 Fan Outlet Heater SSR Heater Outlet TC connector

Software

See Artisan Page

See ESP32 page