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noahrondeau / b-ready

A DIY proofing box for keeping levain, bread dough, and other ferments at stable target temperatures
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Build initial hardware prototype #2

Open noahrondeau opened 4 years ago

noahrondeau commented 4 years ago

Goal

To have an initial, breadboarded HW prototype ready to enable code development

Steps

Thermal Sensing and Heating Components

Thermocouple (K-Type) Sold by Sparkfun This thermocouple uses a sub-mini connector. It is K-type (most common type), with a 20cm long stainless-steel probe (not guaranteed food-safe, but pretty much. If needed, can case in food-safe material). This product is essentially interchangeable with other K-type thermocouples. Two are needed

Thermocouple Amp IC: MCP9600 from Microchip Prototyping Breakout: MCP9600 SparkX Breakout It works over I2C, will selectable addresses. It has a PCC (sub-mini-compatible) connector. Two are needed.

Heating As a prototyping solution, the following pre-assembled flexible heating pads will be used: Link This is likely not a permanent solution. OEM mesh and etched element manufacturers make professional grade products with much better heating profiles. This may be needed to achieve proper PID control.

MCU Platform

Power Requirements

Input:

Peripheral power reqs:

Peripheral Requirements 1x I2C bus

noahrondeau commented 4 years ago

Thermal probe options

Best is probably a K- or J- type thermocouple, already in a stainless steel case. Some are optimized for air, others for liquids and semi-solids. Not sure to what extent this matters (should find out). https://www.digikey.ca/en/products/filter/test-leads-thermocouples-temperature-probes/621?s=N4IgjCBcpgHAzFUBjKAzAhgGwM4FMAaEAeygG0R4AWAVnmpCPgDYAmMKxJtgThoiJUwzKswAMIALpEADgBcoIAMpyATgEsAdgHMQAXz1FmSEOoAmigLRgxAkPMWMQcgJ4y8ijDlQGgA

It seems that the most common connectors are sub-mini (standard thermocouple connectors). Also, a thermocouple amplifier is needed. There are many breakouts built around the MCP9600.

noahrondeau commented 4 years ago

Flexible Heating Element Selection

Want a flexible mesh heating element (probably resistive) that I can wrap around the inside of the box. Selection guide: https://www.globalspec.com/learnmore/manufacturing_process_equipment/heating_cooling_equipment/industrial_heaters_heating_elements/resistive_heating_elements https://thermcraftinc.com/wp-content/uploads/2018/01/Heating_Element_Seminar_Nov_2_2016.pdf

It appears that there are many options for this:

noahrondeau commented 4 years ago

Thermal Components (prototype)

After much research, I am going with the following products purchased through Sparkfun. This is a convenient prototyping setup based around a commonly used thermocouple amplifier from Microchip

Thermocouple (K-Type) Sold by Sparkfun This thermocouple uses a sub-mini connector. It is K-type (most common type), with a 20cm long stainless-steel probe (not guaranteed food-safe, but pretty much. If needed, can case in food-safe material). This product is essentially interchangeable with other K-type thermocouples. Two are needed

Thermocouple Amp IC: MCP9600 from Microchip Prototyping Breakout: MCP9600 SparkX Breakout It works over I2C, will selectable addresses. It has a PCC (sub-mini-compatible) connector. Two are needed.

Heating As a prototyping solution, the following pre-assembled flexible heating pads will be used: Link This is likely not a permanent solution. OEM mesh and etched element manufacturers make professional grade products with much better heating profiles. This may be needed to achieve proper PID control.

noahrondeau commented 4 years ago

Power input to system could likely be 5V regulated USB power, or barrel jack 5VDC. Worst-case scenario total peak current requirements will be upwards of 8x600mA = 4.8 A however, and this is just for the heating.