Grow Module Hardware Design

[djpetti]

The schematics for the grow module controller haven't even been started yet. That can be done as well.

This is a useful Wiki page for anyone interested. Right now it's more focused on the Base Module design, but some stuff is still relevant.

[djpetti]

Just wanted to add more exact requirements for this project:

The grow module boards are less complicated than the base module. Grow modules, however, do use the same MCUs as the base module.

Apart from the MCU, the grow module board should contain the following hardware:

• 3 1A current-controlled channels for driving LEDs. Currently, we are using these discrete driver boards, but in this design, they should be integrated directly onto the PCB. The drivers should tolerate up to a 24V input voltage. The drivers must also support dimming from the MCU, preferably via a PWM signal. It is up to you to select which specific chip you want to use. Furthermore, the power input for all three should be wired to a MOSFET, so we can completely cut power to the LED array if need be.
• A MOSFET with an associated connector that can be used to drive an LED cooling fan with a PWM output from the MCU. The fan that we are using runs at 24V, and draws 140 mA.
• Inputs for a simple photoresistor sensor, as well as three thermistor temperature sensors for the LEDs. These can be fed directly into analog inputs on the MCU. The current schematics in the master branch should contain descriptions of the equivalent circuits as used on the current prototype, including an indication of what resistor values work best for the voltage dividers. Here is a link to the thermistors we are using on Digikey.
• CAN bus signals that will be fed to adjoining modules. The hardware page on the wiki has a link to the particular CAN transceiver chip that I spec'd for the base module board, so I would strongly recommend that you use the same one.
• The only power input this board will be getting is a line straight from the 24V supply. That means that you will be responsible for producing any other voltages you need. Again, this is a problem I've already solved in my design for the base module board. The relevant part numbers for the regulators are listed on the hardware Wiki page. It would be nice if you could use the same ones, but you might have to spec different ones due to different current requirements on this board. (For instance, you don't have the CHIP SBC sucking down 1A from your 5V supply like we do on the base board.)