Source code available at https://github.com/ambrogio-galbusera/gr0g, https://github.com/ambrogio-galbusera/gr0g-ble-android and https://github.com/ambrogio-galbusera/gr0g-ble

Let's now start to build the control board. This is the electrical circuit we are going to build (it's a bit difficult to read, but the original Fritzing file is attached)

Some notes about this diagram

The control board takes a 12V dc power supply. It converts the 12V dc to 5V dc through a 7805. Since the output of a 7805 is not very "clean" (it has ripple and spikes that may cause damages to the Raspberry Pi and the other boards), I choose to connect the 7805 output to the USB connector of the Raspberry Pi. The USB connector has a Zener to eliminate spikes and some circuitry to level the ripple. Then the 5V and 3.3V to power up external boards is taken from the 40-pin header connector
Raspberry Pi absorbs a lot of current (up to 2A), so the 7805 is going to get very hot
The Keypad connector uses four GPIOs to read the status of keys to allow the user to navigate through the screens shown on the display of the PiMoroni Automation Hat. I could have connected the keypad to the PiMoroni Automation Hat inputs, but
- PiMoroni Automation Hat has just three inputs (I need four inputs)
- The library provided to control the PiMoroni Automation Hat tries to access the I2C bus as soon as you initialize the library itself, but I am going to use the sensors on the Enviro Hat
- The PiMoroni Automation Hat inputs are connected directly to the Raspberry Pi GPIO pins

For all these reasons, it's not so bad to connect keypad directly to the Raspberry Pi

The Automation Hat connector takes the SPI signals plus a GPIO (to control display backlight) and power supply (both 3.3V and 5V). The SPI bus is required to control the PiMoroni Automation Hat display. This display will be mounted on one of the vertical panels of the Gr0G box to show astronauts information about the status of the box
The Enviro Hat connector takes the I2C signals and power supply (both 3.3V and 5V). The I2C is required to access hat's sensors. The hat will be mounted on a bracket. The display on the EnviroHat will not be used
The Gertbot board requires an UART to be commanded and controlled. The power section will be connected to the 12V dc (for fan, condenser, and solenoid valve) and 5V (for LEDs)

The Raspberry Pi, the Gertbot board, the PiMoroni Automation Hat will be mounted on a plywood board

The boards have been then put in place. First, the Raspberry Pi

Then, the PiMoroni Hacker board with the connectors for the external boards

Finally, the Gertbot board

Then, the PiMoroni Automation Hat board has been installed on the front side of the plywood panel

UPDATE:

PWM output can not handle the current required by both the dehumidifier (fans + Peltier cell) and cooler. So I disconnected the Peltier cell from the PWM output pins and now I am going to switch on and off the cell itself by means of opendrain output 1. Since opendrain output are rated for 5A maximum (and the Peltier cell draws 6A) I used the opendrain output to drive a relay, and the relay NO pin will then be connected to the Peltier cell. The new diagram in shown in picture

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skruglewicz over 4 years ago

Hi amgalbu

Nice design. Especially interested on how you are utilizing the hacker board. I couldn’t figure out how to implement it. Do you know if you can stack the hats? using the hacker?
I was going to use two raspberry pi ‘s. Then I have to share my logic over the network. That would make the logic more complex.
I’m new to all the circuit stuff. and I’m learning a real lot in this challenge and having fun doing it. . It’s an excellent learning tool...
I appreciate everyone helping me.
Steve K
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amgalbu over 4 years ago in reply to skruglewicz

Hello skruglewicz
As far as I understand (I am not certain because pimoroni do not share the schematics of their products) you can not stack the hats.
Looks like they use the same gpio as spi chip select signal so you can not drive two displays separately. This is why I used the pimoroni hacker board to wire just the signals I need. I really appreciated the labels etched on the hacker board: they are really helpful when you are soldering the wires. But I would have included the 40 pins female header inthe package...

Cheers
Ambrogio
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balearicdynamics over 4 years ago in reply to amgalbu

Just FYI, if the board of Pimoroni is a real HAT – I mean, following the Pi HAT specifications – it should be identified by an EEPROM encoded in a specific way accessed by the I2C 0. This is just to make available other HATs compatible with the same GPIO connector without risks. I have also tried this and it worked almost easily, but not all HATs respect 100% the specifications. Anyway, there are a couple of commands to check if it is a HAT, its ID etc.
Here you find the HAT specifications: https://github.com/raspberrypi/hats with links to further details for software and hardware
Here one of the repos with the specifications on hardware HAT (size, the position of the eeprom, etc.): https://github.com/xesscorp/RPi_Hat_Template

Enrico
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skruglewicz over 4 years ago in reply to balearicdynamics

good to know balearicdynamics
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balearicdynamics over 4 years ago in reply to amgalbu

BTW, Ambrogio, as far as I know, the Pi has two SPI but a couple of displays I think can't be shared together depending on other details of the Pi architecture. At least not in a simple way. Instead, I think that one or more secondary Oled displays controlled by I2C are a feasible option.

Enrico
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balearicdynamics over 4 years ago in reply to amgalbu

BTW, Ambrogio, as far as I know, the Pi has two SPI but a couple of displays I think can't be shared together depending on other details of the Pi architecture. At least not in a simple way. Instead, I think that one or more secondary Oled displays controlled by I2C are a feasible option.

Enrico
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amgalbu over 4 years ago in reply to balearicdynamics

Yes Enrico I think it's possible to use two display by using two GPIOs as CSes for the two displays
I didn't investigate this option but I think it's not too difficult but for sure this does not make possible to stack Pimoroni hats
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dules over 4 years ago in reply to balearicdynamics

You can check my solution for this problem here:
Aquaponics Box: #2 - Hacking the HATs (both HATs from the challenger kit on single RPi)
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amgalbu over 4 years ago in reply to dules

Thank you dules
I read your post and you did a great job!
I expected it was possible but I didn't make further investigations because I just don't need the display on the Enviro Hat but, yes, your work can be of great help to all the challengers
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