11. Raspberry Pi Hat Usage - larry-athey/rpi-smart-still GitHub Wiki

While you might be anxious to jump right in and start hooking up wires to your Raspberry Pi Hat, you should approach this with care and common sense so you don't end up burning up your hat or your Raspberry Pi. Below is a list of things to consider and check first, it's easier to troubleshoot one issue at a time rather than a whole mess of them.

Before powering up your Raspberry Pi with the hat attached, double check the clearance between the hat and any heat sinks that you have installed. You may need to order a GPIO bus extension so you don't short out your hat and cause damage to it. Not to worry too much if you do, the hats are pretty simple to repair since all critial devices are socketed. However, repeatedly replacing the Raspberry Pi can get a little expensive.

If you think that your hat might be fried, I recommend getting a GPIO terminal block with LED status indicators to test your Raspberry Pi with first. The hats are pretty tough to damage, even with a dead short across the motor outputs. I've seen more cases where the Raspberry Pi itself is damaged by 12 volts coming in contact with its GPIO pins. These GPIO pins are only designed for 3.3 volt signals, 12 volts will fry the Raspberry Pi in a fraction of a second.

Power Supply: Make sure that you choose a decent power supply with more than enough current capacity to run all of the motors. My setup only uses a 12 volt, 5 amp power brick because I'm only using 1/4" cooling valves and a 20mm Nema 17 stepper motor. If you choose 1/2" or larger cooling valves or a longer Nema 17 stepper that has a planetary gearbox, you will need to pick a higher current rated power supply.

Cooling Valves: Just because your valves have the same color wires as mine, doesn't mean that those wires are for the same purpose. You should use your power supply to test your valves by running them all the way in both directions and use an ohm meter to verify that you know which wire is which for your limit switches. You should also test both valves at the same time to make sure that your power supply can run both of them without bogging down.

Heating Stepper Motor: The DRV8825 stepper motor driver on the Raspberry Pi Hat is preset to run a 20mm Nema 17 with or without a planetary gear box (Vref set to 0.5 volts). A larger stepper motor, such as a Nema 23 isn't necessary and won't even work here due to their current requirements. If your power supply survived the previous test running both cooling valves simultaneously, then it has enough current capacity to run your heating stepper motor.

DS18B20 Temperature Sensors: All DS18B20 sensors are not created equal and you never know if you got decent ones from Amazon or Ali Express until you get them connected. If you connect them incorrectly, you can toast them in just a few seconds. I recommend getting the ones from Adafruit and just accept the fact that the higher price equals higher quality. If you report a problem to me about temperature related issues, this will be my first suggested remedy.

Connecting Devices: Do not connect all devices at the same time, do things in steps and make sure each device is working before moving on to the next one.

  1. Connect your DS18B20 temperature sensors. Go to Configure Sensors under the Management menu and verify that they all appear in the bottom frame. Identify which one is which by placing it in a glass of ice water and watch for the one where the temperature is decreasing. Assign it to the Depleg, Column, or Boiler and mark the sensor with a label.

  2. Make sure that your cooling valves are fully closed and connect them one at a time as instructed in the Raspberry-Pi-Hat-Usage.pdf document. Run the valves full open and full closed in the user interface. If you run one valve full open and a few seconds later the dashboard shows it jump back to 0%, then you have the limit switch wires reversed. Don't run the valve calibration function until after you have confirmed that the motors and limit switches are connected correctly. Otherwise, you'll hang the system and have to reboot it.

  3. Identify which of the 4 wires on your stepper motor are the coil pairs and connect them as instructed in the Raspberry-Pi-Hat-Usage.pdf document. Test your stepper motor the same way that you tested your cooling valves or use the Heat Jump feature under the Management menu. If your motor is turning the wrong direction, you can swap your coil wires or use the Inverted Stepper Rotation option in the heating configuration section.

If you are using my Boilermaker instead of an SCR controller or gas valve, you can safely skip step 3 in the above and only connect two DS18B20 temperature sensors to your hat since the Boilermaker has its own temperature sensor.

NOTE: While I do not sell turnkey RPi Smart Still controller systems, I am willing to allow you to drop ship your Raspberry Pi (or clone) and SD card to me so I can set it up and test it to make sure that all is working and send it out to you along with your hat. There is an additional fee for this service.

I also offer another service that attaches your RPi Smart Still controller system to my remote monitoring and management service that provides automatic updates and remote troubleshooting. Contact me from my website for more information.