GPIO output flickers and Output can't be set in Mycodo

Hello there,

I am having problems with my outputs. The plan is to controll SSR to alter the environment of my mushroom tent. The inputs (DHT22 for temp/humidity, MH Z-19B or SCD 30 for CO2) work fine on my RPi 3B. I use FOTEK SSR-25 DA and a 4 way SSR but i get the effect on a simple diode (LED) with a resistor too:

The output fluctuates which causes the connected device to flicker (changes fast between on and off). I meassure 0.4 V or 1.6 V but i guess it changes ON/OFF since the reading is not steady. I am using a free GPIO (17 or 27 for example). Tried to change them to on in the terminal with RPi.GPIO or WiringPi commands but it does not change anything (V stays =0). After I start the RPi they are in input mode and when I change them to output (or use mycodos settings) they start doing those things.

Furthermore I can’t configurate the output in Mycodo. They sometimes activate themself for a few seconds but get inactive again.

Sometimes the outputs behave differently after a reboot. I can then send a short on signal during mycodo when I either activate the output (goes to inactive immediately) or set a duration and click on send (does not matter how long - used to work in the beginning though [so duration 3 = 3 s on]). Same goes for the commands in the terminal.

The weird thing is: It used to work when I first set it up. I changed the power adapter from a smartphone charger to MW HDR-30-5 and it worked again yesterday evening! But now, when I start my RPi, it does not work again…

I have not a lot of experience with the RPi, so I hope to find some help here. Thanks in advance.

Here are some things to do/check:

  • Disconnect all devices when testing pins and only connect one device at a time when testing devices
  • Only after ensuring each device works by itself, connect them together to test if they work
  • Measure the voltage of output pins with a volt meter to verify they are outputting the proper voltage when switched high/low (3.3v/0v)
  • Measure and verify the voltage from your power supply, at the Pi (5v pin)
  • When connecting devices to output pins, do not allow them to exceed the current draw limit of any single pin or the total current draw of all pins combined
  • When using switching devices with output pins, ensure the device can properly switch with the voltage (3.3 volts) and current supplied by the pin