Help Tuning Brewpi System

I recently got my brewpi installed in a chest freezerbalong with a light bulb in a paint can for a heater. Everything seems to be working correctly, but for some reason I can’t get my 5 gallon carboy of water up to the temperature I have set in the software. It always stops about 1 degree Fahrenheit short of the target. Any suggestions? I have the carboy filled with 5 gallons of water and the temp probe in a thermowell. I would upload a screen shot of the graph, but I can’t because I am a new user. Thanks!

I have changed the trust level requirements for uploading images. I’ll wait for your chart before before replying.
Please make sure that the fridge setting and fridge temperature lines are enabled in your chart.

Thanks. The graph is attached.

A few observations:

  • Your fridge temp is higher than your beer temp at all times. This is probably due to how the sensors and heater are arranged. You would expect the beer temp to rise otherwise. Please think about your sensor placement. Away from the back of the fridge and the heater is best.
  • This situation should be corrected by the integrator: the error would accumulate and the fridge setting will rise. However, there is a setting in Advanced Settings --> Control constants that deactivates the integrator when the temperature difference is higher than 0.5C. This is to prevent integrator windup, but the range is too small for your setup apparently. You can increase that range to 1C/2F.
  • Check the Control Algorithm tab to see how the fridge temperature setting is calculated from the proportional, integrated and derivative error of the beer. You can scale these by adjusting Kp, Ki and Kd. My guess though is that the integral is at zero, due to the situation above.