Chamber heater hysteresis
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I have a large chamber heater thats set up in bang bang mode on out8 on my duet3. The chamber heater has a controller board with a relay on it for the heater and heats up just fine. The problem im having is the relay is clicking on and off too quickly and eventually i know it will burn out. Chamber is set to 60 deg so is there a way i can set a hysteresis of say 5 deg so the chamber turns off at 60 and then back on at 55?
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@3DDP I don't believe there is any way to alter the hysteresis. If you are using a mechanical relay, changing it to a solid state one would work.
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@3DDP Are you sure it's set to bang-bang, not PWM? How often is it clicking? Please post your config.g, and if you've tuned the heater and saved it with M500, your config_override.g. Your M307 command for the chamber heater should include 'B1' to enable bang-bang mode. If using PWM mode, you can change the 'Q' parameter (PWM frequency in Hz) in M950 command that defines the heater to make the switching much slower, eg Q1 for 1 switch per second. Not sure if you can use Q0.1 (which would be switching every 10 seconds) to reduce it even more.
Ian
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I was just wondering if the hysteresis could be changes. The relay is only clicking intermittently once the temp reaches the set point. I guess ill just have to mod the controller board with a solid state relay. Thanks everyone
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I have this same issue going on. Is the only option still switching to a solid state relay?
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@taylo708 Does anyone have an easy fix for this?
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@taylo708 As @droftarts says above, are you sure you're in bang bang mode and not PID? When in PID/PWM mode you can adjust the switching frequency down.
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I am in bang bang mode are you suggesting switching to PID/PWM mode with a super low frequency?
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@taylo708 That could be an option. You may be able to PID tune the chamber heater to solve the temp oscillations and use a switching frequency slow enough that it won't hurt the mechanical relay. FW 3.2 has a new heater tuning algorithm that may handle slow heaters better, but the tuning process can take a while. You can also try and derive your own PID values to use.
https://duet3d.dozuki.com/Wiki/Connecting_and_configuring_a_chamber_heater
https://duet3d.dozuki.com/Wiki/Tuning_the_heater_temperature_control