Mains bed pwm frequency/flickering lights.
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Hey all,
I have a 800w mains bed hooked up to my printer. I've done all the tuning and it works great. The only issue I have is that when it gets up to temp, the pid control kicks in and starts switching the bed on and off with the SSR. With a 800w bed on this circuit that I have in my house it's causing lights to flicker. I was wondering if I can modify the frequency, so instead of the 20hz it's switching at, I can maybe bump it up to 100-200hz so I'm not being driven crazy by my lights flickering. I looked in the documentation and saw that I can set a pwm value from 0-1, but not sure if this is what I want.
Thank you
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@Surgikill What firmware version are you using? If you're using RRF 3.x, you should have an M950 command in your config.g that creates the bed heater, eg
M950 H0 C"bedheat" T0. You can set 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. See https://duet3d.dozuki.com/Wiki/Gcode?revisionid=HEAD#Section_M950_Create_heater_fan_spindle_or_GPIO_servo_pinIf you're on RRF 2.x, use the F parameter in M307 to set PWM, see https://duet3d.dozuki.com/Wiki/Gcode?revisionid=HEAD#Section_M307_Set_or_report_heating_process_parameters
Ian
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pwm freq is set with m950 when defining heater with Q parameter , in your case Q200 .
i would check why 800w heater is causing your lights to flicker . its not much when you're talking mains power . -
@droftarts I'm on 2.03. I need to upgrade and find a way to do it without losing my configuration. That's my next item on the list.
@hackinistrator It's 110 on a 14 wire circuit on the other side of the house from the breaker box. Also has a desktop pc that pulls 300 or so watts on the same circuit. I don't really have an option to move it to another circuit. I was debating on dropping a 12 wire dedicated outlet to my printer, but that's a lot of climbing through the attic I don't want to do.
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@Surgikill You can still set the PWM in 2.03, using F parameter in M307.
For what you'll need to change, see https://duet3d.dozuki.com/Wiki/RepRapFirmware_3_overview#Section_Summary_of_what_you_need_to_do_to_convert_your_configuration_and_other_files
Usually, the best method is to generate a set of configuration files using the configuration tool https://configtool.reprapfirmware.org/Start, as close as you can to your existing config. Then go through it and see what has changed.
To update your firmware, you should be able to do it all through DWC. Upload these 3 zip files, one at a time. Don't extract them. Reboot after each.
https://github.com/Duet3D/RepRapFirmware/releases/download/2.05.1/Duet2Firmware-2.05.1.zip
https://github.com/Duet3D/RepRapFirmware/releases/download/3.0/Duet2and3Firmware-3.0.zip
https://github.com/Duet3D/RepRapFirmware/releases/download/3.2.2/Duet2and3Firmware-3.2.2.zip
That will get your firmware and DWC up to date.Ian
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Zero-crossing SSRs can only pass complete half cycles of mains to the heater, so if you use frequencies higher than about 20Hz you will get odd beat frequency effects between the PWM and the mains frequency.
If an 800W load is sufficient to dim the house lights, it implies that your mains supply or distribution panel has significant source resistance.
To get fine control of heater power without dimming the lights, you would need to use a phase angle controller.
Duet WiFi hardware designer and firmware engineer
Please do not ask me for Duet support via PM or email, use the forum
http://www.escher3d.com, https://miscsolutions.wordpress.com -
@dc42 It's only the lights on this circuit. The wonderful idiots who built this house did about a 100 foot run of 14 wire to feed 2 bedrooms, and daisy chained it through all the outlets. Not really much I can do unless I drop another line in or move my printer to the living room, which isn't happening.
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@Surgikill
I also had some kind of "music" in my power suppy. (ssr +800W heater)
Try to set the Q value to 10. -
@Surgikill said in Mains bed pwm frequency/flickering lights.:
@dc42 It's only the lights on this circuit. The wonderful idiots who built this house did about a 100 foot run of 14 wire to feed 2 bedrooms, and daisy chained it through all the outlets. Not really much I can do unless I drop another line in or move my printer to the living room, which isn't happening.
Are they LED lights, or another sort? You might find that LED lights are less sensitive to mains voltage variations than older types.
Duet WiFi hardware designer and firmware engineer
Please do not ask me for Duet support via PM or email, use the forum
http://www.escher3d.com, https://miscsolutions.wordpress.com -
@dc42 Both, the LED's are actually worse, but they are cheap 40w led strip lights. Apparently they double as a strobe as well.
@DIY-O-Sphere I think once I insulate the bed and get a chamber on it I might be able to get away with a low q value so it's not as bad. I wish I could put the printer in the garage so I could just put a new circuit into the panel and be done with it.
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you can add capacitors to led power supply / bridge
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@hackinistrator I don't think I can because they are direct connect A/C led's.
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@Surgikill, what is the size of your bed? Do you really need 800W?
Also, running it on DC may smooth the load fluctuation on your main.
Another option is running your printer on some sort of UPS.
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@Surgikill there should be bridge rectifier after the AC in . leds work on DC .
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@Surgikill said in Mains bed pwm frequency/flickering lights.:
I think once I insulate the bed
Depends on your bed. Mine is isulated and 8mm thick. There I could set the fequenz even further down because the thermal inertia is high. 10 means 10 times per second, if I remember correctly this was once the default setting in the FW. So it should work.....
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@DIY-O-Sphere said in Mains bed pwm frequency/flickering lights.:
@Surgikill said in Mains bed pwm frequency/flickering lights.:
I think once I insulate the bed
Depends on your bed. Mine is isulated and 8mm thick. There I could set the fequenz even further down because the thermal inertia is high. 10 means 10 times per second, if I remember correctly this was once the default setting in the FW. So it should work.....
Indeed. 10Hz always used to be the default frequency for bed heaters and that's what I still use, with a bed configuration similar to yours (8mm, insulated etc).
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@hackinistrator I can try it, would just rather fix the problem at the source.
@zapta The bed is 489x355, with build area being around 320x320. I'd have to buy a new bed heater in order to run it, or get a high voltage DC power supply. At 24V the bed would only be producing about 40 watts, which isn't enough. 64V would put me around 270 watts, which might work, but would be slow as hell.
@DIY-O-Sphere My bed is only about 3mm thick, so not a lot of thermal mass, but heats up quickly.
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@Surgikill said in Mains bed pwm frequency/flickering lights.:
@hackinistrator I can try it, would just rather fix the problem at the source.
I think this means fixing the house's wiring.
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@zapta Unfortunately you're right. Also unfortunately I bought it a year ago and don't plan to live in it for more than 5 years, so I'm just trying to find the best bandaid I can.
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I see similar light flickering when the bed heater kicks on and off, especially on dimmed LED bulbs which seem especially sensitive to the line voltage. I've seen similar flicker from fluorescent lamps.
An 800W heater takes almost 7A from a 117VAC line. The printer operates in parallel with the lights. If there's only an Ohm between the load (printer and light) and the "source" (breaker panel) that will cause a 7V drop in the line voltage when the heater switches on, hence the flicker. It doesn't matter if you have a zero crossing SSR or not, the voltage will drop and the lights will flicker.
The solution is to either turn off the lights or plug the printer into a different power circuit.
