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Use of SLOW_PWM?  

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RetireeJay
(@retireejay)
Reputable Member
Use of SLOW_PWM?

I have found that when the bed heater is in the default PID mode using PWM (Pulse Width Modulation) that the pulses are spaced at a fraction of a second. The resulting on-off load of 100watts or so is causing a "strobe" flickering effect on light bulbs that are on the same circuit in my house. If I switch the bed to Bang-Bang control, the flickering is not noticeable.

But in researching this issue to see if I could slow down the pulse rate, I discovered these lines in Configuration.h
#ifdef PIDTEMP
//#define PID_DEBUG // Sends debug data to the serial port.
//#define PID_OPENLOOP 1 // Puts PID in open loop. M104/M140 sets the output power from 0 to PID_MAX
//#define SLOW_PWM_HEATERS // PWM with very low frequency (roughly 0.125Hz=8s) and minimum state time of approximately 1s useful for heaters driven by a relay

So my question is, if I uncomment the line to #define SLOW_PWM_HEATERS will this change the pulse rate for ALL the heaters including the Hot End, or just for the Heated Bed? I would NOT want to have an 8-second cycle time on the Hot End, but I think it would be perfectly fine for the Heated Bed.

Posted : 04/06/2018 3:26 pm
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