220 volts AC bed heater.

Hi.

I would like to install a 220 volts AC bed heater. I'm using a 12 VDC relay connected to the bed heating output on the control card.

It works fine but, while heating, the relay sounds "click click click click click ..." several times per second, although the relay switch is always ON (no sparks from turning on and off on the 220 volts side). It looks like the output from the card is a train of pulses instead a constant value. I dont' have an oscilloscope, so I can't check it. Am I right?

Anyone tried this solution?

Thank you. Manolo.

 

Hi Mark. Thank you.

With your advice I found I should edit configuration.h and change:

#define MAX_BED_POWER 256

I'll try next week.

Thank you. Manolo.

 

Hi Mark.

I think you are talking about PID/Bang-Bang control for the nozzle.

For the bed, just #define MAX_BED_POWER 256 works fine. In fact the control is Bang-Bang for the bed already. I didn't touch the code since I got my printer:

// Uncomment this to enable PID on the bed. It uses the same frequency PWM as the extruder.
// If your PID_dT above is the default, and correct for your hardware/configuration, that means 7.689Hz,
// which is fine for driving a square wave into a resistive load and does not significantly impact you FET heating.
// This also works fine on a Fotek SSR-10DA Solid State Relay into a 250W heater.
// If your configuration is significantly different than this and you don't understand the issues involved, you probably
// shouldn't use bed PID until someone else verifies your hardware works.
// If this is enabled, find your own PID constants below.
//#define PIDTEMPBED
//
//#define BED_LIMIT_SWITCHING

// This sets the max power delivered to the bed, and replaces the HEATER_BED_DUTY_CYCLE_DIVIDER option.
// all forms of bed control obey this (PID, bang-bang, bang-bang with hysteresis)
// setting this to anything other than 255 enables a form of PWM to the bed just like HEATER_BED_DUTY_CYCLE_DIVIDER did,
// so you shouldn't use it unless you are OK with PWM on your bed. (see the comment on enabling PIDTEMPBED)
#define MAX_BED_POWER 256 // limits duty cycle to bed; 255=full current


Best regards.

 

Exactly. This is how i had it since i run the printer from the first day.

I had some time to check it an hour ago, I just changed the 255 with 256 and now works fine.

Thank you so much.

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