New 380mm x 380mm (800 watt 120v) alirubber silicone heated bed with dual thermistors.

New 380mm x 380mm (800 watt 120v) alirubber silicone heated bed with dual thermistors. 3/4" MDF routed insulator bottom board. 1/4" aluminum heat spreader. Omron SSR.

Just sprayed the first coat of high temp enamel black paint on the MDF after taking the picture.

I am excited to complete the build so I can install this upgrade to #HercuLien and run a PID tune.

Always excited to see what comes out of the Lien factory!!!

What do you do with dual thermistors?

Redundancy. Dual thermistors cover you if there is an open circuit on a thermistor, preventing the bed from getting too hot.

That thing is going to be a power house ! just make sure you don’t heat the glass to fast :wink: Can’t wait to hear your feedback !

@Jean-Francois_Coutur I am a little worried about the glass.

@Eclsnowman Unless you have borosilate glass (high temp glass like stove or a car window) to many watts/in² could result in glass shatter if the temp is ramped to fast, you have to ajust the firmware to compensate.

I got a 600W as a spare just in case :slight_smile:

Do not worry about the glass. I’ve got a 1000W AC silicone mat and a home depot mirror tile on top of it (5 for $10 or something). Zero issues.

@Matt_Miller and you ramp up the heat as fast as possible ? with 1000W, it should take less than 2min. to got from 21C to 110C

This is why you enclose the build platform. :smiley:

@Jean-Francois_Coutur yes. I’ll look at the PID settings and post them, but 20C to 90C in less than 2 minutes.

I can run a test tonight to give a more definitive timing.

Or tomorrow morning…

Without the heated chamber on, 20C to 110C = 3min 31 sec.

With the heated chamber on, 36C to 110C = 2min 42sec

Kp 51
Ki 1.76
Kd 368.5

@Matt_Miller what are you using as an insulator below the bed?

Nothing. I really should have something under there but it’s a moving Y and extra mass is my enemy.

@Eclsnowman How are you wiring the 2 thermistors?

@Wayne_Friedt at first I was thinking just as a backup for failure then I would just swap leads. But if anyone knows how to use two: one as primary and one as a backup(check for a difference) I am all ears.

@Eclsnowman If you see all 3 hotends on the LCD, connect to that input and you can compare by eye. :wink:

@Eclsnowman Ah i see. I have had that happen before where the thermistor stopped working and i just stuck another one under the bed. Works fine. Cant tell any difference if there is any. One thing as i suspect you guessed is anyway you wire those two thermistors together will change the resistance.

@Wayne_Friedt the azteeg x3 has plenty of extra thermistor inputs. I just don’t know how to handel it in firmware to use one as a watchdog for the other.