1 Topic by kr15_uk

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Topic: Jr heatbed wired internally + unpopulated connectors/parts...

Ladies and gents,

I'm doing heat bed upgrade on my Jr and instead of having 2x PSU's (original one for the printer itself and additional one for the heatbed etc) I've decided simply upgrade existing PSU to higher AMP and wire heatbed internally.
So I've pulled off the back to see where I can tap in on PCB for my heat bed (DC jack to be safe) and there was this unpopulated pin "BedNTC".
That made me think - If it's there is BedNTC then there should be bed power output as well and technically PCB can run heatbed!
Don't shout, calm down... I said technically... I do understand that bed control not gonna appear magically just because I've plugged in my bed. I get that.
But... As we know all limitations on Jr is software limitations so what if you edit 3w gcode like when you add desired hotend temperature but this time to add desired bed temperature (gcode line for bed temp is M140 S"temp") - in theory that could work, in theory...
To test my theory I just need to wire up thermistor, figure out where is bed power output so I can hook up my multimeter and edit gcode with bed temp line in it and see the magic (or nothing at all).

Also looking at the PCB itself, it has quite a lot unpopulated connectors and parts...
Some of them makes sense now (3dLED, CAM R, CAM L, TopHOME, Laser L, Laser R, Motor 3D, Motor E2) after XYZ's announcement back in Jan of Jr 2.0 which has 3D scanner, laser engraver in-built and dual extruder head. I'm guessing it uses the same PCB just with fair amount of extra SMD components.
But what about other connectors, those white ones in the middle or the big unpopulated part with XYZ logo underneath, sd card?!
Anyone figured it out already?!

Thanks.


Regards,
Kris M

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2 Reply by carl_m1968

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Re: Jr heatbed wired internally + unpopulated connectors/parts...

kr15_uk wrote:

Ladies and gents,

I'm doing heat bed upgrade on my Jr and instead of having 2x PSU's (original one for the printer itself and additional one for the heatbed etc) I've decided simply upgrade existing PSU to higher AMP and wire heatbed internally.
So I've pulled off the back to see where I can tap in on PCB for my heat bed (DC jack to be safe) and there was this unpopulated pin "BedNTC".
That made me think - If it's there is BedNTC then there should be bed power output as well and technically PCB can run heatbed!
Don't shout, calm down... I said technically... I do understand that bed control not gonna appear magically just because I've plugged in my bed. I get that.
But... As we know all limitations on Jr is software limitations so what if you edit 3w gcode like when you add desired hotend temperature but this time to add desired bed temperature (gcode line for bed temp is M140 S"temp") - in theory that could work, in theory...
To test my theory I just need to wire up thermistor, figure out where is bed power output so I can hook up my multimeter and edit gcode with bed temp line in it and see the magic (or nothing at all).

Also looking at the PCB itself, it has quite a lot unpopulated connectors and parts...
Some of them makes sense now (3dLED, CAM R, CAM L, TopHOME, Laser L, Laser R, Motor 3D, Motor E2) after XYZ's announcement back in Jan of Jr 2.0 which has 3D scanner, laser engraver in-built and dual extruder head. I'm guessing it uses the same PCB just with fair amount of extra SMD components.
But what about other connectors, those white ones in the middle or the big unpopulated part with XYZ logo underneath, sd card?!
Anyone figured it out already?!

Thanks.


Regards,
Kris M

The bed is going to be disabled in the firmware. Otherwise the firmware would throw up errors for no bed being there when it would be looking for one. So even if you did all the hardware and gcode mods the firmware would still break you. This was the other reason I was pushing for a Repetier port instead of just an RFID hack because it would open so many other possibilities.

All of their boards for the 1.0 to the Aoi are the same, they just have more or less parts depending on the model. So the Jr. being the first of it's generation would be the same way. It to will have the same board as future models in this line just with more or less parts. It save money and design cost doing it this way. All you have to do is change the firmware to support or not support the parts present or missing.

Printing since 2009 and still love it!
Anycubic 4MAX best $225 ever invested.
Voxelabs Proxima SLA. 6 inch 2k Mono LCD.
Anycubic Predator, massive Delta machine. 450 x 370 print envelope.

3 Reply by kr15_uk

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Re: Jr heatbed wired internally + unpopulated connectors/parts...

I do totally agree that ANY open source firmware would be the best choice but as you can see no-one is really keen to spend too much time porting it and those who want - don't know how... So they keep spending their time finding alternatives around this.


But have you actually tried to write up heatbed?! Which pins are for the heatbed power out?!

I know that would be logical to firmware disable it, but is it really the case?!
Just don't want to assume and lose out because of my assumption.

"firmware would throw up errors" - not really, when I was playing with gcode editing I've managed to add some random commands and didn't had any errors what so ever, it just ignored them and moved on...

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4 Reply by carl_m1968

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Re: Jr heatbed wired internally + unpopulated connectors/parts...

I mean errors at boot. If the bed where enabled in the firmware then so would the thermistor. At boot up all printers test for max and min temp error. This confirms the thermistor is present and not shorted. If they enabled the bed with no thermistor support the there would be no feedback for temp control and you have a bed with thermal runaway. If the bed and thermistor are enabled but not present then you would get error codes at power up.

Printing since 2009 and still love it!
Anycubic 4MAX best $225 ever invested.
Voxelabs Proxima SLA. 6 inch 2k Mono LCD.
Anycubic Predator, massive Delta machine. 450 x 370 print envelope.

5 Reply by kr15_uk

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Re: Jr heatbed wired internally + unpopulated connectors/parts...

I do totally agree that most other printers does all that but does XYZ Printing follow this "trend"?!
Unless someone performs a test it's just an assumption. Trial and error is the only way.

So I've decided to do quick test myself to see if Jr does self check.
I've basically turned off the Jr, took hotend head apart unplugged thermistor and powered up the Jr.
And it booted up fine!
Then I checked system info from the LCD and it states extruder  temp is 10 degree C. (Why do they call hotend extruder btw)

And just for the kicks I tried to print something.
Ok it failed with the error BUT it heated up hotend to 160 degree (hooked up multimeter to hotend which also measures temp)
It went through the file checking stage and then to initialising where it sat for more than a minute. Probably then realised that temp is still 10 degree C.

Looks to me XYZ devices (Jr to be precise, haven't tested others) doesn't check thermistor presence, just temp rise.

Next step. I'll try to add heatbed gcode line to the print file and see if it will spit any errors...

kr15_uk's Website

6 Reply by carl_m1968

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Re: Jr heatbed wired internally + unpopulated connectors/parts...

If that printer will heat the hotend without the thermistor present, I would get rid of it as it has the greater than normal potential to burn your house or shop down. If there is no thermistor present on most printers they will throw up an error on power up and WILL NOT all ow power to be applied to the heating circuits.

Look at it this way. What happens if you are printing and a wire breaks from the thermistor. Same as it not being there but in the case of your Jr. at least it continues to heat and heat till something burns through and you had better that something does not ignite something else that burns bigger.

It sounds to me there are no safety checks or they are not working on yours and maybe all JR. printers. again a printer should not allow power to be applied if the thermistor is reading a lower than room temp reading meaning it is open, or a higher then max temp reading meaning it is shorted.

You might want to read through that post about the guys house that was destroyed because he walked away from his printer for 30 minutes and it went into thermal runaway during that time.

Printing since 2009 and still love it!
Anycubic 4MAX best $225 ever invested.
Voxelabs Proxima SLA. 6 inch 2k Mono LCD.
Anycubic Predator, massive Delta machine. 450 x 370 print envelope.

7 Reply by kr15_uk

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Re: Jr heatbed wired internally + unpopulated connectors/parts...

I've performed another test to see if Jr is "evil house burner".

I've extended thermistor wire so I can easily unplug it while it's printing.
Attached multimeter's temperature probe to the hotend and started the print job.
After 5mins of printing I've unplugged thermistor wire and in 10sec it paused and displayed error message.
Temperature jumped from 200 degree C to 210 and after error message it started to come down.
Seems to be there is continues temperature monitoring at least.
So we are safe.

Anyway it's not a good practise to leave 3D printer unattended, at the end of the day that is the machine heating up to 200+ degree C.


Also, by your comments looks like you don't own Jr.
Can anybody who owns Jr can join the discussion?!
I need someone who owns one...

Thanks.

kr15_uk's Website

8 Reply by cmcc

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Re: Jr heatbed wired internally + unpopulated connectors/parts...

carl_m1968 wrote:

If that printer will heat the hotend without the thermistor present, I would get rid of it as it has the greater than normal potential to burn your house or shop down. If there is no thermistor present on most printers they will throw up an error on power up and WILL NOT all ow power to be applied to the heating circuits.

Look at it this way. What happens if you are printing and a wire breaks from the thermistor. Same as it not being there but in the case of your Jr. at least it continues to heat and heat till something burns through and you had better that something does not ignite something else that burns bigger.

It sounds to me there are no safety checks or they are not working on yours and maybe all JR. printers. again a printer should not allow power to be applied if the thermistor is reading a lower than room temp reading meaning it is open, or a higher then max temp reading meaning it is shorted.

You might want to read through that post about the guys house that was destroyed because he walked away from his printer for 30 minutes and it went into thermal runaway during that time.

Hes just removing the thermistor from the hot end, not disconnecting it from the board. Most software will heat the hotend up at least somewhat if it is at least reading ambient temperature, you only get an instant error if there is a short or open circuit. The only real danger is when the thermistor is comes loose and but is still connected, and is hanging near or against the heater block. The thermistor will still read an increase in temperature, but it will be much lower than it actually is. I've heard stories of people melting their aluminium hotend because of that kind of problem.