BLTouch alternative for hotbed with magnets

[jensus11]

That sounds good, what I have to change it?

M307 H0 R0.475 K0.931:0.000 D7.84 E1.35 S1.00 B0

M308 S0 P"e0temp" Y"thermistor" T100000 B3950 C7.06e-8           	; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bed" T0                                        			; create bed heater output on bedheat and map it to sensor 0
M140 H0                                                  			; map heated bed to heater 0
M143 H0 S100								             			; set temperature limit for heater 0 to 100C 

[dc42]

@jensus11 add the F Q parameter to the M950 command. Assuming it's a DC heater, try e.g. Q10, Q30, Q100.

[jensus11]

I want to test the F25 and became this message.

Fehler in Startdatei macro Zeile 69: exactly one of EFHJPSR must be given

M950 H0 C"bed" T0 F25

[droftarts]

@jensus11 Use the Q parameter for PWM frequency. See https://docs.duet3d.com/en/User_manual/Reference/Gcodes#m950-create-heater-fan-spindle-led-strip-or-gpioservo-pin

Ian

[jensus11]

I'm using this external mosfet. If I use a different one, will the noise go away?
With Q50 the annoying sound is almost silent. Can I use it or will something break?

[dc42]

@jensus11 Q50 is fine. You will probably hear a slight buzz.

[jensus11]

@dc42
I haven't bought an inductive sensor yet. I can't find one, they're sold out everywhere.

But an idea is, of it is possible to define measuring points for the BLTouch so that I can find the position of the magnet and measure there and use this for the heightmap.

[droftarts]

@jensus11 you can define points in the mesh for the BLTouch to avoid, see the notes on G29 S4 here: https://docs.duet3d.com/User_manual/Reference/Gcodes#notes-8

Ian

[jensus11]

I have defined the mesh point in the probePoint.csv file.
But the result looks not good. I think the magnets are so strong and interfere with the BLTouch when measuring.
So on, I need an inductive sensor.

[jensus11]

I have now installed an inductive sensor. Unfortunately it doesn't work that way either.
The measurement stops above a magnet and this message appears.

Error: M280: Probe already triggered before probing move started.

What can I do?

[troydeming]

I have been using a bltouch with a magnetic bed for years with no issues. did you get it figured out?

[fcwilt]

@jensus11

In my opinion your best bet is to replace that sheet of magnets with 3M flexible magnetic self-adhesive sheet.

I've used that with all sorts of Z probes and they seem to work just fine.

I used to be a fan of BuildTak until the went with a sheet of little magnets - I've moved on from them.

Frederick