well i broke my thermistor.
first link looks like a perfect match being 1.25mm dia
second link is 2.0mm dia - has anyone tried using this one?
the hole for it seems to be 2.5mm diameter
any advice would be appreciated
Not all 100k thermistors are created equal... Beta is important
Not only that^ but I thought the heated bed is measured with a thermocouple.
Hi everyone I'm a newbie to this forum but have had a davinci 1.0 for about a year.
Like everyone it seems I have had my share of failures and faults with the printer, most recently being the print bed thermistor burning out and giving me a "003" bed temp reading all the time, not allowing me to print.
So I thought I might drop in on this topic and give others a hint on a quick fix that I did that works well and gets you up and printing with minimal fuss.
Like most I started looking to see if I could find a replacement thermistor for the bed online, or something similar from a third party, and after a short bit of research I found that the thermistor is a 500k and most on sale are 100k, and I am running xyz firmware still, so I can't adjust thermistor tables.
Now I have previously replaced my bed with a reprap mk2 pcb heater because I did a 14 hour print and bits of glass came away with the finished item, then after much swearing and fiddling around with the stupid stick-on heat pad I decided to just replace the heater to a more stable version and turn the glass over and print on the other side, anyway with this pcb heater I got a 100k glass bead thermistor and I thought Ok lets make it work.
Sorry, I know this is a bit long winded but here's what I did,
firstly I cut and soldered the new thermistor into the original lead and checked the readings, the bed was now saying it was about 70 degrees when it was actually around 20.
I then grabbed a cheap pack of assorted resistors for about $8 and a little probe type lcd thermometer for $9 and started to play.
I knew I needed to add about 55k of resistance to the thermistor to get the temps to line up at 90 degrees, so I tried it and found it was reading about 10 degrees under actual bed temp at 90 degrees.
After a bit of playing I found the closest I could get was using a 47k resistor in-line with one of the thermistor wires and that gave me an actual bed temp of 94 when the printer was saying 90.
So after all that bla bla bla, Yes you can use a 100k thermistor with the stock firmware but you will need to add an approx. 47k resistor to it for the bed to read properly, of course the lower end of the temp readings will be out, mine says like 60 when its actually 25, but at the business end it's spot-on for printing.
I also have a suspicion that the glass bead type thermistor will outlast the little cheap thin film thermistor it comes with.
Anyway thanks for reading my ramblings and I hope this helps for all those with this problem.
If anyone has a question about the pcb heater setup feel free to ask, it is 100 times better and more stable, even heat distribution and no more broken glass.
Ok, update to bed thermistor with standard firmware / software.
I purchased a 504GT-2 500k 3% thermistor from MOUSER.COM (Mouser Electronics) and it works perfectly right through the temp rang from 0 - 120 degrees.
It's a tiny glass bead style at about 1.5mm diameter and I just used kapton tape to stick it to the underside of the heat plate on the right rear of the bed in the recess for the bed heater wiring.
Hope this helps.
Thanks for the input Ryan. Even when I disconnect the thermistor I get the error 0013 (heat bed max range). Im wondering if it is the Atmel chip on the board that has shorted.
Or you blew a "fuse" resistor, as has been discussed on here NUMEROUS times...