In case anyone is interested. I took the temp vs.

(Zane Baird) #1

In case anyone is interested. I took the temp vs. resistance values Alirubber gave me for the Herculien heated bed (100k thermistor, 3950 beta value) and fit it to the Steinhart-Hart Equation. The values for the A, B, and C coefficients come out to ~ 0.0006454337947, 0.0002239473005, and 0.000000087, respectively.

This is implemented in the smoothie config file by commenting out the line for beta value (if that’s what you were previously using) to look as such:

#temperature_control.bed.beta 3950

and adding the following line:

temperature_control.bed.coefficients 0.0006454337947,0.0002239473005,0.000000087

This should allow for accurate temperature readings from 15-125C

(Zane Baird) #2

Note: while it doesn’t show up this way on the post, the numbers and “temperature_control.bed.coefficients” should appear on the same line

(Jo Miller) #3

Thanks Zane

Just what I was looking for. :slight_smile:

(Jeff DeMaagd) #4

Thanks, I’ve put it in my notes.

I used r0 and beta to get going, this looks even better.

I don’t think their supplied beta number was right either.

(Zane Baird) #5

@Jeff_DeMaagd Yeah I’m not confident in the temp readings I was getting using the beta value. I wasn’t too concerned as it was for the bed, but I wasn’t satisfied in the end. This fits the data they supplied with an RSS of ~3.4 over the 17-125 C range, so it’s definitely a much better approach (especially for ABS bed temps)

(Jeff DeMaagd) #6

Yes. Seriously, thank you.

I had r0 at about 2700 (approximate resistance at 25˚C) and Beta seemed to be most accurate around 3500.