Installing e3d Hotend

Re: Installing e3d Hotend

academicdave — Thu, 05 Mar 2015 12:40:05 -0500

That did it. Thanks so much. I would have never figured out that it was a wiring problem.

Re: Installing e3d Hotend

nophead — Thu, 05 Mar 2015 11:38:03 -0500

You wouldn't notice the thermistor wires being swapped, the polarity only matters because it shares a ground with the probe. And I think the photo in the manual is incorrect. The wiring table is accurate. If you correct the thermistor polarity it should work but the reading may shift a bit due to the fan current dropping a small voltage in the ground lead to the thermistor.

The fan should be wired to the P and H terminals nearest to each other. At the Melzi end the spare ribbon wire intended for the probe can then be grounded using one of the limit switch terminals.

Re: Installing e3d Hotend

academicdave — Thu, 05 Mar 2015 08:28:49 -0500

I wired the ground (black wire) to the left probe (labeled P), and the 12v (red wire) to the left heater.

I suppose I could have the thermistor wires swapped at the Melzi, but I didn't change the Melzi wiring at all from before (when the printer was working with the Jhead end-no extruder fan).

Re: Installing e3d Hotend

nophead — Thu, 05 Mar 2015 08:01:56 -0500

What did you ground the negative side of the fan to? Seems like it was the thermistor input line.

If you used the probe ground then it looks like you have the thermistor wires swapped at the Melzi. You should use the probe signal pin for fan ground as sharing the ground with with thermistor will cause a small error (not 400C at room temp though).

Re: Installing e3d Hotend

academicdave — Thu, 05 Mar 2015 07:25:02 -0500

Yep sure enough its the wiring, although not the thermistor. I actually got it to work fine by disconnecting the fan that is attached to the e3d hotend. So I must have this fan wired wrong. I had it wired to the heater and to the left pin "P", so I guess this is not the way it is supposed to be?

Re: Installing e3d Hotend

nophead — Thu, 05 Mar 2015 05:29:54 -0500

I think it must be a wiring fault because all 100K thermistor tables will give roughly the right reading at room temp as they are all 100K at 25C.

I think you must have wired the heater to the thermistor terminals to get a reading so high.

Re: Installing e3d Hotend

academicdave — Wed, 04 Mar 2015 17:29:07 -0500

So I've installed and wired up the e3d hotend I had.
But, my problem is that I have something wrong, I think in the configuration.h file, but can't figure it out.

When I connect to the printer, with the extruder, not heated up, at room temparture it is returning a temp of 400 degrees.

I changed the settings in config_h to

#define TEMP_SENSOR_0 5
#define TEMP_SENSOR_1 0
#define TEMP_SENSOR_2 0
#define TEMP_SENSOR_BED 9 // 1 for Mendel90 kits 1-6, 9 for kits 7 onwards

But that doesn't seem correct. So is this the wrong config settings, or is something else the culprit here?

Re: Installing e3d Hotend

nophead — Tue, 17 Feb 2015 05:57:00 -0500

Use any table that is for 100K thermistor with 4K7 pullup. The simplest is to use the one you are already using if it allows you to achieve the temperatures you want.

Re: Installing e3d Hotend

jamesmoe — Mon, 16 Feb 2015 20:07:41 -0500

So last of this .. use one of your tables .. crank up the heat and put the measured temps in the script? Correct?

Re: Installing e3d Hotend

nophead — Mon, 16 Feb 2015 16:47:38 -0500

If you are able to run it at a stable temperature you must be using a table. It might not be right for your thermistor but it doesn't matter as long as you are able to run it at representative temperatures and it is stable.

You don't need to know the resistance because you can get the ADC value from that table and my script will calculate the resistance. You do have to know which table you have selected and you need to pick temperatures that have entries in that table with corresponding ADC values. You then measure the actual temperature and you have a tn, adcn pair.

Re: Installing e3d Hotend

jamesmoe — Mon, 16 Feb 2015 15:11:34 -0500

Sorry being so dense .. I do not have the table that corresponds to this thermistor. All I have is 100K with a Beta of 3950 .. how do I build a table for that?

Because I can't measure resistance as the thermistor is used, I can't take data points when the hot end is at a stable temp.

Re: Installing e3d Hotend

nophead — Sat, 14 Feb 2015 14:01:16 -0500

In my fork of Marlin for Mendel90 I added two Steinhart-Hart tables for the two Epcos thermistors that I use as tables 8 and 9.

Table 8 corresponds to the default values in the script but 92 and 42 are not resistances, they are ADC values from which resistances are calculated. It is also the same table shown on my blog.

More than likely you are using a different table to start with as I assume you are using a different thermistor. If so you need to use two temperatures that are actually in your table and the ADC values that correspond to those. Then you know your measured temperatures correspond to those ADC values. You input those into the script and it converts the ADC values to resistances and makes a new table.

Re: Installing e3d Hotend

jamesmoe — Sat, 14 Feb 2015 07:58:14 -0500

Which table is your table? I hate temperature!!! :) So confusing

Re: Installing e3d Hotend

nophead — Sat, 14 Feb 2015 06:45:22 -0500

It would only be correct if you started with my table. If you are starting with a different table you don't have the resistance values so you need to use ADC values from that table instead.

Re: Installing e3d Hotend

jamesmoe — Fri, 13 Feb 2015 16:09:48 -0500

So here is what I did .. Took a real T0 .. room t0=20 and r0=120700

For the t1 in the script the resistance was 94 and t2 was 256 with resistance 42

When I set the host to 209 .. the real temperature via a thermocouple was 178.3, and at 256 .. it was 218.5

So .. I put t1=178.3 and t2=218.5 leaving the resistance alone and generated the script ...

Is that the idea??

Thanks!

Re: Installing e3d Hotend

nophead — Fri, 13 Feb 2015 14:11:53 -0500

This one does: [github.com]

Re: Installing e3d Hotend

jamesmoe — Fri, 13 Feb 2015 12:17:55 -0500

Which script specifically has the inferred ADC value calculations?

Re: Installing e3d Hotend

nophead — Fri, 13 Feb 2015 07:34:20 -0500

You can't measure the resistance directly without disconnecting it. But the method I described and my python script can use inferred ADC values to calculate the table.

E.g. if you set it to say 240C with an existing table you know when it has stabilised the ADC value must equal the value for 240C in that table. If you measure it as say 245C then you know the ADC value at 245C is what is in the table for 240C. My script can then work out the resistance from the ADC values.

Re: Installing e3d Hotend

jamesmoe — Fri, 13 Feb 2015 06:44:59 -0500

How do I measure the thermistor resistance when it is also connected to the controller board? I tried to measure on the screw terminals of the connector on the board (it is a Melzi board .. all the connectors are screw connectors which are very nice), and that does not work.

Re: Installing e3d Hotend

nophead — Wed, 11 Feb 2015 03:36:43 -0500

Yes, the table format hasn't changed.

Re: Installing e3d Hotend

jamesmoe — Tue, 10 Feb 2015 22:01:35 -0500

Do the scripts mentioned in your blog post a couple years ago produce tables as are reflected in the current Marlin tables .. the look a bit different.

Re: Installing e3d Hotend

nophead — Mon, 09 Feb 2015 09:39:16 -0500

Just use the highest. I think the Steinhart-Hart equation is accurate to less than a degree over the full range with just three accurate widely spaced points.

Re: Installing e3d Hotend

amr_dwarf — Mon, 09 Feb 2015 05:01:02 -0500

Guess I need to learn how to run Python-scripts :-)

But the point at extrution temp, I use at least three different temps for different materials.
Should I try a average?

Re: Installing e3d Hotend

nophead — Mon, 09 Feb 2015 04:30:36 -0500

You could do that but you only need three points: room temp, one at extrusion temp and one in the middle. The Python script will then calculate the rest of the table for you.

Re: Installing e3d Hotend

amr_dwarf — Mon, 09 Feb 2015 03:26:46 -0500

OK, reading thruu the page you linked to I think I understand what I need to do.
Based on this:

"If you set the temperature to a value in an existing table and let it settle and then measure it with a thermocouple you know that the ADC value for the measured temperature is the value in the table for the set temperature. You can then produce a new more accurate table."

I set the temp to a value at the time in the table. Let it settle and then take a measurment with my thermocuple inside the hotend. The measured value is then inserted at that point in the table. If I do this for all points in the table I have corrected it.

Am I right in my assumption?

Regards
Amr_dwarf

Re: Installing e3d Hotend

nophead — Sun, 08 Feb 2015 19:13:19 -0500

You need to make a new table for the thermistor. See [hydraraptor.blogspot.co.uk]

Re: Installing e3d Hotend

amr_dwarf — Sun, 08 Feb 2015 16:18:34 -0500

Since asking these questions I got the printer running well with PLA and did not bother with the temperature difference.
But I have now been trying ABS and I now again notice the incorrect readings of temp.

So now its time to measure the temp inside the extruder.

But then I have a new question. If I plot my measured values vs. thermistor readings in pronterface how do I correct the difference?

Cheers

Re: Installing e3d Hotend

nophead — Wed, 21 May 2014 17:37:50 -0400

It needs to be on the inside to read an accurate value. It definitely won't work pressed against the outside, it tends to read much lower.

To measure accurately from the outside it would need to be embedded into the heater block like the thermistor is.

Re: Installing e3d Hotend

amr_dwarf — Wed, 21 May 2014 16:38:09 -0400

I am not quote sure I get correct readings from the thermistor.
If I should measure the temperature of the hot end where should I put the thermocouple?
Should I just hold it against the nozzle tip from the outside?
Should I stick i down the same way as the filament an measure the nozzle from the inside?

Re: Installing e3d Hotend

amr_dwarf — Mon, 19 May 2014 14:25:10 -0400

There is a small gap. The instructions where very clear on this point.