Different versions of Pt100 Temp Daughterboard

Veti

dc made come comments about it here
https://forum.duet3d.com/topic/10579/pt100-board-wishlist-emi-component-maybe/8

dc42

The version 1.1a has pads for additional capacitors to reduce the effect of interference. However, the initial production of daughter boards using the revision 1.1a PCB didn't have those capacitors fitted, because we didn't have time to qualify the effect of fitting them before we had to go to manufacture.

Urban

@Veti Thank you for responding!
@dc42 OK, Thank you for the info. What type and size of capacitor do you recommend?
I have two daughterboards and one is used for the chamber and bed. These signals are good. For the board used for the two extruders the signal i jittery. I have done an extensive work trying to improve the situation but it is clear that it can't be as good as for the bed-chamber sensors.

I have done everything except grounding the hotted itself (tried by holding a ground wire manually, and it did not help). I have a better version of Pt100 that I don't think connect to the heater block, and I have tried several. The jitter can be seen for both channels on one board, but not the other board.

Would it be a good idea for the Duet 3 to have a separat ground connection that you can take to the common ground for the machine?

dc42

@urban said in Different versions of Pt100 Temp Daughterboard:

@dc42 OK, Thank you for the info. What type and size of capacitor do you recommend?

If you have the 1.1a PCB but there are 2 pairs of pads for each channel that are not populated, then the recommended capacitors to go on those pads are 0603 size 100nF X5R or X7R MLCC.

The PT100 sensor element must be isolated from the heater block, like the E3D ones are.

Urban

@dc42 OK, thank you.
I have the 1.1a.
Yes, they are isolated and the cable shielded.

Urban

@dc42 I checked the solder pads this morning and I can't solder that small. If you would like you could send me a board with the capacitors on so that I can test it since I have the problem very consistent.

dc42

@urban said in Different versions of Pt100 Temp Daughterboard:

@dc42 I checked the solder pads this morning and I can't solder that small. If you would like you could send me a board with the capacitors on so that I can test it since I have the problem very consistent.

I am not directly involved with production, so I don't known whether we have any with the capacitors fitted yet.

Soldering 0603 capacitors is not difficult, even for me with deteriorated eyesight due to age; but it does require a fine-tipped soldering iron and a pair of tweezers to hold the component. Alternatively, wire-leaded ones can be soldered on the underside of the board

A Former User

You might be able to get these guys to help you out, usually a friendly bunch. http://www.makersofsweden.se/makerspace/collaboratory_goteborg/

But as dc42 says, its really not magic. Tin one pad, place cap with tweezers and solder the other pad, touch up first solder joint with fresh flux if it doesn't look smooth and shiny.

Urban

@dc42 said in Different versions of Pt100 Temp Daughterboard:

Alternatively, wire-leaded ones can be soldered on the underside of the board

I could solder the underside with normal capacitors . However, there is no drawing (that I have found) and the text on the board is almost unreadable. I assume the capacitors should be between the two pin pair that can be closed by a jumper?

@bearer Thank you for the info! You know your own hometown least! And maybe I should give SMT a try someday.

dc42

@urban said in Different versions of Pt100 Temp Daughterboard:

@dc42 said in Different versions of Pt100 Temp Daughterboard:

Alternatively, wire-leaded ones can be soldered on the underside of the board

I could solder the underside with normal capacitors . However, there is no drawing (that I have found) and the text on the board is almost unreadable. I assume the capacitors should be between the two pin pair that can be closed by a jumper?

@bearer Thank you for the info! You know your own hometown least! And maybe I should give SMT a try someday.

The wiki page on connecting thermocouples links to an image of a similar modification for the older version of the thermocouple daughter board. The modification to the PT100 daughter board (any revision) would be the same, with the capacitors connected between each of the middle 2 pins of each connector and the ground plane.

Urban

@dc42

The wiki links to an earlier post, no picture on the wiki.
The capacity recommended is different from the 100nF you recommended in this post
I mounted two 100nF for one channel between the inner pins and ground. I have a four wire configuration with maybe 2m cable. When I use the jumpers on the board to make it a 2-wire configuration the signal is improved significantly. When I remove the jumpers the signal deteriorate.
The signal is poor even before the first usage of the steppers in the extruder.
Shouldn't all four pins into the Wheatstone bridge have this capacitor?

I am using the 2-wire connection now (with jumpers) and the result is really good. I will try to add two more capacitors to the same channel (total of 4 per channel ) to see if this improves the 4-wire connection.