Extuder with max6675 Hi, i am trying to do the extuder with a thermocouple and max6675 i made this mtgtttmax667510refsch.png mod_embed_images_loadimage('4523496c4f39975b15c203ef876b98f7', 'https://reprap.org/forum/addon.php?4,module=embed_images,url=http%3A%2F%2Fimg819.imageshack.us%2Fimg819%2F688%2Fmtgtttmax667510refsch.png', 'http://img819.imageshack.us/img819/688/mtgtttmax667510refsch.png', 'https://reprap.org/forum/addon.php?4,module=embed_images,check_scaling=1,url=http%3A%2F%2Fimg819.imageshack.us%2Fimg819%2F688%2Fmtgtttmax667510refsch.png', '', 181511, 800, 400, 'Loading image ...', false); I connect Vcc to 5 volts I connect 5 (SCK) and 7 (SO) of the max6675 to the TEMP_EXT of the gen 7 board. I am using teacup , but it does not work . Extruder temp is T:16383. What am i doing wrong? https://reprap.org/forum/read.php?4,181511,181511#msg-181511 Mon, 20 Jul 2026 06:33:36 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?4,181511,185519#msg-185519 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,185519#msg-185519 I made another ,seperate circuit with atmega8 which is controling the hotend
I use another one mosfet IRFZ44 and i control the extuder totaly seperate!
I know its not the best solution but temperature seems to be stable enough
I am waiting now for the filament to print something

]]> alfadex Reprappers Sun, 17 Feb 2013 20:32:59 -0500 https://reprap.org/forum/read.php?4,181511,184187#msg-184187 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,184187#msg-184187 -------------------------------------------------------
> I tried without pullup resistor but the same. I
> tried to measure CS to watch the pulses with
> osciloscope but when i connect it ,printer goes
> offline.

Im no electronics expert, but Im pretty sure it shouldn't be doing that. May be worth trying another pin on a different port.

> I tried a second max6675 and doing exactly the
> same things!
> I am thinking to replace thermocouple with a
> thermistor to make things easier. My thermistor is
> this
> But datasheets says max temperature for thermistor
> is 125 degrees. Extruder reach 200-220 degrees,
> Isn't there any problem of destroying the
> thermistor? If thermistor is not touching the
> extryder head, will i have a reliable measurement?

You're going to need a thermistor rated for extrusion temperatures. Glass bead thermistors are the most common, but axial thermistors are easier to secure in place. This will require a second thermistor table, but thats not difficult. Don't even attempt your idea of having the thermistor out of contact with the extruder head.]]> Andrew Smith Reprappers Tue, 12 Feb 2013 17:29:57 -0500 https://reprap.org/forum/read.php?4,181511,184179#msg-184179 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,184179#msg-184179 Greg Frost Reprappers Tue, 12 Feb 2013 16:59:40 -0500 https://reprap.org/forum/read.php?4,181511,184074#msg-184074 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,184074#msg-184074 I tried a second max6675 and doing exactly the same things!
I am thinking to replace thermocouple with a thermistor to make things easier. My thermistor is this
But datasheets says max temperature for thermistor is 125 degrees. Extruder reach 200-220 degrees, Isn't there any problem of destroying the thermistor? If thermistor is not touching the extryder head, will i have a reliable measurement?]]> alfadex Reprappers Tue, 12 Feb 2013 09:55:07 -0500 https://reprap.org/forum/read.php?4,181511,183604#msg-183604 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183604#msg-183604
Anyway, the firmware looks right so it has to be a hardware problem. I'd try removing the pullup resistor and going straight to the cs pin.]]> Andrew Smith Reprappers Sun, 10 Feb 2013 11:59:10 -0500 https://reprap.org/forum/read.php?4,181511,183575#msg-183575 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183575#msg-183575
// enable TT_MAX6675
WRITE(DIO14, 0);

// disable TT_MAX6675
WRITE(DIO14, 1);

but i mean if i want to see the measurment to pronterface i have to set manualy CS from high to low.
If i want to see a new measurment to pronterface i have to set again from high to low.I have to trigger every time from high to low to see the changes of the temperatue. If i set CS to low, temperatures does not change

I discover when printer is online ,when power supply is working ,pin 20 where CS is connected is 4.9 volt.But it supposed CS for max6675 is enabled with low logic]]> alfadex Reprappers Sun, 10 Feb 2013 08:50:13 -0500 https://reprap.org/forum/read.php?4,181511,183574#msg-183574 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183574#msg-183574 Andrew Smith Reprappers Sun, 10 Feb 2013 08:39:58 -0500 https://reprap.org/forum/read.php?4,181511,183566#msg-183566 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183566#msg-183566 But the problem is, that max6675 can read the temperature when i set from 5 volts to 0.I mean i have to trigger from 5volts to 0v so that read the new temperature. If i set CS always to 0v it does not change,it stays at the last meseared temperature. So how can i trigger CS from 5 volts to 0volts ,maybe needs pwm?]]> alfadex Reprappers Sun, 10 Feb 2013 07:32:05 -0500 https://reprap.org/forum/read.php?4,181511,183564#msg-183564 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183564#msg-183564 Andrew Smith Reprappers Sun, 10 Feb 2013 07:28:01 -0500 https://reprap.org/forum/read.php?4,181511,183557#msg-183557 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183557#msg-183557 alfadex Reprappers Sun, 10 Feb 2013 06:56:39 -0500 https://reprap.org/forum/read.php?4,181511,183550#msg-183550 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183550#msg-183550
EDIT]

I linked the table above - PD6 is DIO14.]]> Andrew Smith Reprappers Sun, 10 Feb 2013 06:24:16 -0500 https://reprap.org/forum/read.php?4,181511,183546#msg-183546 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183546#msg-183546 I suppose i have to use an unsed output pin of the atmega because DIO4 is used,am I right? Which one should i use?

I have found that is i change CS from high (5V) ,to low (0v) ,it reads the temperature right!




If i want to use pin 20 of atmega (PD6) DIO? which nimber is?]]> alfadex Reprappers Sun, 10 Feb 2013 06:12:52 -0500 https://reprap.org/forum/read.php?4,181511,183353#msg-183353 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183353#msg-183353
[reprap.org]

And the table here:

[reprap.org]

To find a digital pin you can connect CS to. I'd use one that goes to the expansion header and nowhere else.

Then open temp.c and edit line 128 and 145. Replace 'SS' with 'DIO'.]]> Andrew Smith Reprappers Sat, 09 Feb 2013 07:31:59 -0500 https://reprap.org/forum/read.php?4,181511,183215#msg-183215 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183215#msg-183215
But any spare digital IO pin can be used for CS I think, but you will need to change the firmware. In temp.c, change references to SS to the pin you have used. It think there are spare pins on the expansion connector. The SPI pins are also on this connector, so that may be more convenient.]]> bobc Reprappers Fri, 08 Feb 2013 20:30:43 -0500 https://reprap.org/forum/read.php?4,181511,183165#msg-183165 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183165#msg-183165 Andrew Smith Reprappers Fri, 08 Feb 2013 16:46:45 -0500 https://reprap.org/forum/read.php?4,181511,183083#msg-183083 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183083#msg-183083 datasheet for max6675 i connect everything , i use two theromocouple and the temperature it reads is 0 deegrees celciou

P.s i have set CS to low,so that to enable serial output]]> alfadex Reprappers Fri, 08 Feb 2013 11:59:07 -0500 https://reprap.org/forum/read.php?4,181511,183067#msg-183067 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183067#msg-183067 alfadex Reprappers Fri, 08 Feb 2013 10:52:20 -0500 https://reprap.org/forum/read.php?4,181511,183062#msg-183062 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183062#msg-183062 forums.reprap.org]]]> bobc Reprappers Fri, 08 Feb 2013 10:38:58 -0500 https://reprap.org/forum/read.php?4,181511,183059#msg-183059 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183059#msg-183059 alfadex Reprappers Fri, 08 Feb 2013 10:27:56 -0500 https://reprap.org/forum/read.php?4,181511,183042#msg-183042 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183042#msg-183042 If you have nothing else on the SPI, you can connect CS to ground.

ETA: I just realised another problem, the TEMP_EXT connector will only work with a thermistor. The MAX6675 is an SPI device, so you need to connect it to the SPI pins on the ICSP header.

ETA2: sorry, should have read datasheet more carefully, you need to set CS low only when reading from the chip. Therefore connect it to the SS pin on the ICSP connector.]]> bobc Reprappers Fri, 08 Feb 2013 09:16:28 -0500 https://reprap.org/forum/read.php?4,181511,183033#msg-183033 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,183033#msg-183033 i am sure there is somethign that i have not understand.
here is max6675

and here mosfet




the circuit is this



pin 6 is going to a resistor 10K and after to 5volt. What is JP2-2 and JP1-1 at this pin for??

pin 5 ,7, is going to TEMP-EXT at the board. I invert these but nothing hapens

RT2 at GEN7 board is 10k, is it ok?

I am using teacup

Pronterface always says 16383

]]> alfadex Reprappers Fri, 08 Feb 2013 08:46:09 -0500 https://reprap.org/forum/read.php?4,181511,182239#msg-182239 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,182239#msg-182239 alfadex Reprappers Tue, 05 Feb 2013 13:02:42 -0500 https://reprap.org/forum/read.php?4,181511,182194#msg-182194 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,182194#msg-182194 ekaggrat Reprappers Tue, 05 Feb 2013 09:42:24 -0500 https://reprap.org/forum/read.php?4,181511,181954#msg-181954 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,181954#msg-181954
As an aside...you're aware that the MAX6675 is a 'not recommended for new design' part, right? fwiw, the MAX31855 is the replacement family.]]> xiando Reprappers Mon, 04 Feb 2013 11:21:16 -0500 https://reprap.org/forum/read.php?4,181511,181776#msg-181776 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,181776#msg-181776 Andrew Smith Reprappers Sun, 03 Feb 2013 19:14:27 -0500 https://reprap.org/forum/read.php?4,181511,181767#msg-181767 Re: Extuder with max6675 https://reprap.org/forum/read.php?4,181511,181767#msg-181767 here somewhere in config.h ????]]> alfadex Reprappers Sun, 03 Feb 2013 18:27:55 -0500 https://reprap.org/forum/read.php?4,181511,181511#msg-181511 Extuder with max6675 https://reprap.org/forum/read.php?4,181511,181511#msg-181511
i made this


I connect Vcc to 5 volts
I connect 5 (SCK) and 7 (SO) of the max6675 to the TEMP_EXT of the gen 7 board. I am using teacup , but it does not work . Extruder temp is T:16383.
What am i doing wrong?
]]> alfadex Reprappers Sat, 02 Feb 2013 17:48:38 -0500