Discovery wiring to Mendel 3 Rep Rap


Hi to everybody!
My name is Mariglen from Rome, Italy. I have recently bought Discovery and trying to connect it with my Mendel 3 3D printer(Rep Rap). After I have been assembling Mendel 3 and fixing it, I try to connect and fix Discovery extruder, but with no success.
First of all, I wire it up but I am not sure if it is correct or not. Discovery has 4 wires black, green, blue and red instead the colors of my 3D printer are different and are put in that order from the top: yellow, green, blue and red. I am showing you a photo of the duet and I would like to have your suggestions if there is something wrong.

Any suggestion is appreciated and helpful.
At the beginning I used Pronter Face to connect to the discovery, which it was impossible to find the discovery. Then, I jumped to Repetier that was able to find the discovery and communicate with it. Here, the problems come. The motor does not rotate and I have found that it is a problem of the speed of the motor, which I tried to increase it by taking many parameters into account. First, I decreased the ‘size of the filament’ but nothing. Second, I decreased the diameter of the nozzle and nothing. I use Cura and here there are some screen shots of the software parameters. I have not put any past into the syringe during the tests. I do not know if it effects them or not.

Finally, I increased the EEPROM of the motor with commands on Repetier. I tried many commands that I am attaching to you by changing the values of E into the command M92 E[….], but nothing anyway. I do not know what to do anymore. After I put all the commands I wait for the printer responding to me and to what I have understood the motor receives the current and I hear a clicking sound from the motor, but the gears are not moving. So, I do not know if there is a problem of high or low power to the motor. Here in the attached file, there are all the commands that I have inserted.


Hi @Mariglen_Angjellari,

One of the first suggestions I am going to make is to change the wiring to RED/BLUE/BLACK/GREEN. The wiring pairs in the NEMA motor are RED / BLUE and GREEN / BLACK.

Everything else you are doing seems correct.

Are you able to tell me the version of your electronics board? It should be printed on the PCB somewhere.

I am going to make sure you get printing successfully!


Thank you for your kind reply!
I changed the wiring and I am not able to hear any noise that comes from the motor. In addition, I could not rotate the upper rod manually with my hand (before I was able to do it, now it becomes harder and the motor is blocked).

Regarding the versions of my electronics board: It is exactly the same as the board in this link:
At the end, I am still unable to rotate the motor even by putting commands that correspond to high EEPROM. I repeat again, I am carrying out tests with no pastes in the syringe. First lets rotate the motor and then testing the real pastes.
Thank you again
Looking forward hearing from you


Can you take one step back and try a normal nema17 motor? Verify this works first.


Thank you!
It works with the extruder of Mendel 3 Rep Rap and I do not understand why it is so difficult to find a solution. Could you suggest any other external wiring to connect with the Duet?
In addition I am confused regarding colors, because on your manual is written:

I think that the colors of Rep Rap are those in the middle, aren’t they?
Thank you


We found the problem. We managed to connect the motor of discovery with another mini duet in order to amplify the current that enters into the motor. Obviously, i can have only a manual control of the feed rate of the discovery. So, my printer duet is not enough to feed with current discovery motor.
Thank you for your time


Glad to hear you have found a solution.

Checking out the page for the Duet board, it states that it uses A4892 drivers with 2A current, which should be plenty for the Discov3ry. I am still curious why it was not working.

Did you try using Slic3r instead of Repetier Host to adjust the EEPROM (M92) values?

Try also:

G0 Y100 F100

to extrude small amounts.


Probably the current is ok, but I donot understand why it is not working. Anyway, I feel perect with the way I fixed the problem. I will publish also other news in the future regarding printing of new materials. I think that it is a problem regarding the communication between Discov3ry and some types of Duet. Probably it is related to the quality of the 3D printer
All the best


Thanks @Mariglen_Angjellari