# How do I wire the z-axis motors in parallel on the Prusa i3?

There is a little circuit board, or breadboard or something in the diagram of the wiring for the i3.

And it's mentioned that the z-axis motors need to be wired in parallel but beyond that they don't give you much detail about parts or how the wires go in.

Can someone provide me with some more detail on this?

In the diagram, they do show the wires connecting together, which is right. You can accomplish that just about any way you like, so long as you pair up the wires correctly from one motor to the other.

I'm assuming both "Z" motors are the same type and have the same color-coding for their wires. If not, you'll need to figure out the correspondences first (you may want to post another question if you need a hand with that, since it's pretty specific and generally useful).

Many control boards have "headers" sticking up, with 4 bare pins for each motor. Connectors that plug right onto those are readily available, such as at https://www.sparkfun.com/products/10364.

Some ways you can wire the motors in parallel:

• Some control boards, like my RAMPS 1.4, provide 2 sets of header pins next to the Z stepper driver board. In that case, just put a connector on each motor (if they're not there already), and plug them in next to each other.

• If there's just one set of header pins (or one Z-motor socket of some other kind) on your controller, make a "Y-cord" by soldering the wires from one connector (that plugs to the controller) to 2 4 pin connectors, one to mate with each motor.

• Or you can skip the 2 extra connectors entirely, and just solder the motor wires to the wires from the connector: 2 reds to red, 2 blacks to black, or whatever.

• If your controller just has empty holes, either solder in header pins and do as above (preferred, IMHO), or wire directly into the holes, splicing the 2 sets of motor wires if there's only one set of holes.

Motor and connector wires are wildly inconsistent, so make sure you get them sorted out right if they aren't already. The first thing is to check continuity: find 2 pairs of wires, which are the ends of two separate coils. If your motors have more than 4 wires it's trickier.

With RAMPS (see handy diagram RAMPS 1.4 RepRap Arduino Mega Pololu shield),

the 4 pins are commonly labelled (starting from the one nearest the power-supply end of the RAMPS board):

2B 2A 1A 1B


It means coil 1 and coil 2, each of which has ends A and B. I find this unclear because it could just as well have been numbers for the coils, and letters for the ends (if you wire it that way it won't work). So be sure you have continuity (maybe 15 ohms or so) between the wires you connect to 2B and 2A, and between the wires you connect to 1A and 1B.

The really good thing about this pin order is that if a motor is running backwards all you have to do is power off and then turn the plug around. That's one reason I think it's important to keep connectors in there, rather than soldering directly.

For some unknown reason, everywhere everybody is saying that Z stepper motors need to be connected in parallel... And this was always the only obvious way, until recently some people started to connect these motors in series.

And I personally started to believe the right way is to connect them in series.

All stepstick drivers are some kind of current limiting devices (you could read more about chopper mode). It is all about current. Connecting in series will guarantee that both motors receive the same current in all situations. And as result you could expect the same behaviour from both of them.

The bad thing when they are in parallel, is that the motor with the bigger load will get more current and as a result the other one will get less current and could skip steps. Of course, in an ideal situation, this should never happen but don't forget about Murphy's law ("whatever can go wrong, will go wrong").

One more thing - why did I change my wiring and connected my Z motors in series: At some moment I found that one Z motor was disconnected but the other one was working and this resulted in a broken printer geometry. When Z motors are in series and if one of them fails or disconnects, the other one will not work either. You will get always synchronous operation from both of them!

I made this Z splitter that works fantastic:

• There are two coils in each stepper motor driven by different pair of wires. This is a really helpful contribution how to connect 2 z-axis motors to a mainboard with only 1 z-axis socket. Apr 15 '19 at 10:54
• The wiring in this splitter pairs are red-blue and green-black, so the Splitter puts the "lower" pins on one circuit, and the "upper" on the other. As a result, step commands from either circuit affect the motors synchronously. To minimize errors, it would be a good idea to make both branches connecting to the splitter as even in length and as short as possible. Apr 15 '19 at 12:04