I’m hoping for some product advice for extending and adding to the wiring on my Ender 3 v2. I am changing to direct drive, a BTT mainboard and dual Z motors. Could you let me know if the below product are correct or a better alternative?
Just a heads up before we jump into the details, the Ender 3’s power supply can sink some serious current so you have to make sure each connection is solid or things can snowball into a seriously HOT situation, not to mention the chance that a swapped connection could fry the motherboard.
From what I could find online the stock hot end consumes 40W at 24v that’s just under 2A, using this tool from the Engineering Toolbox we can size up some wire.
Depending on the motors and fans you use there will be similar wires being used between all of them, you can use the tool above to size up your wires and confirm, just make sure each connection is solid!
The limit switches and thermistors won’t be sinking too much current so that should be fine.
If you have the option to grab some extension wires when you pickup your direct drive kit and the second z-motor it would definitely be worth it!
Generally, you’ll want to stick to a high core count for wires that move, as they tend to be more flexible and will last longer. Higher core counts are usually found in wires with silicone or PTFE insulation, so you’ve made some good choices there already.
Going on what popular DIY printers go with for wiring, 20AWG is a little oversized (good) for heater wiring, and 24 should be ok for everything else. Some high torque steppers can draw up to 1.6A or so per phase, so keep that in mind (your ender steppers are likely drawing a lot less)
Keep in mind that your Ender 3 V2 actually uses the same SKR E3V2 boards you can get from BTT, so you might not even need to upgrade.
-James
P.S. Back when I had my E3V2 , I believe I didn’t have to do any wiring to go to DD or install a BLTouch. just a new shroud to hold everything together
If you are doing your custom wiring, you’ll likely need a big JST XH kit for your connectors on the motherboard side, and something like MicroFit 3.0s if you want connectors at your toolhead/motors.
Hi Liam
As a point of interest what are these limit switches doing so as not to draw too much current???
“Proper” limit switches should physically cut POWER to the motor(s) involved. If you are just providing a signal to the controller to stop any motors best of luck when something drastic goes wrong.
I think most controlling systems using brushed or stepper motors with PWM or stepper drivers with or without H bridge utilise one or more Mosfets and flywheel diodes across the motor. I have found most faults seem to be shorted Mosfets usually due to the failure of the diode(s). Now, if this occurs with a brushed motor it does not matter what signals you send to the controller the motor is going to go flat out until something stops it. If your "limit switch’ is depending on a signal to stop the controller it is just not going to happen. The motor will stop when it runs out of somewhere to go mechanical, usually with some damage.
You may have some chance of no damage with a stepper motor where probably one or more coils will be permanently powered if shorted Mosfets happen. I have no idea exactly what would happen but the motor might stop before the “limit” switch. There may be no mechanical damage but could be smoke, or current limits might take care of it.
I don’t have a 3D printer but I believe all the motors to be steppers so your software limit may be OK. However if I were building one of these I would tend to “err on the side of caution” as the saying goes and cut primary motor power.
One thing regarding brushed motors when the limit switch operates the motor has to be immediately stopped as it could over run past the switch and keep going when the switch closes. This is normally done by switching in a diode polarised so it shorts out the GENERATED voltage (as distinct from the Flywheel diode which grabs the opposite polarity spike) and generally stops a motor dead in its tracks. Another diode has to be connected across the NC contacts to allow reverse voltage to back the motor off the limit switch situation.
Cheers Bob
I can agree with you that most failure modes can be catastrophic(as James mentioned, some juddering and annoying sounds) when you tinker with the switches outside of the machines normal operating conditions. Thankfully the onboard microcontroller has some homing routines it runs before every print so it’s all good in that aspect.
Interesting set up there, for some of my smaller projects where a bit more power might be used (nominally 24v @ 10A from an RC LiPo) I’ve baked in some relays that close and cut power to the whole circuit as soon as a fault is detected (both analog and digital).
It’s pretty clear you come from a background of industry and safety! Nothing chumps a real limit switch when it comes to that, but for 3D printing, the worst that can happen is usually not too bad.
I’ve built printers from scratch, where if you stuff up the wiring, your limit switches won’t work, and your axis or head will bump into the end of its travel, and the motor will lose steps and judder as it tries to move the immovable. The worst that can happen here is that your steppers bend an extrusion or crack a plastic part.
If you’ve got good firmware and hardware, your stepper drivers will actually report back that they have lost steps or are encountering an overload condition, this will shut down the printer.
I can totally imagine a CNC machine causing serious damage to itself if a stepper goes rogue, so the extra expense of hardware limiting there would not go to waste.
Thank you all for your help and replies, you have all been a big help.
I am struggling to find any listings of 22 and 24AWG wiring with silicone/PTFE insulation.
I can find 8-18 then 26-30 that list silicone insulation, are any of the 22 or 24 you sell silicone/PTFE?
For the connectors I was looking at the big JST kit for the board side and JST PH 2.0mm kit for the steppers. I like the idea of the MicroFit 3.0 for the tool heads.
I had a look at our 22AWG stranded wire such as the following:
You are correct in that they don’t mention the insulation type, but I was able to do some more digging and found that the wire insulation is PVC.
I found a good comparison of PVC and Silicon insulation here, but your use case might be different. Just a nice little description of some of the main features really.
Would be nice if some of these suppliers published the stranding as well as the size. The stranding makes all the difference to flexibility (which has been mentioned).
Cheers Bob
