RAMPS 1.4 with NEMA 23 steppers?

I just need clarification before I get in too deep with what I have going on.
I was given quite a few NEMA 23 motors. They are 1.8* steps, 12V and either .42A or .68A. These motors also have 6 wires coming from them.

Could I make a 3D printer using these steppers with the RAMPS 1.4 board with Pololu A4988 drivers? They state that they can do 2A per coil.

Is it even worth the headache using the larger motors or should I just stick with NEMA 17's like everyone else.


Thanks all!

You might be able to do it, but you will need to make sure that the Pololu drivers are properly cooled with a fan, and I would most definitely put heatsinks on them.

I would consider replacing the Pololu A4988's with Pololu DRV8825 boards (which can drive slightly bigger motors). They work as a "almost" drop in replacement for the Pololu A4988, except the mapping for the microstepping are different (1/32 max for DRV8825 vs 1/16 for the A4988). If you only want to use 1/16 mode with a DRV 8825, you will need to use a different arrangement of jumpers compared to the A4988 - check the DRV 8825 data sheet for details.

Regarding 6 wire motors - Two of those wires will be the centre wire for each coil. You should simply be able to 'ignore' this wire and not use it. First find a group of three wires that are all connected by a lowish resistance using a voltmeter (low ohms range - like 200). Then find the two wires that have the highest resistance between them - this is one coil, and you hook that to two of the pins on the stepper driver (two on the left side of the connector, or two on the right). Repeat this for the remaining two pins.

If the motor seems to vibrate a lot, you can reverse two of the wires on one side of the connector (eg: If you have from left to right blue, red, green, black - you could try blue, red, black, green, or red, blue, green, black) and try again.

You should be able to use NEMA23 motors, but it all depends on just how power hungry the motors are. The ones you have sound to be suitable for such use, but bigger motors could cause problems.

Notes:
The colours referenced above a simply EXAMPLES and should ALWAYS be tested before connecting. There is no standard colour coding, and even some brands change wiring colours between batches, so ALWAYS test your motors before connecting.
Testing also shows other issues such as motors which have a direct short between wires or coils, which could be less than useful.
If you're running 2 motors in parallel (eg: Prusa Z axis, etc) then make sure that the motors are both the same spec.

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You might be able to do it, but you will need to make sure that the Pololu drivers are properly cooled with a fan, and I would most definitely put heatsinks on them.

Maybe I misinterpreted the OP, but 0.68 A aren't exactly much for A4988 based drivers. Also, bigger diameter steppers have more torque at the same current.

Not so ideal is the 12V rating of these motors. Torque will go down quickly with speed. Operating them at 24V would solve this. Ideal steppers have 1V to 4V rated voltage when running at 12V.

The drawbacks of NEMA23s are:

- You have to adjust the motor mounts (fastening holes, etc.).

- They're typically heavier.

No reason not to start with them, though. I run my WolfStrap with NEMA23s, too. If you find out it doesn't fit, you can replace just the motors and keep everything else (belts, electronics, etc.).

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Ive just posted a very similar question on the forum.
I cant get my head around the 4v thing when the ramps and DRV8825 are running off 12v. Im sure they are just being over driven on a short duty cycle or something but it makes motor selection more of an art.
Im wanting to use nema23 size with a ramps and DRV8825 from a 12v supply.
I think the 4v 2.1A version is the best choice but I am far from certain.

Thanks guys!
I was just unsure if using these free steppers would be a blessing and money saver or a big headache and a show stopper.

I think im just going to get some NEMA 17 motors like everyone else in the reprap community and go from there.

Your 12V steppers are going to need something higher than 12V to run them in micro stepping mode at the speeds we typically run them at. If you are comfortable with 24V power into the Ramps they will do fine. Be very careful about that qualifier, the Mega board is not going to be happy much over 12V without some customization ....

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uncle_bob
Your 12V steppers are going to need something higher than 12V to run them in micro stepping mode at the speeds we typically run them at. If you are comfortable with 24V power into the Ramps they will do fine. Be very careful about that qualifier, the Mega board is not going to be happy much over 12V without some customization ....

Hello Uncle Bob,
could you give me maybe a hint or even some further explanations about how to customize the board for a safe 24 Volt stepper motor use?

To do a 24V board you probably need to:

1) Come up with a supply for the Mega
2) Come up with a supply for your 12V fans

One approach is to have both a 12V and a 24V power supply. In that case, you cut diode D1 on the ramps board and feed the 12V into the place where it used to be (12V to the Mega regulator input side of the diode). The rest of the board simply gets 24V and you move on. Any fans go across the 12V supply and run all the time.

Another approach is to have the fan's still under Ramps control. In that case you have the + marked fan signals on the Ramps disconnected. The top side of the fan goes to the +12 supply and the bottom side goes to the MOSFET. You probably should pull the LED's off of the MOSFET's if you want to be sure of things in this case. This setup also eliminates the protection provided by the Ramps fuses (see below).

Next approach is to run 24V fans, they do exist and then all you need to do is come up with a supply for the Mega. In that case I'd mount a 7808 regulator somewhere. Feed it off of the 24V and use the +8 out of it for the Mega regulator input that used to come from D1.

All of this assumes you go to 24V heaters on the hot ends and heated bed. If you are going to keep them at 12V then: The heated bed supply (11A input) goes to the 12V supply. The hot end heaters get wired like the fans above. You don’t use the + outputs on the Ramps and you lose the fuse protection.

Speaking of losing the fuses: The ones on the Ramps are only rated just so high in voltage. For a 24 V system I’d take them out and put in jumpers. Get a good fuse block from somewhere and use real honest to goodness 24V DC rated fuses. I would not recommend pulling the Ramps fuses and simply running without any fusing at all. Be sure you get DC rated fuses, the rating at AC is often higher than at DC. Automotive fuses are a good choice if you do a little checking on them first. You can find 32V versions fairly easily. You can also find 58V parts with some effort.

Next layer to all this - is it a 24, 28, 32 or 35V design? I'd argue against the last one, there's not much margin on some of the parts. 24 and 28 are both pretty safe.

Edited 1 time(s). Last edit at 11/18/2013 04:52PM by uncle_bob.

Re: Running the Mega off something like a 7809/7808 linear regulator....

Put a diode on the output of the 7808 before you feed the output into VIN on the Mega (which is where D1 feeds it).

Most linear regs will allow voltage on the OUTPUT to flow back out the input (which includes the reg on many Mega's and clones). This will lead to things like fans running when you connect the Mega via USB.

Regarding using 24V on RAMPS, I replied in great detail in thread at: [forums.reprap.org]

I really should move some of that to a wiki page.

Good point on the diode on the 7808, I left that out.

Hello,

On this topic how does a taurino mega help basically my understanding is its a mega 2560 but setup to handle 12v to 35v. Would you be able to put 24v through to run a nema 23 and can the stepper drivers handle that?

BV3D: Yes, with a Taurino Power, you should be able to use 24V.

The stepper drivers (eg: A4988, DRV8825) will handle 24V, but I do not know if they will handle the current you require (as this will depend entirely on which steppers you use, not just on the drivers).

Whatever you do, the stepper drivers will need heatsinks AND active cooling (ie: A fan, with a lot of air flow), especially if you're anywhere near (or over) 1/2 the current limit of the driver boards.