Azteeg X3 - Secondary power input for stepper motors

Anyone know how to use power aux in for the steppers? Right now it measures the same 12V I supply on the main power input. I have some steppers that need 9V. Thanks.

What means "Need Nine V" I'm not involved into printing things that much, but as I thought it would be better to switch current mean value to a certain level the motor is able to bear instead of "taking the bite" from the steppers by reducing the clamp voltage???? Power is same then but the current raise in the windings is faster on higher clamp voltage... SO you might have a little more power in the windings due to the faster current response- but could compensate this by lower current limitation Level...

My stepper windings are rated 0.63 amps and 13.1 ohms = 8.25 volts. 12V is probably OK, but I have a separate supply anyway, which would be good for keeping motor separate from the the micro and RAMPS.

The "rated voltage" of a stepper is just the voltage that gives the rated current when applied continuously, and can be ignored when using a current-limiting driver (which Polulus are); you just need to set the current low enough (note that you should not use full rated current on a RepRap, to avoid melting the brackets).

The 24V-boost option suggests that the Azteeg X3 has the ability to use a separate supply for the motors, but I don't know how to do it, and a lower voltage will make them run slower.

Thanks much for the info.

I'll send a PM to Roy to see if he can she light on aux input jack.

Roy sent the following reply: "Remove the X3 top cover and disconnect the solder bridge right below the 2x2 pin header. This will isolate the Voltage for the motors which can now be fed through the AUX connector. Please make sure that the solder bridge is disconnected/desoldered completely and make sure both power supplies have their grounds connected properly. A lot can go wrong with using 2 power supplies. Check and double check before powering up."

Removed the solder bridge and now have separate supplies for the board and the motors.

I was curious about the AUX power aspect to Azteeg X3. I am having problems with my Z Axis, there is not enough power to the stepper motors. I have switched my wiring to Series from Parallel from forums that I have read in finding a solution. The Steeper motors are the Nema 17 the are rewired, Rated Voltage: 3.6v, Current Per Phase 1.2A. Somewhat lower rating than other standard Nema 17 stepper motors. The Stepper Drives I am using are panucatt SureStepr SD8825 which are rated at, current Motor Supply : 2.5A max, Motor Voltage: 35V max. I do need to clean up the length of the stepper motor wiring, I am not sure how much resistance is estimated as a loss per foot.

Sorry for the long explanation, but it might help in better understand the problem I am having...

Since I am not the best at electrical matters I was wondering if it is possible to use the 5v rail to power the AUX power on the board alongside the main 12v 22amp that I am using to power the Azteeg X3 main power for the board. PSU ... There are some basic aspects of power that I might not understand because i am not an engineer, but the 5v 30amp rail is equal to 150watts, which is more than enough power for the stepper motors. My basic understanding of Ohms law is that all three elements are balanced between V Amps and Watts, though if i am correct you cannot exceed the amps or volts that the rail is regulated at. So... the 5V rail wired in the AUX would be able to power the stepper motors, with more than enough amps (exceeding the 20amp limit for the Controller card.

I am not sure why you conclude that the motors are not getting enough power. Unfortunately running at lower voltage is unlikely to help. The stepper drivers run in a current limiting mode, so the motors will get less than half power from 5V vs 12V. The SD8825 should be able to provide plenty of current for the motors. have you tried increasing the current limit?

I would advise running a seperate stepper driver for each Z motor as the X3 as 5 slots. If you are already using the slots for dual extruders, I suggest getting a bigger 12V PSU.

However, I suspect the real problem is that the motors just don't have enough torque, in which case you would need higher torque motors.

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There is something else regarding the motors.

The motor side of the DRV8825 chips (the chip on each Panucatt SD8825) requires a minimum working voltage of 8.2V. 5V simply won't cut it.

Regarding the motors:

In parallel the current will be higher. Do you have heatsinks on the driver chips, and do you have a fan blowing on them? 2.4A is very close to the 2.5A limit of those drivers, and they'll definitely need active cooling to allow them to run at that temp.

In series, the voltage needs to be higher. The way voltage works for these motors is that the supply to the drivers "should" be a fair bit higher than the voltage the motors need. By "fair bit", I tend to allow at least 8V difference when using a 12V supply (so no more than motors that are rated for 4V). Because your running 2 motors in series, this means the motor voltage gets treated as 7.2V.

If the Azteeg X3 can take supply voltages for the motors >12V (the SD8825's should handle well over 30V), then perhaps try running the motor drivers off a laptop PSU that is 15-20V.

WARNING: I'm specifically stating just running the motors. I am NOT AT ALL familiar with the Azteeg designs, and don't know if the motor input runs anything else apart from the motors, or what voltages the components on it are rated to. PLEASE check the design first, specifically things like Capacitor voltage ratings, active components (chips, regulators, etc) and if the input runs any other circuitry other than the motors (eg: it powers the CPU core on the Azteeg).

The printer is currently setup for dual extruders, I could disable one but the goal was to have dual extruders. I do have the expansion card, but mind you I am not the best at all the configurations that are able to be done on this board. I thought that the power supply rail that I was using was more power than that bard needed at 12v and 22amp, if I remember correctly the Azteeg X3 board is rated at 12v 20amps. Besides using a 24v PSU, I was going to attempt to de-solder the AUX power and us the 5v rail with 30amp. I was worried that 30amp could blow the fuse, but that is something else an I don't know once you de-solder the connection if the fuse is an aspect of that circuitry after that adjustment to the board..

Do you think that using the AUX power is not a good idea? especially with the other rail within the power supply. I thought that 5v 30a would be more than enough for the 6 stepper motors.

Nema 17 | 4.32 watts - 3.6v 1.2a
Total 6: 25.92 watts

5v rail (30amp) = 150 watts

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I did have the stepper motors wired previously in Parallel, which I am going to rewire again.

There are also Heat Sinks on each of the Stepper Drives, no fans for colling as of yet.

Edited 2 time(s). Last edit at 02/13/2014 04:54PM by bishupz1.

Oddly enough I went through some basic trial and error to see if I could replicate the motor problem. I did rewire the Z Axis motors back to parallel and shortened the wire length. Using the original z pins on the board the motors still stuttered, I moved the wires/connector for the Z motors to the Y pins, and the worked perfectly (shocking...). I tried switching the stepper controller board to see if that was the problem, but all the stepper controllers all worked fine, it seems that the board is the problem. Just to through through a red flag up, it could be some solder shorting that an area of the board. I will have to disassemble some plastic housing and remove the wires to inspect the boar. I want to thank those responded in trying to help me out with this problem. For now I am going to finish the custom printer with one extruder, and get it working...

(I do think the Azteeg X3 is a quality product, so I am guessing that it was in some way my doing that shorted the board. I am very careful, but things do happen.)

Thanks again for the help.

Bishupz1: While 5V may "technically" be enough for the motors, the issue is that the chips that drive the motors (the drivers) need an absolute minimum of 8.2V. As 5V is LESS than 8.2V, they simply will not work.

The drivers need the extra voltage so that the motors move reliably. Without it, they won't work.

For the case where you have 1 motor on a driver, this works fine with 12V. The difference between the voltage you give the driver and what the motor needs is 8.4V (12V - 3.6V).

For the case where you have 2 motors in SERIES on a driver, you're effectively wiring up the equivalent of a 7.2V motor. The difference between the voltage you give the driver and what the motor needs is 4.8V (12V - 3.6V - 3.6V).

IMO 4.8V is too LOW an overhead to get reliable steps out of a stepper motor, and you want at least 6-8V overhead. If you don't change your motors, the only way I can recommend to do that is to UP the voltage to something higher than 12V.

In series, current stays the same and voltages add. In parallel, currents add and voltages stay the same. This is why most machines use 2 motors in parallel on Z, because they do not need to use higher voltages. They don't use motors that draw the amount of current that yours do. Are you sure you really need stepper motors that are that powerful on the one driver? How much weight is the Z axis moving? When you hooked up the Z motors to the Y Axis, did you hook up both, or just one at a time?

Edited 1 time(s). Last edit at 02/14/2014 01:44AM by Cefiar.

This actually saved me on the Azteeg X3.
The extruder motor was acting eratic and would quit after only a few seconds of extrusion.
Finally turns out that the power for the steppers runs through the expansion board, and the soldering job (i guess) on the 2x2 is crap.
I removed the expansion board and wired in the stepper power via AUX IN. All is well now with my extruder.