At the moment, I am using a mimusi stepper motor which contains five wires: red, black, orange, brown and yellow.
So far, I use the sequence: 0x01,0x02,0x04,0x08 at 12 times in order to complete one revolution with my AVR chip. It works well then I tried to reverse the direction and to my surprise, it still goes in the same direction instead of going backward.
Forward
Pin 16 of ULN2003 - Yellow - 0x01
Pin 15 of ULN2003 - Orange - 0x02
Pin 14 of ULN2003 - Brown - 0x04
Pin 16 of ULN2003 - Black - 0x08
Backward
Pin 16 of ULN2003 - Yellow - 0x08
Pin 15 of ULN2003 - Orange - 0x04
Pin 14 of ULN2003 - Brown - 0x02
Pin 16 of ULN2003 - Black - 0x01
I could not understand why. Any suggestion?
MM
What kind of CNC machine are you trying to make?I'm working on a stepper controller for a CNC I'm making this is where I'm at now, allmost done with the program for 16F628A.
What kind of CNC machine are you trying to make?
I went through a lot to set up a CNC machine. There are a lot of subtle problems to getting performance at useful speeds. The basic "this steps a stepper motor" circuits are not practical for CNC work. Unfortunately, there's a lot that's wrong with this drive you've got there that'll basically reduce the performance to like 5%-10% of what it needs to be for a CNC machine.
The circuit you're discussing is just not remotely appropriate for so many reasons for a setup needing performance:Oznog,
I confused now I thought the speed of the stepper motors are determined by the computer’s (step pulse rate), the manual mode on my circuit is so I can run the stepper without the computer control. Is there something I’m overlooking? This is my first stepper motor project I’m aiming to build a 4’x4’ CNC Router
Hey I'm with you. I'm the king of overdoing a project to save a dime or some intangible "DIY" virtue. But your plan won't work at all, that's not a CNC driver circuit. The ULN2003A cannot drive a CNC stepper, period. For many reasons. That circuit can't drive a small mill, much less a monster router (4'x4' is big!). And it can't be improved into one that will work. And I did a fair amount of advanced stuff to try to build a new CNC driver for a mill I got that already had a CNC driver professionally designed for it- one which never actually worked because the designer didn't know what they were doing. And it's not that the circuit you have won't work to some high standards I have in mind or will only work at 1/4 the speed I'd call "performance".I see what your saying Oznig, I just watched some video on YouTube on the G540 impressive I’ll have to get some more information on how they work but for now I have to watch my budget, I’m disabled and on a fixed income I have about 95% of the material to make the CNC table, 4’x6’ metal table, 6 steppers ok for testing, 10 pic16F628A and I just got LinuxCNC on a bootable 8 Gig. Flashdrive. My main goal is to build the CNC table for now I think I’ll use what I have just to get it working and then upgrade the motors and controller later.
Hey I'm with you. I'm the king of overdoing a project to save a dime or some intangible "DIY" virtue. But your plan won't work at all, that's not a CNC driver circuit. The ULN2003A cannot drive a CNC stepper, period. For many reasons. That circuit can't drive a small mill, much less a monster router (4'x4' is big!). And it can't be improved into one that will work. And I did a fair amount of advanced stuff to try to build a new CNC driver for a mill I got that already had a CNC driver professionally designed for it- one which never actually worked because the designer didn't know what they were doing. And it's not that the circuit you have won't work to some high standards I have in mind or will only work at 1/4 the speed I'd call "performance".
People have tried to DIY stuff, with plans which are vastly more capable than that circuit, but they typically run at least several hundred in parts and generally end up badly flawed.
BTW, advance warning: this is the Internet, and there are some odd ideas on the CNCZone forum (most advice is great though). The one I'd caution against is that there are people swearing you need a huge, 60Hz transformer "for stability" and swear switching power supplies are unstable and failure-prone (though, to my knowledge, no one has ever documented such a failure or even instability). It's bunk. The 60Hz transformer is phenomenally expensive, poorly regulated, and requires very huge and expensive caps which are often replaced by grossly undersized caps by people who don't understand the subtleties of ESR and ripple current rating, and the linear regulator (if they even use a reg) and heatsink need to be enormous too. They're just absurdly unnecessary substitutes for switching power supplies, which are really good stuff, reliable, fairly clean DC output, and far cheaper, smaller, and lighter.
Oznog,
I confused now I thought the speed of the stepper motors are determined by the computer’s (step pulse rate), the manual mode on my circuit is so I can run the stepper without the computer control. Is there something I’m overlooking? This is my first stepper motor project I’m aiming to build a 4’x4’ CNC Router
I'm using the ULN2003 just for software testing I know it will not handle the load on a CNC.
Well that's not gonna fix much, because a stepper must be current-driven, not voltage-driven like audio. In fact it's in great danger of smoking a motor without current control.Anyway I found an old 500 watt auto audio amp. I took out 4 of the smaller power transistors (NEC–K2724) could not find a datasheet on them so I made a test circuit and hooked it a coil (1.4 ohm) to it and to my 35 amp. power supply set at 15 volts, I ran it about an 1/2 hour it was pulling about 7.9 amps. The heat sink got a little warm but not bad. I think I might use them for now.
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