Since this is my first post i would like to congratulate you on the wonderful forum that you have here and indeed it has a lot of info for everything and since a lot of people take the cnc machining as a hobby i decided to give it a try. Well i did some research and read few thing about cnc machines and in short they are not that difficult to build (if you buy all the parts of course, mainly the electronics). It seems that everything starts with the motor that you are going to use and in most cases is the NEMA32 stepper motor. I found this stepper motor http://www.kelinginc.net/KL23H286-20-8B.pdf the one that is bipolar parallel. Now on to the drivers. A couple of people here have a schematic using the TA8435H with a complete PCB design, but the TA8435H can produce only 2.5 A peak. Google Translate. Is there any way to replace the TA8435H with something that goes up to 3.0A since the stepper is 2.8A. Another question that i have is the voltage, what are the Vm and the X1-1 from the link??? Another schematic can be found here Oatley Electronics, but i can't build a PCB since i don't know how to read the schematic, or at least alter the first one to suit the stepper motor. Could somebody post a PCB design and it's parts so i can build one myself? Or at least guide me to a web page?
If you want to use the referenced motor wired as unipolar, the H01259-01U kit sold by there guys work great. The schematic is shown on the datasheet link next to the photo of the board. The circuit is a full step driver and works best with hybrid types of stepper motors. If you want to use bi-polar wiring you must use the "H" driver type of drivers. H drivers comprise transistors wired to reverse the voltage on the motor winding(s), (plus and minus swapped), thus reversing the magnetic field of the winding. On unipolar windings, you usually ground one or the other winding with the centertap going to plus voltage. Since this circuit does not use pulse width modulation (PWM) you would need a series limiting resistor to maintain the static current. I have built a couple of driver boards using four of these circuits, one for each motor. The cost of one board from these guys (which is not bad) is $23.00, or about $100.00 for a 4 motor CNC. You could make your own by buying 16 (4 motors) MOSFET transistors (IRFZ44) for about $1.50 each, that will sink 40-50 amps each. More than enough to drive your motors. You also need 8 IC's, 4-4013's (F/F), 2-4013's) Quad 2 input Exclusive OR's), and 2-4093's (Quad 2 input Smitt trigger NAND's) or about $4.00 plus shipping. Cheap and works fine.
Only problem I have had is that some parallel ports only output 3.6 volts, not 5 Volts. The Smitt trigger do not like these low inputs and will likely fail to work. I replaced mine with standard NAND gates and they seem to function OK at those low outputs. I plan to use the 74HCT00 NAND gate to see if they will work better, because the are designed to be used with TTL outputs (like 7400 series IC's) but output CMOS 4000 series IC voltage levels. The 4013 Flip/flops will drive the MOSFET's fully on with no resistor in the gate circuit and because they have such low source to drain junction resistance, do NOT get hot, or even warm. You can wire a bunch of MOSFET's into an H drive configuration but I haven't needed to so haven't figured out how. Maybe when I take the leap to servo's I will make H drives. Joe
PS. I think the K-142B kit from Oatley reference is an H driver. http://secure.oatleyelectronics.com/...bcfbd768daf74b
Last edited by toughtool; 06-09-2011 at 05:30 PM.