Hiya all!
I made a post in a different forum about an idea i have for an arduino shield. (see here: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1189567413)
To bring you up to speed, I decided to use the L297 / L298 combo to drive the stepper motors. In the setup I'm trying to do, each motor will have 2 wire control: direction and step. Full/half stepping will be selected by a jumper, and the vref is controlled by a potentiometer.
Here is the datasheet I've been working off of that details about how to use the circuit: http://www.st.com/stonline/books/pdf/docs/1334.pdf
I've read through it a few times, but I still have a couple questions:
on L297 pin 3 (home) what do i connect this to? can i leave it unconnected? i dont think i need to know when its at home. datasheet says: Open collector output that indicates when the L297 is in its initial
state (ABCD = 0101).
The transistor is open when this signal is active.on L297 pin 1 (sync) do i connect this to the other L297's on the board? i'm a bit hazy on what it means to sync them. one of the main uses i have in mind for the stepper shield is to control a 3 axis CNC machine / 3D printer. i'm guessing i'm supposed to connect them, but i'm just not sure. datasheet says: Output of the on-chip chopper oscillator.
The SYNC connections The SYNC connections of all L297s to be
synchronized are connected together and the oscillator
components are omitted on all but one. If an external clock source
is used it is injected at this terminal.on L297 pin 20 (reset) i dont think i'm going to use this. do i leave it unconnected? connect it to ground? vcc? data sheet says: Reset input. An active low pulse on this input restores the
translator to the home position (state 1, ABCD = 0101).is the potentiometer wired up correctly? also, what is the value i should use for it? i specified 10K, but somewhere else i saw they used 2K. any suggestions?
on L297 pin 10 (enable) i want the stuff to always be on. i hooked this directly up to vcc. is this the right way? is there any reason why i would want to have the arduino control it?
are there any things you see that might be wrong about the design? this is my first time in Eagle, although i've spent alot of time in kicad.
I dont know how to attach files to the forum (or if you even can), so heres the link where you can download it: http://www.osotite.com/stepper-shield.sch
Thanks in advance guys!
I did some research and here are the answers I cam up with to my questions. I'm somewhat confident in them, but please let me know if you notice any mistakes.
- i'm just leaving the home pin unconnected. i dont need it.
- i'm connecting all the sync lines together. i found a circuit someone had made for a 3 axis machine (which is what I want this for...) and he had them all connected.
- i added a 10k resistor inline with it to Vcc.
- i'm going to use a 1k pot. hopefully this is the right value.
- added a 10k ohm resistor in series to Vcc.
- i sure would love it if someone looked over my design... i'm going to upload version 2, you can download it here:
you can download it here: http://www.osotite.com/stepper-shield-v2.sch
there are a few things i still need to do:
- add molex power connector for 12v in.
- add 7805 power circuit to create Vcc
- add analog header so one can use the unused analog arduino pins (0-6)
any other suggestions of things to add to this board? input is welcome.