reprap stepper driver

[student1616]

hello all,
in search of a best and tough bi-polar stepper driver ,i ended up at

reprap's stepper controller.they built it for rapid-prototyping

machine.but as it accepts pulse and direction commands i guess it can

be used for CNC too.
http://www.reprap.org/bin/view/Main/...tor_Driver_1_1

the point that why i got impressed with this board is,bcz it accepts

inputs of max and min travel from the limit switches.this saves my lot

of input pins.

but befor building it i have some doubts in the schematic.(as iam little dumb at undestanding schematics now and as this forum visited by best CNC experts,iam posting here)

1.the power connector has input for both 5v and 12v.that 12v is ment

for stepper.say if my stepper is rated at 24v,then can i connect 24v

instead of 12v?
2.i don't understand the purpose of stepper adjust in the schematic at

all.what is the TP1 ment for?
if it to tune the current of stepper,how can i do it?
3.and what is for the Master and slave pins?
4.can i avoid connections SYNC,SYNC,ENABLE at input side?
are they required?

please help in understanding these issues.
Thanks and Regards

[student1616]

little help here pls.

at least help me in understanding the purpose of TP1 and sync pins.
Q.2 and 3

[darkith]

little help here pls.

at least help me in understanding the purpose of TP1 and sync pins.
Q.2 and 3

From what I can tell:

The Sync pins are all intended for having multiple axis' chopper drivers all in sync by using a shared clock source. You could probably just set them all as master and ignore the sync.

There's a quote further down:
"It turns out that you can also just set all your boards to 'Master' and ignore the 'Sync' lines."

TP1 looks like a voltage divider to set the current on Vref. Turned one way will give you full current (2A on the 298?), the other way will give you no current (motor won't turn). Adjust it for the highest current that doesn't overheat your motors. Read the section "Current Adjustment" on the page.

Google for
AN470 APPLICATION NOTE THE L297 STEPPER MOTOR CONTROLLER
and the L297 and L298 datasheets for more info.

Not sure why you're happy that the board accepts Min/Max inputs...it just passes them from the switch headers pins to the IO signal wires...you still have to hook these wires up to your controller.
If it were me and I had limited IO, I'd just hookup all the limit switches as a loop with the switches NC, so if any switch is triggered it breaks the loop and halts the machine. Only needs one input.

D.

[student1616]

Thanks for the reply.
and i was not properly reading the schematic.by looking at the data provided in the site i thought it can take inputs directly.my mistake.
and regarding the current adjustment,i have to measure the voltage between the TP1 and ground of the circuit?
i found the formula from pminmo site adj= 0.5*rated current of motor.but don't understand the measurement points.

[darkith]

Yes, measure the voltage with respect to ground.

The Vref value setting you want depends on the sense resistors (R1 & R2). The max current formula would be Imax = Vref/Rsense.

D.