Just joined the forum as looking to purchase a smoothie board and in need of advice.
Almost finished my laser and at the stage of buying and fitting the electronics. I have been thinking about the smoothieboard for sometime and think it will handle all my needs except possibly this one.
My lifting Z table is 1200mm x 600mm and I have fitted leadscrews at each corner to raise and lower it. These are driven (or to be driven) by 4 nema 17 steppers. One on each screw. I thought about one motor and driving the other screws by belts but could not find any belts long enough.
My question is this. I want to drive the 4 steppers together as one axis. Can the smoothie handle 4 drivers from one output. Does it have enough current. I think most drivers only need a few millamps and most controller boards the current must not exceed 100 milliamps I think. I have seen in the smoothie documentation that you can links the pins of 2 outputs together. Could I link the 3 of the axis on the 5x board together to produce enough to drive 4 stepper drivers?
if not does anyone have any ideas how I may be able to do this.
Level shifters are traditionally used to take a 3.3v pin and bring it up to 5v.
However, they have the added side benefit that they can ( most of the time, check yours before buying it ) handle much more current than a pin too.
Search google images for level shifters and you’ll find a ton of schematics of how to do this, it’s pretty easy.
Level shifter input to Smoothieboard pin, level shifter output to the 4 driver pins, done.
LPC176x can source or sink 4mA on pin configured as output.
So, for example:
DRV8825 - max 100uA input current. You can drive over 40 of these.
A4982 - max 20 uA, > 200.
TMC2100 - max 30uA, so > 133 can be driven directly.
Check electrical characteristics section of the driver, find input current. Divide 4000uA by specified input current and You will know how many drivers can be connected directly. That’s assuming everything works on 3v3 logic level.