troubleshoot motor shield

[adafruit_support_bill]

In theory, with the power jumper removed, there should be no connection whatsoever between the positive external power terminal and the Arduino (The grounds of course are tied together).

Check to make sure that there is no contact between the metal casing of the USB jack and exposed traces on the bottom of the shield. A piece of tape over the top of the jack is good insurance.

[titous]

In theory, with the power jumper removed, there should be no connection whatsoever between the positive external power terminal and the Arduino (The grounds of course are tied together).

Check to make sure that there is no contact between the metal casing of the USB jack and exposed traces on the bottom of the shield. A piece of tape over the top of the jack is good insurance.

i think we are getting somewhere now! i've put a piece of tape on the usb plug and here is where i'm at:

if i power the arduino with a +5v & GND from the PSU, stack the shield on top, and then use only the +24v from the PSU, all the LEDs go green; although it should be noted that i'm only getting ~12v instead of +24v. at this point, if i hook up (what i think is) the GND from the +24v we get PSU turn off.

now, if i reconfigure the PSU as +12v instead of +24v, then i'm able to hook up both the +12V and GND no problem and i get all green go!

so, through all this, i must have fixed some other short, bug, etc; and stumbled into another one - i'm creating +24v with a -12v and a +12v output. i'm using the +12v as my + and the -12v as my GND. so i guess i cannot do this because i'm not getting a true ground? how can i setup this configuration to give me a true +24v and a ground?

[adafruit_support_bill]

You should stick with the 12v supply. The motor you have is designed for ~10v operation. (0.7A * 14 Ohms = 9.8v via Ohm's law)

24v is going to overload both the H-bridges and the motor. Considering the ~1.2v drop through the bridge, a simple 12v supply would deliver ~10.8v to the coils and draw about 0.77A per phase.

[titous]

IT WORKS!!!!

thank you for your continued help, i really do appreciate it.

i have one final question about the power source. i was under the impression (after talking to Anaheim automation) that as long as you control the correct current per phase, you could feed the stepper almost any voltage (within reason) to get more power out of it.

[adafruit_support_bill]

i was under the impression (after talking to Anaheim automation) that as long as you control the correct current per phase, you could feed the stepper almost any voltage (within reason) to get more power out of it.

That is correct. Current limiting is a feature found on industrial quality motion control systems (with industrial strength pricing to match!). The Adafruit motor controller (like virtually all low-power stepper controllers) do not actively limit the current.

Motor coils are inductors, and with a fixed voltage source the current rises gradually until the coil is fully energized. This means less current and less torque at the start of the step. More sophisticated controllers start off with a higher voltage so that they can put more current through the coil at the start of the step, but limit it to a safe level so they don't damage the motor.