Thanks for the quick response.
Great write up.
I missed this concept initially
"Stepper motors pretty much draw their full current all the time, even when they are stationary - that is how they resist being moved from their present position. "
which makes total sense. I falsely thought it would pull more amps based on load.
I also missed the amp rating was per coil. So I was putting 4A through the L298 which probably could only safely handle about a third of the amp rating. That explains the heating issue for sure!
I have ordered 5 DRV8825. Since these only use 2 outputs from my 8266 it is a superior solution for that reason alone. Thanks for that info.
So according to the spec, I can go 1.5a per coil without a sink.
1) comparing 2 motors
a) 85oz 0.64a 15ohm 12v 17HS24-0644S $13 42x42x60
b) 92oz 1.20a 6ohm 12v 17HS24-1206s $15 42x42x60 500g
"Generally speaking the motors with low coil resistance and high currents (and low nominal voltages) will be most suitable for higher speeds"
so the 85oz motor @ 15ohm will have slower rpm than the 92oz @ 6 ohm at 12v?
2) Which motor would you choose from the 2 motors listed (assume 7oz torque difference is negligible) for use with the DRV8825? Assume rpm speed is important?
A) has lower amps but slower and
B) is faster but is right at the safe amp threshold of the DRV8825?
I think the answer is (B) since I want a faster speed, get a few ounces of increased torque and am within 80% of the rating and could slap on a small heat sink if I have to.