bookmaker32
USA
Asked
— Edited
Hi guys, Here I am back in bewilderment land. I am trying to run a stepper motor with a Spark Fun Big Easy stepper motor driver. No problem except no matter what PWM I put in the motor runs at the same speed. About 24 RPM. I checked the PWM and it is doing exactly what the EZ-Bv4 tells it to do but the Big Easy just runs the motor at the same speed. Anybody know what is going on?
Can you post your code you are using to control it?
Hi @bookmaker32 where are you applying the PWM signal to on the Big Easy Driver?
From just an initial look, it seems if you apply a PWM signal to the "STEP" connection it probably won't work, but if you apply it to the "ENABLE" it may work.
This is the product?
https://www.sparkfun.com/products/11876
From what I'm reading it does not look like your would send the board PWM commands. It looks like it should be High/Low values, like an h-bridge.
Here is the Manual. Big Easy Manual I am driving it on the step input with PWM and it works fine, it just doesn't make any difference what the PWM is set at. It runs at the same speed. I tried the Enable but that doesn't work. Does anyone have any experience with another driver? What speed can one expect to get out of a say Nema 14 Bipolar Stepper 7.5V 0.5A 23Ncm(32.6oz.in)?
I've been reading the manual and from what I'm reading it looks like the STEP pin is suppose to receive high low values, not necessarily PWM.
On page 3: STEP: This input is tied high with a 20K Ohm resistor on the BED. Each rising edge of this input will cause the stepper driver to advance one step in the direction specified by the DIR input. The STEP input must be high for at least 1us, and low for at least 1us.
Someone (maybe a new EZ-Bit) needs to build a controller that takes the thought out of driving stepper motors. Every time someone posts about them, there seems to be a lot of confusion about what the EZ-B needs to send or even if it is capable of it. We need something that looks like a servo or H-bridge from the EZ-B side but converts the signals to step controls. I have searched a few times for Stepper controllers just out of curiosity (no plans to actually use one at this time), and I haven't seen anything that makes it simple.
Alan
On the Arduino hook up it says to connect to PWM. I made the assumption that it would be the same.
Hi @Bookmaker,
I don't have a good idea of what the Arduino Library is doing but looking directly at the datasheet it looks like you can take full control of the Big Easy Driver via the Enable pin. Here's what the Allegro chip datasheet says:
You will still have to send a constant PWM signal to the STEP connection at the same time as the enable to make the driver move.
There is a pull down resistor on the board (R10) that keeps the driver constantly enabled so you'd really just have to send it a high pulse from the EZ-B when you want it to slow down.
Another option is to use the MS1, MS2, & MS3 ports to change the default settings from sixteenth step to a slower step pattern, they are all default high so you'll need to send them a low signal.