Ok thank you for trying to get back on track :) The pulse time was just a random number I chose to use but can be adjusted. If I understand correctly which is what I was assuming before, the pulse time from the micro controller doesn't actually do anything to the current, it is just a signal to the driver to turn on or off. Looking at the A4982 data sheet I can see that for one pulse, the pulse from to the driver is roughly 50% on then 50% off. I also understand that the drivers operate step by step but the pulse frequency from the micro controller is relevant to determine information about a single pulse.
It sounds like what you are saying about reaching the max current is the driver is capable of reaching voltages higher than the supply voltage in order to dictate the current limit which I've also read in the data sheet but I wasn't 100% certain about. This makes me think that the supply voltage dictates how high the driver can pump the voltage and/or how fast it can pump it because even if the driver can get a higher voltage to reach the current limit there has to be some limitation as to how high a voltage it can produce and consequently how fast it can get to the current limit. I'm assuming that the driver pays attention to how long the pulse signal on time is and then multiplies it by 2 to determine the time frame that it needs to turn on the current and then off based on the decay mode. My understanding of the decay modes while not through an equation, just from the datasheet images is that slow decay will leave you with 90% of the current, fast decay will get you roughly back to 0% and mixed will do fast then slow yielding roughly 75% of the current by the time the next step on/off sequence starts.
So how do I find out what the maximum voltage is that can be produced by the driver?
To go off on the driver tangent a bit, if the driver can charge pump to a higher voltage than the supply, lets call it Vx, then why doesn't the driver apply Vx until the current approaches the current limit and starts dropping the voltage in-sync with the current rise so that when it reaches the rated current it is at the rated voltage of the motor. Then it can hold the current steady without decay until the next step. This would seem to be ideal for an increasing current per step situation. In a decreasing current per step situation couldn't it flip the voltage polarity for a very brief period to pull the current down faster and rapidly increase up to the steady state voltage requirement for the new current level?
Back on topic, I know that assuming the driver on time being 100% is a theoretical best case scenario but it does set an upper limit showing me that the actual numbers must be below that value. I'm still wanting to figure out how to determine the minimum torque required to move a load with a specified max acceleration. If I know the moving mass and the desired acceleration then I can calculate the force, over-compensate that number some to account for friction and other things that would just require even more complicated math to specifically define. Is that correct? Then that becomes my target value to base my motor selection on but I would also need to know my distance traveled per full step so I can compute a target torque value, is this also correct? I understand there is a lot regarding the driving of the motor and motor selection that I need to account for and I appreciate that you're helping me along with those things but can you confirm or correct the remainder of my logic so I can understand which parts of the big picture I have correct and which ones I need to go more in depth on?
Again I want to emphasize I do appreciate your time and effort, you seem to be plenty capable of teaching me a lot about things I don't know which is more than I hoped for but am glad to get to know even more details so I can have a better understanding.
It sounds like what you are saying about reaching the max current is the driver is capable of reaching voltages higher than the supply voltage in order to dictate the current limit which I've also read in the data sheet but I wasn't 100% certain about. This makes me think that the supply voltage dictates how high the driver can pump the voltage and/or how fast it can pump it because even if the driver can get a higher voltage to reach the current limit there has to be some limitation as to how high a voltage it can produce and consequently how fast it can get to the current limit. I'm assuming that the driver pays attention to how long the pulse signal on time is and then multiplies it by 2 to determine the time frame that it needs to turn on the current and then off based on the decay mode. My understanding of the decay modes while not through an equation, just from the datasheet images is that slow decay will leave you with 90% of the current, fast decay will get you roughly back to 0% and mixed will do fast then slow yielding roughly 75% of the current by the time the next step on/off sequence starts.
So how do I find out what the maximum voltage is that can be produced by the driver?
To go off on the driver tangent a bit, if the driver can charge pump to a higher voltage than the supply, lets call it Vx, then why doesn't the driver apply Vx until the current approaches the current limit and starts dropping the voltage in-sync with the current rise so that when it reaches the rated current it is at the rated voltage of the motor. Then it can hold the current steady without decay until the next step. This would seem to be ideal for an increasing current per step situation. In a decreasing current per step situation couldn't it flip the voltage polarity for a very brief period to pull the current down faster and rapidly increase up to the steady state voltage requirement for the new current level?
Back on topic, I know that assuming the driver on time being 100% is a theoretical best case scenario but it does set an upper limit showing me that the actual numbers must be below that value. I'm still wanting to figure out how to determine the minimum torque required to move a load with a specified max acceleration. If I know the moving mass and the desired acceleration then I can calculate the force, over-compensate that number some to account for friction and other things that would just require even more complicated math to specifically define. Is that correct? Then that becomes my target value to base my motor selection on but I would also need to know my distance traveled per full step so I can compute a target torque value, is this also correct? I understand there is a lot regarding the driving of the motor and motor selection that I need to account for and I appreciate that you're helping me along with those things but can you confirm or correct the remainder of my logic so I can understand which parts of the big picture I have correct and which ones I need to go more in depth on?
Again I want to emphasize I do appreciate your time and effort, you seem to be plenty capable of teaching me a lot about things I don't know which is more than I hoped for but am glad to get to know even more details so I can have a better understanding.