TIC825 - Need clarification on Torque Setting in serial mode

Hello again!

I have made great progress with the TIC825 and it is doing a wonderful job for me. I do have a question though regarding the current limit setting via serial control.

My stepper motor is 2.5 Amps per phase. The TIC825 can provide up to 4.0 amps.
The range we can use to specify the current is a value from 0 ~ 124 based on what I found in the directions.

This is what I calculated for a low and Hi setting for my stepper motor.
31 for 1000 mA of output (Low setting for my motor)
78 for 2500 mA of output (High setting for my motor)

I selected 1000mA for low current based on testing with the TIC Control Center software wherein at that setting the motor spins fine at speed, but once I add a little resistance the motor stalls - which gives me a good idle current.

The instructions started to confuse me in this area…

Disregarding the maximum allowed current limits documented above, the achievable current limits are as follows: 0 through 31, even numbers from 32 to 62, and multiples of four from 64 to 124. If you set a current limit that is not achievable, the Tic will generally accept it and store it in the “Current limit” variable, but it will actually have the same effect as the highest achievable current limit lower than it. For example, a current limit of 33 is the same as a current limit of 32, and a current limit of 66 is the same as a current limit of 64.

Thanks Again for the help and a great product!

Chris D

Hi, Chris.

I understand how that paragraph can be confusing. For the Tic T825 the range of possible values for the current limit is broken into three sections with different resolutions: 1 - 31, 32 - 62, and 64 - 124. For the lowest range, 1 - 31, the resolution is 1, so all numbers represent actual current limits that can be set. For the T825 you multiply by 32 to get to actual milliamps, so in the lowest range you can select current limits of 32mA, 64mA, 96mA, …, 992mA. In the middle range, 32 - 62, the resolution is 2, so only every other number (every even) represents a real current limit setting: 32, 34, 36, …, 62. Those correspond to 1024mA, 1088mA, 1152mA, …, 1984mA. In the highest range, 64 - 124, the resolution is 4, so every fourth number represents a real setting: 64, 68, 72, …, 124. Those correspond to 2048mA, 2176mA, 2304mA, …, 3968mA. Note that 78 is not one of the valid settings, so if you set the limit to 78 the next highest setting will be used: 76 which corresponds to 2432mA. Also note that the T825 is only rated to handle up to 1.5A without additional cooling and 2.5A max with sufficient cooling. If you need more current, you might consider the Tic 36v4.



Thank you very much for the explanation, I very much appreciate the help! I believe I understand it now.

Chris D