T-Series/Commands/Set Hold Current/Motorized non-NMC Devices

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Instruction Name Set Hold Current
Applies to T-series motorized devices (excluding T-LSQ, T-LST, T-MCA)
Firmware Version 5.xx
Command Number 39
Command Type Setting
Command Data Value
Reply Data Value
Safe to retry? Yes
Returns Current Position? No
Persistence Non-Volatile
Summary Sets the desired current to be used when the device is holding its position.

It is typical to run stepper motors at their rated current only during moves (for highest torque) and reduce the current when idle just to hold the position.

Typically the hold current can be set to around 25 - 50% of the running current. In some applications, the friction of the drive system alone is sufficient to hold the microstep position of the motor, and the hold current can be turned off completely. The hold current can be turned off by issuing the "Set Hold Current" instruction with data of 0.

When the device is moving, it applies running current to the motor. When the device stops moving, running current is applied for an additional 0.1 second before hold current is applied.

The current is related to the data by the formula:

Current = CurrentCapacity * 10 / CommandData

The range of accepted values is 0 (no current), 10 (max) - 127 (min). CurrentCapacity is the hardware's maximum capability of output current.

To prevent damage, some devices limit the maximum output current to a lower value. In that case the valid range is 0, Limit - 127. Current limits are listed under the device specifications.

Some devices limit the voltage rather than the current. In this case the same formula can be used by replacing Current and CurrentCapacity with Voltage and PowerSupplyVoltage.


For example, Suppose you connect a stepper motor rated for 420mA per phase to a T-CD2500. Reversing the equation above and using 420mA as Current gives:

CommandData

= 10 * CurrentCapacity / Current
= 10 * 2500mA / 420mA
= 59.5 (round to 60)

Therefore CommandData = 60.