psmd


Posted on Feb 6, 2014

The A4988 driver IC has a maximum current rating of 2A per coil, but the actual current you can deliver depends on how well you can keep the IC cool. The carrier’s printed circuit board is designed to draw heat out of the IC, but to supply more than approximately 1A per coil, a heat sink or other cooling method is required. This product can get hot enough to burn you long before the chip overheats. Take care when handling this product and other components connected to it. Please note that measuring the current draw at the power supply does not necessarily provide an accurate measure of the coil current. Since the input voltage to the driver can be significantly higher than the coil voltage, the measured current on the power supply can be quite a bit lower than the coil current (the driver and coil basically act like a switching step-down power supply). Also, if the supply voltage is very high compared to what the motor needs to achieve the set current, the duty cycle will be very low, which also leads to significant differences between average and RMS currents.


psmd
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This product is a carrier board or breakout board for Allegro’s A4988 DMOS Microstepping Driver with Translator and Overcurrent Protection; we therefore recommend careful reading of the A4988 datasheet (380k pdf) before using this product. This stepper motor driver lets you control one bipolar stepper motor at up to 2A output current per coil (see the Power Dissipation Considerations section below for more information). Here are some of the driver’s key features: Simple step and direction control interface Five different step resolutions: full-step, half-step, quarter-step, eighth-step, and sixteenth-step Adjustable current control lets you set the maximum current output with a potentiometer, which lets you use voltages above your stepper motor’s rated voltage to achieve higher step rates Intelligent chopping control that automatically selects the correct current decay mode (fast decay or slow decay) Over-temperature thermal shutdown, under-voltage lockout, and crossover-current protection Short-to-ground and shorted-load protection (this feature is not available on the A4983) Like nearly all our other carrier boards, this product ships with all surface-mount components—including the A4988 driver IC—installed as shown in the product picture.





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