Hardware Description
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SLCU002 – September 2016
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BOOSTXL-ULN2003 Dual Stepper Motor Driver BoosterPack Hardware
2.6.2
Disabling the On-Board LEDs
Figure 16
shows the section of the board with the LEDs. The R5 resistor is labeled
LED ENABLE
because
when a 0-
Ω
resistor is populated here, it allows a path for current flow through the LEDs. The on-board
LEDs can be disabled easily by depopulating this R5 resistor.
Figure 17
shows the resistor depopulated,
so there is no longer a path for current to flow through the LEDs, thereby disabling them.
Figure 16. Board Image of LED Section
Figure 17. LED Section With R5 Depopulated
2.6.3
Enabling Quick Inductor Discharge
The ULN2003A has internal flyback diodes to suppress voltage spikes due to inductive kickback. Stepper
Motors and relays have inductive kickback that is suppressed by these internal diodes. The rate of
discharge of the inductor is also directly proportional to the voltage across the inductor when discharging.
Figure 18
shows the section of the board near the COM pin of the ULN2003A device. Diode D5, also
labeled
Flyback COM diode
, is a 12-V Zener diode that is in series with the internal flyback diodes of the
ULN2003A. Normally there is a 0-
Ω
resistor (R14) in parallel with this Zener diode, also labeled
Diode
Bypass
, effectively bypassing the Zener diode. To enable the quick inductor discharge, the
Diode Bypass
resistor (R14) should be depopulated.
Figure 19
shows the board with this resistor depopulated, ultimately
enabling quick inductor discharge.
Figure 18. Board Image of COM Diode Section
Figure 19. COM Diode Section With R14 Depopulated
