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I'm having some trouble using a motor driver board. I'm pretty sure its being driven properly since there is ~3V @ the output v.s. none when its off. However it should be supplying ~2A (rectifier bottleneck) of current, rather than topping out at 120mA. I've tried both outputs, both give the same results.

I'm using this motor driver: http://www.amazon.com/gp/product/B00CAG6GX2/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1 enter image description here

I have both output enable jumpers in place, and have tried with and without the 5V enable jumper in. I tie one logic input to 5V and the other to GND. The driver is powered through a 5V DC-DC converter (~2A verified). Am I doing something silly, or is it likely a dead H-bridge?

UPDATE (moved from self-answer): I'm sorry for not being more specific. It turns out that for the 3v motors I was attempting to drive the L298 is not the best solution since it has a few volts drop at high currents, leaving the motors with almost nothing across them if using a rectified 3V power source.

Note: The following is based upon using the L298 on its own, NOT with the original board. I've tried increasing the voltage supply to 6V, and this seems to be working. I intend to increase to a higher voltage, as well as using pwm across a smoothing capacitor in parallel with the motor in order to give a proper output voltage while using a large enough source to account for the drop across the internal transistors in the L298.

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    $\begingroup$ If you have access to schematic can you please post a link $\endgroup$
    – Mahendra Gunawardena
    Feb 9, 2015 at 11:55
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    $\begingroup$ I'd add: how do you measure the sourced current? If you just plug an ampmeter between the terminals, it has resistance low enough that the chip may detect it as overload (short circuit) and engage overcurrent protection limiting sourced current to "sensing" level which determines if the overcurrent is gone. In that case measure the current in series with the intended load (motor). $\endgroup$
    – SF.
    Feb 9, 2015 at 12:37
  • $\begingroup$ @SF I've tried with the motors as well, and it doesn't seem to work. However, I will try using a pot to see when the current stops increasing. $\endgroup$
    – rasz
    Feb 9, 2015 at 17:02

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Make sure that the 12V supply is capable of sourcing sufficient current. This the source that powers the output A & B. The 5V input supply is most likely to power the logic circuitry. On PCB board 12V supply power supply should be routed to the H-bridge which will provide the voltage to both Output A and Output B as mentioned above.

Also when you are measuring current at output A or B make sure their a load. I suggest placing a 1K or 10K resistor. It is best that you select an appropriate load resistor representing the actual load.

Product Description from Amazon Feature

  • Chip: L298N
  • Logic voltage: 5V
  • Logic current 0mA-36mA
  • Storage Temperature: -20°c to +135°c
  • Operating mode: H-bridge driver (dual)
  • Drive voltage: 5V-35V
  • Drive current: 2A (MAX single bridge)
  • Maximum power: 25W
  • Dimensions: 43x43x27mm
  • Package includes: 1x L298N Module

References:

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