Hello everybody.
When I connect my DC motor directly to battery it consumes about 1A.
When I run it with h-bridge (L298N) it draws 0.5A but this h-bridge should be able to provide up to 4A.
What could be the problem?
The L298 has a voltage drop across its internal transistors that presents a lower voltage to the motor, thus the motor draws less current. You can compensate by turning the input voltage up (as long as you don't damage anything).
And an L298 is not going to provide anywhere near 4A unless you heat sink it (see our application note).
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The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons
Thank you for your replay.
What if I use L293 or SN754410 (I don't need more than 1A of current), will there be smaller voltage drop?
Which property in datasheet tells me how large the voltage drop will be? For L298 I found property "Total drop" which is between 1.8V and 3.6V for 1A current. It that a right property?
For other two I can't find any similar property.
No, they all have darlington output stages with 1.2V voltage drop or so under load on both high-side and low-side, so that perhaps 2 to 3V is lost (and much heat generated). These devices work best with 12 or 24V motors really, a MOSFET H-bridge is much better for low voltages like 6V. There is a real lack of suitable devices in through-hole format alas... I've used an LMD18200 before which is a 3A MOSFET H-bridge, but its expensive and needs 12V minimum...