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H Bridge

2. The device

2.2. H bridge and indicator LEDs

The H bridge is built by using N-channel MOSFETs (FDP7030BL). The diodes in the schematic are there to protect the MOSFETs from back EMF. The actual H bridge circuit is placed on the stripboard, which acts as a lower lid.

LEDs on the upper lid are not connected to the output of the speed controller. This would interfere with the functionality of the circuit. Instead, they are operated by a 3-way switch (on-off-on), which also controls the H bridge.

It is important that the current always goes through the load (DC motor). All the MOSFETs are not to be turned on simultaneously. Therefore the correct wiring on the switch is essential.