User manual

Figure III.1 H-Bridge Switching Device

In the design of the MDM5253, only one PWM control signal is required to control both the direction

and the magnitude of the output for each channel. The H-bridge’s diametrical opposite pairs (control

input 1 and 4, control input 2 and 3) are connected and driven HIGH and LOW together, and the two

pairs are controlled with strictly inverted signals.

Figure III.2 shows the relationship between the PWM duty cycle and system output. The zero average

output occurs when the duty circle is 50%. The direction of the output (in speed control, for example,

the direction of rotation) depends on whether the duty circle is larger than 50% or lower. The

magnitude of the output (rotation speed in speed control) depends on the absolute difference

between the duty circle and 50%.

Figure III.2 Theoretic waveforms of PWM control for the MDM5253

In addition to the PWM control, the MDM5253 can connect up to 3 sensing feedback devices (e.g.

MRS3302). DC motor control schemes, such as position and velocity control, can be implemented by

installing feedback device on DC motor and connecting these devices to MDM5253.

III.2.2 Running as Part of WiRobot System

When using the MDM5253 with the WiRobot system, users simply plug the module onto one of the

DC motor drive expansion connector sets on the PMS5005 Sensing and Motion Controller board

(maximum of 2 MDM5253 modules are supported) and the PMS5005 on-board firmware and device

driver will take care of the motor control and sensing feedback. Since PMS5005 can support 2

MDM5253, it is able to connect and control up to 6 DC motors and have 6 position sensor channels

(POT1-POT6).

Users have an option to use single rotary sensor (e.g. MRS3302 on the Position Sensor Connector),

dual rotary sensor (e.g. 2 MRS3302 on 2 Position Sensor Connectors), or single encoder (Encoder

port on PMS5005) as the feedback device to control each DC motor, if needed. PMS5005 already

has built-in DC motor control schemes and users simply need to select the type of the feedback device

for each DC motor. Note that for single rotary sensor setting, DC motor 1 must use POT1, DC motor 2

must use POT2 and etc.; for dual rotary sensor setting, DC motor 1 must use POT1 and POT6, DC

motor 2 must use POT2 and POT5 and DC motor 3 must use POT3 and POT4; for encoder setting,

DC motor 1 must use ENCODER1 and DC motor 2 must use ENCODER2.