2.1 General Description
The Designer Systems pHAT-RV is a fully featured remote vehicle driver solution with four [4]
unipolar stepper motor drivers, four [4] servo motor drivers and Lithium battery power
control features. Specifically designed for the Raspberry-Pi Zero (other Raspberry-Pi boards
fully supported) the pHAT-RV features Lithium battery power regulation, a battery charging
system and high speed I2C communication for easy project integration.
pHAT-RV supports the majority of analogue servos and unipolar stepper motors (selectable 1
or 2 phase) and also provides global activation of new motor positions & movement complete
registers for superior control. Motors can be fully speed controlled, reversed, started/stopped
and stepper motors stepped with up to 65535 steps.
pHAT-RV provides a 5V @ 1A power supply (link selectable) to power the connected R-Pi Zero
and features an on-board Lithium Polymer charge controller that can charge the battery at 1A
(2000mAh min capacity) from an external 9-12VDC power adaptor (not supplied).
Due to compact form factor, ultra-low power consumption and extended temperature range,
pHAT-RV is a best choice for a wide range of robotic applications.
The module fully complies with the RoHS directive of the European Union

2.2 Key Features
The following table describes the key features of the pHAT-RV.
Table 1: Key Features
Features Details
Servo motor 4 x Analogue (standard)
Servo Voltage 6.0 ~ 7.4V
Servo Power 2 Amps (stalled)
Servo Control
 Enable/Disable/Reverse
 Soft Start
 Position with speed control
 Position complete flag
Servo Connection 4 x 3pin header (standard)
Stepper motor 4 x Unipolar stepper
Stepper Voltage 5.0 ~ 7.4V
Stepper Power 600mA per phase max.
Stepper Control
 Enable/Disable/Reverse/Stop with/without holding torque
 Full/half step selection
 Continuous step with speed control
 Step 1-65535 with speed control
Stepper Connection 4 x 5pin JST ZHR 1.5mm pitch
Lithium Battery Voltage 7.4VDC nom.
Lithium Battery Capacity 2000mA/h (2A/h) min.
Lithium Battery Charge 1A @ 8.4V max.
R-Pi Output Voltage 5.0VDC ± 0.1V
R-Pi Output Power 1A max.
I2C Speed 400kHz max.
Environmental Operating Temperature -10℃ to 50℃
Dimensions 65 x 30 x 8.5mm
Weight 14g approx.

3 Application
3.1 Stepper Motor Connection
The stepper motor connections are marked ‘MOTOR 1’ to ‘MOTOR 4’ and consist of a five (5)
pin JST ZHR 1.5mm pitch connector, see section 3.4.3 for pinning.
This connection is standard for most 24mmD stepper motors, such as the DS-STMOT1, but
there is also a pre-made 200mm JST ZHR cable available, DS-STCAB1, and the JST ZHR mating
receptacle and pins are also available from Farnell electronics as items 2078162 and 1830898
respectively.
Most unipolar stepper motor phases are wired as follows:
It is recommended that you double check your motor phase connections before power
application. Six wire stepper motors are also supported by connecting the two centre taps
both to MOTOR +.
3.2 Servo Motor Connection
The servo motor connections are marked ‘SERVOS’ from 1 to 4 and consist of three pins
marked ‘GND’, ‘V+’ and ‘SV’. Analogue servos should be connected to these pins, noting
polarity, BLACK is normally GND, see section 3.4.4 for pinning.
3.3 Raspberry-Pi Board Support
The RV supports all of the current Raspberry-Pi board versions. However, when powering a
Raspberry-Pi from the RV there is a 1A power limitation on the 5V supply from the RV. This
means that some Raspberry-Pi boards such as the newer Model 3 B & B+ may struggle to
operate correctly especially when other peripherals such as USB keyboards/mice/drives are
connected. The RV is not designed for these types of applications and the 5V supply will shutdown
if overloaded.
3.4 Operation
When the Lithium Battery is connected to the XT60 connector 5V power will be delivered to
the connected Raspberry-Pi board and it will boot normally.