Demand Peripherals     Robotics and Automation Made Easy

PD25: Power Distribution Card

The PD25 power distribution card is a break-out card which makes it easy to control, protect, and distribute power from a battery.


- Up to 25 Amps
- Up to 48 volts
- Fused with automotive style fuses for easy replacement
- Battery connection using #6 brass bolts or 15 amp screw terminals
- Four 15 amp output screw terminal connectors
- 5.5/2.1 mm barrel connector for 2 amp battery charger
- Either horizontal paddle or vertical toggle on/off switch
- Connector for a remote on/off switch
- Connector for battery voltage sense



The PD25 can handle up to 25 amps and has a fuse to limit the maximum current. The card uses an ATO blade style automotive so you can easily set the maximum current you want.

The PD25 provides a low current on/off switch which in turn controls five 20-amp AOD409 PMOS FETs. The FETs act as a kind of power relay for the card and using PMOS FETs lets the card switch the "high side" of the battery. Switching the high side of the battery lets you use battery ground as system ground.

A two terminal input lets you control the device remotely. This is handy for switches that have to be mounted away from the card and for timed on/off using a real-time clock card.

Power output is on four mechanically secure and easy to use screw terminals. Each screw terminal can handle at most 15 amps and the sum of all the currents through the screw terminals should not exceed 25 amps or the fuse value.

Battery charging is made easy by the inclusion of a 5.5 mm barrel connector that is tied directly to the battery. Current into this connector should not exceed 2 amps.

The input battery voltage can be sensed from two pins available on the PD25 card. The voltage is one-twelfth (0.083) of the battery voltage. The voltage sense is a little above ground and should be measured differentially for best results.

The schematic and layout of the PD25 are shown below. The Eagle schematic and board files are available here: pd25.sch and pd25.brd. The bill-of-materials file is available here: and pd25.txt.