Power supply
Iono Pi can be powered with DC voltage only:
✓
DC: nominal voltage range 9.0V to 28.0V.
Respect the correct polarity shown in the schematic diagram (+ -). The power supply
circuit implements reverse polarity protection using an auto resetting fuse and surge
protection up to ±500V/2ohms 1.2/50
μ
s.
A blue on-board LED, also visible through the front panel of the DIN-rail case, is lit when
power supply is available.
When a Iono Pi board is used, never connect the Raspberry Pi micro-USB power plug.
The Iono Pi power supply stage is optimised to deliver up to 3A total current at 5V.
Considering the amount of current needed to drive the relays and open collector outputs, it
could provide up to 2.5A at 5V to the Raspberry Pi. Because Iono Pi has a 1.1A resettable
fuse (polyfuse) on the power supply line, the maximum current that its regulator can deliver
is also limited by this fuse, and depends on the input voltage. The following table lists the
typical measured output current of the power supply stage at different input voltages, and
the corresponding input current.
IONO PI POWER SUPPLY STAGE TYPICAL IN/OUT VOLTAGE AND CURRENT
Auxiliary voltage outputs
Iono Pi has an auxiliary 5Vdc voltage output pin on the terminal block, labeled 5VOUT, to
supply power to external 1-Wire devices or other low-power loads. Never exceed the
maximum rated current of 50mA on this output.
Another auxiliary voltage output pin, labeled VSOUT, is also available on the terminal
block. It is intended as the voltage source for small loads connected to the open collector
14
User Guide
