www.hamgadgets.com
2014-01-17
ID-O-Matic III
18
Connecting to Your Equipment
Power
The ID-O-Matic III has two possible power sources. One is the terminal block, positions 1
(ground) and 2 (power). The other is the mini USB connector, which can be used to provide a
5V power source. Naturally, this makes it easy to set up the board – just plug it into your
computer’s USB port, and it will draw power from the computer.
The USB connector can be used as a source of backup power. Both a DC power source via the
terminal block and a USB power source can safely be connected at the same time - assuming you
take care to keep the grounds at the same potential! Diodes will keep one power source from
affecting the other, and the ID-O-Matic III will draw its power from whichever source has the
highest voltage. This means you could, if you wish, attach a 12V DC power source to the
terminal block, and put a mini USB plug on a small backup battery pack to keep the board
powered in the event of a failure of the main power source. Older mini USB cell phone chargers
are also suitable for powering the ID-O-Matic III.
Power input to the terminal block must be a stable DC voltage between 6 and 20 V. Although
the power input pin is protected from reverse polarity by a diode, care should be taken not to
connect power backwards – especially if you have any other equipment (like a computer or
repeater gear) connected! If you are just programming the ID-O-Matic, it’s a good idea to
disconnect everything from the terminal block before plugging in the USB cable.
Signal Levels
Each input signal is clamped by a series 1K resistor and a Zener diode before being fed to the
corresponding CPU pin. This protects the PIC input pin from damage due to over-voltage.
Signal levels
must not
be allowed to drop below ground, as this can damage the CPU. Input
voltages in the 0 to 20 Volt range are acceptable. It is safe to leave unused inputs disconnected.
Outputs are open-drain MOSFETs, capable of sinking up to 200 mA at up to 60V. These are
absolute maximum ratings, and I recommend keeping currents low if possible to avoid
overheating the output devices.
Summary of Contents for ID-O-Matic III
Page 1: ...www hamgadgets com 2014 01 17 HamGadgets ID O Matic III Assembly Setup and Use Guide ...
Page 26: ...www hamgadgets com 2014 01 17 ID O Matic III 26 PCB Layout Schematic Rev C ...
Page 27: ...www hamgadgets com 2014 01 17 ID O Matic III 27 PCB Layout Schematic Rev D ...
Page 32: ...www hamgadgets com 2014 01 17 ID O Matic III 32 ...
