Gasboy Gilbarco Interface Unit - Manual (Page 41)

Gilbarco Interface Unit v2.1 Hardware 33
Gasboy CFN Series
Current loop driver board
The current loop driver board (part number C05374 or kit C07249) contains two current loop
ports, a 5V to 40V dc-to-dc converter that supplies power for two of the current loops, a battery
to back up CPU board RAM, battery trickle charger, battery fail detect, and DC power fail
detect. The board draws 5V power for battery and control through P3, and 5V power for the
current loop supply through P4. Signals are passed through P3. Current loops plug into P1 and
P2. Board ratings are shown below:
Power: +5v, .3A nominal, .6A Maximum at P3
5v, .9A nominal, 1.2A Maximum at P4
Current Loop Outputs: 40 mA nominal at idle, 45V maximum open loop voltage.
Baud rate is 5800. Current loop will endure short circuit
operation indefinitely with 40 degree C rise in current source
transistor temperature.
Battery: 3.6V nominal, 110 mA-hours charge. Backup time at .1 mA
nominal exceeds two weeks.
Battery fail: Indicates failure if battery fails shorted, battery fuse is blown
or battery jumper is missing.
Powerfail detect: RESET asserted if DC power falls below 4.65V nominal. Trip
level is screwdriver adjustable.
Status LEDs: LED #1, red, on if battery low or fuse blown or jumper
omitted. LED #2, green, on if battery OK. LED #3, green, on if
5V DC OK.
The interface board has undergone three revisions. The only boards that should be continued
in service if difficulties are observed are the revision 3 boards.
Jumpers
These are the functions and settings of current loop driver board jumper positions K1 and K2:
Jumper Function
K1 Baud rate clock source. Must be installed in position 1.
K2 Battery backup enable. Boards should be stored with this jumper out. It should
be installed at assembly time. The red battery fail lamp will light if K2 is
omitted.
Fuses
Fuses F1 and F2 protect the current loops. These are 1/8 amp picofuses. A blown F1 or F2
indicates a blown transistor Q12 or Q13, or other serious circuit malfunction.
Fuse F3 protects BATT1. A blown F3 usually indicates a momentary short from the positive
side of the battery to ground. Lamp I1 will not go out while power is applied if fuse F3 is blown.
F3 is a 1.25 amp Picofuse. Smaller values may be used, as maximum working current is less than
20 milliamps.
P1 and P2 current loop connectors
These connectors each provide an active current loop port. The loops expect less than 20
milliamps for an active state, and up to 48 mA for an idle state. Current loop power and ground
are fully isolated from logic power and ground. Transient suppressors prevent excessive voltages
being generated across loops. This table shows the pinout on P1 and P2: