Break Out Box Design Notes
This page contains random notes we wanted to save on the design of the break-out box.
Notes on the Schematics
- LED channel indicator
- LSDiodes 5mm T1-3/4 Green
- 3.3V 20mA nominal
- Calculating the limiting resistor for the indicator diode:
- 1N4148 @ 20mA has a 1.0V forward drop
- 8V supply
- MOSFET = IRF3709 has a
negligible on-voltage drop
- LED + diode have 4.3V forward drop
- need 3.7V resistor drop
R=V/I R = 3.7/0.020 = 185 Ohm
Using actual 200 Ohm
- Jumper wires are 12 gauge (These are used for a number of high-current internal connections on the PCB)
- 16AWG wire for high-current connectors (Wires from the PCB to the high-current connectors.)
Cable and Connector Pinouts
- Signal Cable Pinout
The signal cable connector is designed for a 9-wire cable.
We've wired it with a cat-5 cable (4 twisted pairs).
We've left channel 5 unwired as a result.
- Solenoid Cable Pinout
The solenoid cable is a simple two-wire power cable.
The + wire is connected (through a fuse) to the positive supply voltage. The Vsw signal is switched by a power MOSFET to ground.
- Power Cable Pinout
The power cable is designed to conform to the solenoid cables. Thus solenoids can be tested by simply connecting the power cable to a solenoid cable, bypassing the break-out box.