Wiring and Physical Specifications
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[edit] Technical Specifications
Technical Specifications - Power requirements, etc.
[edit] Wiring the I/O
The BCS-460 has the following Inputs and Outputs available:
- 6 Discrete Outputs (Outs)
- 4 Discrete Inputs (Dins)
- 4 Analog Temperature Probe Inputs (Temps)
- Expansion Port for Future Upgrades
The BCS-462 has the following Inputs and Outputs available:
- 18 Discrete Outputs (Outs), (6 PWM + 12 on/off)
- 8 Discrete Inputs (Dins)
- 8 Analog Temperature Probe Inputs (Temps)
- Expansion Port for Future Upgrades
Discrete Outputs (Outs) are rated at 5VDC up to 20mA each. The BCS is designed to control relays, and not to drive high current loads. A typical application is to use Solid State Relays (SSR) for this purpose. To control SSRs, wire the SSR Input positive (+) terminal to Out0 (or other Out) located in connector P0, and the SSR Input negative (-) terminal to GND, respectively. There are three identical GND terminals available, use the one that is most convenient.
| Tip: Solid State Relays (SSRs) do require heat sinks of some sort when controlling high energy, i.e., they must be fastened to a larger metal item than themselves. Use a heat sink paste between the SSR and the metal to help the heat dissipate. |
Discrete Inputs (Dins) are available for switches, push buttons, etc. They are also rated at +5VDC. To assert a Din, connect the Din terminal to the +5VDC terminal (presumably through a switch). To deassert the Din, simply disconnect the Din terminal, as there is a weak pulldown resistor that will pull the Din to ground.
Analog Temperature sensor inputs support thermistor based temperature probes. Probes must be NTC (Negative Temperature Coefficient) thermistors with a 10Kohm ambient reading. Users can connect any thermistor based sensor within these specs, by simply programming the temperature coefficients into the BCS that are provided by the sensor manufacturer. See Calibrate Temperature Probes
When wiring the temperature probes the polarity of the sensor wires is not relevant, the thermistors work equally well in either orientation. Connect one wire to the TEMP terminal, and the other to GND. Additionally extending the length of the temperature probes can easily be done due to the minimal resistance the extra wire adds to the circuit, so extending a probe to have a 20 foot (or more) lead can be done without impacting the accuracy of the thermometer.
The +5VDC pin is provided mainly for low current Din connections. However it can also be used to power external components, such as expansion cards or sensors, as long as they don't exceed the maximum current. The maximum current sourced from the +5VDC pin is 300mA.
In addition to the physical I/O, there are also 4 web button inputs that can be programmed and used in control algorithms.
[edit] Longer runs
The length of runs can be practically infinate for any realistic single premise use. The thermistor based probes are 10k(10,000) ohm resistors and any wire offers less than a ohm of resistance at run lengths of 1000 feet(taken from: http://www.powerstream.com/Wire_Size.htm based on 32 gauge wire). Runs of 60 feet with cat-5 controlling 2 ssr's and reading a single temperature probe on a single cable have been successfully used.
Keep in mind as the run length increases the likelihood to go near a magnetic field increases(specifically compressors on refrigerators). If this is an issue the use of a shielded cable for at least the portion that passes the magnetic source should be used for the temperature probes as the values will fluctuate noticeably as a result of the magnetic field. Radio Shack sells some stuff that has been successfully used to fix noticeable fluctuations in the past. radio shack wire
Each piece of cat-5 cable has 8 individual wires, offering a number of possibilities, in particular you could use a single wire as a shared ground on the cat-5 and have the remaining 7 wires available for whatever nefarious purposes required...
