I have been tasked with writing a software to calculate the maximum cable length of the fire detection loop, I am not a electrical engineer myself and therefore I am struggling with some of the calculation aspects, please help.
So having data:
- Wire type i.e. wire with cross sectional area 1.5 mm square has the resistance of 12.1 Ohms/km or 3.688 Ohms/1000 ft. Or for the USA folks 12 AWG.
- Vopmin (Minimum operating voltage) 17 V
- Voutmin (Minimum output voltage) 24 V
- Total devices current consumption i.e. 400 mA
We calculate the worst case scenario, i.e. all of the detection devices are based at the end of the line.
Having this data, how to calculate the Vdrop (voltage drop across the length of the wire). And the maximum cable length of this circuit?
Please if possible provide the formulas with the example calculation, thank you in advance.