Wiring 12VDC lighting in a fire station


Old 09-03-18, 05:36 PM
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Wiring 12VDC lighting in a fire station

Hey everyone,

This is a little bit of a different setup than has probably been posted before. I'm currently building/have built an alerting system for our station to alert the crew members when there is a call. Basically how the system works is, a radio waits for a certain tone to be played over the radio, the radio then grounds a trigger pin which trips a relay/timer that triggers an alert tone to play through speakers in the station. After the tone plays the radio opens up the radio audio in the station for about 30 seconds. Then the entire system closes up until it is triggered again.

What I want to do is also have lights turn on in the bedroom and day room when the tones go off. I can wire another relay timer into the circuit for the lighting.

Given our small budget I've been thinking about installing 12VDC light strips or some sort of 12v fixture. Maybe even 12V A19 bulbs in normal fixtures (Obviously marked as 12V only one the inside) I have seen other systems using this, but I want to make sure I do it correctly. The maximum distance would be appx 25-30', and the maximum amperage would be 2.5A. I was thinking of using CL2 rated 18/2 thermostat wire. This would be tied into the same 20A 12V power supply that powers the radio. The lights would only be on for 2 minutes at a time before the system auto-resets.

Anyone know if this would have any issues? Given the short distance and short time on I'm assuming the voltage drop would be minimal and there isn't any risk over overheating, but I would appreciate any input.
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Old 09-03-18, 06:08 PM
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I am not sure of how sensitive LEDs are to undervoltage. Some may blink; some may fail to light.

Using the 18 gauge wire, the worst case voltage drop within the wires you will have is about 8%. The loading of the transformer may or may not add more voltage drop. Good practice has not more than 4% voltage drop which in your case would require 14 gauge wires.
Old 09-03-18, 08:01 PM
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The current will depend on how many lights you will be running on each circuit. To limit voltage drop I would recommend running a separate cable for each room and combining them at the power supply. I would suggest using LED strip lights for light output and ease of wiring (Although you may need to connect the wires with solder) you can put them almost anywhere. You can even get them in red!
Old 09-04-18, 03:20 PM
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Be cautious about adding loads to the power supply for the radio. If anything happens, the radio won't work and the station wouldn't get any calls.

Suggest you consider a separate power supply for the lights and timer. And use a low current relay powered from the radio's power supply to trigger the timer and lights.

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