Thread: Low Voltage Wire Questions

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I'm using some of the 12VDC/4rpm vent motors and wiper motors for props. I've found lots of information on motors and power supplies, but not much about wiring. So here are some questions for you electronics gurus:

What gauge of wire should I use for the 12Vdc vent motors?

What gauge of wire should I use for the wiper motors?

I'm making a prop using 2 of the vent motors. The controlling switches and power source (12VDC, 8A) will be 60 +/= feet away from the motors. Will I need to use a heavier gauge wire for this longer distance?

Any info would be much appreciated.

This chart was for electric security door locks, but it should work for your application as well. You just need to determine how many amps you will be pulling between your 2 motors.

I personally would go with a 12 gauge wire. 14 gauge is for something more like a light bulb. It is not the voltage that I would worry about, but it is the amps in your case.

The first thing you should do is figure the TOTAL amperage of all loads concerned. Then figure the distance, you have done that already, and use a chart like Diabolik has posted. As Skeered stated 12 gauge would handle almost any thing you could through at it . But, my question is what are you trying to do, how many props are you trying to trigger at once. As an example you could run 60' of 12 gauge to a terminal strip. This will power the props. from there you could run a much smaller gauge wire going to each prop via a relay or some sort of controller. You could use a 16 gauge wire to energize the col of a relay and a short piece of 12 gauge to actually run the prop. If you have any more questions that I can help you with please pm me and I'll try to help you . Hope I did'nt confuse you !!

For long runs the issue will be impedance in the wire. I've successfully used 18 ga. zip cord with 9 volt batteries to run small motors (~100mA load) over a 50' run. The rule is the smaller the wire, the higher the impedance. For example, a 12" length of solid/stranded 30 ga. wire can have as much as 5 ohms impedance, depending on the alloy used in the wire. The 12VDC vent motors probably don't pull much current - I'd go with 16 - 18 ga. lamp cord. Even with the inrush current load on startup, you should be fine.

Okay, here's what I have in mind.

I'm making a scarecrow that can move it's head up and down and from side to side. I want to use these motors as 'servos' for the movement



And use this joystick switch to control the motors. The joystick is made up of 4 SPDT snap switches:



and use 4 of these as cutoff switches to stop the motors at the end of their range of movement:



The scarecrow will be 50-60 feet from the house, at the corner of the intersection (we get a LOT of pedestrian traffic at this intersection).The power supply will be inside the 'control center'. 12VDC power will go via the joystick switch out to the prop motors. One of the leads from each of the 4 component switches in the joystick will run through the cutoff switches. These switches will turn off power to the motors when the head turns or tilts to the maximum of it's range.

I'll be using a mini camera mounted inside the head (via AV cables to a monitor) as the "eyes" to watch, listen to, and follow people, and possibly a small speaker inside the head as well.

The "control center" will have the joystick controller, a video monitor, and a headset with a microphone. I could possibly opt for an MP3 player with sound effects too.

If I get this up and running the way I envision it, I foresee big fun all throughout the month of October with this prop. Picture a pleasant fall day, when an unsuspecting pedestrian stops in front of my yard to admire my scarecrow. Suddenly, without warning, the scarecrow turns it's head and looks directly at the admirer, and says in a chilling whisper. "I seee you."
Another pedestrian is walking by and suddenly jumps when they realize that the scarecrow's head is turning to follow their movement as they walk past.