# Need help determining correct wire gauge

Discussion in 'General Electronics Chat' started by 3dOptics, Mar 15, 2009.

1. ### 3dOptics Thread Starter Member

Mar 15, 2009
13
0
1) Servo motor requires 5 volts DC and 500 mA. I need this cable to be 100 foot long. What wire gauge should I use?

2) I have another motor that uses 36 volts DC and 1.6 amps(max). This cable also needs to be 100 foot long. What wire gauge should I use?

Thanks.

2. ### leftyretro Active Member

Nov 25, 2008
394
2
Depends on how much voltage drop you can tolerate. Use the below chart to look up the ohms loss per 1,000 ft scaled to 200 ft (two wires remember) and use ohms low to calculate the voltage drop, what's left over is avalible for the devices.

http://www.powerstream.com/Wire_Size.htm

Lefty

3. ### thatoneguy AAC Fanatic!

Feb 19, 2009
6,357
718
For the 500mA (calculated at 200ft, as two wires are involved, doubled current for headroom)

• 16 ga stranded wire would have a resistance of 0.8Ω, giving an endpoint voltage of ≈ 4.2V after 200ft@1A

• 14 ga stranded wire would have a resistance of 0.5Ω, giving an endpoint voltage of ≈ 4.5V after 200ft@1A
For the 36V/1.6A (Calculated at 200ft, as two wires are involved, doubled current for headroom)

• 14 ga stranded wire would have a resistance of 0.5Ω, giving an endpoint voltage of ≈ 34.5V after 200ft@3A or ≈ 35.25V@1.5A

• 12 ga stranded wire would have a resistance of 0.3Ω, giving an endpoint voltage of ≈ 35V after 200ft@3A or ≈ 35.5V@1.5A