AWG Wire Size and Voltage Drop

What formula can I use to work out that I am using the correct 7 core cable for my system and also determine its voltage drop?

With the 7 core cable the solenoid only uses two wires one for +24 and one for GND, the other 5 are used for USB to Arduino. The 7 core cable is incased in corrugated tubing. I do need the external diameter of the 7 core cable to be less than 6 mm if possible, no larger than 7 mm. Voltage drop between 1- 3%.

Solenoid Specifications:
Volts: 24 VDC
Solenoid Temperature: 14 Celsius maximum
Resistance: 15 ohms
Amps: 1.6 Amps (I am using a 2 amp power supply with an additional 3 Amp fuse wired to the solenoid)
Length: 1 meter is the 7 core cable + & - then from GX16 to DC socket is a 1 meter 26 AWG wire for + & - (not sure if correct to use 26 AWG)

Cable Specifications (need to determine if these are the correct specifications):
Cores: 7
Wire Gauge: 24 AWG
Conductor Area CSA: 0.2 mm²
Max Recommended Current: 1.75 Amps per conductor @ 25 Celsius
Max Operating Voltage UL: 300 V RMS

The 7 core cable is in corrugated tubing.


Hi Tom
Basic ohms law. Voltage drop = current X Resistance. Voltage drop in Volts, Current in Amps and resistance in ohms.
If you are using a 2A switch mode power supply it will probably stop and die before the 3A fuse blows
Max recommended current is to prevent wire overheating, nothing to do with voltage drop.
24AWG wire is 84.208 ohm per kilometre or about 0.1 ohm per metre. at 1.6A a voltage drop of 0.16V. Remember there are 2 wires here so total drop would be 0.32V which should not worry the solenoid at all but wire temperature should be considered if enclosed with any other heat producing wires in close proximity. Mutual heating is something often overlooked.
26AWG seems a bit small for power. Depends on the current involved. Why are you changing wire sizes. If only a few mA should be ok but I personally would probably stick with 24AWG.
Cheers Bob

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