Can 12 volts - supplied by a car battery - be put through a 100 foot section of telephone extension wire that is rated at 26AWG? I figure if you have enough amps this should be OK.
I have the “Build Your Own Underwater Robot” book and they recommend #24 AWG for a 20 foot tether and if a longer tether is used maybe go with #22 AWG or #20 AWG. But a ROV builder used a telephone extension wire for his tether but did not give the length on his site. I will be getting a Multi-Meter soon to check this stuff out but in the mean time I would like to know what you people think.
Thanks for the replies. I just came across this control kit which will allow me to control 10 devices over two wires, and it’s only $30.00. But I will have to assemble it. I will also look into the basic transistor switching circuit as mentioned in post #2.
A lower gauge wire (smaller number means larger diameter) for the same given core material usually acts to decrease the resistance. The current rating is also proportional. powerstream.com/Wire_Size.htm
Increasing the resistance translates to losses in power P(loss);
P(loss) = R*(I^2) where Ptotal=IV
substituting I,
P(loss)=R(Ptot^2)/(V^2)
Therefore to reduce the loss, a higher voltage would help.
The book’s suggestion of a smaller gauge wire for longer distances seems correct. Hope this helps.
My first question here would be whether you are trying to push power to drive the motors through the wire, or just some control signals.
Low-level control signals should pass even long lengths of phone wire without any significant issues, but I would suspect that if you’re trying to drive anything with a significant current draw with a simple thin-gauge telephone extension wire, you’ll have problems.
I believe that you had previously indicated that you wanted to use a switchbox-type of arrangement to energize relays, which would in turn switch the current to your ROV’s motors. My earliest introduction to control systems was similar - I was trying to use a switch at the end of a long wire (telephone extension wire, if I remember correctly) to complete a circuit that would energize a relay remotely. I was shocked at how large a battery I needed to get the relay to activate due to line losses over such a long circuit. A short while later, I learned about using a basic transistor switching circuit to translate small signals into larger ones, and things became much easier very quickly.
Then again, I don’t know all the details of your particular application, so your mileage may vary.
