Raspberry power, which wire to choose?

Question

Electronics

I want to put it in the greenhouse in the country. The greenhouse is located approximately 30 meters from the house. The question is what cable to use for power to minimize the loss of DC power from the PSU that will be turned on in the house? 220 fundamentally do not want to pull.
I tried to use a twisted pair cable as a power cable - it let in 12 volts, at the other end I cut off the fan, the rotation power fell by 2 times. I don't want it to be the same with raspberry.

Answer 1

First of all, you need to determine what load you will connect to the power source. As I understand it, an empty RPI draws about 500-700mA . If you add additional modules there, the load will increase.
Suppose you load the source with a current of 1A. Let's assume that we don't want a voltage drop of more than 0.2V ( up to 4.8V ). Then the cable resistance should not exceed:
And the resistance of 1 meter of cable (taking into account the total length of 60m) - 3 mOhm.
You can see that this corresponds to a cross section of 6 mm ² . Even stoves are connected with wires of a smaller cross section!
Therefore, in this case, it is better to use a source of higher voltage. When using a 48V voltage source, it will be quite possible to get by with a twisted pair cable.
There is one more thing when laying a cable in open conditions - interference. In particular, during a thunderstorm, you can get a fairly large number of pickups. If, when using mains power, they are likely to go into the network without creating a large voltage due to the low internal resistance of the network, then when powered through a transformer, its relatively large internal resistance can greatly spoil the matter. This is important to consider

Answer 2

Do not connect the raspberry to a voltage higher than 6V! You run the risk of burning, despite the drawdowns. In your case, it is better to bring 12V to the greenhouse, and in the greenhouse, next to the raspberry, put a 5V DC-DC converter. Then you get a stable 5V and you can use wires that are not too thick.