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As a part of a measuring project by a mobile phone on the top of a 100 meter tall mast, the mobile phone will be powered by 5V DC of a DC-DC converter output where its input voltage is 12V DC on the ground.

schematic

simulate this circuit – Schematic created using CircuitLab

There are many reasons to use DC-DC converter but some of them are power efficiency and isolation of the input and output grounds which I guess is good for long distances.

So the converter and the mobile will be in an enclosure on top of a mast. In terms protection such as type of enclosure, ESD, lightning protection ect, what type of extra interface would be a good practice along with the diagram above? I marked the terminals. And does the 100 meters cable need to be twisted and shielded? Which specs should I consider to look for a DC-DC converter for such application? Do most of them have isolated input output grounds? Does anybody have experience with similar scenario?

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200m of 1mm diameter cooper wire have a 4 ohm resistance, you have to take into account the voltage drop on the line. If you need 2A at 5V the current through the line will be above 1A and the voltage drop above 4V, that means you could get under 8V at the top.

You can find insulated DC-DC converter modules at Farnell but most have a minimum input voltage of 9V which can be an issue if you use thin wires as you see above. If you're not tied to 12V then you can use a higher voltage which will really reduce the losses.

I don't think twisted or shielded wires are needed. A lighting protection yes but it's out my area of expertise.

Somehow you have to join the source and phone ground using a high value resistor 100k to 1M to avoid accumulating static charges in the insulated phone area which can damage the converter.

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