How to convert 270 Ac volts in to 5 Dc volts

Try using a DC power supply of the VA size equal or greater than than load to be served.

We have a 277 volts coming out and we need to install an electronic sign that only uses 115 volts.

Can this be converted to 115 volts

Try using a DC power supply of the VA size equal or greater than than load to be served.

Could you please explain this is layman terms

This current is coming from parking lot lights. We are trying to avoid trenching under the road

you could tap the circuit that supplies the poles...
mount a small transformer on the pole or preferably at the sign.
What is power requirement of the sign? 115 volts AC and how many amps?
Volts x Amps = the VA requirement of the transformer.
sounds like you could use to hire an electrician?

By the way, if the pole lights are controlled by an integral photocell the sign will be on all the time...
If they are controlled by a contactor the sign will only be on when the lights are on...