Digital ammeter power supply - problem
Iím in a bit of a dilemma, can anyone give me any advice?
I am trying to wire a Digital Panel Ammeter via a shunt which is not the problem, the problem is the power supply for the ammeter, it cannot be from the same source it is measuring otherwise it just shorts out. Is there a device I can use to take the power from the same source, reduce it to 5 volts DC and separate it to power the ammeter? I donít really want to use a separate battery to power the ammeter. The source is the engine battery, thanks in advance.
"Isolated DC-DC converter" is what you need.
e.g. NME1205S - 200ma at 5V from 10-15V in (15V is the absolute maximum input voltage for this one though).
RS DC-DC converter
Many others in a similar vein. Just connect 12V to 2 pins and it gives out a completely isolated 5V from the other 2 (see the datasheet on the above link for which pin is which).
That's what I would do, make sure you get an isolated one as per that example, there are others around where the 0V is common. Bear in mind these things contain high speed switching circuits, so check sensitivity of VHF, GPS and so forth is not compromised. Navtex can be very susceptible.
Originally Posted by misterg
Cheers lads, many thanks.