I'm building a lamp and want to integrate an analog voltmeter (0-300 volts AC) in to the circuit. It has an LED backlit dial that requires a separate, 6.3v power supply. Any suggestions on how an idiot (that's me) can pull this off inside a very small wooden box that I am using for the base of the lamp?

  • \$\begingroup\$ 4 x aa batteries and a switch comes to mind. \$\endgroup\$ Commented Apr 14, 2015 at 17:31
  • \$\begingroup\$ Bridge rectifier, zener diode, resistor? \$\endgroup\$ Commented Apr 14, 2015 at 17:46
  • \$\begingroup\$ Not exactly what I was going for. The lamp will have 4, 15 watt light bulbs that plugs into a regular 120vac outlet. I was going to splice the voltmeter into the power cord. I thought maybe a small transformer would do the job. \$\endgroup\$
    – user72285
    Commented Apr 14, 2015 at 18:06

1 Answer 1


You could use a small 4.5v transformer with a bridge rectifier and filter, but that would be overkill. And a transformerless design most probably too dangerous, so yes, go with the batteries.

  • \$\begingroup\$ OK, well the case that the meter will be housed in does not open so the battery option won't work because there will be no way to change the batteries. Guess I will go with a meter that has an integrated incandescent light. It won't look as good (can't find a round one) but if I can't supply it from the same source as the lamp, then it is pointless. Thanks for the advice. \$\endgroup\$
    – user72285
    Commented Apr 15, 2015 at 5:00

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