Nekmech

Just finished adding a 12v 500ma transformer to my charger to power the DC meter. Seemed to be the easiest solution.

Thanks. Will do.

I looked at my transformer and I don't think I'll be able to do that although I like the suggestion. I'll try to remember it. This sounds interesting. I've never heard of a galvanic DC-DC converter. I'll look it up and see if it's something I can implement. It's either that or buying a new transformer. Thanks for the help.

Ah. Now I get it. Thanks.

Thanks for trying to help audioguru. The meter and charger don't share a common supply ground. The only part they have in common is the ac transformer secondary. How is this done in a tradtional power supply with digital readout?

Usually it does, but as I said, I hacked up a cheap one and am trying to supply it's power from the chargers transformer instead of from a 9v battery.

Hi, I'm new to the Forum so be kind please. I have a battery charger I built from a schematic I found a long time ago. Basically it's a transformer, bridge, filter caps, LM350K regulator circuit with an op-amp stage and current sense resistor. It works fine charging my lead-acid batteries. I wanted to add a DC panel meter to watch the charge progress, so I took a really cheap far-east type multimeter and hacked it. Instead of the battery I added to it a simple bridge, filter caps and a 7809 regulator. The multimeter ac source is coming from the same ac transformer which powers the charger. I jumpered the required pads on the multimeter to lock it into the correct mode and range I want. The DC meter works fine as long as I'm measuring anything besides the charger voltage. As soon as I measure the output voltage of the charger, the meter fluctuates all over the place. I was hoping to overcome the "floating ground" problem by taking the meters dc power feed from the transfomer, but it doesn't work right. Can I get some advice? Thanks.