Isolating DC-DC converter

[akis]

I have bought some cheap ammeters off China, but they require independent power supply. In the past I used similar devices by winding a few extra turns around a the main toroidal transformer, so as to get the required, isolated voltage.

In my current project I do not have a toroidal to tap, so I need something like a "DC to DC isolating converter". I have looked up the available ICs and there aren't that many: most DC-DC converters are non-isolating, ie they share a common ground.

I was thinking of making my own HF oscillator --> small transformer --> bridge+filter --> isolated voltage. But this requires a lot of components. It would need: op-amp, 6 resistors, 2 caps, external pass transistor, transformer, 2 or 4 diodes (bridge), filter cap.

Is there a better way to do this?

Thanks

[ovnr]

Just buy an isolated DC/DC module? I've been using some RK-0515S modules, which work fine for my needs. I'm sure there's something out there that'll work for you.

Just stop by Digikey and look for something suitable.

[Psi]

You can get pretty cheap 5V in 5V out modules which are isolated
http://www.digikey.com/product-detail/en/RBE-0505S/945-1653-5-ND/3461634

[David_AVD]

As the other have said, off the shelf isolated DC-DC converters are very common and not expensive.  Just be away that the cheaper ones tend to be "semi regulated" and may also have a higher minimum load requirement.

[Marco]

I have looked up the available ICs and there aren't that many

You didn't search right then, the most common are the ICs supporting flyback and there are a huge amount of those. Probably not worth it to do it yourself with the integrated modules available.

[akis]

I have found these which seem to be what I need: Murata MEV1 series, XPPower IA and IQ Series 1W. These are DC to DC *and* isolating, ie they have 4 pins, not 3.

[AmmoJammo]

Have you tested your gauges? Because the cheap ones I bought from China don't need an isolated supply.

[Monkeh]

I use these for such meters: http://uk.farnell.com/jsp/search/productdetail.jsp?SKU=1818325

There are a variety of input voltage ranges available. I strongly doubt you need the 3kV versions.

Have you tested your gauges? Because the cheap ones I bought from China don't need an isolated supply.

Some do. I think it's fair to assume he's found out the hard way.

[AmmoJammo]

Some do. I think it's fair to assume he's found out the hard way.

Might be cheaper and easier to just get some meters that don't need isolation though

[Monkeh]

Some do. I think it's fair to assume he's found out the hard way.

Might be cheaper and easier to just get some meters that don't need isolation though

I doubt it's cheaper to get another decent meter (three wire toys from eBay need not apply) than it is to buy an off-the-shelf DC-DC module.

[AmmoJammo]

Some do. I think it's fair to assume he's found out the hard way.

Might be cheaper and easier to just get some meters that don't need isolation though

I doubt it's cheaper to get another decent meter (three wire toys from eBay need not apply) than it is to buy an off-the-shelf DC-DC module.

Ah, his were ammeters, not volt meters anyway

I think we need to know specifically what he has, they're probably ebay spec anyway.. lol

[Monkeh]

Some do. I think it's fair to assume he's found out the hard way.

Might be cheaper and easier to just get some meters that don't need isolation though

I doubt it's cheaper to get another decent meter (three wire toys from eBay need not apply) than it is to buy an off-the-shelf DC-DC module.

Ah, his were ammeters, not volt meters anyway

I think we need to know specifically what he has, they're probably ebay spec anyway.. lol

I'm going to take a wild shot in the dark based upon prior experience: ICL7106/7 single-supply meters.