Quick question, how do I supply +-5V?

...

: I don't know what you people are talking about. : Back to my question, how do I make a +-5V?

'Buy one' is the most sensible suggestion I've seen elsewhere on the thread.

*BEWARE* Another one I've seen mentioned is to get 2 stock 5V supplies, A and B, and connect the +5V of A to the 0V of B, and call pair this 0V, thus making the 0V of A -5V and the 5V of B +5V. *BEWARE*

This may or may not work - many lab power supplies and some bricks conenct the 0V from the DC side to the mains earth, so doing this with two such supplies will cause funny noises, bad smells and possibly worse as the magic smoke escapes.

If you're not sure, don't try ths aproach!

--
cds
Reply to
c d saunter
Loading thread data ...

The bricks I've used have always isolation, but I live a relatively sheltered life. Where have you seen them, mainly?

--
Regards,
  Bob Monsen
 Click to see the full signature
Reply to
Bob Monsen

: The bricks I've used have always isolation, but I live a : relatively sheltered life. Where have you seen them, mainly?

Some of the transformer based ones I have at work are - mind you I'm in the UK where almost everything has an earth (mechanical interlocks stop you plugging anything in without the third pin...) - I'm guessing this isn't an issue in places like the USA as the various American bricks I've accumulated don't have an earth pin...

Cheers Chris

Reply to
c d saunter

I know that you Brits have a very positive outlook, but there surely must be a way to supply a negative voltage?

Jerry

--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
Reply to
Jerry Avins

So, wall warts almost never have an earth, even in the UK! Our wall warts usually have a plastic 'earth' pin to overcome the interlock. Most power supplies that are a separate 'brick' connect with a two wire connection to the mains, live and neutral, as in the US. Here's a photo of a UK mains lead for this:-

formatting link

In the UK, such things are called 'double insulated', see :-

formatting link

That said, some bricks do have an earth connection as Chris says. These often use a IEC connector like this:-

formatting link
Dunno if the output 0V is connected to this earth. I suspect not in most cases.

All the bench DC power supplies I've used, both in the UK and in the US, have separate isolated 0V and earth, usually connectable with a bit of metal.

FWIW, Syms.

Reply to
Symon

My first reply would be "buy one". Cost of a PSU is a lot less than the cost of an average board...

Otherwise, and assuming your load is less than ~40mA, you can use the circuit in

formatting link
with a 10v supply. Be careful to separate GND's (since the GND of your +/- 5V is really at

5V....)

Simon

Reply to
google

I have quite a lot of experience with power supply modules (the "open frame type") and I dear say that for instance NONE of the types offered in the Farnell catalog have their - or 0 connected to the PE. From a manufacturer's point of view this would be absolutely stupid because it means that he would have to have two types of each model, one with the + to PE and another with the - to PE. Also in lab supplies you will always see an extra ground terminal, often between the + and - and possibly with a supplied bracket between the ground and -.

Besides, many applications need a complete separation from mains, even from ground. So that is another reason for manufacturers not to connect the - to PE(ground).

Meindert

Reply to
Meindert Sprang

You are quite right. We had to pull our power supplies apart and disconnect the mains earth connection or they would get very hot. They have been in service for 5 years now and are still running OK.

Peter

Reply to
Peter

For any low level measurements, the PE is badly polluted by the noise from switching mode power supply EMC filters etc. For this reason, a separate technical earth (TE) network is often used with only a single contact point between the neutral, grounding electrode and PE and TE earths.

A single power supply with the DC side connected to PE would pollute the whole TE network and you would very quickly get rid of such power supplies.

Paul

Reply to
Paul Keinanen

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.