Omnivorous supply question.

[itsmoked]

I need discussion.

This is a product that will be tacked to the wall by an electrician or technician. They will run conduit to it and wire it.

I am trying to make it omnivorous with respect to power sources.

I am having the usual fusing issues 120 verse 240(USA).
I want it simple.
I am seeing issues with fuse sizing and in certain configurations, having a fused neutral.

Have you got any ideas.

Note: Ignore any component values or part numbers, they where just yanked into the schematic.

Note: This supply needs to provide a power of only about [red]3 or 4 Watts[/red]!

Note: The output can be between 10V and 40VDC as it is a feeding a switcher that will create 5V for all internal requirements.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[davidbeach]

I think you forgot to post the sketch/diagram/etc.

 

[MacGyverS2000]

Didn't we have a discussion a couple of months ago about putting fuses on the neutral line?

Also, I don't know if it would be an issue (connector type, etc.), but what if someone tried to hook up 120/240 to the 12-24VDC input? I would consider some form of clamp there if it's a possibility...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[itsmoked]

Picture is there David. You must concentrate to see it. LOL

There are limits to idiot proofing Dan.

I don't spend the money when the end user being 8~10 dumb, (on a scale of 0-10), results in obvious damage that will not be covered under warranty. If it would cause inexplicable damage I do spend on it.

All three transformer fuses are not expected to be used. If the neutral fuse is removed then there is no fuse on one of the hots during 240V usage. (argh)



Keith Cress
kcress -

http://www.flaminsystems.com

 

[itsmoked]

Okay here's a design that was completely VDE/UL'd.
(I am not lobbying for that dang 120/240 disaster switch.)

It has a single fuse and takes both 120 & 240 sources. This means if the fuse blows one side of the transformer can still be hot. Device stops. This means in my first picture it would seem I could do away with F3 (down from the top).

I may also be able to wire the system for 240 in and 24VAC out and then just let them hook 120 at the same terminal (100-240V) as 12VAC can still run the device. I need to think about that. It reduces the idiot factor even more and drops off one terminal block. Reduces the instructions too.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[VEBill]

For the AC-to-DC aspect, I have numerous tech-toys that have universal AC adapters, accepting 100 to 240 VAC 50-60 Hz input and producing various DC voltages output.

A crystal clear example is the sort of PS brick used with laptops (anything AC in, often 15.6 VDC output at several amps). And they accomplish this with no requirement for jumpers nor switches. And they're covered with approval emblems from every corner of the globe.

The possibility I'm suggesting would be to purchase-in that part of the PS. The LV DC input would be added after - as you've shown.

 

[waross]

I was going to suggest the 240 volt only option,and was happy to see that you were considering it.
How about a 2 pole breaker instead of the fuses? That handles the neutral problem.
From the field prospective, make it very clear that the input is suitable for both 120 and 240 volts. I have seen good electricians confused by such equipment when the instructions were not clear. A lot of time is wasted and mistakes happen out of confusion.
Good electricians are a pleasure to work with. I can handle bad electricians. The excitement comes when an electrician that I thought was good turns out to be bad.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[davidbeach]

Well, it shows up now (at home), but sitting in the Denver Airport 5 hours ago there was no image, or the connection was so painfully slow that the image never loaded.

 

[itsmoked]

VE1BLL; First place I went. Would be easy if it was only affordable. 4W. No one wants to service that market. The smallest AC/DC would be about $30 that adds $90 to the price. I can do this for about $14.

Bill I am very sensitive to labeling. I spend extra money to make it clear. I think I will go for one fuse and 100-240 to just 2 screws. I need to model it.


Denver.. It's slow because the speed of light over such large facilities turns out to be too slow.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[roydm]

Did you mean to label the 240V input terminals L1, L2 requiring 2 fuses or should it be L1, N requiring only 1 fuse (for 230 V phase to neutral e.g. Europe).
Why would you supply it from 240 in NA when you have 120 & Neutral?
Just a minor point, I would use 2 terminals and a voltage selection jumper with one fuse otherwise when on 120 V you have 240 AC on the top terminal
Roy

 

[itsmoked]

Hi Roy.

[green]"Did you mean to label the 240V input terminals L1, L2 requiring 2 fuses or should it be L1, N requiring only 1 fuse (for 230 V phase to neutral e.g. Europe)."[/green]

If you are referring to the first schematic it would be L1/L2 as that is the common designation for 240 NAmerican power.

[green]"Why would you supply it from 240 in NA when you have 120 & Neutral?"[/green]

Many applications have no neutral. Some refrigeration control panels for instance, as everything runs from three phase.

[green]"Just a minor point, I would use 2 terminals and a voltage selection jumper with one fuse otherwise when on 120V you have 240 AC on the top terminal"[/green]

Good point. I added the bridge to the low voltage supply just to prevent generating 120/240 up on those terminals.

To get rid of switches and strapping issues this is what I'm thinking of using now:

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

Off the wall, but can you get enough current from a capacitor in series with a Zener diode? Yes there will be losses but a transformer is not lossless either.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

3W may be pushing that method a bit Bill. Besides for those over 24V sources I'd need the isolation as the product has lots of sensor inputs, etc..

Keith Cress
kcress -

http://www.flaminsystems.com

 

[burnt2x]

itsmoked,
I guess there is something wrong with the diagram you posted! Why do you need additional bridge rectifier after your tx rectifier? Maybe you could trim your costs by deleting the last rectifier.

 

[itsmoked]

Hi burnt2x; Those are both power supply inputs. You can supply the unit with line voltage OR 12/24 AC/DC. How else could I do it?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[burnt2x]

Okay, I got it. If the lower circuit is for DC supply, then you could just replace the bridge circuit with line blocking diodes (2), not bridging where you need 4 diodes.
hope this helps.

 

[davidbeach]

Could you bring your 12-24V input to terminals 5 & 8 of the transformer and just use one bridge?

 

[ScottyUK]

David,

If it was a 12-24V DC input then it would short through the transformer windings.

If it was 12-24V AC then there would be a back-energised primary with 120V and 240V present on it. Input connectors often have exposed pins when not mated to the other half so that would be potentially dangerous.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[davidbeach]

Scotty,

Yeh, I guess you're right. Maybe that's why I don't do any of that wimpy wire stuff...

 

[VEBill]

Are there now manly 'wireless' power supplies?

;-) !!!