Hypocritically off topic, help with things electrical please.

[Julian]

Trying to fit LED lights in the kitchen.  I want two strips of multi coloured and two white.  Jules expertly pointed out that the little controllers sold with the multicoloured strips are only rated for one strip and I want to run two.

No problem I thought and bought a higher rated controller and transformer.  On opening the transformer it's electronic, what ever that means, and requires a load of 35w to work.  It is not marked with positive or negative, just 11.6v output.  I understand for a normal lamp (for which the transformer is designed) the pos and neg are unimportant, but these LED strips are positive cathode so obviously polarity is important.

When I put a multi meter on the transformer output, it measured nothing ... needs a 35w load thinks I so I stuck a lamp on it (which lit) and tried testing for polarity again.  The merer still refuses to show any reading and obviously polarity.

Anyone any idea where I'm going wrong ... I'm obviously doing something stupid, but I'm not smart enough to work out what.

Can I damage these strips or the controller if I get the polarity wrong?

[Dickjotec]

Sounds like the transformer is outputting AC not DC. Try the AC reading on your MM and see what you get. You will need to put a rectifier on it to get DC.

Dick

[julesandtash]

You could try putting a diode in series with your lamp (use a decent current rating rectifier diode - 5A or so).
If it lights with the diode in either polarity then your transformer is putting out AC

If it lights with the diode one way round but not the other then you can work out which is the positive and which is neutral.

Alternatively, could you not use two controllers but just one remote. I'm pretty sure (although not tested this theory) that the remotes all use the same codes so, presumably, proving both IR receivers were able to 'see' the remote then both controllers would react identically.

[Julian]

Dick ... I tried the meter on AC and got a reading but only 0.7v!

The more I think about it, it may well be AC.  The transformer is for these dichroic 12v lamps ... are they AC or DC?

Jules ... I can just about handle rudimentary electrics, but electronics has always baffled me.  I think I can tell a diode from other components, but how would I know the rating?  My only source of parts will be electronic gadgets I have hanging around.

I did think of a separate transformer and controller for each strip and I also though that the signals would be the same, but they aren't always very responsive and would probably not control simultaneously.  Th one I bought is wireless instead of IR so the receiver can be tucked to the back out of sight.

[1958steveflying]

Trying to fit LED lights in the kitchen.  I want two strips of multi coloured and two white.  Jules expertly pointed out that the little controllers sold with the multicoloured strips are only rated for one strip and I want to run two.

No problem I thought and bought a higher rated controller and transformer.  On opening the transformer it's electronic, what ever that means, and requires a load of 35w to work.  It is not marked with positive or negative, just 11.6v output.  I understand for a normal lamp (for which the transformer is designed) the pos and neg are unimportant, but these LED strips are positive cathode so obviously polarity is important.

When I put a multi meter on the transformer output, it measured nothing ... needs a 35w load thinks I so I stuck a lamp on it (which lit) and tried testing for polarity again.  The merer still refuses to show any reading and obviously polarity.

Anyone any idea where I'm going wrong ... I'm obviously doing something stupid, but I'm not smart enough to work out what.

Can I damage these strips or the controller if I get the polarity wrong?

You wont damage the strips by putting the wrong polarity across them they just wont light, you will need a 12v ish dc supply for them to work.On the other hand the controller is likely to get damaged from wrong polarity.

[Julian]

Trying to fit LED lights in the kitchen.  I want two strips of multi coloured and two white.  Jules expertly pointed out that the little controllers sold with the multicoloured strips are only rated for one strip and I want to run two.

No problem I thought and bought a higher rated controller and transformer.  On opening the transformer it's electronic, what ever that means, and requires a load of 35w to work.  It is not marked with positive or negative, just 11.6v output.  I understand for a normal lamp (for which the transformer is designed) the pos and neg are unimportant, but these LED strips are positive cathode so obviously polarity is important.

When I put a multi meter on the transformer output, it measured nothing ... needs a 35w load thinks I so I stuck a lamp on it (which lit) and tried testing for polarity again.  The merer still refuses to show any reading and obviously polarity.

Anyone any idea where I'm going wrong ... I'm obviously doing something stupid, but I'm not smart enough to work out what.

Can I damage these strips or the controller if I get the polarity wrong?

You wont damage the strips by putting the wrong polarity across them they just wont light, you will need a 12v ish dc supply for them to work.On the other hand the controller is likely to get damaged from wrong polarity.

Thanks for that, I could test it using the white strips (although they appear to be the multi coloured strips wired differently) as they don't need the controller.  What if the output is AC ... will that do damage?

[Julian]

Just put my glasses on and strained to read the tiny printing on the transformer ... it's inconveniently located on top of a tall larder unit and I can just make out a small squiggle after the 11.6v, so I'm guessing that means it's AC ... bugger!

[julianf]

I suspect you would have no issues feeding AC, but i dont know whats in the box.

However,

If youre only after 35w, then a diode ring would be, well, 4 diodes, and then youre to DC, all be it with some ripple (which, on somthing like this, wont be an issue, im sure!)

Here you go -



Personally, id just plug it in a see if it worked.  I think the chances of the magic smoke leaking out are slim.

[Julian]

It was 35w minimum load to get the transformer to operate, it's rated at 25 amps on the secondary.

I did a bit of Googling on rectifiers for LEDs and several forums said that you needed capacitors along with the rectifier, I'm guessing from a perspective of little electronic knowledge , to smooth the output.

Anyhow realising that it's an AC output, it's not what I need, so I've ordered a 30 amp output dedicated LED driver which is cheaper.  The 25 amp unit was from Screwfix so hopefully they'll take it back.

Thanks to everyone for the assistance ... fingers crossed everything works this time!

[kamaangir]

Can't believe you lot are letting him get away with this thread, I for am going to retaliate by excessive use of  the following:

 

[Rotary-Motion]

i got a question on therse RGB lights if i cut the strip into 3 do i need 3 controllers?

i got 1 box/remote and 1 strip light

[Julian]

No, if you can join the three strips with wire, they will still run off the one controller.

[Rotary-Motion]

No, if you can join the three strips with wire, they will still run off the one controller.

kool

but if i only want 2 jioned and the third with just an off on switch via 12 volt is the odd strip ok for this?

i guess i have to jion 3 wires togethrer and thats the live, and 4th the earth, is this right?

[Julian]

Re the third strip on 12v, I'll have to check.  I've got multi colour bought as white with only two wires attached (they obviously don't need the controller) ... I'll check how they are connected an report back.

In joining the other strips, there are four wires, 12v positive and the three colours (RGB), you'll need one wire for all 4.  I bought some connectors that work quite well, but as Jules stated, you can just solder to the contacts once the silicone is cleaned off.

[Rotary-Motion]

Re the third strip on 12v, I'll have to check.  I've got multi colour bought as white with only two wires attached (they obviously don't need the controller) ... I'll check how they are connected an report back.

In joining the other strips, there are four wires, 12v positive and the three colours (RGB), you'll need one wire for all 4.  I bought some connectors that work quite well, but as Jules stated, you can just solder to the contacts once the silicone is cleaned off.

cheers