230v DC

[steptoe]

I've acquired some LED rope light,
It runs on 230v DC ,
Can I just stick one of these on the end of it to run it off a standard 230v AC supply,?
Current draw is negligible

20 Pcs Bridge Rectifier DB107 1A 1000V Bridge Rectifier Bridge Lead Diode Bridge for Household Appliances Industrial Electronic Circuit

 

[Geoff1946]

NO. Full wave rectification will produce a DC voltage much higher than the quoted AC. Add to that most UK supplies are actually more like 240 volts in practice and you will overrun your led strip.

Where did you find 230volt led strip? Unusual in my book and I would have thought whoever supplies that should also supply a suitable supply unit.

 

[steptoe]

NO. Full wave rectification will produce a DC voltage much higher than the quoted AC. Add to that most UK supplies are actually more like 240 volts in practice and you will overrun your led strip.

Where did you find 230volt led strip? Unusual in my book and I would have thought whoever supplies that should also supply a suitable supply unit.

Its actually rated at 490v DC , although it's usually run off 220v and simply plugged in.
We use it at work for temp lighting, (I work a lot in mainland Europe) ,
As supplies it does come with a little sealed rectifier unit, that must obviously use some jiggery pokery to keep the voltage as X in = X out ,
We had some damaged lengths so the ends were cut off them and I thought it would make good lighting in the shed/workshop.
It runs fine off 230v AC , but obviously flickers at 50Hz , so far from ideal.

 

[Geoff1946]

If it will go to 490 volts then your solution will be OK. There will still be ripple but it won't show anything like 50 Hz flickers, (when it probably only running half wave.)

 

[Richard-the-Ninth]

I understand that you have it at work, and at work it does not have its ends cut off, DC being what it is, it contracts your muscles and an RCD will not work, I would not use it at home.

 

[steptoe]

I understand that you have it at work, and at work it does not have its ends cut off, DC being what it is, it contracts your muscles and an RCD will not work, I would not use it at home.

Its designed to be cut every metre, has markings in it,
It comes in something like 500m lengths,
with a bag of end caps for the cut ends, and a piercing plug like old style festoon cable for the "LIVE" end.

 

[Geoff1946]

Obviously with getting on for 500 volts the supply needs to be properly packaged and insulated, but as a regular here I'm sure Steptoe understands that and knows how to do it. (I'm thinking fully double insulated.)
An earth fault on the DC side would still trip an RCD on the AC supply if there is only a rectifier in between.

 

[steptoe]

Obviously with getting on for 500 volts the supply needs to be properly packaged and insulated, but as a regular here I'm sure Steptoe understands that and knows how to do it. (I'm thinking fully double insulated.)
An earth fault on the DC side would still trip an RCD on the AC supply if there is only a rectifier in between.

Thanks @Geoff1946
So I should be ok simply putting a basic rectifier inline,?
I'll double check the voltage out, but I'd imagine it won't get anywhere near the 490v quoted rating of the strip.
Otherwise, is there An easy way if reducing the voltage easily and cheaply, is it just a matter of resistance,? I could always add a couple of resistors to be on the safe side.

 

[Geoff1946]

If you put a rectifier, the type you showed above, on a 240volt supply you should get approximately a ripply 350 volts DC.
If you want to drop it, find or measure the current drawn by your light strip and use ohms law to choose a resistor. Similarly calculate the wattage of resistor, ( I squared R).
Fuse the input to the bridge, say 1 amp, in case a surge takes out the semiconductors, then it won't burn.
It would be good practice to put a small but adequately voltage rated capacitor across the DC to eliminate any RF rather than radiate it from your wiring. If you don't you probably won't notice though!

 

[Phoenix]

If you put a rectifier, the type you showed above, on a 240volt supply you should get approximately a ripply 350 volts DC.

You'll get a unsmoothed 240v RMS, with the negative parts of the supply flipped positive.

Its when you add capacitors to smooth it that you'll end up with a 360v DC supply

 

[Geoff1946]

Agreed but remember the peak of 240 RMS is about 350.

 

[steptoe]

Deleted

Video wouldn't work

 

[Stuboy1]

Can you post info on these as never heard of this before! You have to be very careful running 360V DC if its running on a flexible pcb, I assume its on wires but from what you said with the cut points it sound like its not. U sure its not 49v DC? That would then come into the low voltage banner and has a different set of rules?!
Looking forward to some details and possibly pics

Stu

 

[BorisJ]

Agreed but remember the peak of 240 RMS is about 350.

Indeed, that applies whether it is raw AC or full wave rectified AC.

 

[ProDave]

You will be fine doing this.

The "end caps" supplied contain a bridge rectifier and the piercing connectors to terminate the strip.

I have done exactly this with offcut bits, soldered a bridge rectifier to the strip and heat shrunk all the connections and it works just the same as the end pieces that are supplied.

It is a shame you only get 1 or 2 end pieces with each strip, and you can't buy spares to use up all the offcuts more easily.

 

[steptoe]

Cut point on strip, and reverse side showing the wires along the edges and how it joins the flexible PCB either side of the cut point.

 

[steptoe]

Showing the flickering of the AC fed strip compared with the DC supply as OE

 

[Geoff1946]

The construction of that strip looks just like the 12 and 24 volt stuff, with umpteen circuits of three leds and a resistor across the supply. Obviously must be a much higher resistor for the higher voltage. The only advantages I can think of are that it doesn't need a separate low voltage PSU and very long lengths will be possible without volt drop problems. Is that it, or is there some other reason?

 

[steptoe]

The construction of that strip looks just like the 12 and 24 volt stuff, with umpteen circuits of three leds and a resistor across the supply. Obviously must be a much higher resistor for the higher voltage. The only advantages I can think of are that it doesn't need a separate low voltage PSU and very long lengths will be possible without volt drop problems. Is that it, or is there some other reason?

I honestly have no idea why it's 230/220/490 or whatever volts .
But, the solution of sticking one of those cheapo rectifiers on has done the job,
I actually took a voltage measurement before heatshrinking it all up and it was reading on or abouts 233VDC , using an RMS meter, dunno if applying the load would change that tho, ,,,

Just an afterthought, could you stick one of these on a Tx for ELV LEDs,??

View attachment VID_20220216_190220.mp4

 

[Geoff1946]

Just an afterthought, could you stick one of these on a Tx for ELV LEDs,??

The little bridge rectifier you have shown? Yes the principle should work as long as you stay below the 1amp current rating.