Dimming 12v dc power supply

[freddy871]

Recently purchased some LED tape for Kitchen canopy. Tape is 12v and came with 12v 8amp DC adapter that has input rating of 240v-50/60Hz 1.9A. LED tape is a tad brighter than i would like so looking to control output via dimmer.
My question is - Looking to switch these from wall plate and rather than use 1 way switch was going to use VPro dimmer. LED tape is suitable for dimming but not sure if the dimming can be done on 240v side of DC adapter or if i need to dim on 12v side.

 

[bernardgreen]

Tape is 12v and came with 12v 8amp DC adapter that has input rating of 240v-50/60Hz 1.9A.

A picture of this adaptor would help in maybe finding out more about it. Odd that it outputs 96 watts ( 12 x 8 ) but consumes 456 watts ( 240 x 1.9 ). Some what dubious.

Can it be dimmed ? Probably not if it is designed to provide a fixed 12 volt output.

Resistors between the power supply and the tapes would dim the LED elements but the resistors would get warm if not hot.

 

[freddy871]

This is link to item in question,, http://www.ultraleds.co.uk/8a-96-watts-240v-ac-to-12v-dc-power-supply-led-driver.html Really want to control ligt output from fixed wall dimmer using vpro.. So if constant would the best route be a dimable AC/DC supply.? maybe supplier will exchange for correct unit..

 

[ericmark]

The unit linked to states output 8A 12V input 110/220V switched 47-63Hz Efficiency 80% regulated ±10% there is nothing which says the output can be altered by phase clipping so it would seem any regulation in output would need to be after the power supply. The 1.9A clearly refers to 110 volt input at 220 volt it will be half that current.

So how to regulate DC?
The easy way is a simple resistor, that is assuming the built in driver in the LED strip is a simple resistor which is very likely. 8A however is a fair current you would need some where around 1Ω or less and the heat produced would be more than could be dissipated in a standard switch box so it would be a large unit. If I wanted to do it I would use a couple of old car headlamp bulbs in parallel, in series with the LED's.

But there are pulse width modulated controllers which will regulate the output by switching it on/off very quickly also called switch mode power regulators however the problem is will these upset the existing power supply?

Best option is a new power supply which is able to give a variable output.

What I did to easy drop power was use an old wagon back lamp assembly with some thing like 6 bulb holders which I wired in parallel the more bulbs the higher the output. Clearly placed out of sight.

 

[bernardgreen]

I just tried connecting two strips (*) in series so that each got 6 volts. The LED elements were still quite bright and may well be bright enough for the application.

Both strips connected in series would have to be the same length

(*) It was two left over segments each with 6 LED elements and two resistors.

 

[freddy871]

Lost me there gents,, but thanks for the answer that new power supply is easiest option..

 

[freddy871]

had a look around and quite like the look of this ,, any comments from the experts would be appreciated .. will it do the trick..???

https://www.amazon.co.uk/niceeshop-...qid=1464723970&sr=1-2&keywords=12v+led+dimmer

 

[stillp]

had a look around and quite like the look of this ,, any comments from the experts would be appreciated .. will it do the trick..???

https://www.amazon.co.uk/niceeshop-...qid=1464723970&sr=1-2&keywords=12v+led+dimmer

This doesn't fill me with confidence:
"Detailed Seller Information

• Business Name: Shen Zhen Shi Mu Zi Guo Fang Ke Ji You Xian Gong Si
• Business Type: LTD
• Trade Register Number: 440307106413677
• Phone number: +8618929395320
• Customer Services Address:
  • Room 306,Unit 3,Building 5-4,Zhen Ye City 2
  • Shen Hui Road, Heng Gang Street
  • Shen Zhen
  • Guang Dong
  • 518000
  • CN
• Business Address:
  • Long Gang Qu Heng Gang Jie Dao Shen Keng Cun
  • Wu Tong Lu Zhen Ye Cheng Wu Qi 5-4 Dong 306
  • Shen Zhen
  • Guang Dong
  • 518000
  • CN"

 

[freddy871]

i hear you,, i do see them on the uk site wjere i purchased the led tape.. must all come from the same neck of woods .. seller aside will they work to dim my tape , ??

 

[ericmark]

had a look around and quite like the look of this ,, any comments from the experts would be appreciated .. will it do the trick..???

https://www.amazon.co.uk/niceeshop-...qid=1464723970&sr=1-2&keywords=12v+led+dimmer

The spec seems to fill the bill, as to quality unknown.

 

[Echo the husky]

Business Name: Shen Zhen Shi Mu Zi Guo Fang Ke Ji You Xian Gong Si

Now that's a catchy and memorable business name!