12v LED strips. Old 2amp dc transformer

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Chuffchuff
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12v LED strips. Old 2amp dc transformer

#1

Post by Chuffchuff » Tue Mar 24, 2020 3:41 pm

I am using some cut 12v led strips (3 leds per strip) for model building lighting. All tests with a 9 volt battery seem to work ok and give a suitably bright light.

So I am thinking of using an old dc supply (I have a feeling came from an early scalelectrix set as the power source running through a dc dc buck converter to give an output of 10volts.

From what I understand, leds need a regulated supply that gives a smoother output on startup, whereas the older metal cased dc supplies run at 14v or so until a load comes on, then they run at 12v ( or so ?)

I am wondering if using the old dc supply might fry the buck converter on startup, or worse still fry the leds.

Plan B. Just buy an adjustable dc plug thingy from well known internet suppliers ?

Any comments would be useful.

Thanks

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Walkingthedog
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Re: 12v LED strips. Old 2amp dc transformer

#2

Post by Walkingthedog » Tue Mar 24, 2020 3:49 pm

I used the controlled output from an old controller for years and never had a problem.
Nurse, the screens!

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Brian
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Re: 12v LED strips. Old 2amp dc transformer

#3

Post by Brian » Tue Mar 24, 2020 7:08 pm

A Buck converter will give a constant output and should be fine. Do remember you need around a minimum of 2 volts more DC input than the output needed.
But do not use an unregulated power supply such as the unregulated output of any train controller (or Scalextric etc) power supply - It is not set at a constant voltage regardless of load. It also is highly unlikely to be smoothed DC! It will have a lot of AC ripple on the supply! Many of these will provide well beyond 12 volts DC on a little loading and typically up to around 18 volts DC and this drops as the load is increased = Unregulated supply!
Use a regulated and smoothed DC power supply, ideally at 12 volts DC. Many are available on ebay or Amazon for sub £6 GBP and are of good quality! Look for LED or CCTV power supplies.
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Chuffchuff
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Re: 12v LED strips. Old 2amp dc transformer

#4

Post by Chuffchuff » Thu Mar 26, 2020 4:23 pm

Thanks for your replies, I left it a while just in case anyone else joined in.

I think I'll play around with the old DC supply and Buck bits to see how things work out. I am after about 10v and 3 volts for lights. The Supplies from the internet generally seem to be above those values so would need a DC DC converter anyway, so replacing the old DC supply if it does not work out with newer ones is no problem apart from readjustment of the output voltages.

Oops lost a bit !

Just to add that it's a lot neater not having great lumps of vintage electronics to trip over so will go down that route when allowed out the house ( for those reading this in future, written in the days of the World pandemic)

Rgds

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Brian
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Re: 12v LED strips. Old 2amp dc transformer

#5

Post by Brian » Thu Mar 26, 2020 5:27 pm

Hi

Dont quite understand your meaning re DC to DC convertor? Buck convertors do just that.. DC in and DC out?? This one is from UK sale (Much cheaper if imported from China, but can take 4 weeks) Example link, click here will do all you want from a DC input The digital display can be switched between input volts and the adjustable output voltage.
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Steve M
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Re: 12v LED strips. Old 2amp dc transformer

#6

Post by Steve M » Thu Mar 26, 2020 5:29 pm

In the past I have used converters similar to this. The beauty of this is that you can adjust the output in 0.1v steps and have a digital display for reference.

https://rover.ebay.com/rover/0/0/0?mpre ... 2720086770

Edit. Brian always types faster than me.
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Chuffchuff
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Re: 12v LED strips. Old 2amp dc transformer

#7

Post by Chuffchuff » Fri Mar 27, 2020 7:19 pm

Thanks for the links, personal recommendation always welcome.

Last time I had anything to do with electronics was soldering wires in chassis with valve bases! So my description of modern bits n bobs are a bit vague :roll:

El84 and El83 valves seem to ring a distant bell.

Rgds

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teedoubleudee
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Re: 12v LED strips. Old 2amp dc transformer

#8

Post by teedoubleudee » Fri Mar 27, 2020 10:03 pm

Chuffchuff wrote:
Fri Mar 27, 2020 7:19 pm
Thanks for the links, personal recommendation always welcome.

Last time I had anything to do with electronics was soldering wires in chassis with valve bases! So my description of modern bits n bobs are a bit vague :roll:

El84 and El83 valves seem to ring a distant bell.

Rgds
Strange you should say that. I have been thinking of a non-railway project to while away the hours (days) during this time and been fancying a valve amplifier kit but they are either very expensive or come from China and might take weeks. Anyone remember the Heathkit brand? They still have a web site but only sell in USA and just upgrades, not complete kits.
Most people are shocked when they find out how bad I am as an electrician

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Walkingthedog
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Re: 12v LED strips. Old 2amp dc transformer

#9

Post by Walkingthedog » Fri Mar 27, 2020 10:08 pm

I built a Heathkit amplifier and an electronic ignition for a car.
Nurse, the screens!

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