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Old 10th January 2017, 01:32 PM   #11
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Order one of these. Whack the end off and connect to two of the power connections. (Center and to either of the other two) Ya can't hook it up wrong..

US EU 100-240V Converter Adapter 12V 2A Power Supply For LED Strip - US$4.21
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Old 10th January 2017, 02:37 PM   #12
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Quote:
Originally Posted by OffGridKindaGuy View Post
Order one of these. Whack the end off and connect to two of the power connections. (Center and to either of the other two) Ya can't hook it up wrong..

US EU 100-240V Converter Adapter 12V 2A Power Supply For LED Strip - US$4.21
I believe the OP wanted a 12V AC output on the secondaries. Not a 110/230V AC to 12V DC converter (your model above states clearly that it is an AC to DC adaptor).

Best,
Anand.
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Old 10th January 2017, 05:05 PM   #13
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Much less hassle and regulation with the wall wart.
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Old 11th January 2017, 02:08 AM   #14
PRR is offline PRR  United States
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> Order one of these.

He needs AC to derive a bipolar DC supply.
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Old 11th January 2017, 05:14 AM   #15
DIM44 is offline DIM44  South Africa
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I have already built a mains bulb tester and intend to use it - often.

Thanks to everyone who responded to my question. However, I have not a direct reply regarding the transformer I need to get. In post #9 I have listed four possible model which to me appear to be either close to or ideal for my purpose. The most expensive toiroidal is around $16 and I don't mind paying that for the best one.
Could someone please comment on my post #9? Thanks.
Nico
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Old 11th January 2017, 09:41 AM   #16
AndrewT is offline AndrewT  Scotland
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They are virtually the same. All are 5VA, all are 230Vac
Choose one.

If cost is not an issue I would suggest you buy one 12Vac and one 15Vac. then test the actual DC voltage when under load.
The regulation of these very small transformers is very high and leads to very high DC voltages when the loading is low.
You may find that the 15Vac is just too high a DC voltage and then you would fit the 12Vac to keep the regulators cooler.
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Old 11th January 2017, 10:13 AM   #17
DIM44 is offline DIM44  South Africa
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Thanks Andrew. Appreciate your help.
Take care
Nico
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Old 11th January 2017, 10:44 AM   #18
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My bad. I seen (what I thought was) a full wave bridge behind the power input and assumed a single D.C. supply would be sufficient. The other thing(s) I missed were the two 15 volt regulators. (7815 / 7915) Not enough coffee, I guess..

They suggest a 12Vac transformer with no mention for the need of a center tap.
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Old 11th January 2017, 10:53 AM   #19
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by OffGridKindaGuy View Post
My bad. I seen (what I thought was) a full wave bridge behind the power input and assumed a single D.C. supply would be sufficient. The other thing(s) I missed were the two 15 volt regulators. (7815 / 7915) Not enough coffee, I guess..

They suggest a 12Vac transformer with no mention for the need of a center tap.
the PCB is labelled AC GND AC.
That means a 3 wire ac connection is required.
The gnd is mislabelled and should read CT for centre tap.
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Old 11th January 2017, 11:35 AM   #20
DIM44 is offline DIM44  South Africa
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I found this also at lower cost. Any good?

12V ac 1 Output Through Hole PCB Transformer, 5VA
  • RS stock no. 732-0411
  • Manufacturer Block
  • Mfr. Part No. VC 5,0/1/12
There are other similar ones offered but specs differ.


Thanks

Last edited by DIM44; 11th January 2017 at 11:49 AM.
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