I have an electronic transformer input 220VAC output 12VAC 50W made for use with 12v halogen lights. I connected it to the mains and checked the output voltage as I wasn't sure that the gadget was OK. When I checked the output voltage I got a reading of 7.12v. When I reversed the test probes I received a reading of 9.3 volts. I had connected the output wires of the transformer to cable connectors and had pressed the probes down firmly on the screw heads which were tight on the output wires of the transformer. I repeated this test several times and received the same result. What's the explanation? I want to use the transformer via a bridge to power a series of leds that were originally supplied by a 6v supply. Which way of connecting should I use?

 

A LED with a Vf of 3.6 V won't work on a 3.6 V supply. Vf has a range of voltages as well.
When driving with a solid state device you also have to account for that drop too.

 

Welcome to AAC!

A thread belongs to the OP (original poster). Trying to take over someone elses thread is called hijacking, which is not allowed at All About Circuits. I have therefore given you a thread of your very own.

This was split from
Might be a stupid question to most...

 

Welcome to AAC!

A thread belongs to the OP (original poster). Trying to take over someone elses thread is called hijacking, which is not allowed at All About Circuits. I have therefore given you a thread of your very own.

This was split from
Might be a stupid question to most...

 

Sorry that I erred. It was completely unintentional. I just thought it fitted in with the title of the thread.

 

Electronic transformers are really a switch-mode power-supply, and some do not work if run unloaded. You should repeat your tests with a test load to simulate the halogen lamp(s) that would otherwise be connected.

 

Electronic transformers are really a switch-mode power-supply, and some do not work if run unloaded. You should repeat your tests with a test load to simulate the halogen lamp(s) that would otherwise be connected.

Thank you I will try it again with a 12 v halogen lamp. Is it possible to reduce the voltage and use it via a bridge to power a set of leds with input voltage of 6vdc or is the type of power produced not suitable for powering leds?

 

Do you have a part number for the supply. It is possible that it is doing PWM for soft-start or dimming of the halogen, in which case, it may not be well suited to LEDs.

 

I presume that your meter was on a AC V range? Only thing that comes to mind for strange readings is if transformer wewe ferro-resonate & was screwing up the waveform. A bridge rectifier will not care of AC connection. if you no not filter output,& under load ( 5 to 8 A ? ), output might be close to 6 V of pulsing DC.