LED Lights and Transformer
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How to Install Electrical Wiring for LED Light Fixtures
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Guide to Residential Electrical Wiring
How to Install Electrical Wiring for LED Lights
Electrical Question: I just bought a led spot light MR16 12volt to change them with the old one I had which was a spot light MR16 12volt. The replacement lamp is not working ? Do I need to get a different transformer for the led lights?
This electrical question came from: Giacomo, from London, UK.
Dave’s Reply:
Thanks for your electrical question Giacomo
Electrical Wiring for LED Light Fixtures
- When installing LED or any low voltage lighting fixtures a transformer is used to reduce the voltage from 120 volts to 12 volts.
- The number of lights that will be installed will determine the size of the transformer, and the size of the low voltage electrical wiring.
Testing a LED Transformer and Light bulbs
- Giacomo, If there are any other lamps that are working which were connected to the transformer then the transformer may be working.
- A voltage tester will be needed to test the output of the transformer at the wiring of the mr16 lamp socket to see if there is 12 volts present.
- An ohm meter may be used to check the mr16 light bulb to see if it is defective as well.
RESOURCES
Lighting For The Home
Using Electrical Testers
Understanding Electrical Testers
When working on home electrical wiring using voltage testers can play an important part in electrical safety. Electrical testers enable you to identify electrical circuits and help prevent the possibility of accidental electrical shock.
Types of Electrical Testers
Repair Electrical Wiring
Troubleshooting and Repairing Electrical Wiring
Licensed Electrician Reveals the Secrets of Successful Electrical Troubleshooting Methods used to solve the majority of the home electrical problems and wiring failures encountered.
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You Can Avoid Costly Mistakes!
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Here's How to Do It:
Wire It Right with the help of my Illustrated Wiring Book
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How to Troubleshoot and Repair Electrical Wiring
Wiring Methods for Upgrading Electrical Wiring
NEC Codes for Home Electrical Wiring
....and much more.
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Be Careful and Be Safe - Never Work on Energized Circuits!
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Electrical Tips to Help You Wire it Right
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The Safest Way to Test Electrical Devices and Identify Electric Wires!
The Non-Contact Electrical Tester
This is a testing tool that I have had in my personal electrical tool pouch for years, and is the first test tool I grab to help identify electrical wiring. It is a Non-contact tester that I use to easily Detect Voltage in Cables, Cords, Circuit Breakers, Lighting Fixtures, Switches, Outlets and Wires. Simply insert the end of the tester into an outlet, lamp socket, or hold the end of the tester against the wire you wish to test. Very handy and easy to use. |
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The Quickest Way to Check for Faulty Electrical Wiring!
The Plug-In Outlet Tester
This is the first tool I grab to troubleshoot a problem with outlet circuit wiring. This popular tester is also used by most inspectors to test for power and check the polarity of circuit wiring.
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Light indicates if wiring is incorrect
Very handy and easy to use. |
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Strip Off Wire Insulation without Nicking and Damaging the Electric Wire!
The Wire Stripper and Wire Cutter
My absolute favorite wire stripping tool that I have had in my personal electrical tool pouch for years, and this is the tool I use to safely strip electrical wires.
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One of my Christmas inflatable’s light wire pulled apart from the terminals, and at the time I didn’t have a way to fix them so I just threw the three LEDs away. I now am trying to wire 3 white LEDs in Series to my inflatable to get it to light up. I initially hooked up 9 incandescent to the blower motor and had problems with it working, although the light would glow dim it was not my desired effect. So, not knowing anything about LEDs I cut a string of LED lights that I bought and wired 9 up in series and tired to get them to work. As you guys probably know, there wasnt enough volts to light them. I then did research and found that my inflatable had a 12v adapter and I figured I had picked to many LEDs to light. I then tried to light 3 LEDs and that did not work. Thinking that the LEDs were burnt out I made a LED tester from 2 AA batteries and found that all my LEDs worked. I did even more research and found that LEDs have to be hooked up a certain way to work and can not be run in reverse polarity.
With all this new knowledge I thought I had figured it out. I ran my lights and thinking my lights were rated for 3.4v I figured 12v would be plenty to run 3 of these LEDs and not t much to make them burn out. Well I plugged them in and still no light.
Here is the information I have so far:
The string was 50 mini LED warm white lights. The string is rated 4.8 watts (.04amp). The lamps are to be replaced with 3.8v .076watt LED only. That converts to 5.6ma per LED.
I checked each of my LEDs with my 2 battery LED tester and they all glow. What I have found now is my DC power supply is alternating volts from 8 to 11 and back again. I think my Power Supply may be bad. My latest test was like this. ” I Plugged in my power supply. Tested the volts and got 12.24v. Connected my string of 3 warm white LEDs at that are rated for 3.8v, and nothing happened. I checked my voltage from the beginning of the string to the end of the string and got 12.24v. Scratched my head and asked my self “Shouldn’t I have had some sort of power drop through the whole string?” I am not sure but I think I should have. I tested again and the Volts started alternating. I checked my outlet and was getting a steady 116v.
Why is it people say 20ma across the LEDs and these are needing 5.6ma? Can to much amps cause them not to light up?
Hi Zach,
Here is what I believe you have identified about LED lights: LED lights work with DC voltage and they are polarity sensitive because they are basically a diode which only allows voltage to flow in one direction. This is why they worked when you tested them with standard DC batteries and the polarity was correct. From what you have described, the power supply is the problem because it does not have a DC output. The oscillating output of the power supply will not work with the LED lights. The ma is simply the amount of power that will be required and consumed by each LED light, therefore the new DC power supply must be rated for at least the combined total of ma required for the number of LED lights that will be connected.
I hope this helps,
Dave