Transformer requirement for LED lights

[Aquacrazed]

12v it is I ordered this one: https://www.amazon.ca/gp/product/B01...?ie=UTF8&psc=1

12v 5A

[mike31154]

That should work fine. With respect to how the Dual Ramp Timer works, none of us have the internal circuitry so we can only guess at how it really functions. If you look at page 1 of the instructions, the diagram shows "12-24VDC Transformer" for both hook up configurations. There are no warnings or cautions regarding using one voltage over the other. There are plenty of DC to DC voltage converter circuits that can reduce a given voltage without the use of large heat sinks or heavy transformer coils, particularly for low power applications such as this. Could be as simple as a zener voltage regulator diode, or more complex. In any case, getting the 12 volt supply is your best bet. You can use it on your LEDs without the Dual Ramp Timer if you wish.

[calo247]

Originally Posted by mike31154

That should work fine. With respect to how the Dual Ramp Timer works, none of us have the internal circuitry so we can only guess at how it really functions. If you look at page 1 of the instructions, the diagram shows "12-24VDC Transformer" for both hook up configurations. There are no warnings or cautions regarding using one voltage over the other. There are plenty of DC to DC voltage converter circuits that can reduce a given voltage without the use of large heat sinks or heavy transformer coils, particularly for low power applications such as this. Could be as simple as a zener voltage regulator diode, or more complex. In any case, getting the 12 volt supply is your best bet. You can use it on your LEDs without the Dual Ramp Timer if you wish.

there are no warnings because they give you the list of compatible lights and they intend for you to use the power supply that is included with those lights.

if you ever find a transformer that works on DC you should notify the world, you would be a very rich man

there is no such thing as a zener voltage regulator diode, in order to get a voltage drop out of a zener diode you need to introduce a current limiting resistor (ie. heat) before it, and you would need to have so many of them as they have a very tight tolerance, so you would need differently rated one for each level of dimming you wanted.

in terms of the circuit we are not really guessing, it says its pwm based, which makes sense as it is really the most efficient


hopefully the adapter comes with the same size barrel connector, it would suck to have to lop it off

[Aquacrazed]

Ok so I got the 12v 5A adaptor and my Fluval light bar is not as bright now. It is a fair bit brighter with the 13.5V 1500ma power supply it came with.

[mike31154]

Are you running the light through the timer/dimmer or straight off the power supply?

[Aquacrazed]

The dimmer doesn't seem to have any effect, it simply seems to just pass the current. So weather I connect it through the dimmer or not, the brightness is more when I connect it with the 13.5v power supply.

[mike31154]

Since the voltage vs current relationship for a diode or LED is nonlinear, the fact that your LED runs brighter with the 13.5 volt vs 12 volt supply makes sense. What doesn't make sense is that the "dimmer doesn't seem to have any effect". Not sure I'm fully understanding that part of your statement.

Depending on the load connected to a power supply, especially a smaller one loaded to near max, it will drop to a lower voltage level. That is, if you were to measure the voltage output of your 13.5 volt supply while it is under close to maximum load, I suspect you would read less than the rated 13.5 volts.

Here is a graphic of the voltage vs current curve of a LED or diode.



As you can see as the voltage nears the rated/maximum forward voltage of about 3 volts for the diode, the current rises sharply. This is why using a power supply of the correct voltage is so important, or you risk cooking your diode. However, something as simple as resistor in a circuit running a LED can keep the current at a safe level by dropping the voltage available to run the LED to its rated value. This is not efficient since the resistor wastes power & creates heat in doing so. This is why PWM (pulse width modulation) is commonly used to dim and control the current to LEDs, it is more efficient. That doesn't mean you can't also include components such as resistors and zener diodes in conjunction with PWM circuitry to help sense & control both voltage and current in designing your hardware. Often tradeoffs are made in efficiency vs simplicity of design in most of these components. This is why I was suggesting that it may be possible to use a 24 volt supply feeding your dimmer to safely run your 12 volt LEDs. Again, that may not be an experiment you wish to carry out. If I'm wrong, you could cook your lights.