Jump to content

The Cheap Transformer and why You Shouldn't Use It.

Recommended Posts

Transformers come in many shapes, sizes, and prices.  You may be tempted to purchase the cheapest transformer for running your LEDs that fits your specs.  That may not be a wise decision.  You may think that as long as a transformer says that it will output the correct voltage and has enough amperage to drive your load you are golden. But what you really need is a REGULATED transformer.  Here is why.


Many cheap transformers are nothing more than, well, transformers.  They'll have a rectifier circuit to change AC to DC, and then a couple of coils of wire around a core to drop the voltage.  The problem here is that there is no check on the voltage output.  Remember our friends I=P/V and W=V*A?  They taught us that voltage and amperage are tied together at the waist. 


That cheap transformer is rated at X Amps at Y Volts.  But what happens when you attach a SMALLER load than X?  If the amperage DECREASES, then the voltage MUST increase.   For example, lets say you have a 12V transformer that is capable of outputting 5A.  If you measure the output of this transformer without a load on it, you maybe surprised to see it is actually outputting 16-18V or more.


Now lets say you are using that transformer to drive some of your very expensive 12V LEDs.  Do you know the ONE thing that will kill an LED fast?  Excessive voltage.  You hook up 1A of LEDs to a cheap 5A 12V transformer, and the next thing you know, your LEDs are dead.


That's where the more expensive REGULATED transformer comes to the rescue.  Regulated transformers can have the same rectifier circuit and wire wrapped core, but they have one very important addition:  The Regulator.  The regulator's job is to adjust the voltage to a constant, regardless of what load is attached.  Even without a load, if you measure the output of this 12V transformer it will be a rock solid 12V. 


In both of the cases above, we are talking about a linear power supply.  You would be surprised to find how large (physically) some of them can be.  You'll also notice that they will be warm to the touch - even if nothing is running.  That means you are wasting electricity - the same electricity you should be saving by using LEDs.  The next step up from the linear supply is the switched supply.


The switched supply is going to be even more expensive, but has additional benefits.  Not only is the output voltage going to be regulated and rock solid regardless of load, they are much more efficient.  This is especially true when there is no load - you are not wasting power to warm the air.


Don't skimp on your power supply.


  • Like 1
Link to post
Share on other sites
This topic is now closed to further replies.
  • Create New...