Myths and Facts about LED's
All LED's are dimmable
FACT - But it is not the LED that is dimmed, it is the driver, which must be of a dimmable type. There are two main types of dimming systems: 0-10 volt and triac dimming.
Halogen lamps produce more heat
FACT - Tungsten lamps product 25% light and 98% heat. LED's produce approximately 30% light and 70% heat.
Soviet inventor Oleg Loosev invented the first LED in 1927
FACT - However, LED's were not commercially used until 1968. The current blue version LED with phosphor over the top was invented in Japan in 1992.
There are two types of LED drivers.
FACT - There are constant current and constant voltage drivers. Constant current is used to wire LED's in series. This is the way Christmas lights are connected. Constant voltage is used for LED's that have a built in low voltage driver.
A 10 watt LED will produce more light than a 6 watt LED.
MYTH - This is a major error made by most people. If an LED requires 10 watts to power it, this does not mean that it produces more light that a 6 watt LED.
Any driver will power a string of LED's
MYTH - Each LED has two specifications that must be taken into account. The first is forward voltage (vF) and the second is its maximum current rating measure in milliamps (mA). As an example Cree manufacture a MTG-2 LED. It is a 6vF (forward volt) with a maximum drive current of 2000mA, provided that the heat sink will not allow the LED to exceed 105 degrees Celsius at its junction point.
LED's don't produce much heat.
MYTH - LED's produce head in a very confined space (the foot print of the LED itself). If the LED requires 6 watts to operate then about 3.6 watts is wasted as heat.
There is no benefit in wiring to wire LED's in series.
MYTH - There is a great deal of money to be saved by wiring in series. As the driver is a constant current device it will compensate for the volt drop in the cable as a function of its design. Therefore much smaller cables can be used compared to parallel wiring. Parallel wiring requires each light fitting to have its own built in driver (a constant current device) plus it requires considerably larger cables (which make wiring connections much more difficult) to compensate for voltage drop over longer distances.
You can connect a string of LED's to a live driver.
MYTH - This is called 'Hot Plugging". If the LED driver is connected to the mains before connecting the LED's it will instantly output its maximum voltage and current thereby blowing up the LED's
You can use a transformer if you don't have a driver.
MYTH - A transformer is an AC device. It delivers alternating current, not DC (direct current). LED's require a DC power supply.
You do not need to worry about what polarity the LED connections are.
MYTH - LED's are a one shot opportunity to do it right. If the positive wire is connected to the negative side of the LED or vice versa it will seriously damage the LED. It may not destroy the LED immediately but it will certainly shorten the life of the LED and may reduce the light output.