By Gurinder Singh Lali
Although LED and LED lighting industry in India is still in its infancy, many unscrupulous players and unhealthy practices are already well established. One needs to be cautious and ensure that one gets the right quality at the right price. For example, a 1W LED sells in India at different prices, based on its lumen output. LED lighting manufacturers are confused about what the right LED for their applications should be. Is a specification of 80 or 100 lumens actually going to deliver 60/80 lumens?
An LED labelled as 80 lumens could actually imply a lumen output of:
An LED labelled as 100 lumens could actually imply a lumen output of:
A buyer should always ask for minimum 100 lumen.
In India, there is no comprehensive testing facility, which can be used to ensure right lumen output and other parameters. If you buy a 100 lumen LED, how would you know that it is indeed a 100 lumen LED? Although all LED manufacturers and traders specify 100 lumens, when we look at the specifications, the reality becomes obvious. The specifications would show minimum, typical and maximum lumen output. To be on the safer side, your lumen output requirement should match the minimum lumen output specification and not the typical or the maximum specification.
The LED lumen output depends on colour rendering index (CRI). When CRI is low, you get more lumens but the light output is of low quality. Always purchase LEDs with a CRI rating that is more than 80-85.
Let’s look at another important aspect—the thermal resistance. The higher the thermal resistance of the LED, the bigger the heat sink is required. Choose LEDs with only 5° celsius per watt to 7° celsius per watt thermal resistance. A lower thermal resistance is always better. The view angle is another important parameter. The lower the view angle, the higher the lumen output. Always choose products with a view angle of 120° to 140°.
Let’s look at another example. A branded LED is sold as having a 20 lumen output, and driven@50ma. However, its view angle is 80°. If with the same 20 lumen, the LED has a 120° view angle, then its lumen output would become 15 lumens. So always buy 120° view angle LEDs.
While purchasing LEDs, look for the following parameters:
- High >85 CRI
- View angle of 120°-140°
- Low thermal resistance of 5° to 7° celsius per watt
- Minimum lumen output specifications
- Single bin or max 2 bin for colour tempK
- Manufacturers usually make codes like b1, b2, b3, b4, b5, b6 colour temp bin
- Ask for colour temp bin code data if they offer b2-b6 bin, it means they give you 5000k-7500k colour temp LED, which will not give the right colour. So ask for only b2 and b3 bin
- Low voltage bin
- Max 45 milimeter chip size
- MCPCB always use 3.0W/mk
- Junction temperature should be below 80° celsius
- A constant current LED driver with a life of at least 25,000 hours
- A driver efficiency more than 85 per cent
- Ask for a three year warranty on all raw materials—LED, heat sink, power supply, etc
A multi-chip LED is better due to:
- No MCPCB is required
- No shadows & Small heat sink
- Low thermal resistance
- Ceramic based substrate
Price of LED has gone down in international market. Branded LEDs are now available just for Rs 55. Customers should not buy LED from unauthorised suppliers. They do not have technical knowledge but tend to confuse customers. It’s time that we build up the reputation of LED products in the Indian lighting industry.
The author is founder of Nano Power LED Lighting Solutions