User:Mentar/LED lighting proposal

mentar's LED lighting proposal

Given the cost and lack of reliability of the current lighting fittings at the space I'd like to propose we run a small trial with custom built LED arrays?

• 

  Adjustable constant current driver

• 

  3watt star leds

• 

  Galvanised steel stud

Approach

The approach I'm proposing is to use 3 watt star leds mounted on the inside of galvanised steel channel. The led driver is a an adjustable constant current source, this can allow us to use varied power supplies to power the strips including some of the old laptop chargers that have been gathering dust downstairs for some time.

Pros/Cons

• Pros
  • Relatively cheap
  • Reliable in theory (including overtemp and shortcircuit protection)
  • The galvanised steel stud provides a basic reflector and heatsink while the lip allows mounting of diffusion plates. Can also be used as the ground plane, simplifying connections.
  • Makes use of a range of un-needed power supplies
  • Modular, so easy to replace broken parts

• Cons
  • Requires some effort to put together

Costs

For an LED strip of say 15 leds (around 45 watts) 2.4m array

• LEDs: £10 (£0.66p per LED from PowerLedWorld)
• DC-DC switching converter: £2.49 (from ebay)
• 50W laptop supply: £0 as we have a few downstairs (need to count how many we have!)
• Galvanised Steel Channel: £6 per 2.4m (from B&Q)

Total cost: ~ £18.50 (to compare 8ft 100W fluorescent tube only, no fittings! costs £15.59 on LampsOnline)

Implementation

At 3.5V each LED consumes around 750ma. 5 LEDs in series would need 17.5V across them. We need 3 of these arrays to make up 15 meaning that we have a current draw of 2.25A for a total of 39.375W. Which is well within what even my weak 60W X220 thinkpad PSU can deliver.