Lightbox refurb using white LED backlight modues

Discussion Electronics
1

I recently bought some (8) 84mm x 45 mm white LED Backlight Modules (https://shop.pimoroni.com/products/white-led-backlight-module) to refurbish a light box which currently uses an incandescent bulb for illumination.

As I am a bit out of practice in electronics has anyone got any ideas for circuits?

The lightbox is currently mains powered so it needs a mains socket to work. My idea is to make it USB powered so it can run either from the mains or from a portable power pack.

Because I want to power it by usb the I/P voltage is 5V I am aiming for an I/P current of 1A. (as that is the O/P of most of my portable power packs)

I have 8 modules which I suspect would be best wired in parallel, am I right?

2

According to the spec (linked from the product page) the typical current is 15mA and forward voltage 3.2v.
LEDs are usually best paralleled including the dropper resistor (rather than paralleling the LEDs and using just one dropper resistor)
So put one resistor in series with each module then parallel all 8 combos together.
What resistor?
5v source - 3.2v LED panel = 1.8v to drop
15mA recommended current
Resistance ohms = Voltage / Current = 1.8 / 0.015 = 1800 / 15 = 120 ohms for each panel.

8 panels at 15mA = 120mA = easily supplied by any USB wall wart.

Hope this helps.

3 Likes
3

thank you… that is a great help