Project Light box - Building controls and Power Supply. - Page 1
Forum section: electronics / projects

author: mictas
author_rank: Regular Contributor
timestamp: July 16, 2016, 04:28:21 am
content: Okay, so what is my grand master plan? That is easy, to build a light box/panel, that I can put on a desk or table.What do I have, well a LED TV panel, the LCD screen has been cracked, and it was easy to see that. So I have taken the LCD panel and tossed out the rest of the junk.But what really made me think this was possible, the fact when I took apart the TV, the LED driver for the screen wasn't apart of the logic board and yes to date, I have once fired up the LED panel using the recovered driver, using an old Bigpond 12v 1.5A power brick, along with a breadboard power supply with 5v and 3.3v option.Please look at the Driver Back and Front images (I didn't take these photos, but it is the same board), I have attached to this post.I did test fire, of this panel and found that by applying 3.3v to each of the On/Off and ADJ pins, the panel seem to light up at its full brightness. I also linked the ground pin to the breadboard power supply's ground and one of the VIN pins, directly to the 12v power brick, why directly to the 12 power brick?The logic board from the TV has a 12v 30A input and as shown on the switches scan, you can see the DC input is linked directly to both of the 12V pins on the logic board. I don't have a 30A power supply, but my guess is that the 30A is for other things in the TV, like the DVD player and the rest of the logic board.The LED Driver has a TL494 PWM control IC, along with a UT9435 P channel Enhancement mode TO-252, plus some other supportive components.----Right now, I want to build a control box. (Later will come the power supply)My idea is to use a rocker switch to cut the power to and On/Off pin, and 5v and 3.3v SMD voltage regulators, with some supportive components, I have a few of this voltage regulators and I doubt if it will waste too much power.Why this?Well, I have a HP printer power supply, that outputs 16v and 625 mA ( as said on the label), my guess is that should happy power the LED Driver, but not before passing it through a 12v regulator, I am looking at getting this onehttp://au.element14.com/on-semiconductor/ncp7812tg/linear-voltage-reg-1a-12v-to-220/dp/2534227I wanted to ask if those1AM 7SMD's were required on each of the On/Off pin and ADJ pin, if so I found the data sheets and they seem to be nothing more then a 2N3903, I already have a packet of them and have some set aside for this project.---I want to cut the whole thing back, where a wire goes from the 3.3v voltage regulator to a rocker switch, then before the On/Off pin, a 5k resistor to ground, along with a 0.1nF capacitor to ground, and then the On/Off pin on the LED Driver.For the ADJ, I am guessing voltage controls the brightness, I am planing on using a 4x3 Rotary switch, along with some resistors to drop the voltage, before passing onto the 5k resistor to ground, along with a 0.1nF capacitor to ground. Before hitting the ADJ pin.---With what I have said, just about this. Would this be a safe way of powering the LED Driver or have I messed up somewhere?