DIY Projector Summary

Right, just to conclude on the DIY projector. I completed that project shortly after starting it...it works as a proof of concept, but needs some work before I can use it in place of my TV.

The Build:

•  I found the 3.5" car reverse monitor on ebay, it was similar to this one. They all look identical. Pulling apart the LCD was relatively simple, I had heard some horror stories of the glass cracking but I was slow and careful and it work relatively well. I would recommend the 'type' of the linked LCD - there is a significant amount of ribon cable between the LCD and the board which suits the application well.
• I then mounted it onto a peice of cardboard with a cutout (I tried thick card with no luck) and slotted it into the centre of my enclosure.
• Prior to this I had cut a hole for the slide projector lens in the front of the box and used some gardening foam to prop it up before supergluing it in place. Once this was in place I tacked the LED.
• After soldering a simple circuit where a red light indicates that there is power to the projector, and a green light indicates the switch is on, I then soldered the 10W LED (very similar to this one on ebay) to a power resistor 4.7ohms which was solered in parallel to the LCD board. After several failed attempts to fit a heatsink to the LED I ended up just supergluing a peice of tin foil to either part and it seems to hold (and not ignite!).
• I then superglued (heavily used in this project) a clear acrylic dome ontop of the LED - it was intended to spread the light better but I couldn't tell any difference
• The 'fresnel' lenses are essential!!!!! In my last post I said I would try without, a bad bad move, after purchasing a shedload of credit card magnifiers I placed 7 ontop of each other between the LED and LCD, and one between the LCD and projector Lens.

Does it work? Well....sort of.

The 10W LED is the only thing holding it back from replacing my TV, it simply isn't bright enough for me. However, with curtains closed and all lights of it does a respectable job of projecting a video of about 1.25m by 3m on by wall, and it is mostly visable, however it is too dark to show up on a photo. Obviously reducing the size of the projected image increases the brightness of the image - and focusing it couldn't be easier - just move the position of the fresnel lens between the LCD and the projector lens...job done! However it sits on a bookshelf at the moment.

Now, why not just swap out the 10W LED for a higher power one when 50W LED's are easily available? Well it's something I have been considering for a long time...however the cost of it has held me back. There are two issues that cause the cost to skyrocket with higher power LED's:

1. Power Supply Voltage. Most higher power LED's (with the exeption of a few 20W LEDs with crazy current requirements) requrie 34V. This brings with it two issues - one is that I now have an LED and a LCD board running at two different voltages, I need some sort of up/down convertor to keep both running - at additional cost. The second issue is that 34V psu's are hard to find - my best solution is to buy a 60W 19.5V, use a step up voltage booster to power the LED and a step down voltage convertor for the LCD. It certainly has enough power to run both - ebay examples are: 50W LED, Step Up Voltage Convertor, Step Down Voltage Convertor.
2. Heat and Space. 50W LED's are big, in addition to the voltage convertors - they are pretty much the size of my enclosure, so I'd need a new one. Also they are HOT....I mentioned early about my shoddy solution to superglue a heatsink to the LED. It works, but I wouldn't trust it for long. For a 50W LED I'm looking at attaching a computer heatsink with a fan (which would run off the 12V circuit). Also I should probrably address the shoddy wiring around the plugs, and my indicator circuit wouldn't be too happy running at 34V.

I've currently paid about £40 on the projector so far, for which I could have bought a broken projector on ebay and swapped out the dead bulb for a high power LED. To bring it up to 50W I would be looking at another £25-30...for which I could probrably have bought a working one. At present I don't have that amount to waste, but I will wait and see....I'm sure I'll be back in a few months having another attempt!

For your viewing pleasure, here are some videos of it.

Having said I have no pictures of it working...here is a video before I seriously stepped up the number of frenel lenses (read credit card magnifiers) between the LED and LCD pannel - the image looks small, but its about half the size of the actual image that is being projected (the centre appeared brighter than the rest).

 This is a quick video of what it looks like on the outside.

Diamond Jubilee Desktop Background

Right, I havn't used this in forever but as it is the Queens Diamond Jubilee I thought I'd make a desktop background to celebrate it. I have shamelessly stolen the Union Flag Diamond on the front of Gary Barlow's 'Sing' album (I strongly recommend you have a listen), widened it and repositioned the coat of arms to lie just above the taskbar on the right side. It's not great, but a crude effort that's good enough for me, only in 1440x900 I'm afriad. Enjoy.

DIY Standalone Projector

So,
I'm quite far through this project, but in this post I will write up what progress I have made so far.
All credit for the idea goes to these instructables:
http://www.instructables.com/id/DIY-Multimedia-LED-Projector/
http://www.instructables.com/id/homemade-projector-cornflake-box/

Essentially the idea is to create a homemade projector using a cheap LCD T.V. (I'm using a car reverse monitor), tear it out the case to reveal the translucent LCD screen then place a really bright light behind it and use a lens of some sort to focus it to a point on the wall.

 (This fantastic image has been shameless taken from http://www.instructables.com/id/DIY-Multimedia-LED-Projector/)

I'm using a 10W high power led as the light source and a second hand slide projector lens to focus the image, as for the lenses either side of the LCD in the diagram - I am going to try and get away without buying them. If the image produced is too out of focus then I will buy two credit card sized magnifying glasses. Also, the condensor lens has been omitted (mostly because I couldn't find one anywhere).

Some have said that there might be some difficulty in projecting a screen larger than a slide (1.8") with a slide projector lens - I can happily say that in a dark room with my brightness on my iPhone at the max, I have been able to project a video onto a white wall quite well. The LCD I am using should be the same dimensions as the iPhone screen (when it arrives from Hong Kong).

Electronics
I chose to use a 12V power supply as the LCD is intended to run off the car battery (12V). The LED runs at 9V (900mA) so I have a very large ceramic 5W resistor that I will use to drop the voltage. A very shoddily drawn circuit diagram below explains very simply what I plan to build (apologies if any of the symbols are wrong).

A Note on PWM: I intend on taking the +ve connector to the backlight on the LCD and connecting it through a transistor (now a MOFSET) to turn the LED on and off when the backlight would be turned on and off. I assume that the backlight is controlled by a PWM signal and by connecting that through the MOFSET I should be able to use the original brightness controls to control the brightness of the LED and projector.

Progress so far:

So I now have everything apart from the box, power supply and LCD display (on its way from china). In the mean time I tested the LED and resistor using the same circuit as in the diagram above, replacing the 'LCD Backlight In' with an arduino running the Fade Example (http://www.arduino.cc/en/Tutorial/Fading) which essentially sends out a PWM signal, adjusting the duty cycle to give the impression of dimming...and it worked!

Here's the video:

So that's all for now. There is a box waiting for me at the Post Office Depot, so hopefully that will be the LCD screen, and I should have an update once I've wired that up and bought a box from Maplin.

Thanks,

Chris

Hello World.

Hi,

I'm Chris, I'm an Engineering Student, and this is my blog to share and help myself document (and hopefully finish) my various electronic/software projects.

A lot of my projects will be based around the arduino, and nearly all will be building on, based on or exact replica's of projects other people have completed I've seen on the arduino playground, instructables or similar. Where possible I will try and reference the original project or idea that inspired me (because that's just fair), however please don't be offended if I have lost or forgotten the link and have not referenced you/someone you know of.

Anyway, here is a list of projects I'm hoping to undertake (at some point!):

• DIY portable projector
• Standalone Arduino Oscilliscope
• RGB Audio Spectrum Analyzer with a range of animations
• Build a RepRap!

 Obviously as a student, time and money are in very short supply, so progress will be slow, but I will update the blog whenever progress is made.

Thanks,

Chris