# Building a HD LED Projector help needed: What Watt is this COB LED? & other questions

#### Craig Nash

Joined Aug 30, 2016
6
I recently bought part to build an LED Projector and made some mistakes and bought all the LED parts individually. When I got the driver, the cheapest one available with Amazon prime for the 50 Watt LED I ordered came with a chip LED. Here here are the specifications

GLW Waterproof 50W led Driver Power Supply + 50W LED Chip Bulb Energy Saving For DIY Cold White
Type of Bulb: LED
Wattage: 50 watts
Incandescent equivalent: 375 watts
Color Temperature: 6000 Kelvin
Light Output: 3500 Lumens

Now, the chip I got with it is a weird design, and much, much brighter than the 4,000 Lumen 50 Watt chip I ordered on its own. However, as far as the individual LED's, it has 70 of them, 10x7.. instead of 10x5. So, is this a 70 watt? The driver I am using with it is:
Led driver
=^_^= input: AC 85-265V
=^_^= outputC:36V
=^_^= current£º1500mA
=^_^= Max power supply£º50W

I am curious if I get a 70 watt driver, if the brightness will be increased? Right now, I am not getting any light on the wall past 4 feet with the 50 watt, and that is while using a 44mm lens & 50 mm collimator reflector on the LED. I have a innolux 7" 1280x800 LCD for a raspberry pi I am using, and then 2- 240mm focal rigid 'acryllic 1mm page magnifier fresnels, and another 2 flimsy paper thick fresnel page magnifiers at about 220 mm Focal that I can mix and match, along with a Kodak Ektanar 100-150mm 5 inch F: 3.5 Slide projector lens for a Carousel 650 slide projector. It does not appear as though this kodak projector lens will fit the light cne from any of the fresnels, even if I double them.

Does this seem right, in terms of light output forcing me be within 3 feet of the wall, and being dim even then? That is with the LCD brightness turned all the way up, and it has no other film on it or anything,.. Or should I upgrade to a 100 Watt LED? Any recommendations on the lenses? I would like to get a 80-100" screen at about 3500 mm, though with these fresnel lenses, I think I am stuck at a 170" screen.How much light loss does a fresnel cause? Any tips would be great!

Attached is picture of the LED am trying to identify the wattage on.

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#### wayneh

Joined Sep 9, 2010
17,152
It's hard to follow exactly what you are doing. We don't know the specifications of the LEDs, we don't know how you are cooling them, how they are hooked up to the supply, and so on. Is the supply a constant current 1500mA supply? What current does the LED require?

That said, I think the bottom line is that you have a low wattage for a projector. Your results don't seem all that surprising. For instance I just looked at a cheap unit for sale at Walmart, and it uses a 160W LED lamp. Even if you were using all 50W (and I'm not convinced that you are), it would not be very bright.

#### Craig Nash

Joined Aug 30, 2016
6
Thanks, when I first started looking at DIY projectors, I saw 30 Watt being used, and grabbed a 50 watt COB LED thinking it would be sufficient, since 4,000 lumen was specified as the output needed for daytime viewing in a non-curtained viewing of a projector on several sites I checked, and the 50 Watt was pecified at around 4,000 lumens. It is looking like 100 watt is actually the bare minimum. I would go Metal-Halide , but got injured by an exploding MH lamp once and stay far, far away from them now.

Here is what I am using or have available right now:

I have a GLW IP65 LED Driver:
=^_^= input: AC 85-265V
=^_^= outputC:36V
=^_^= current£º1500mA
=^_^= Max power supply£º50W

One LED that came with the driver is a GLW 50 Watt COB (supposedly) that is the 7 by 10, I posted trying to find out if it might really be a 70 watt, as I have seen complaints of this place selling 30 watts as 50 watt:
=^_^= Color: Cool White, 6000K-6500K
=^_^= Waltage £º50W
=^_^= Lumen:3500 lm

The other LED I got is a Chinese 5 by 10 50 Watt COB:
• Drive Voltage:30-34V;Chip power:50w
• Size (L*D):50mm*45mm Viewing Angle: 140 degree
• Color Tempreture: Cool White 6000-6500K
• Luminous(lv):4000-5000lm
I am cooling with a passive heatsink for a 40 watt LED COB that I mounted a CPU fan to to boost the capability, I also have a 50 mm collimator reflector housing and 44mm lens for the LED:
• Details for the lens; Diameter: 44mm,Compatible with 10-100W led chip.
• Angle: 60 degree.
• Material: optical Aspherical glasses
• Temperature: -30-120°C,Light transmittance: 98%
The LCD I have is a 7" Innolux TFT 1280x800 for a Raspberry Pi with a PCB800099 driver board I am powering with USB.

• Driver element: a-Si TFT active matrix
• Resolution: 1280*3(RGB)*800
• Display mode: Normally white, Transmissive
• Dot pitch: 0.05(W) x 0.15(H) mm
• Interface: Digital
Driver Board: PCB800099 based
• Power supply(5-12V 2A)
• 1HDMI / 1VGA / 1 AV1
• Keyboard 7.TTL Signal
• LVDS Signal 1/2 ch 6bit 8bit
I got a 3M 66 Overhead projector from the mid 1980's last night that I took the 2 projection lenses and fresnel doublet out of. I also have 2 rigid fresnel acrylic page magnifiers, and 2 flexible fresnel page magnifiers, along with a Kodak 100mm - 150mm F:3.5 5" Slide Projector Lens.

I think the parts from the 3M overhead projector are the best, along with possibly using the rigid fresnel page magnifiers. The flexible lenses are crap.

Right now I am mounting it in a cardboard box... and took the MB out of a Acer One 10 S1002 Windows tablet that I broke the screen on, and mounted it in the box with a HDMI cable going to the board, though might replace it with a Chrome Cast.

I jumped into acquiring parts a little too quickly, but think I have the right stuff now, just not the "Optimal parts" I am trying to build it as cheap as possible, then once it is working, I will swap out components with higher-end ones that wont be in constant risk of breaking, and will transfer it to a new case.

Other than a 100 Watt LED, any other hints/tricks or potential issues anyone sees?

#### wayneh

Joined Sep 9, 2010
17,152
So the Chinese LED draws 50W at 32V, which equates 1563mA. That should be OK with your driver. The documentation is cryptic for that $1 device. The e-bay ad says a 1050mA setting is ideal but I think the photo shows the output is 1300mA. It's very hard to tell what's happening. More clarity around this would be nice. Perhaps you could even measure the current with your two LEDs. One thing is for sure, you cannot get the power and lumens you expect without adequate current. #### crutschow Joined Mar 14, 2008 27,010 I have an LG PF1500 LED HD projector which takes 90W (at maximum brightness setting) which has good brightness on a 100" (diagonal) screen in a dark room at the medium power setting, so it doesn't take a lot of LED power for good brightness in a dark room. It's great for watching football. Thread Starter #### Craig Nash Joined Aug 30, 2016 6 So, bit of an update, I managed to tear the LVDS FPC cable on my 7" LCD, doh! I dont feel like trying to patch it, or see if I can find a replacement, was only$30 for the LCD plus the driver.

I do have an Acer Switch 10 S1002 Windows Tablet I got about a year ago, then got hit by a Muni train, and the screen, PLUS keyboard dock got cracked, though the LCD itself was fine. I didn't think it would be possible to get the LCD out of the digitizer module without breaking it, but I managed it, and I was able to get the LED backlight off of it also, and the entire thing still works perfectly. Since everything is soldered to the board, it is very small, maybe 2.5" x 2.5", and the LCD is 10.1" 1920x1080, which will be a LOT better than the 7", and I noticed that with the backlight off, the 7" display was transparent even when off, and this acer display is solid black except for what is being displayed, which will give much better blacks, letting more light be utilized in dark scenes.

I am going to combine it with the doublet fresnel from the 3M projector, and use the doublet projection lens for now, until I can get a triplet. My big thing is the LED. I am not quite getting why the specs of all the 50 Watt LED COB's say 50 - 100 lumens per watt, and claim 3,000 - 5,000 lumens for a 50 watt, and I cant even see it. In theory, the 100 watt 8,000 lumen should do in a high level HD projector pre-assembled, and yet I have read that they dont get close to even 2,000 lumen pre-made projector. I would really like to utilise the 50 watt, but think I will have to get a 100 watt. In terms of my original question, any chance the 7x10 LED is actually a 70 watt sold as a 50 watt and being under driven? It has no real specs, but GLW does claim to have a 50 watt 7by10, just an odd setup, even if it is 50 watt, how much can an LED COB be over-driven before dying?

I know I get much better output when I have the 44mm LED lens attached with the collimator relector base, but the beam is so tight, I couldnt even cover the whole 7" lcd,so the 10" wont work. I was thinking of making a sort of 4 sided light cone with aluminum foil or something to go fro the edge of the LED to the edge of the LCD, would that work? I see all the diy projectors using a LED colimator lens, plus the 2 fresnels even with 10" LCD's, so any tricks to get it to light the display? Without putting it 10 feet from the led? Any other way to get the max brightness?

I had gotten hurt pretty badly in that train accident, so being able to actually put this acer to use would be such awesome closure.

Oh, since I have the PCB800088 driver for the 7" display, which does LVDS, anyone know if I could connect that to the webcam port of the Acer? It appears to be 40 pin, but I can not find ANY specs on the board anywhere, but would be nice to have HDMI & AV inputs, though not necessary since I can play anything that is usable on WIndows.

#### ajtechie

Joined Jan 10, 2017
1
Try using 100W or higher LEDs of 45x45 mil, and having 140-160 Ln/Watt. You can try Bridgelux LEDs. Costs around \$25 for 100W. This can give you a light density of about 15,000 lumens from a 100W LED. Use better cooling for this.
Try to get a better light hotspot on the Rear Fresnel, from the condenser lens, with 100% coverage(by adjusting the distance from LED).
Recommended Fresnel for 7 inch and 10 inch LCD are, Rear- F120mm, Front- F200mm. Use a triplet projection lens of 210mm.
This arrangement will give an image size of more than 120 diagonal inches from 4 meters, with better corner brightness.

After a lots of light loss inside the projector, the projected image will have a brightness of 1000 to 1500 lumens from this particular 100W LED.