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Help with ohms resistance with projector lamp

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StealthRT

Member
Hey all,

My projector lamp recently died after a few years. I had a good idea to use high-powered LED's in place of the $250+ lamp replacement. However, there is a problem at hand in doing that.

The projector will not operate if it detects no bulb connected. A friend of mine and i have figured out the resistance of the bulb itself:

165W / 220V = 0.75
220 / 0.75 = 293.333333

So i am looking for a Ohm value of 293. I just wanted to make sure what i am getting is what will be needed. Here is the local Radio Shake parts list that i think i will need:

- 1 x 270 ohm 1/2W 5% Carbon Film Resistor(270 ohm 1/2W 5% Carbon Film Resistor pk/5 - RadioShack.com)
- 2 x 10 Ohm, 1/2W 5% Carbon Film Resistor(10 Ohm, 1/2W 5% Carbon Film Resistor (5-Pack) - RadioShack.com)

Now how would i make the last 3ohms? I can not find any 1ohm on radio shakes site. The lowest being 10ohms.

Any help would be great! :)

David
 

Hero999

Banned
Don't worry about it, it probably doesn't have to be that accurate, 330R (probably even higher) will probably do.

Those resistors you've selected don't have a high enough power rating, they'll blow.

It might not be possible anyway, when the bulb is off it will have a very low resistance, probably just a few Ohms, and it might look for a very low resistance before turning the lamp on, it's worth giving it a go though.

How are you powering the LEDs?

You'll need a bridge rectifier or diode in reverse paralle to protect them from the reverse mains voltage.
 
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Nigel Goodwin

Super Moderator
Most Helpful Member
There are just too many problems with this crazy idea :D

First, they aren't conventional lamps.

Two, they don't check for simple power consumption.

Three, they run off VERY high voltages, in the thousands.

Four, LED's aren't that bright (by a LONG, LONG way)

Five, LED's aren't that white either.
 

Hero999

Banned
First, they aren't conventional lamps.
That depends on what you mean by conventional, som projectors have halogen lamps.

Three, they run off VERY high voltages, in the thousands.
That's only if it's an HID lamp.

Four, LED's aren't that bright (by a LONG, LONG way)
A couple of 20W power LEDs will give a similar amount of light to a 165W halogen lamp.
 

audioguru

Well-Known Member
Most Helpful Member
Halogen bulbs don't cost $250+, HID lamps do.
Nobody makes a big screen bright projection TV that uses LEDs.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
That depends on what you mean by conventional, som projectors have halogen lamps.
Never seen one with halogen, apart from antique film projectors :D

That's only if it's an HID lamp.
Every one I've seen has been.

A couple of 20W power LEDs will give a similar amount of light to a 165W halogen lamp.
I seriously doubt it, and if it was a viable option it would have been done commercially by now - and be HUGE selling point.

If you have a projector, budget to replace the lamp yearly.
 

Hero999

Banned
Halogen bulbs don't cost $250+, HID lamps do.
Nobody makes a big screen bright projection TV that uses LEDs.
He didn't say it was a big screen projection TV.

I've seen plenty of small projectors that use halogen lamps.

Nigel said:
I seriously doubt it, and if it was a viable option it would have been done commercially by now - and be HUGE selling point.
40W of LED power is pretty close to 160W of halogen power.

Luminous efficacy - Wikipedia, the free encyclopedia

I suspect the reason why LEDs aren't used for projectors has more to do with colour rendering than efficiency.
 
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Hero999

Banned
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tcmtech

Banned
Most Helpful Member
Actually the HID type lamps just use a high voltage pulse to get them going. The actual running power of a Metal halide bulb in that wattage range is around 60 -80 volts at around 2 - 3 amps.
Your $250 bulb is the same one used by normal commercial lamps that you by for around $20 each. Being projectors use a white light its most likely a metal halide or an over driven mercury vapor bulb. ;)

Find yourself a standard issue HID bulb of the same over near same wattage. Any rated for 140 - 180 watts are close enough. They are not as fussy about wattage as most people think! A cheap 165 watt metal halide ballast can run +- 20 watts of what its rated at and you would never notice.
I have three 175 watt mercury vapor bulbs running off of 250 watt ballasts in my shop and they are identical to my 200 watt metal halides for color and brightness. And they have over 1500 running hours on them and have yet to even have the inner arc tube start to blacken! :)

Take the New standard type bulb and bust the outer glass off of it and take out the inner arc tube. retrofit that into the projector. Make sure you wash the arc tube with alcohol after you assemble it. If you dont it will burn out rather quickly. ;)
 

StealthRT

Member
Wow thanks for all the feedback :)

Here is some specs on the projector we are using for this project:
Brightness (Lumens) : 1400 ANSI
Contrast (Full On/Off) : 2000:1
Throw Dist (feet) : 5.0 - 32.0
Image Size (inches) : 38.0 - 290.0
HDTV: 720p, 1080i
EDTV/480p: Yes
SDTV/480i: Yes
Component Video: Yes
Video: Yes
Digital Input: **
Computers: Yes
Color Wheel Segs: 4
Color Wheel Speed: 2x
Native: 800x600 Pixels
Maximum: 1600x1200 Pixels
Aspect Ratio: 4:3 (SVGA)
Max Power: 230W
Voltage: 100V - 240V
Here is the full link: Toshiba Projectors: Toshiba TDP-S20U DLP projector

Here is the bulb: Newegg.com - TOSHIBA TLP-LV4 Replacement Lamp For TDP-S20U/SW20U Projector - Projector Accessories

As for what it will be used for.. Just mostly xbox games and some movies. It wont be a huge screen, maybe 60-70 inches max. The LED's we bought are high-power 20w white led high-brightness 1000LM although it would have been ideal to have just one like this one High Quality 30W White 1800 Lumen.

David
 

Hero999

Banned
Did you look at the links posted by the original poster?
Toshiba Projectors: Toshiba TDP-S20U DLP projector

It looks more like an electronic projector than a film projector to me.

It probably uses a halogen lamp and it's probably 12V to 24V not mains.

EDIT:
I've just Googled for the TLPLV4 and couldn't find much information on it. It's probably some proprietary lamp.

Here's a picture, it could be halogen or HID, I don't know, I've never seen anything like it.
 
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Nigel Goodwin

Super Moderator
Most Helpful Member
Did you look at the links posted by the original poster?
Toshiba Projectors: Toshiba TDP-S20U DLP projector

It looks more like an electronic projector than a film projector to me.
So why did you post a link to a film projector bulb?.

It probably uses a halogen lamp and it's probably 12V to 24V not mains.
Yes, it's an electronic projector, and it absolutely 100% WILL NOT use a halogen bulb, and won't be low voltage.

EDIT:
I've just Googled for the TLPLV4 and couldn't find much information on it. It's probably some proprietary lamp.

Here's a picture, it could be halogen or HID, I don't know, I've never seen anything like it.
So you've never seen a projector bulb, because that's what they look like - and they are never halogen, at least not any I've ever seen or heard of (and I've seen a fair few).

Electronic projectors bear no relation to film projectors, which appears to be all you've ever seen.
 
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