disable lamp in DLP projector

[Hans Christian]

I'm helping my daughter's school on a science project. Basically we
need to remove the lamp on a DLP projector and shine laser light into
the optics. However after we removed the lamp and placed the cover
back the DLP projector would not start. It seems that there's a
protection mechanism that recognizes the fact that the lamp is not
there. How do we disable this mechanism?

The projector in question is Infocus LP120.

Many thanks

Hans

 

[BOB URZ]

I'm helping my daughter's school on a science project. Basically we
need to remove the lamp on a DLP projector and shine laser light into
the optics. However after we removed the lamp and placed the cover
back the DLP projector would not start. It seems that there's a
protection mechanism that recognizes the fact that the lamp is not
there. How do we disable this mechanism?

The projector in question is Infocus LP120.

Many thanks

Hans

I think you have chosen a project that is NOT a good one.
The power supply probably has a sense circuit for the bulb.
No proper start, no run. You probably have s single chip DLP.
If you do, there is a color wheel that filters the color from the bulb.
Since the color from the laser is monochromatic, what are you trying
to accomplish? There is a reflector behind the bulb to collimate and
focus the light into the optics. A narrow beam laser will not come close.
So, i think you have chosen a questionable project.

There have been speciality laser projectors in the past.
The strategic air commend used to use them in the command bunker.
I once watched general hospital on 6 screens at once on the laser
projectors (long gone now). They were dye pumped and definitely
had a very saturated look to them. The system looked like a cross
between a heart lung machine and a movie projector.

Bob

 

[kip]

Dont even think about doing it..
Find another project to do.

kip

 

[Sam Goldwasser]

Dont even think about doing it..
Find another project to do.

Probably but - and I'm guessing here:

It probably senses both of the following:

1. That the lamp starts and current is flowing and regulating properly.
2. That there is adequate light reaching the optics.

(1) can be faked out by simply moving the lamp out of the projection path
but this probably won't be easy since there may be up to 30 kV on the lamp
when starting and it still will need to be cooled..

(2), if present, could present more of a challenge. Without service info -
gererally not available - no way to figure that out.

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[James Sweet]

Probably but - and I'm guessing here:

It probably senses both of the following:

1. That the lamp starts and current is flowing and regulating properly.
2. That there is adequate light reaching the optics.

(1) can be faked out by simply moving the lamp out of the projection path
but this probably won't be easy since there may be up to 30 kV on the lamp
when starting and it still will need to be cooled..

(2), if present, could present more of a challenge. Without service info -
gererally not available - no way to figure that out.

I would think the thing to do would be look at the ballast board for the
lamp and find a line that goes logic high or low when the lamp starts
successfully, however I too question the purpose of this project, the result
is likely to be a dim blob of laser light on the screen, if it can even be
aligned well enough to put anything at all on the screen. Not very exciting
at best.

 

[Sam Goldwasser]

I would think the thing to do would be look at the ballast board for the
lamp and find a line that goes logic high or low when the lamp starts
successfully, however I too question the purpose of this project, the result
is likely to be a dim blob of laser light on the screen, if it can even be
aligned well enough to put anything at all on the screen. Not very exciting
at best.

Depending on what the objective really is, could be intertesting.

After all, you basically have control of half a million mirrors.....

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Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
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[Hans Christian]

Thanks everyone for your inputs. The idea is to demonstrate a
programmable hologram. Some additional lenses may be necessary.

Anyway, I just figure that when people repair a projector they must
have a way to trun on the control electronics without the lamp. The
answer is out there.

 

[James Sweet]

Thanks everyone for your inputs. The idea is to demonstrate a
programmable hologram. Some additional lenses may be necessary.

Anyway, I just figure that when people repair a projector they must
have a way to trun on the control electronics without the lamp. The
answer is out there.

I'm not sure why one would need/want to fire up the projector without the
lamp to repair it, the lamp is needed to see what's wrong with the thing and
if the lamp isn't firing up that's the first thing to fix.

 

[Sam Goldwasser]

I'm not sure why one would need/want to fire up the projector without the
lamp to repair it, the lamp is needed to see what's wrong with the thing and
if the lamp isn't firing up that's the first thing to fix.

Maybe if something in the logic or power supply needs to be tested.

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[BOB URZ]

Maybe if something in the logic or power supply needs to be tested.

--- sam | Sci.Electronics.Repair FAQ Mirror:

Even if he did get the optics on, what about light output?
A collimated projector light is 200 to 400 watts of full spectrum
light. And you want to put a laser in there with a watt or
2 of power? And then have even that small level cut down
by the rotating color wheel. How do you propose to get
by that issue? And how are you going to spread out the laser
enough to cover the area of the image sensor?

Bob

 

[Sam Goldwasser]

Even if he did get the optics on, what about light output?
A collimated projector light is 200 to 400 watts of full spectrum
light. And you want to put a laser in there with a watt or
2 of power? And then have even that small level cut down
by the rotating color wheel. How do you propose to get
by that issue? And how are you going to spread out the laser
enough to cover the area of the image sensor?

No one claimed to be attempting to replace the HID lamp with
a laser, only to be using the DMD/DLP device as a programmable
hologram generator or something along those lines.

Here is a paper which I'm guessing describes what he's interested
in doing:

http://innovation.swmed.edu/research/instrumentation/dh3p.pdf

As a practical matter, DMD/DLP development boards are available
which would make this more straightforward.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
+Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
| Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

Note: These links are hopefully temporary until we can sort out the excessive
traffic on Repairfaq.org.

Important: Anything sent to the email address in the message header above is
ignored unless my full name is included in the subject line. Or, you can
contact me via the Feedback Form in the FAQs.

 

[James Sweet]

No one claimed to be attempting to replace the HID lamp with
a laser, only to be using the DMD/DLP device as a programmable
hologram generator or something along those lines.

Here is a paper which I'm guessing describes what he's interested
in doing:

http://innovation.swmed.edu/research/instrumentation/dh3p.pdf

As a practical matter, DMD/DLP development boards are available
which would make this more straightforward.

What's involved in driving the bare chip? I seem to recall they're
essentially DRAM chips.

 

[BOB URZ]

What's involved in driving the bare chip? I seem to recall they're
essentially DRAM chips.

http://focus.ti.com/pdfs/vf/onet/blazeevalkit.pdf
http://oemagazine.com/fromTheMagazine/may03/prodtrends.html

Have fun!

Bob