Heya Raf, i let mine cool down without the fan, having a fan running on a hot bulb without the lamp being on is infact more dangerous then with the lamp on with the fan at the same time, having a fan run on after the bulb is off may cause it to crack as the glass may contract too quikly, condensers also are viable to the same problems.
One thing ill tell you guys not to do at all ever, never turn on a fan when a lamp and condenser is hot, the lamp will surley explode and you can kiss your condenser goodbye, this is caused from too much of a temperature variance to soon, turbulent cold airflow over a lamp can cause the same problems hence why sucking the hot air is safer. never run a fan on a halogen either as they will surley explode, if it dont, you run a very high risk, a finger print can wipe out a halogen, same with metal halide, but most metal halides are protected by the outer shell, halogen have no protection whats so ever.
Trev
Thanks for the reply, Trev.
I agree with what you said, it makes sense. It's just that I've noticed that commercial projectors keep the fans running for a while after the lamp turns off, and was wondering why.
Anyway, I will do just that, suck the hot air off of the bulbs case and not blow air directly to it.
I ordered fans that ramp-up as temp rises; are they OK for a PJ, or are they a bad idea?
Thanks!
Raf.
I agree with what you said, it makes sense. It's just that I've noticed that commercial projectors keep the fans running for a while after the lamp turns off, and was wondering why.
Anyway, I will do just that, suck the hot air off of the bulbs case and not blow air directly to it.
I ordered fans that ramp-up as temp rises; are they OK for a PJ, or are they a bad idea?
Thanks!
Raf.
Focal length w/ mirror
Hey guys,
I'm new to the forum and have been allocating about 5 hours every day to reading the posts on this site, there is alot of information out there.
Anyway, to my question. I looked at mathias' picture of mirror size calculations and I had a basic question. I from what I have gathered one must match the fresnel's (the one between the light source and LCD) focal length with the distance from the light source, or the condensor. With a mirror does one only need to measure this focal distance as the distance from the fresnel to the center of the mirror and then off at a 90 degree angle to the light source. Sorry if this is a newb question or it has been covered in another forum, I havent found it yet and I have done quite some extensive searching. Thanks in advance.
Hey guys,
I'm new to the forum and have been allocating about 5 hours every day to reading the posts on this site, there is alot of information out there.
Anyway, to my question. I looked at mathias' picture of mirror size calculations and I had a basic question. I from what I have gathered one must match the fresnel's (the one between the light source and LCD) focal length with the distance from the light source, or the condensor. With a mirror does one only need to measure this focal distance as the distance from the fresnel to the center of the mirror and then off at a 90 degree angle to the light source. Sorry if this is a newb question or it has been covered in another forum, I havent found it yet and I have done quite some extensive searching. Thanks in advance.
Well, after seeing smoke coming out of my fans when I turned them off with the light; I decided to leave them running for a while after the lamp is turned of.
I'm thinking about programming a small microcontroller to do all that for me.
(turn fans on, lamp on, lcd on, and also off at the right times when a switch is pressed)
I'm thinking about programming a small microcontroller to do all that for me.
(turn fans on, lamp on, lcd on, and also off at the right times when a switch is pressed)
ace3000_1 said:
Size and flow do corelate but I agree that some smaller fans will outflow much larger ones; it's all in the speed and blade design.
About the noise, I disagree 100%. The noise can for sure increase (and decrease) with rpm but the angle and shape of the blades is what will truely determine how loud or quiet a fan is. The S-shaped blades are usually the quietest, and the loudest are the flat-looking ones where you see only the edge.
-Steve
Helo,
there I draw an idea, for replacing the first fresnel with right shaped reflector:
http://buildart.lv/Faili/paraboliks.gif
-- the reflector are taken from Satelite antenna (the stuff what catches tv signal from satelites, without any tech, but with its special lever who holds the lamp in precision focus point, that the reflected light makes a paralel beam. and i place aluminium foil, inside, to make better reflection, than original white matte coating.
this i have not tested in projector, but i tested it with 500W conventional light bulb
- the results vere fantastic - we get a light beam, and we can hit the clouds with this light beam! - so, i decided that it works - light beam are parallel. so it is the same what first frensnel does. and many comercial projectors dont have the first frensenl so, they have a reflector what makes paralel light beam.
the fresnel are absorbing the light, but good reflector will be absorbing much smaller percent of light, so, we wil get brighter images?
sory for my bad english
there I draw an idea, for replacing the first fresnel with right shaped reflector:
http://buildart.lv/Faili/paraboliks.gif
-- the reflector are taken from Satelite antenna (the stuff what catches tv signal from satelites, without any tech, but with its special lever who holds the lamp in precision focus point, that the reflected light makes a paralel beam. and i place aluminium foil, inside, to make better reflection, than original white matte coating.
this i have not tested in projector, but i tested it with 500W conventional light bulb
- the results vere fantastic - we get a light beam, and we can hit the clouds with this light beam! - so, i decided that it works - light beam are parallel. so it is the same what first frensnel does. and many comercial projectors dont have the first frensenl so, they have a reflector what makes paralel light beam.the fresnel are absorbing the light, but good reflector will be absorbing much smaller percent of light, so, we wil get brighter images?
sory for my bad english
ywh has ellipsoidal reflectors for sale but they will not be suitable for standard MH, need to use the small UHP lamps (ywh also sells them)
EDMUNDOPTICS.com sells ellipsoidal reflectors that may fit 150W CDM-T Philips lamp if you want to use Metal Halide lamp
Additional optics may be required to expand light cone from ellipsoidal type reflector since beam angle usually not very large
I will be testing with ellipsoidal and short arc uhp lamps in DIY projector soon and will post results (if succesful)
EDMUNDOPTICS.com sells ellipsoidal reflectors that may fit 150W CDM-T Philips lamp if you want to use Metal Halide lamp
Additional optics may be required to expand light cone from ellipsoidal type reflector since beam angle usually not very large
I will be testing with ellipsoidal and short arc uhp lamps in DIY projector soon and will post results (if succesful)
I've been reading this thread for a while, and even though this was a while back, I must throw in my two bits about the reflector shapes. Parabolic is used to create parallel rays from a point source at it's focus. Elliptical is for focusing said source to the ellipse's other focus (like convex lens). Hyperbolic is to spread out the source as if the virtual image was behind the reflector (like concave lens). Spherical is just a variation of elliptical with both focal points together. The shape is geometrically dependent on the principals of conics and is not universally applicable. Any attempt to move the source in or out to achieve a different focal range will result in aberrations and "smear" out the point source. All shapes can be made shallow or deep, in the ellipse or sphere they will just begin to wrap back around, potentially controlling more light. Just like lenses, no one shape is universally optimal.
However, play with an overhead projector focus, and you will see where the focal point for the light source is. It is contained within the circumference of the objective lens, and has nothing to do with the projected image. Ideally it is a small spot to avoid lens aberrations, but if the lens is large you can get away with a less than ideal light source. The reflector aberrations themselves don't affect image quality as long as the LCD is evenly lit and all that light goes through the objective and is very close to the size of the projected image. I hope my opinion is correct, relevant and therefore can be used to settle some disagreements on here. I am no engineer but I work with my hands and have a good feel for geometry.
However, play with an overhead projector focus, and you will see where the focal point for the light source is. It is contained within the circumference of the objective lens, and has nothing to do with the projected image. Ideally it is a small spot to avoid lens aberrations, but if the lens is large you can get away with a less than ideal light source. The reflector aberrations themselves don't affect image quality as long as the LCD is evenly lit and all that light goes through the objective and is very close to the size of the projected image. I hope my opinion is correct, relevant and therefore can be used to settle some disagreements on here. I am no engineer but I work with my hands and have a good feel for geometry.
if you want to project image for about 5-6 feet distance then use some good quality laptop screen as a source no need to disassemble screen just turn ON the laptop as usual and go to display properties or Graphic properties now rotate desktop by 180 degree(flip image upside down) using settings available. Now place a Fresnel Lens in front of screen to get a nice descent projection on wall at distance of 5-6 feet from laptop.
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