Looking to power a mini halogen bulb to do film capture. It would be great if I could power it off the movie projector itself without having to get an additional power supply. The socket for the projector reads slightly over
24v. However, the lamps it uses are 21v. Someone has stated that load is a factor. Does that mean that the voltage needs to be higher than the bulb rating or not necessarily?
What I wonder is if this 24v bulb should work off the 24v socket on the projector?
The actual no load voltage will almost always be higher than the under-load voltage - unless the power supply is regulated (most movie projectors aren't regulated unless you have a theater projector)
Voltage ratings on incandescent bulbs have to be taken with some skepticism. They are usually intended to be "nominal" ratings.
For instance, a 12 Volt bulb intended for auto use will spend most of its life working at 13.8 or higher and the people that make the bulbs know that and take it into account.
Likewise projectors. The 21 volt bulb may be intended to run at 21 volts or 24 volts - unless you see the manufacturers curves regarding ambient temperature, color temperature of the light, voltage and life expectancy you're just "whistling in the dark."
Sometimes a lower voltage bulb is used at a higher voltage - it shortens the life, but puts out more light and puts out higher color temperature light - so color renditioning may be better.
Likewise, under load, your 24 volts will almost certainly be lower than 24V.
Get a 24 V lamp and try it. If you can't live with the color (should be "warmer" -less blue) be happy and expect the lamp to last longer than a 21 V lamp in the same application .
----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
formatting link
The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----
He seems to be implying that the 24 volts is measured output and 21 volts is the proper bulb for the projector - so the voltage under load is expected to be lower. In that case using a 24 volt lamp to replace a 21 volt one will be less strain on the transformer.
----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
formatting link
The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----
A 24v bulb is likely to be a 28-29v bulb in reality, running this on
21v will give a very poor result. OP needs to tell us if the 24v reading is under load or not. If its with no load, OP needs a 21v bulb, anything else will just be crap. Depending on the type of psu, it may be possible to change the output voltage to suit other bulbs voltage-wise. Whether they will have the right optical situatoin is another matter.
Then one is "second guessing" the lamp specifications, the manufacturer specifications, and the ops application.
To make a really good "informed judgment" one would have to know how the manufacturer originally intended the lamp to work - perhaps they were sacrificing some life to add better color rendition.
Anyhow the op may be transferring film to video or digital.
He states: "Looking to power a mini halogen bulb to do film capture."
That could easily mean transferring film to digital (or tape). If it is done via computer he could just as easily adjust the white level / color temp, as fiddle with the hardware.
----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
formatting link
The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----
Not really. The vast majority of 24v bulbs are for road use, where nominally 24v systems are IRL approx 28-29v. The lamps are designed to run on those systems.
I suppose the OP could underpower the bulb as you say, but its not the best option. It should work, but 21v on a 28v bulb will give lousy results.
Not really true: all of those various designations--110 volts, 117 volts, 120 volts--are just that, *nominal* designations for standard line voltage, which can vary but is somewhere in the range 110-120 volts. It's not as if light bulb manufacturers rate their bulbs for a higher voltage than that actually used.
By the way, for those who don't know, it's true that light bulbs run at less than their "rated" voltage will last longer--in some cases, a *lot* longer--than if used at normal voltage (for instance, there's an original Edison bulb somewhere which is still burning). But there's a downside: when you run a bulb this way, you get more heat than light, and they become even more inefficient. (Their light is also a lot more reddish.)
--
"In 1964 Barry Goldwater declared: 'Elect me president, and I
will bomb the cities of Vietnam, defoliate the jungles, herd the
population into concentration camps and turn the country into a
wasteland.' But Lyndon Johnson said: 'No! No! No! Don't you dare do
that. Let ME do it.'"
- Characterization (paraphrased) of the 1964 Goldwater/Johnson
presidential race by Professor Irwin Corey, "The World's Foremost
Authority."
Actually there's a specific reason to use a lower wattage mini-bulb. I need a less powerful lamp to project a useable image through a diffuser and condenser lens and bounce it into the camera with a front surface mirror. Normal projector lamps are too bright.
That's news to me, it was 110V back in the 1950s but has been 120V nominal for quite some time. I just measured mine and it's 121.4V at the moment.
If you undervolt an incandescent bulb the light output drops far more rapidly than the wattage and for a given amount of light you end up spending dollars more on electricity to extend the life of a 25 cent bulb.
Don't know, I just turned it to "lamp" and put the multi tester leads on it, came up with about 24.2 V. I know the bulbs it uses are rated at 150 w.
Actually, that's another thing, how do I know if I can use a much lower wattage lamp without doing damage? Is there some way to tell? Any markings on the electronics of the projector I should look for?
If you are going from 150 watts to 10 watts . . . that is much less strain on the transformer and you'd want a 24 volt lamp as opposed to a 21 volt one - the voltage drop due to loading will be less
As a general rule, you can always use less current/power safely - It is when you go higher that things tend to smoke.
----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
formatting link
The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----
Here in the states, most cars use 12 volts. I've seen some indication that 42 volts may be in the offing in future cars. There are still a few 6 volt systems around in vehicles.
We do have some 24 VAC equipment; it is a popular "control" voltage for relays, valves, HVAC control circuits, etc.. and some lighting . . . like "landscape","accent" and pathway lights.
He's talking about reducing the power used dramatically - so he will have close to 24 volts under load - assuming I'm following all this correctly.
----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
formatting link
The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----
It screws up the color temperature of the lamp, and if the voltage is low enough on a halogen bulb, it causes problems with the tungsten being deposited on the glass, rather than back on the filament. I ran a B&W film chain at a TV station back in the '70s. The bulbs were rated at 20 hours when run at 120 volts. I couldn't get two dozen new bulbs a month, so I ran them at 90 volts, and got a minimum of 300 hours out of each lamp. I had to increase the gain on the camera to compensate, and the picture was quite red. If I went any lower than 90 volts the video was so grainy I couldn't use it. This was on a pair of RCA TP-66 projectors.
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.