Powering a on camera light with AC at DVinfo.net

Go Back   DV Info Net > The Tools of DV and HD Production > Photon Management

Photon Management
Shine an ever-loving light on you.


Reply
 
Thread Tools Search this Thread
Old September 29th, 2009, 10:29 PM   #1
Trustee
 
Join Date: May 2004
Location: USA
Posts: 1,554
Powering a on camera light with AC

I have a NRG on camera light and I want to use it to light interviews but I don't want to haul the 12 lb battery with me. Is it possible to bridge the AC Battery charger to the light without the battery. Basically I need a power cable with cigarette (female) connector on both ends.

NRG | 56001 Varalux Pro DC Dimmer On Camera Light | 56001 | B&H

Only thing I can come up with is buy two of these cables, cutting them in half and splicing the two female end together
http://www.bhphotovideo.com/bnh/cont...u=92992&is=REG
Pete Cofrancesco is online now   Reply With Quote
Old September 30th, 2009, 04:17 PM   #2
Trustee
 
Join Date: Nov 2008
Location: Miami, FL USA
Posts: 1,483
The specs at B&H say this is a 100 watt light; I'm guessing your battery charger doesn't put out 100 watts, it wouldn't need to do that just to charge the battery. I don't think it's an ac power supply, which is what you would need...you could check the specs on the charger itself... iirc, 100 watts at 12 volts is a little over 8 amps.../Battle Vaughan
Battle Vaughan is offline   Reply With Quote
Old September 30th, 2009, 05:44 PM   #3
Inner Circle
 
Join Date: Jan 2003
Location: Chicago, IL
Posts: 6,609
it doesn't appear this light is compatible with AC. I have an old Bescor that can be useed with AC by 1) changing to a 100W bulb and 2) pulling the cig adapter off the end of the cable from the light since it already has a 2 prong plug on it. I have used it in the same way you are talking about. It sure keeps the weight of that battery belt in the car.

If you're going to be on a tripod why not wrap the battery belt around the tripod legs and then run the light. No weight on you and you don't have to worry about AC cords. Of course you do have to watch your run time so you don't run out of battery power.
__________________
What do I know? I'm just a video-O-grafer.
Don
Don Bloom is offline   Reply With Quote
Old September 30th, 2009, 07:52 PM   #4
Trustee
 
Join Date: May 2004
Location: USA
Posts: 1,554
Quote:
Originally Posted by Battle Vaughan View Post
The specs at B&H say this is a 100 watt light; I'm guessing your battery charger doesn't put out 100 watts, it wouldn't need to do that just to charge the battery. I don't think it's an ac power supply, which is what you would need...you could check the specs on the charger itself... iirc, 100 watts at 12 volts is a little over 8 amps.../Battle Vaughan
I think you're right. The power supply outputs DC but not enough amps. I looked at the battery charger and it says input 32w AC and an output of 13v DC 1A.
Pete Cofrancesco is online now   Reply With Quote
Old October 1st, 2009, 06:05 AM   #5
Trustee
 
Join Date: Nov 2005
Location: Sydney Australia
Posts: 1,570
To power this light you'd need a 12V 10amp transformer, the lamp will be just as happy running off AC or DC. Such things are available and would be a safer solution than changing the lamp for a 110V one and running 110V AC to the lamp. Also a 100W 12V lamp produces a bit more light than a 100W 110V lamp and is more robust because of the thicker filament.
Bob Grant is offline   Reply With Quote
Old October 1st, 2009, 06:40 AM   #6
Regular Crew
 
Join Date: Jul 2005
Posts: 110
Powering a dc bulb is not the same as ac. The amperage differs by about 10x's. Example: a 100 watt dc bulb needs about 8.3 amps whether you use a battery or a transformer that puts out dc. A 10amp transformer rivals the weight of your 12 lb battery.
A 100 watt ac bulb needs .83 amps at 120 volts ac. Unfortunately there is no benefit to what you want to do.
That cigarette lighter extension can only handle a couple of amps, it will get very hot and start smoking almost immediately.
By the way, why do you want to use an on camera light for an interview? That type of lighting will look horrible.
Gary
Gary Moses is offline   Reply With Quote
Old October 1st, 2009, 08:54 AM   #7
Trustee
 
Join Date: May 2004
Location: USA
Posts: 1,554
Quote:
Originally Posted by Gary Moses View Post
By the way, why do you want to use an on camera light for an interview? That type of lighting will look horrible.
Gary
I'm glad you guys warned me. I did deposition where the camera was wide open and at 6db gain. I was going to bounce my camera light off the ceiling to increase the exposure a couple of stops so I wouldn't have to use any gain. I could have brought 9" clamp light you find at the hardware store, but they're cumbersome, delicate to pack, don't mount securely, and don't look as professional.
Pete Cofrancesco is online now   Reply With Quote
Old October 1st, 2009, 08:15 PM   #8
Trustee
 
Join Date: Nov 2005
Location: Sydney Australia
Posts: 1,570
Quote:
Originally Posted by Gary Moses View Post
Powering a dc bulb is not the same as ac. The amperage differs by about 10x's. Example: a 100 watt dc bulb needs about 8.3 amps whether you use a battery or a transformer that puts out dc. A 10amp transformer rivals the weight of your 12 lb battery.
A 100 watt ac bulb needs .83 amps at 120 volts ac. Unfortunately there is no benefit to what you want to do.
That cigarette lighter extension can only handle a couple of amps, it will get very hot and start smoking almost immediately.
By the way, why do you want to use an on camera light for an interview? That type of lighting will look horrible.
Gary
That's horribly mixed up!

A 12V 100w light bulb will use exactly the same amount of current running off 12V AC as it will running of 12V DC. In both cases the current = 100 div 12 = 8.33 Amps.

Assuming the light with it's cigarette lighter plug can happily run from a 12V battery it'll run just as happily from a 12V AC transformer. Those cigarette lighter plugs and sockets come with a fuse. All the ones that I've bought have a 10 amp fuse in them. The cigarette lighter in a car draws around 10 amps. We've run lots of gear from the lighter sockets in vehicles. The wire in that extension lead does look a bit thin for 10A though.

[edit]
A horrible thought entered my head after posting this. This light uses a dimmer and is speced at 12V DC, the lamp will not care if it's DC or AC but the dimmer very likely might. Anyways I found you a 12V 10Amp DC power supply that'll work as a battery replacement here: OFNA 12V/10A Regulated DC Power Supply [OFN92135]

Sorry about the confusion

Last edited by Bob Grant; October 1st, 2009 at 09:40 PM. Reason: Additional information
Bob Grant is offline   Reply With Quote
Old October 1st, 2009, 09:51 PM   #9
Trustee
 
Join Date: May 2004
Location: USA
Posts: 1,554
Quote:
Originally Posted by Bob Grant View Post
Anyways I found you a 12V 10Amp DC power supply that'll work as a battery replacement here: OFNA 12V/10A Regulated DC Power Supply [OFN92135]
How would you connect that to a light with a cigarette lighter cord end?
Pete Cofrancesco is online now   Reply With Quote
Old October 2nd, 2009, 04:59 AM   #10
Trustee
 
Join Date: Nov 2005
Location: Sydney Australia
Posts: 1,570
Quote:
Originally Posted by Pete Cofrancesco View Post
How would you connect that to a light with a cigarette lighter cord end?
You need to get someone to make you up a lead with a cigarette lighter socket on one end and banana plugs on the other. A bit more Googling found this unit:PS15KX, Pyramid PS15KX, Pyramid 12V Power Supplies, Pyramid 12V Power Supplies It's a bit bulkier but comes with exactly the socket you need on the front of the unit. Don't be put off by the 13.8V part of the specs as lead acid batteries are 13.8V anyway.

There's also at least one vendor selling suitable switch mode power supplies on eBay NEW 12V 10A Adapter Power Supply for LCD monitor +Cord - eBay (item 220405347954 end time Oct-25-09 23:26:03 PDT) This one would need someone to fit the cigarette lighter socket for you.

To be honest though if you intend to stick with using an on camera light it might be time to consider an LED or HID light. They're way more efficient than a tungsten light so they need less power and produce less heat. They're also lighter.
Bob Grant is offline   Reply With Quote
Old October 2nd, 2009, 07:52 AM   #11
Regular Crew
 
Join Date: Jul 2005
Posts: 110
Bob Bob. If you look closely I didn't mention using anything about diodes to covert the voltage to dc. As you must agree it doesn't matter whether it's ac or dc the amperage is the problem. An 8.3 transformer (before conversion or not to dc) weighs a ton which is the reason why Pete wanted to convert it to ac. He didn't want to carry around a heavy battery.
I have used a newer version of converters for my high amperage LEDS which are made for car coolers, etc., they use electronic transformers. The problem is that I haven't seen anything above 6 amps.
Gary
Gary Moses is offline   Reply With Quote
Old October 2nd, 2009, 09:13 AM   #12
Trustee
 
Join Date: Nov 2005
Location: Sydney Australia
Posts: 1,570
Quote:
Originally Posted by Gary Moses View Post
Bob Bob. If you look closely I didn't mention using anything about diodes to covert the voltage to dc. As you must agree it doesn't matter whether it's ac or dc the amperage is the problem. An 8.3 transformer (before conversion or not to dc) weighs a ton which is the reason why Pete wanted to convert it to ac. He didn't want to carry around a heavy battery.
I have used a newer version of converters for my high amperage LEDS which are made for car coolers, etc., they use electronic transformers. The problem is that I haven't seen anything above 6 amps.
Gary
What you're after is a switch mode power supply. The enclosed ready to use ones that'll deliver 10A at 12V are not very common, I doubt you'll find them in retail stores but they are made. If you're really stuck for one I can get one of these: http://www.powerbox.com.au/pdf/TRG150.pdf and ship it to you. I'll even fit whatever socket you need just for the cost of the parts and postage.
Bob Grant is offline   Reply With Quote
Old October 2nd, 2009, 11:38 AM   #13
Regular Crew
 
Join Date: Jul 2005
Posts: 110
I'm not if your post was to me, but I have the 6amp converters with cigarette light plugs on them already. My maximum demand for the crees is 4 amps.
Gary
Gary Moses is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > The Tools of DV and HD Production > Photon Management

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 08:43 AM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network