electrical question
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Posted on Mar 08, 2007 08:57 pm
zekthedeadcow
Eat Spam before it eats YOU!!!
Member Since: May 11, 2002
I have a 12volt motorcycle battery... I need it to output 8volts for a 16mm movie camera... how do I do that? :)
can I just get a pot/fader and a voltage reader and turn up the pot until I get 8 volts on the screen or am I being an idiot?
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steveopop musicMember
Since: Sep 27, 2005
Mar 08, 2007 09:13 pm It could be done but you would be wasting a some of your battery power as heat.
Recent devices are likely to have voltage limiting circuitry but I doubt a 16mm camera has that capacity.
Can you even purchase 16mm film these days??
zekthedeadcowEat Spam before it eats YOU!!!Member
Since: May 11, 2002
Mar 09, 2007 05:12 am It's my understanding that most TV shows are still shot on 16mm along with quite a few indie movies.
The circuit seems fairly simple... on/off switch and motor...with an offshoot to power a second motor (for external reels)... it's the second motor that is apparently the problem... the camera will run an internal load from a 6v battery buy it's not enough to run the external reels.
pjkPrince CZAR-mingMember
Since: Apr 08, 2004
Mar 09, 2007 09:56 am hmm, seems a voltage divider would work quite well, but I'm not quite sure what your total resistance would be.
There's a tech calc for stuff like that:
www.riedon.com/us/index.p...3&Itemid=23
that i've been using to do some of my calculations.
If you know the amps the device will take, then you could calculate out a voltage divider, that creates the total resistance, and keeps the limit at your amperage, so you don't cook anything.
I'm kinda leary of a pot, as that's a lot of amperage that could go through the pot as heat, and just drain the battery. I guess it's worth a try though. All you'd do if your off is drain the battery quick.
pjkPrince CZAR-mingMember
Since: Apr 08, 2004
Mar 09, 2007 10:08 am Here's another calculator, for all the different types of formulas of ohms law
www.the12volt.com/ohm/page2.asp
I did a quick calcy:
12 (v1) volts, with a supply of 200mA (I=.002a) = 6000 ohms (rT)
I'm just guessing at the Amperage.
So if you have a voltage divider that can pass 200mA, and tap voltage out at 8 volts (v2), you would need 2 resistors: 2000 (r1) and 4000 (r2). 2k between v1 and v2, and 4k between v2 and ground.
v1 = 12 volts
|
r1 = 2k resistor
|
v2 = 8 volts
|
r2 = 4k resistor
|
v3, 0v = ground
I hope that's right.
Get your amperage needs, and re-calc to get your accurate total resistance, then 2/3 that number for r1 and r2.
DISCLAIMER: I'm no EE, don't take my word as gospel. I only goof around with this stuff for a hobby, and don't totally know what I'm talking about =).
Mar 09, 2007 10:34 am Rather than trying to convert a 12 V source, I think you'd be better off using "D" cells in series. Five cells would give you 7.5 V, six cells 9V. Try each voltage and see which one operates the camera closest to the correct speed.
zekthedeadcowEat Spam before it eats YOU!!!Member
Since: May 11, 2002
Mar 09, 2007 04:20 pm I was actually thinking I bought a 6volt battery :) but 12 volts runs my other video camera... plus I'm not terribly concerned about wasting electricty... as long as it operates for a couple hours and is rechargeable...
Noize2uCzar of MidiAdministrator
Since: Apr 04, 2002
Mar 14, 2007 10:30 pm zek, you just want a simple voltage regulator circuit as that will allow you to run the 12v battery and only let the line see 8 volts or whatever is needed.
zekthedeadcowEat Spam before it eats YOU!!!Member
Since: May 11, 2002
Mar 15, 2007 04:02 pm lol look at the price:
List $82.50
Your Price $104.40
WTF! makes me feel special...
thanks for the link though! I'll see if I can get one locally.
Mar 15, 2007 04:08 pm I only posted the link so you could see the specs, that's why I put, "Here's an example" in my post. I'm pretty sure you can get one cheaper somewhere else... maybe even free if you know someone who works at a golf course or something like that...
pjkPrince CZAR-mingMember
Since: Apr 08, 2004
Mar 15, 2007 04:22 pm I think he meant that the list was 82$, but for Zek, they'll charge him 104$.
Nice to be loved =).
Mar 15, 2007 04:26 pm I see, did the same to me...
WaltChief Cook and Bottle WasherMember
Since: May 10, 2002
Mar 18, 2007 12:33 am Quickest easiest way would be to pick up a little car inverter and generate 110ac or 220 if you are euro. Then use the ac adapter that comes with the unit.
