Badcaps.net Forum
Go Back   Badcaps Forums > General Topics > Off Topic / Lounge
Register FAQ Members List Social Groups Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 12-11-2011, 12:52 PM   #1
cb92
Senior Member
 
cb92's Avatar
 
Join Date: Jul 2008
City & State: Atlanta, Ga.
My Country: USA
I'm a: Knowledge Seeker
Posts: 162
Default More AA battery salvage

My AA battery/joule thief lantern is working fine, now I'm trying a regular flashlight. No joule thief this time, the bulb is incandescent, and I'm really cramped for space. I do have a series/parallel setup, hope to accomplish that with a simple wire swap.
My problem is the AA battery receptacle is putting out over five volts from each receptacle. I'm afraid I'll blow the 3 volt bulb. Is there anything I can do to protect the bulb that doesn't draw too much from the batteries? Will this remedy keep the bulb bright as the batteries run down? When the batteries drop to a low voltage, I plan to switch to series.
cb92 is offline   Reply With Quote
Old 12-11-2011, 12:54 PM   #2
ratdude747
Black Sheep
 
ratdude747's Avatar
 
Join Date: Nov 2008
City & State: New Albany, IN
My Country: USA
Line Voltage: 120VAC 60Hz
I'm a: Student Tech
Posts: 13,280
Send a message via Yahoo to ratdude747 Send a message via Skype™ to ratdude747
Default Re: More AA battery salvage

zener diode?
__________________


(Insert signature here)
ratdude747 is offline   Reply With Quote
Old 12-11-2011, 01:45 PM   #3
cb92
Senior Member
 
cb92's Avatar
 
Join Date: Jul 2008
City & State: Atlanta, Ga.
My Country: USA
I'm a: Knowledge Seeker
Posts: 162
Default Re: More AA battery salvage

Thanks, Ratdude, this looks good. I'll do the math to determine what resistor is necessary. I'll see if I can find one in my junk pile, but it's just as simple to get some from Radio Shaft.
This will be a good exercise for me, I can learn much better by doing than just reading text books.
cb92 is offline   Reply With Quote
Old 12-11-2011, 01:57 PM   #4
mariushm
Badcaps Veteran
 
Join Date: May 2011
City & State: Romania
Line Voltage: 230VAC 50Hz
I'm a: Hobbyist Tech
Posts: 3,118
Default Re: More AA battery salvage

You could use one or several of these in parallel:

http://search.digikey.com/us/en/prod...FTO-ND/1098462

They generate 3v @ 250mA from anything up to 13v and have only about .625v drop so as long as you give it at least 3.6v it will generate stable output.

Besides the 50 cents piece you only need a couple of 1uF capacitors, see the datasheet.

or this... http://search.digikey.com/us/en/prod...FDB-ND/1635997

a bit harder to solder but can manage up to 1a and has only 0.25v dropout

Last edited by mariushm; 12-11-2011 at 02:01 PM..
mariushm is offline   Reply With Quote
Old 12-11-2011, 04:43 PM   #5
cb92
Senior Member
 
cb92's Avatar
 
Join Date: Jul 2008
City & State: Atlanta, Ga.
My Country: USA
I'm a: Knowledge Seeker
Posts: 162
Default Re: More AA battery salvage

The flashlight bulb measures 1.8 ohms. The input voltage will be 5 to 10 volts. This makes for about 1.6 amps. The second voltage regulator has more power.
My text book shows a zener diode in parallel and a resistor in series with the load for this simple circuit. Does this mean the zener consumes all the current over it's avalanche level? Does the resistor in series with the load (which will be about the same resistance as the load, apparently) also consume current? It seems this setup would draw the batteries down.
I like the idea of a regulator chopping the current to protect the bulb. This chopping should consume less power, right?
I'll check my files for schematics using these power regulators. Maybe a data sheet may have a typical schematic.
cb92 is offline   Reply With Quote
Old 12-11-2011, 05:35 PM   #6
mariushm
Badcaps Veteran
 
Join Date: May 2011
City & State: Romania
Line Voltage: 230VAC 50Hz
I'm a: Hobbyist Tech
Posts: 3,118
Default Re: More AA battery salvage

You said you have a 3v bulb and you were afraid of burning it, that's why I gave you links to those regulators. There are lots of designs, with fixed voltage output as I gave you, or with adjustable output.

Digikey has a ton of those, various voltages and maximum amps they're capable - just pay attention to the dropout voltage they have. Ideally, you'd want to use a device with as low as possible dropout voltage.

The datasheets do have schematics but they're basically 3 pin devices, in, ground and out - can't be simpler than that. You just add two capacitors at each end.

These regulators are better than just diodes and resistors but not by much - their efficiency is about 75-80% - it depends on what you choose and what you feed into them.
mariushm is offline   Reply With Quote
Old 12-11-2011, 07:30 PM   #7
cb92
Senior Member
 
cb92's Avatar
 
Join Date: Jul 2008
City & State: Atlanta, Ga.
My Country: USA
I'm a: Knowledge Seeker
Posts: 162
Default Re: More AA battery salvage

I went ahead and tried the setup with no electronics. The battery pack is putting out about 5 volts, the bulb did not blow. It seems these bulbs will take extra voltage. I'll see how long it lasts. These used AA batteries should not stay at 5 too long. I did wire the system for series/parallel, so we will see just how much time I can get out of batteries that my cameras and mice rejected.
cb92 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 10:27 AM.


Badcaps.net Technical Forums 2003 - 2014
Powered by vBulletin ®
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.

Did you find this forum helpful?