Idea for a light

I do a lot of work for the NYC Amateur Radio Emergency Service, and I have a light idea, and need to flesh it out

When I go on a call out, I'm usually lugging 2 12v 7Ah batteries to power my radio. This summer I responded to a blackout. It would be real nice to be able to setup a LOW draw, long burning lantern/table light that runs on one of these batteries.

The goal here is a small amount of light (enough to write by), and to use as little power as possible (save as much for the rig as I can)

Ideas?

Try using a MAX727 to reduce the voltage to 5v, and run a luxeon off the regulated voltage.

2 nichia's will provide very adequate light to write by...I sat up till the early hours of the morning at my camp site reading and writing by the light of my 2-nichia 3D cyan torch... I've had hundreds of hours usage out of a set of cheap D cells so the amount of power drawn is very small. Make sure that the colour pof the pen you use is in contrast to the LED colour. You will not be able to read green pen by the light of a green LED, but red will come out almost black.
To run your LED's off 12 V connect them in series and resistor off the excsss voltage.
For cyan LED's this is about 4.2V per LED.
If using Gallium arsenide (red orange and sodium yellow) technology LED's you can connect about 5 in a series row as thier voltage is about 1.8V.
This could be a very efficient light source.

Matt.

LEDs are an excellent idea! If you want something to place on table, there is the Eveready 2 LED Folding Lantern: 4AA and choice of 1 or 2 LEDs on. 200 hours of light for 1 LED and 100 hours for both on, using Alkalines. Very nice, smooth, white area light. Nice and compact. Well designed and engineered. Looks and feels very robust. $8.76 at Ohio Walmart (don't know about NYC).

Next option is either a CMG Infinity or Infinity Ultra. Both use a single AA and come with neck lanyard and clip. Put clip on so it points to tail of light, and you can mount it on ballcap. Ultra is twice as bright as regular at half or less of runtime. Rated waterproof to 10-15 feet.

Third option is something like the Princeton Tec Matrix Headlamp. Runs on 2AA and has 3 white LEDs. Runtime is 40 hours on Alkaline and 100+ hours using Lithium AA. Rated waterproof to several hundred feet.

Why limit yourself to a luggable lantern?? The best thing about LEDs is that they don't attract bugs aka pesky mosquitos!

The Infinity and Ultra can't be used in winter, unless you wear a winter cap with bill.

The Matrix can't be used with ballcap, but can be used while wearing a warm watch cap, and with Petzl Helmet clips, you can mount it to a hardhat.

The lantern mention above has a fold out hanger.

http://www.brightguy.com/ carries the CMG and Princton Tec products, but I am not sure about the lantern.

My last callsign was KC8HN (advanced class), but I gave it up for a variety of reasons. I used to work ARES and Skywarn, so I know exactly how battery hungry the rigs are. I had a Yaesu 2M/70Cm dualband HT that got stolen years ago.

At least with the options I gave you, you can let your rig hog those 12V 7Ah batteries.

Originally posted by Charles Bradshaw:
LEDs are an excellent idea! ...snip...

My last callsign was KC8HN (advanced class), but I gave it up for a variety of reasons. I used to work ARES and Skywarn, so I know exactly how battery hungry the rigs are. I had a Yaesu 2M/70Cm dualband HT that got stolen years ago.

At least with the options I gave you, you can let your rig hog those 12V 7Ah batteries.

Click to expand...

<font size="2" face="Verdana, Arial">Oh, I have all sorts of lights, I was just thinking about some to run off the big batteries.

I saw the first reply - the problem with using a resistor to bleed off voltage is that it's a power waste. I have to think about this a bit. Some DC regulator circuit, and ONE or two Nichia (sp?) LEDS in white or Turquoise

Two LED's in series will be more efficient than one, as you will have to drop more voltage across a resistor and this energy is lost as heat. For the same current draw you will be getting twice th light as with one LED. You might even get aqway with three in series if thier total voltage does not exceed the battery supply voltage.
By the way, have you considered using motorbike batteries for your rig? Modern motorbikes are often fitted with starter motors these days so the batteries used in them have evolved so that they are small and light but have a very high Ah rrating for thier size. They are also coming down in price. Thier high current drain capability could be very useful if you're using a "burner" to put out a lot of watts to your aerial!

Originally posted by EMPOWERTORCH:
...snip...By the way, have you considered using motorbike batteries for your rig? ...snip...

Click to expand...

<font size="2" face="Verdana, Arial">The problem with motorbike batteries are twofold

1)Leaking
2)They usually are not deep discharge

I'm using 12v 7Ah sealed Lead Acid (SLA) batteries (2 of them on a call out). Any bigger, and they are no longer "Backpack" carry, and I'll go to my big Deep Discharge AGM battery, but that is more a "roll it into place" thing

Batteries? We get to know all about batteries on these call outs. Some of the guys even have generators!

My suggestion for something simple and _bright_:

Use three white luxeon LEDs _in series_ combined with a fixed resistor and a pot. The combined forward voltage drop of the Luxeons would be 9-10V, and you would select the fixed resistor so that with the battery fully charged it would limit LED current to no more than 500mA (say about 5 ohms). The pot would be used to adjust the current down to say 20mA (say a 100 ohm pot). Both would have to be rated to carry 500mA.

At 500 mA you would be overdriving the LEDs, and using up lots of battery power (only 14 hours of light with no power left over for the radios (( ) but adjusted down to 20 mA the Luxeons will still produce lots of useful light, and you will have the option of a bright or dim light as needed.

The underdriven Luxeons are more efficient than the Nichias, however when you underdrive a white Luxeon it will often lose color qualities. Alas always a tradeoff.

-Jon

Those camping table lamps that use run on 6 volts, either 4D or 6V lantern: If you can get a 12 volt bulb of the correct base, it should be easy to modify.

Hmmm: there is the PR16, 12.50 Vdc @ 250 Ma, rated life of 50 hours (flange base - standard flashlight type), and MSCP of 2.70. {Radio Shack w/RSU #}

Couldn't find anything for E10 base for 12 Vdc in RS catalog (it is what I use as a reference)

Try http://www.ledtronics.com/ they may have something of the base type.

I was thinking (very dangerous, that) of a standard camping table lamp of the 6V variety and possibly something from the link above. IF it uses 4D, then 7-8 AH NiMH D cells and charger.

Knowing the ingenuity of Hams, I am sure something can be jerry rigged from out ideas.