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**Force Flow** · 01-05-2008, 11:32 PM

I've got a little project in the works here, and was trying to make an infrared LED light.

Now, I'm not very good with electronics past some of the fundamental basics of electricity, but here's what I have:

Two LR41 button batteries, rated at 1.5V (from what I can tell).

A red LED. This plus the two button batteries works in a little keychain light I had, so I figured I could do the same thing, except with an infrared light. Apparently not.

I got an infrared LED found at radioshack. I don't understand the significance of all these when it comes to figuring out what is needed in terms of power and resistors, but here's what was on the back of the box:

electrical characteristics:
forward voltage: 1.2V
forward current: 100mA

absolute maximum ratings:
forward voltage (20mA): 1.6V
reverse voltage: 5V
forward current: 1.2A
reverse current: 10uA

So, what I've tried is first both button batteries, then only a single button battery. Neither worked (I was viewing the IR LED through a digital camera, since it picked up the light from a TV remote).

Any ideas? I've never had much luck with this stuff, so hopefully I didn't blow the IR LED.

Brad the best · 01-05-2008, 11:36 PM

i would try a AA or something along those lines . little more amperage out of it . hooking it up the right way?

Lespaul20 · 01-05-2008, 11:47 PM

I would try reversing the way you are hooking it up. LED are diodes so they only allow current to flow one way.

**Force Flow** · 01-06-2008, 12:30 AM

Yeah, had it the right way.

The AA did work, with the red LED, but dimly. So I tried it with the IR LED, which worked, but dimly.

So, I tried it with the button batteries again. As it turns out, this *did* work. Because of the lighting conditions and moving the LED around, I just couldn't actually see that it was turning on with the camera.

Thanks guys

sgtspector · 01-06-2008, 02:20 AM

Try connecting the leads from the led to the terminals on a 9-volt battery. That will light the led just fine. An expert in the filed once told me that it works just fine. I've been meaning to try it for a while now myself but never got around to it. A couple placed in a room and you could light a whole room up for your video camera. If you look directly at it you will see a tiny red dot from the led if it is lit.

***glc*** · 01-06-2008, 02:57 AM

9 volts exceeds the rating of that LED, it will blow it out.

The_YongGrand · 01-06-2008, 06:58 AM

Put a resistor on it - a 9V will fry the LED!

sgtspector · 01-06-2008, 11:46 AM

Perhaps they used a different led but I was told that you could simply connect the led to the battery and it would work. But like I said I never did get to test it.

**Force Flow** · 01-06-2008, 12:07 PM

To a 9V? No.

Brad the best · 01-07-2008, 12:01 AM

ya a 9v wouldn't work the problem is amperage not voltage .aa has more amperage then a watch battery .

liambl · 01-07-2008, 06:08 AM

You could try connecting two AA batteries in parallel to increase current.

David M · 01-07-2008, 11:49 AM

Borrow a DC power supply, the type where you can control the voltage and the current. Set the current at the diodes rated current. Start out low and slowly bring up the voltage until until it works. Make sure you have the polarity correct. You will then be able to use a battery and a potentiometer to provide the correct voltage. Make sure the battery has at least the same or more current capacity than the diodes rating (amperage). Use a good multimeter for measuring the voltage across the diode...so you know what the voltage is supposed to be by experimentation.

helicopter · 01-15-2008, 09:57 PM

ForceFlow:
I am new to the forum and this is post #2 for me.
Here is the help you need with LED's:
http://ledcalc.com/

You need a bias resistor with this circuit. Any voltage from a battery
can used to calc the correct resistor! So Easy a cave....

Peace!
Helicopter

Petef56 · 01-16-2008, 02:56 AM

Try this...

Use the two 1.5v batts in series so you have a 3v source.
Then use a 15 ohm 1/4 watt resistor in series with the LED.

or...

Use a 9V batt.
Then use a 75 ohm 1 watt resistor in series with the LED.

---pete---

**Force Flow** · 01-16-2008, 08:21 PM

hmm...could've sworn I replied to this and closed this issue...

Oh well...In any case, the wiring I had wasn't making good contact, but other than that, I was able to make it work with the parts I had

Thanks guys

01-05-2008, 11:32 PM	#1
Force Flow Barefoot on the Moon! Staff Premium Member Join Date: Aug 2002 Location: Northeastern USA Posts: 13,285	making a simple LED light I've got a little project in the works here, and was trying to make an infrared LED light. Now, I'm not very good with electronics past some of the fundamental basics of electricity, but here's what I have: Two LR41 button batteries, rated at 1.5V (from what I can tell). A red LED. This plus the two button batteries works in a little keychain light I had, so I figured I could do the same thing, except with an infrared light. Apparently not. I got an infrared LED found at radioshack. I don't understand the significance of all these when it comes to figuring out what is needed in terms of power and resistors, but here's what was on the back of the box: electrical characteristics: forward voltage: 1.2V forward current: 100mA absolute maximum ratings: forward voltage (20mA): 1.6V reverse voltage: 5V forward current: 1.2A reverse current: 10uA So, what I've tried is first both button batteries, then only a single button battery. Neither worked (I was viewing the IR LED through a digital camera, since it picked up the light from a TV remote). Any ideas? I've never had much luck with this stuff, so hopefully I didn't blow the IR LED. Share Share this post on Digg Del.icio.us Technorati Twitter __________________ There are two secrets to staying young, being happy, and achieving success. You have to laugh and find humor every day, and you have to have a dream.

01-05-2008, 11:47 PM	#3
Lespaul20 Member (11 bit) Join Date: Apr 2003 Location: Iowa Posts: 1,652	I would try reversing the way you are hooking it up. LED are diodes so they only allow current to flow one way. Share Share this post on Digg Del.icio.us Technorati Twitter __________________ LP

01-06-2008, 12:30 AM	#4
Force Flow Barefoot on the Moon! Staff Premium Member Join Date: Aug 2002 Location: Northeastern USA Posts: 13,285	Yeah, had it the right way. The AA did work, with the red LED, but dimly. So I tried it with the IR LED, which worked, but dimly. So, I tried it with the button batteries again. As it turns out, this did work. Because of the lighting conditions and moving the LED around, I just couldn't actually see that it was turning on with the camera. Thanks guys Share Share this post on Digg Del.icio.us Technorati Twitter

01-06-2008, 02:20 AM	#5
sgtspector Member (11 bit) Join Date: Aug 2005 Location: Mt. Hope, NY Posts: 1,208	Try connecting the leads from the led to the terminals on a 9-volt battery. That will light the led just fine. An expert in the filed once told me that it works just fine. I've been meaning to try it for a while now myself but never got around to it. A couple placed in a room and you could light a whole room up for your video camera. If you look directly at it you will see a tiny red dot from the led if it is lit. Share Share this post on Digg Del.icio.us Technorati Twitter __________________ Asus P5ND2-SLi-Deluxe Mobo, Intel 3.0ghz P4 w/ht, 2 GB CORSAIR 667 DDR2, 1 GB Ultra DDR2 533 mhz PC4200 ram, BFGTech Nvidia 6600 GT OC SLi video card, WD 4000KS OEM SATA II HDD, Seagate 320gb SATA II HDD 7200rpm, WD 320 gb SATA II HDD, Creative Soundblaster Audigy Platinum, Sony DRU 720 DVD-RW, LG GCE8240B CD-RW, Maddog Multimedia 500w modular PSU & WinXP Pro SP2, Samsung BF960 19" LCD.

01-06-2008, 02:57 AM	#6
*glc* Forum Administrator Staff Premium Member Join Date: May 2000 Location: Joplin MO Posts: 36,460	9 volts exceeds the rating of that LED, it will blow it out. Share Share this post on Digg Del.icio.us Technorati Twitter

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01-05-2008, 11:36 PM	#2
Brad the best Member (8 bit) Join Date: Jan 2006 Location: Kamloops , B.C , Canada Posts: 130	i would try a AA or something along those lines . little more amperage out of it . hooking it up the right way? Share Share this post on Digg Del.icio.us Technorati Twitter

01-06-2008, 06:58 AM	#7
The_YongGrand Member (10 bit) Join Date: Oct 2004 Location: Somewhere in Malaysia... Posts: 953	Put a resistor on it - a 9V will fry the LED! Share Share this post on Digg Del.icio.us Technorati Twitter

01-06-2008, 11:46 AM	#8
sgtspector Member (11 bit) Join Date: Aug 2005 Location: Mt. Hope, NY Posts: 1,208	Perhaps they used a different led but I was told that you could simply connect the led to the battery and it would work. But like I said I never did get to test it. Share Share this post on Digg Del.icio.us Technorati Twitter

01-06-2008, 12:07 PM	#9
Force Flow Barefoot on the Moon! Staff Premium Member Join Date: Aug 2002 Location: Northeastern USA Posts: 13,285	To a 9V? No. Share Share this post on Digg Del.icio.us Technorati Twitter

01-07-2008, 12:01 AM	#10
Brad the best Member (8 bit) Join Date: Jan 2006 Location: Kamloops , B.C , Canada Posts: 130	ya a 9v wouldn't work the problem is amperage not voltage .aa has more amperage then a watch battery . Share Share this post on Digg Del.icio.us Technorati Twitter

01-07-2008, 06:08 AM	#11
liambl Folding at home. Join Date: Jul 2007 Location: Christchurch, New Zealand Posts: 2,126	You could try connecting two AA batteries in parallel to increase current. Share Share this post on Digg Del.icio.us Technorati Twitter __________________ AMD Athlon 64 X2 5600+@3.0GHz - nVIDIA GeForce GTX260@626/1620/2060MHz - 4GB DDR2 800MHz - 320GB WD Caviar Blue + 500GB WD Caviar Blue

01-07-2008, 11:49 AM	#12
David M Techphile. Join Date: Nov 2003 Location: San Francisco Bay Posts: 5,746	Borrow a DC power supply, the type where you can control the voltage and the current. Set the current at the diodes rated current. Start out low and slowly bring up the voltage until until it works. Make sure you have the polarity correct. You will then be able to use a battery and a potentiometer to provide the correct voltage. Make sure the battery has at least the same or more current capacity than the diodes rating (amperage). Use a good multimeter for measuring the voltage across the diode...so you know what the voltage is supposed to be by experimentation. Share Share this post on Digg Del.icio.us Technorati Twitter __________________ Asus P8P67 WS Revolution \| Intel 2600K @ 4.7 GHz \| Win 7 Pro 64 \|8 gigs Corsair 1600 \| Two Diamond 6990's in Crossfire\| Corsair AX1200 \| Thermalright Silver Arrow \| Western Digital Black 2TB 64 meg cache \| Lian-Li PC-A71B \| Logitec Z-5500 \| Three Asus 26" VW266H monitors running under Eyefinity \| Last edited by David M; 01-07-2008 at 11:58 AM.

01-15-2008, 09:57 PM	#13
helicopter Member (3 bit) Join Date: Jan 2008 Posts: 4	ForceFlow: I am new to the forum and this is post #2 for me. Here is the help you need with LED's: http://ledcalc.com/ You need a bias resistor with this circuit. Any voltage from a battery can used to calc the correct resistor! So Easy a cave.... Peace! Helicopter Share Share this post on Digg Del.icio.us Technorati Twitter

01-16-2008, 02:56 AM	#14
Petef56 Member (9 bit) Join Date: May 2007 Location: USA, New Jersey Posts: 427	Try this... Use the two 1.5v batts in series so you have a 3v source. Then use a 15 ohm 1/4 watt resistor in series with the LED. or... Use a 9V batt. Then use a 75 ohm 1 watt resistor in series with the LED. ---pete--- Share Share this post on Digg Del.icio.us Technorati Twitter

01-16-2008, 08:21 PM	#15
Force Flow Barefoot on the Moon! Staff Premium Member Join Date: Aug 2002 Location: Northeastern USA Posts: 13,285	hmm...could've sworn I replied to this and closed this issue... Oh well...In any case, the wiring I had wasn't making good contact, but other than that, I was able to make it work with the parts I had Thanks guys Share Share this post on Digg Del.icio.us Technorati Twitter

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