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692
Junior Member
Username: 692
Post Number: 31
Registered: 7-2002
| | Posted on Sunday, January 23, 2005 - 3:57 pm: | 
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What do you have to do to change over to a Led light, and where can i find them. Do you have to use a resistor with them? I have seen the ones that change colors but i would rather have just one color.
Thanks 692 |
The ELCO guy (Unregistered Guest)
Unregistered guest
| | Posted on Sunday, January 23, 2005 - 5:12 pm: |
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Before we can give you advise on your question I think we need to know what do you want to do with the LED. Where do you want to put it and how do you want to use it?
That ELCO guy |
That Elco Guy (Unregistered Guest)
Unregistered guest
| | Posted on Sunday, January 23, 2005 - 9:08 pm: |
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If you are using a 12 volts to power the LED yes you will need a rsistor in line. Per the ARRL Handbook for 12 volts applied to an LED you will need a 1000 ohm resistor.
A few facts aboout LEDs....
They are for the most part focused. They do not speread out their light like an incandesdent bulb. So you will have to "Point" it in the direction you want the light to go so to speak.
Another thing abut LEDs thats good is that you can get them in various brigntness. The brighter the LED the more costly, however for meter lighting bright is good but also more expensive.
Color, you can get LEDs in all kinds of colors to make the pannel look unique. Standard LED colors are red, blue, green and now they have white ones as well. Select a color that works well with the color of the printing on the face of the meter.
If you use the right resistor and do not apply too much voltage or current to the LED follow the specs as stated on the LED packaging you will find that the LED will last one heck of a lot longer than the light bulbs.
OK now for the hard part a circuit description...
If you have a 12 volt supply built in. Positive connection from the 12 vold power supply runs to the 1000 ohmn resistor after which the connection then goes to one leg of the LED. Ground the othr unused leg to nearest 12 volt ground. IMPORTANT SEE FOLLOWING SUGGESTION. Suggestion: use a VOM to determine the voltage applied to the LED "BEORE MAKING THE CONNECTIONS" to the LED. Adjust resistor up or down to add or subtract voltage being applied to the LED so as to meet LED specs.
IF you do not have a 12 volt power supply built in. Get a Battery box from Radio Shack. The battery box with proper batteries will have a red and black leads, run the positive red wire to a switch and the output of the switch to one of the contacts of the LED. Solder the negative batter box connection directly to the other connection of the LED. As long as the voltage from the batteries does not excede the spec voltage for the LED and you use only those AAA batteries you should not require the resistor in the circuit. If you are using batteries to power the LED dont forget to turn off the LED via he switch. The LED does not use that much juce, but the batteries will last one heck of a lot longer if the LED is turned off.
I hope I did not confuse you. If you have any questions give me a shout.
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692
Junior Member
Username: 692
Post Number: 32
Registered: 7-2002
| | Posted on Sunday, January 23, 2005 - 9:36 pm: |
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Sorry for the lack of info. I was wanting it for the meter light, say a uniden 76, or galaxy 33.
Thanks,692. |
Tech291
Moderator
Username: Tech291
Post Number: 51
Registered: 11-2004
| | Posted on Sunday, January 23, 2005 - 10:14 pm: |
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692,just want to add to Elco Guy's post a few cautions.the new hi-brightness led's are mos technology and are static sensitive devices.so carefull handeling is necessary.also other than special bipolar or 2 color devices,led's are polarity sensitive which means thet have a + and - terminal.the standard T 1and 3/4 size(most common)has a flat molded on the rim denoting the negative terminal.new colors available of the hi-britness types are red,yellow,green,blue,blue/white and purple.the waterclear type lens does focuse the light out the end like a flashlight beam.for backlight porposes look for the difused or milky looking package.for lighting a meter the blue/white would be your best bet.
tech291
CEF#291
kc8zpj |
Chad
Intermediate Member
Username: Chad
Post Number: 102
Registered: 11-2004
| | Posted on Sunday, January 23, 2005 - 9:55 pm: |
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Keep in mind 1K resistor is an arbitrary number, one must do the exact calculation with the current requirements of the LED, they are current driven not voltage driven, so think of the resistor as current limiting not voltage. Also keep in mind that many exotic colors use 5V so 1000 Ohms is way off.
They even have UV, turquoise, pink, you name it colors. I have switched the lighting in my live mixing consoles to LED and enjoy not replacing lamps. You will need to do some diffusing to keep the face from getting splotchy, I use a little silicone around the benzel, If the LED is bright enough you can get by lighting the circumfrence of the meter by placing the LED's sideways in the silicone, thus using the silicone to distribute the light, makes for nice even lighting.
LED nuts need to check out this site!
http://www.ledmuseum.org/
Chad |
692
Junior Member
Username: 692
Post Number: 33
Registered: 7-2002
| | Posted on Sunday, January 23, 2005 - 10:38 pm: |
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Thanks for the response everyone.
The leds i have ordered are blue and supplied with the resistor for 12volt. They are listed as 7000 mcd 3.1~3.5v (12volt with resistor). I am just getting tired of replacing wheat lamps all the time.
Thanks again for the info.
692 |
Racer X (Unregistered Guest)
Unregistered guest
| | Posted on Monday, January 24, 2005 - 4:32 am: |
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You could always throw a resistor inline with the wheat lamp to make it last longer. The resistor will help keep the inrush current from causing damage to the lamp, and you can use just the right resistance to taylor the brightness to your needs.
LEDs are fun to look at though. I've thought about making an LED S-meter with some of the more interesting colors now available. |
