resistors and LEDs

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Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=53636
Printed Date: May 24, 2024 at 7:08 AM

Topic: resistors and LEDs

Posted By: ogkw
Subject: resistors and LEDs
Date Posted: April 10, 2005 at 11:56 AM

I am trying to hook up 2 LEDs(1.7v a piece) to a sewing machine. I do not know what size resistor I need to keep the LEDs from burning out. I want to run them in a series form the lighting socket that is already there. The only information I have on the socket is that it takes a 120v, 15 watt bulb. I plugged this little bit of information into the ohm calculator and was told I need 960ohm resistor. Does this I need one for each LED?

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40oz. and a mule

Replies:

Posted By: auex
Date Posted: April 10, 2005 at 12:09 PM

I only claim knowledge in dc. Unless the sewing machine's light output is dc, which it probably isn't, then you can't use the leds. Just use a light.

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Certified Security Specialist
Always check info with a digital multimeter.
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Posted By: geepherder
Date Posted: April 10, 2005 at 5:04 PM

He's right. Since led's are diodes, they only pass current one way, and block the other. Also since they turn on and off quickly, you'd have an annoying flickering effect.

The best thing would be to use lights as auex mentioned.

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My ex once told me I have a perfect face for radio.

Posted By: ogkw
Date Posted: April 11, 2005 at 7:58 AM

I went to a local radio shack and got two different resistors, one rated at 680 ohms, the other at 1.2k ohm. They both allowed the LED to stay lit without blowing. Within 3 seconds the 680 got too hot to hold. The 1.2 took at least 20 seconds but got just as hot. I will not accept defeat there must be a way.

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40oz. and a mule

Posted By: ogkw
Date Posted: April 11, 2005 at 4:01 PM

If no one knows a way around this, would a AA battery pack be easier?

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40oz. and a mule

Posted By: auex
Date Posted: April 11, 2005 at 4:59 PM

Accept defeat or break out the marshmellows.

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Certified Security Specialist
Always check info with a digital multimeter.
I promise to be good.
Tell Darwin I sent you.

I've been sick lately, sorry I won't be on much.

Posted By: geepherder
Date Posted: April 11, 2005 at 8:21 PM

Yes, a battery back would be much easier, since it will provide the DC your LED's require. Otherwise you'd need a power supply.

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My ex once told me I have a perfect face for radio.

Posted By: ogkw
Date Posted: April 14, 2005 at 9:53 AM

Fine, I will accept it, but not like it. I rigged one LED to a flashlight that takes 2 AAs, and it was the perfect brightness. If I used a battery pack with 4 AAs, for 2 LEDs would that change anything drastically, such as brightness, battery life, excessive heat, or anything?

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40oz. and a mule

Posted By: popeye004
Date Posted: April 16, 2005 at 12:34 AM

Did you try to add a diode in between the resistor and the led.

Posted By: drvnbysound
Date Posted: April 16, 2005 at 4:33 AM

Ive never heard of anyone PIMPING A SEWING MACHINE!! Incredible what people think of. Could be the next big thing to have in your home. Neon manufactures started making kits for computers. I need to start manufacturing a LED kit for a sewing machine. I could make a fortune. LMAO!! posted_image

BTW, just because its AC doesnt mean you will SEE the flicker. The period of a 60Hz signal is 0.016 seconds. This is the same refresh rate a CRT computer monitor or standard TV uses. Its practically impossible to see the LED flashing.

If you seriously want to get something working, e-mail me at: drvnbysound@aol.com and let me know. I will design something for you. I am about to get my BS in Electrical Engineering, Im sure I could come up with something.

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