Go Back   DIY Chatroom Home Improvement Forum > Do It Yourself > Automotive Repairs

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 10-28-2009, 08:31 PM   #1
Newbie
 
Join Date: Oct 2009
Posts: 6
Rewards Points: 0
Share |
Default

Gauge Light Dimmer


I installed a 25 ohm 3 watt rheostat to adjust my gauge lighting. When on, the rheostat gets extremely hot. I dont know much about electricity, just enough to be dangerous. I am thinking that I can install a 47 ohm .5 watt resistor before the rheostat. What do I need to do to keep the rheostat from overheating?

navman28 is offline   Reply With Quote
Old 10-28-2009, 09:22 PM   #2
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 0
Default

Gauge Light Dimmer


Quote:
Originally Posted by navman28 View Post
I installed a 25 ohm 3 watt rheostat to adjust my gauge lighting. When on, the rheostat gets extremely hot.
For 25 ohms to dissipate >3w you'd need sqrt (3x25) = >9v across it.

How much current do your gauge lights draw when full on? If they are incandescent lamps the calc. for a dimmer resistor gets really tricky. Does the 25 ohms make them dim enough?


Last edited by Yoyizit; 10-28-2009 at 09:36 PM.
Yoyizit is offline   Reply With Quote
Old 10-28-2009, 09:47 PM   #3
Newbie
 
Join Date: Oct 2009
Posts: 6
Rewards Points: 0
Default

Gauge Light Dimmer


I know the gauges are LED but dont know what they draw. Yes they do dim, just the rheostat gets really hot.
navman28 is offline   Reply With Quote
Old 10-29-2009, 08:08 AM   #4
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 0
Default

Gauge Light Dimmer


LEDs should be easy to control, but you need to measure the current draw at full brightness.
I^2 = 3w/25 ohms so I is at least 0.8 A. That seems high for LEDs.

Last edited by Yoyizit; 10-29-2009 at 08:12 AM.
Yoyizit is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Motion Light tripping GFCI? Jonobp Electrical 5 09-07-2009 07:52 PM
Please Help! 3 way switches controling 2 light fxtures. HelloMotto Electrical 50 09-01-2009 08:20 PM
Light doesn't turn on immediately on dimmer switch Michblaze02 Electrical 3 03-19-2009 05:14 AM
Dimmer didn't work, now old light switches don't work properly townpump Electrical 9 03-16-2008 07:28 PM
OK to user a dimmer with ceiling light? FreeCashBack.co.uk Electrical 2 06-19-2005 09:16 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.