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led, surface mount resistors.


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oldspark 
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Posted: January 23, 2010 at 3:33 AM / IP Logged  
Yep - the pot theory is good noting that 150R is yet another preferred value, and at 20mA = .02 x .02 x 150 = 1/16 Watt - most resistors & pots should handle it.
I calc currents of 19.5 & 17.3mA for the 5&6V & 82 & 150R combinations.
With the pot you might get a feel for the variation of voltage/current and brightness of the LED. (IMO - the brightness variation is less than the voltage(current) variation (relative to "nominal" voltage) - ie, LEDs are NOT that critical wrt voltage etc.)
Good to hear of cheap eGay alternatives.
I am often amazed at the purchase of $1,000 PCBs when a mere 20c item has failed, but that's just my DIY mentality (resulting from earlier neccessity; and possible use for future inevitabilities...)
sallc5 
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Posted: January 23, 2010 at 10:24 AM / IP Logged  
I got this spare one at salvage for $15. Haha so, I am golden. Like I mentioned it tested in working condition on my vehicle. Anyways here is the ride I am doing this project on. Olds Aurora!
led, surface mount resistors. - Page 3 -- posted image.
knox1138 
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Joined: December 30, 2008
Posted: January 25, 2010 at 9:23 PM / IP Logged  
i dunno of anyone has covered this yet, but usually when surface mount is used that means that there's some high speed switching going on in some ic controller and the surface mount is there so less current is loss. i would personally take the time to redo all the soldering, though it might have just been done to save space, so take my thoughts with a grain of salt
oldspark 
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Posted: January 25, 2010 at 10:25 PM / IP Logged  
Good tip Knox, but I think that has been covered - the LEDs concerned seem to have voltage & resistor values consistent with non-switched circuits (once the 5V rail was determined).
Though many LED were switched anyhow - long before SMD (a good method of color equalisation, extra brightness, power & circuit saving, etc).
Sall - nice ride! Good to hear of the cheap pickup - beats the $1,000.
sallc5 
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Posted: January 26, 2010 at 8:58 PM / IP Logged  
I have another question. Can I simply replace the 3 and 5mm twist-lock style filament bulbs with 3 and 5mm component leds as well?
If so, how would I get a resistor on one of these pc sockets? I would be pulling the filament and replacing the bulb with the respective size LED using the same pc socket.
sallc5 
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Posted: January 26, 2010 at 9:01 PM / IP Logged  
Sorry that is the wrong picture... here it is...
The bases on these are the same except these already have LEDs.
sallc5 
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Joined: November 27, 2009
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Posted: January 26, 2010 at 9:02 PM / IP Logged  
ahh... messed up again.
LINK
sallc5 
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Posted: January 26, 2010 at 9:51 PM / IP Logged  
Voltage is also 5v. Not sure about resistance but they are hooked into a pot dimmer. Taking it I just need to ohm out the dimmer switch and see if the resistance falls into alright area for the LEDs?
oldspark 
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Posted: January 27, 2010 at 12:29 AM / IP Logged  
I don't understand....
It sounds like you want to substitute LEDs in place of filament bulbs.
I presume the filament bulbs are 12V (not 5V).
The NeoWedge LEDs at your LINK operate from 9-15V (& 10-19mA depending on type/color).
Substituting LEDs for bulbs is reasonably common. The problem is the method - mount a LED in a base; with internal resistor etc?
(Reduced contact reliability due to less whetting current.... oh no - more gold contacts (to be used with gold plated fuses and battery terminals of course!)...)
sallc5 
Member - Posts: 45
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Joined: November 27, 2009
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Posted: January 27, 2010 at 12:00 PM / IP Logged  
I apologize that was way too jumbled for anyone to understand really. I looked up some schematics.
There are about 20 total twist-lock style bulbs on the HVAC Panel as well as about 10 or so other ones throughout the car. These twist-lock style filament bulbs on HVAC, etc. are dimmable (unlike the LEDs we discussed earlier). The link was just to describe what the base of the bulb looks like. I would like to remove the filament bulb and drop in an LED. I was not sure at the time if I needed a resistor or not thus why I was asking how in the world would I solder one onto these. I now do not think I need a resistor.
There is a pot dimmer switch on the dash which dims the instrument cluster and all the other twist-lock style filament bulbs.
Here are the schematics:
led, surface mount resistors. - Page 3 -- posted image.
led, surface mount resistors. - Page 3 -- posted image.
There are plenty more if you need to see more. They all pretty much say the same thing.
From these diagrams I can see that dimmer and the interior lights have a 5v reference. The dimmer switch is a pot. It sets resistance on the 5v reference in order to dim the interior lights. The resistance is at minimum 150R and a maximum of 5k R.
I tested this today with a 5k pot on one of the LEDs I got in the mail. Pot set 150R with a 6v reference the LED is nice bright blue, but not too hard to look at. Moving the pot down slowly, I can see the LED dim. At 5k the LED is dim and still visible. A noticeable difference between the 150 and 5k resistance. I usually have the IC and the other lamps on as bright as the go when it is dark. So, I would not be over powering them they basically would see the same resistance and power that the HVAC LEDs we discussed earlier would. Thus both would be at right around 150R when on.
I think I could be happy with results. Otherwise I take it I will need to use a pwm.
Thanks for re-reading this. I definitely jumbled all that last night and made 2 or 3 erroneous posts. Let me know what you all think.
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