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Car LED rear light circuit bulbs

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Right new meter and I have the results.
When using the settings instructed above I have the following readings.
The leds in the set of two measure 16.4
The set of three measure
45.2
Many thanks again for everyones help.
 
Bigkris06 said:
I had the meter set to 200Ma so I would that make it Ma?
Many thanks.
Click to expand...
Well, being pedantic it's mA, short for milli-Amperes, where 1 mA is 0.001 Amperes. The unit of Ampere is usually abbreviated to Amp.

If the meter is set to 200 mA, and the display is 45.2, then it means 45.2 mA. Can you show where you measured that? Were the other LEDs lit up when you measured it?

You need to look for LEDs rated to 50 mA or more.

The 200 mA scale means that the meter can read between -200 mA and +200 mA. It's probably limited to between -199.9 mA and +199.9 mA, but it's easier to print and read "200 mA" than "-199.9 mA to +199.9 mA". If there is a 20 mA scale and maybe a 2 A scale, it's easier to read if they all look very different.

If you read 16.4 mA on a 20mA scale it would read "16.43" (I made up the last digit)
On the 200 mA scale it would read "16.4" or "016.4"
on a 2 A scale it would read ".016" or "0.016"
 
Yes when I took the readings I placed the probes between the legs on the led. When I did this, on the circuit that has three leds I think it was the first in the sequence (if you get what I mean) as I got the reading of 45.2 and the other two leds lit.
With the circuit that has two leds I did the same.. Placed the probes between the led I think was the first, this led went off, gave me the reading of 16.4 and the second led remained lit.
So would I be correct in assuming that I need leds with a rating of 50mA for the set of three and leds with the rating of 20mA for the leds for the set of two with a voltage of 3v and 3mm in size?
Many thanks again, like I said I would be completely lost without the help of people here.
 
My gosh, I didn't realise there were so many variables in leds!
Different voltages, different mA ratings, different angles not to mention sizes!
I honestly thought it would be, get an led, solder it in and happy days!
No so easy it seems!
 
3mm LEDs are tiny and only 2 or 3 would not be used as the rear lights on a full size real car. Is this a toy car?

Three LEDs are in series and you shorted one with your current meter. Since we do not know what limits the current, if it is a simple resistor then if 2 of the 3 LEDs draw 45.2mA then all 3 LEDs in series use less, maybe 28.3mA.
 
Thank you for your input.
Yes I have checked my own measurements and they are actually 5mm.
In the first post there is a picture of the circuit board.
I just really need to get the correct bulbs for the lights to get them working again.
I have attached a picture of the actual lights to give an idea of what the board powers.
The three lines inside the light are like small tubes where the led sits at the end and illuminates them.
Many thanks again.
 

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Bigkris06 said:
The three lines inside the light are like small tubes where the led sits at the end and illuminates them.
Click to expand...
Just an FYI, in case you wish to know, or not...those tubes are known as 'light-pipes'.
 
A clear picture of the etch side of the board with the camera directly above the board and with nothing covering part of the board would help tracing out the schematic of the board. If the picture is not good enough to read the part number on the 8 pin IC then copy down all the numbers on the IC and post that information. IF we can find the data sheet on the IC we can probably work out what current should be supplied to the LEDs. It is quite possible that the IC only has in house part numbers and if that is the case no datasheet will be available..
EDIT. I have just has a look at Farnell's website for LEDs that may be suitable. One I found is the TLCR5800 This is rated 60 mA max forward current. I had a look for them on ebay but they are much more expensive than Farnell.
Les.
 
Last edited:
I think that the two LEDs are in series and the current is controlled by a simple resistor. I think that the current in the three LEDs is controlled by the IC. If the number on the IC can be seen, that could be confirmed.

However, those LEDs are not expensive, so they are worth a try.

As the LEDs are sending light to light pipes, the narrow viewing angle is probably what was designed.
 
Thank you all for your replies.
Diver, may I ask what leds you would suggest I buy?
mA / voltage / angle etc.
Many thanks
 
Sorry Les, I didn't see your reply there.
I have found the same ones in eBay which work out cheaper for me as I only need 15 (10 for job with 5 spares when I break them!)
Due to the postage costs from farnel.
I will order them, get them fitted and see how it goes.
I will post the results here soon.
Many thanks again to everyone for all there help.
 
If I was buying them for your application I would choose a reliable supplier. I have heard reports of some items on ebay being manufacturers rejects or the wrong part. LEDs do not have a part number stamped on them so it would be impossible to know if they genuine. You could also try other suppliers such as RS, Rapid, Mouser or Digi-Key to see if you can get them cheaper. You may be lucky with the ones on ebay. Can you read the part number on the IC ? I would be interested to know if it is a 2 channel constant current driver.

Les
 
Les Jones said:
If I was buying them for your application I would choose a reliable supplier. I have heard reports of some items on ebay being manufacturers rejects or the wrong part. LEDs do not have a part number stamped on them so it would be impossible to know if they genuine. You could also try other suppliers such as RS, Rapid, Mouser or Digi-Key to see if you can get them cheaper. You may be lucky with the ones on ebay. Can you read the part number on the IC ? I would be interested to know if it is a 2 channel constant current driver.

Les
Click to expand...
I agree. Farnell are charging £5.95 postage, but the whole lot is less than £12 for 15 LEDs.
 
Ah. I see. I will do that then, if I went cheap and they didn't work I'd have assumed I'd have done something wrong.
I'll post when the job is done. Thanks to everyone again.
 
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