veroboard led circuit

[fr3ak12]

Hey im busy doing my car up and want to put a led circuit in on the door switch. i will be using vero board and standard(nothing fancy) LEDs. thought of following this, just a couple questions.

http://www.opelownersforum.co.za/viewtopic.php?f=32&t=534

now if i wire the LEDs up the same way, why does it not need resistors? what would be the best power source? would a 12V-14V power souce from the battery be to much? use a 9V battery?

Thanks

 

[kam1787]

Wasn't the link using the LEDs as a parking light?

You are correct - you do NEED to limit the current to the LEDs either via a resistor or current limiting circuit.


It is not 100% clear what you are intending.................as a door light; open the door and the LEDs light up?

Three ultra-bright [white] LEDs in series, with a resistor, would work. Value of the resistor depends on the Vd of the LEDs.

 

[betwixt]

LEDs are current driven not voltage driven although you need enough voltage to enable the current to flow. I would advise you ALWAYS use resistors, especially in automotive applications where the voltage is highly dependant on battery charge and alternator speed.

Brian.

 

[fr3ak12]

@Kam i have got a vent on the inside of my door and want to put the LEDs in the vent, and when i open the door then it must come on.
i want it to be very bright so was thinking of like 9LEDs, its been awhile since i did electronics(at college). could you maybe help with small rough curcuit diagram? and resistor requirements???

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i know how to wire it so that it only comes on when the door is open, just the resistors :???:

 

[kam1787]

.... in automotive applications where the voltage is highly dependant on battery charge and alternator speed.

if I might add to 'betwixt'..............in automotive apps, the voltage can vary from 10V to over 14.4V

while a resistor does work, the brightness will vary.........

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Quality vs Quantity!

You do not need many LEDs when one very high brightness LED will work!

I think you need to do some research [and see actual LEDs in use] to decide..............

No-one can help with the resistor [or circuit design] until you decide on the actual LEDs.

 

[fr3ak12]

il go get some LEDs tomorrow and play around with them.

 

[kam1787]

Be sure to find out the maximum and typical current, as well as the Vd (voltage drop)

The value for the resistor is [V+ minus total Vd ] / I typical

 

[fr3ak12]

hey i got my LEDs after alot of searching around for them, i just got std. red led.
they guy said all i need to know is they are 1,7v and 20ma..
any help?

 

[betwixt]

Lets assume the battery voltage is a constant 12V. It wont be but being a bit higher or lower will not make too much difference.

You need to work out how best to wire them up, in series the total voltage across them will be the sum of each individual LED so if you had 1 it would be 1.7V, two would be 3.4V, three would be 5.1V and so on. I'm not sure how many LEDs you have or need but the simplest circuit would use enough LEDs to give a total close to but not exceeding 80% of 12V (=9.6V). This would suggest you use a series chain of 5 LEDs giving you 8.5V from end to end. If you need more than 5 LEDs, try to keep them in multiples of 5 so the chains are the same length. Each chain needs a series resistor to limit it's current, the value is "total voltage -(number of LEDs in the chain * voltage across each LED)/current you want to flow through them". In figures that's (12 - 8.5)/ 0.02 = 175 Ohms. As this isn't a precision circuit and you are not 100% sure of the LEDs, I suggest you use the nearest standard resistor value which is 180 Ohms. Each chain, including it's series resistor is then wired in parallel and to 12v through your switch.

I should point out that if these are standard 1.7V/20mA LEDs they are probably not high brighteness types!

Brian.

 

[kam1787]

Lets assume the battery voltage is a constant 12V. It wont be but being a bit higher or lower will not make too much difference.

I disagree. Voltage can vary from about 10V to as high as nearly 15V (because of the alternator). See links below . Re-compute the equation given, using 15V, rather than 12V. That will be the worst case. Of course, it also means that at lower voltage the LEDs will not be as bright.

I should point out that if these are standard 1.7V/20mA LEDs they are probably not high brighteness types!

Most definitely NOT high brightness. I have no idea why you bought these - you will need a fist-full to make it 'very bright'. Frankly I would put them away for other projects and get high brightness LEDs.



https://wiki.answers.com/Q/What_is_a_normal_car_battery_voltage
https://www.landiss.com/battery.htm
answers.yahoo.com/question/index?qid=20080824183504AAjhPJi
https://carbatteryworld.com/car-battery-voltage/