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LED not achieving max current
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I have a project that is powered by a 12v power supply. I need as bright of an LED as possible and decided to use this 9v LED. According to the datasheet, its max current is 1A, which is what I would like to get it to. In order to do this, I am using this 3 Ohms resistor
According to my calculations, (12v-9v)/1A = 3 Ohms. This should get my LED to the correct current.
To test the current, I placed a multimeter in series with the 12v power supply, LED, and resistor. However, I am only reading 0.639A. I tried several power supplies and meters and it's all the same.
What am I doing wrong? Is my test setup providing too much resistance, thus decreasing the current?
led current resistors resistance
asked 28 mins ago
Daniel Frenkel
212
add a comment |Â
up vote
2
down vote
favorite
I have a project that is powered by a 12v power supply. I need as bright of an LED as possible and decided to use this 9v LED. According to the datasheet, its max current is 1A, which is what I would like to get it to. In order to do this, I am using this 3 Ohms resistor
According to my calculations, (12v-9v)/1A = 3 Ohms. This should get my LED to the correct current.
To test the current, I placed a multimeter in series with the 12v power supply, LED, and resistor. However, I am only reading 0.639A. I tried several power supplies and meters and it's all the same.
What am I doing wrong? Is my test setup providing too much resistance, thus decreasing the current?
led current resistors resistance
asked 28 mins ago
Daniel Frenkel
212
1
And what voltage did you measure accross the LED?
– Marko BurÅ¡iÄÂ
21 mins ago
2
The datasheet shows a typical forward voltage of 9V at 400mA, not 1A.
– Finbarr
20 mins ago
add a comment |Â
up vote
2
down vote
favorite
up vote
2
down vote
favorite
I have a project that is powered by a 12v power supply. I need as bright of an LED as possible and decided to use this 9v LED. According to the datasheet, its max current is 1A, which is what I would like to get it to. In order to do this, I am using this 3 Ohms resistor
According to my calculations, (12v-9v)/1A = 3 Ohms. This should get my LED to the correct current.
To test the current, I placed a multimeter in series with the 12v power supply, LED, and resistor. However, I am only reading 0.639A. I tried several power supplies and meters and it's all the same.
What am I doing wrong? Is my test setup providing too much resistance, thus decreasing the current?
led current resistors resistance
asked 28 mins ago
Daniel Frenkel
212
I have a project that is powered by a 12v power supply. I need as bright of an LED as possible and decided to use this 9v LED. According to the datasheet, its max current is 1A, which is what I would like to get it to. In order to do this, I am using this 3 Ohms resistor
According to my calculations, (12v-9v)/1A = 3 Ohms. This should get my LED to the correct current.
To test the current, I placed a multimeter in series with the 12v power supply, LED, and resistor. However, I am only reading 0.639A. I tried several power supplies and meters and it's all the same.
What am I doing wrong? Is my test setup providing too much resistance, thus decreasing the current?
led current resistors resistance
led current resistors resistance
asked 28 mins ago
Daniel Frenkel
212
asked 28 mins ago
Daniel Frenkel
212
asked 28 mins ago
Daniel Frenkel
212
asked 28 mins ago
Daniel Frenkel
212
asked 28 mins ago
Daniel Frenkel
212
212
1
And what voltage did you measure accross the LED?
– Marko BurÅ¡iÄÂ
21 mins ago
2
The datasheet shows a typical forward voltage of 9V at 400mA, not 1A.
– Finbarr
20 mins ago
add a comment |Â
1
And what voltage did you measure accross the LED?
– Marko BurÅ¡iÄÂ
21 mins ago
2
The datasheet shows a typical forward voltage of 9V at 400mA, not 1A.
– Finbarr
20 mins ago
1
1
And what voltage did you measure accross the LED?
– Marko BurÅ¡iÄÂ
21 mins ago
And what voltage did you measure accross the LED?
– Marko BurÅ¡iÄÂ
21 mins ago
2
2
The datasheet shows a typical forward voltage of 9V at 400mA, not 1A.
– Finbarr
20 mins ago
The datasheet shows a typical forward voltage of 9V at 400mA, not 1A.
– Finbarr
20 mins ago
add a comment |Â
5 Answers
5
active
oldest
votes
up vote
3
down vote
According to the chart on page 17 of the datasheet, the terminal voltage of a nominal-9V LED rises to between 10.25 and 10.5 V (depending on temperature) at 1 A. You need to size your resistor accordingly.
But it would be far better to use an active current regulator to feed this kind of LED. Then, the current wouldn't depend on temperature. Or on your actual source voltage, for that matter.
answered 12 mins ago
Dave Tweed♦
110k9132237
add a comment |Â
up vote
1
down vote
Look at this characteristics. Measure the teperature as well. For example if case teperature, that means right under the diode, has a temperature of 105 C, then you should get a forward voltage 10.25. That would need a resistor of approx. 1.7 ohm.
answered 14 mins ago
Marko BurÅ¡iÄÂ
9,2262812
Can you provide an attribution for where you got this graph? How is it related to the OP's LED?
– Elliot Alderson
12 mins ago
@ElliotAlderson from the datasheet that OP linked.
– Marko BurÅ¡iÄÂ
11 mins ago
add a comment |Â
up vote
0
down vote
It could well be stray resistance. If you are only getting 640mA, then the resistance you are seeing is (12-9)/0.64 = 4.69 Ohms. That is an extra 1.7 Ohms. Your resistor is 3 Ohms. It looks like it is a 5% tolerance, which means it could be as high as 3.15.
You have the resistance in the multimeter leads, you have resistance in those white wires, and you also have resistance in your terminal blocks, where the wires connect to the breadboard, and the breadboard itself also has resistance.
The next thing to do is measure the actual voltage drop across the LED. That will have some tolerance as well, so you may find it is not exactly as the datasheet says. This will also have some significance.
Check all of this and recalculate.
answered 15 mins ago
MCG
4,82631440
add a comment |Â
up vote
0
down vote
Page 17 of the datasheet shows the IV curve for the 9V version. For 1 amp, you are looking at a Vf of 10.4 volts or so, depending on the temperature of the led.
Note that 1 amp is the ABSOLUTE maximum, and without proper cooling of the led, you are almost guaranteeing a dead led, or multiple internal failures.
answered 3 mins ago
Passerby
54.4k448142
add a comment |Â
up vote
0
down vote
You have to actually READ THE DATASHEET:
Depending on temperature, the LED will drop about 10.2 to 10.5 V with 1 A thru it. Conversely, with 9 V across it, the current will be about 300 to 450 mA.
The datasheet is really quite clear. I can't see how anyone would think this LED would drop 9 V at 1 A.
answered 3 mins ago
Olin Lathrop
278k28331783
add a comment |Â
5 Answers
5
active
oldest
votes
5 Answers
5
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
3
down vote
According to the chart on page 17 of the datasheet, the terminal voltage of a nominal-9V LED rises to between 10.25 and 10.5 V (depending on temperature) at 1 A. You need to size your resistor accordingly.
But it would be far better to use an active current regulator to feed this kind of LED. Then, the current wouldn't depend on temperature. Or on your actual source voltage, for that matter.
answered 12 mins ago
Dave Tweed♦
110k9132237
add a comment |Â
up vote
3
down vote
According to the chart on page 17 of the datasheet, the terminal voltage of a nominal-9V LED rises to between 10.25 and 10.5 V (depending on temperature) at 1 A. You need to size your resistor accordingly.
But it would be far better to use an active current regulator to feed this kind of LED. Then, the current wouldn't depend on temperature. Or on your actual source voltage, for that matter.
answered 12 mins ago
Dave Tweed♦
110k9132237
add a comment |Â
up vote
3
down vote
up vote
3
down vote
According to the chart on page 17 of the datasheet, the terminal voltage of a nominal-9V LED rises to between 10.25 and 10.5 V (depending on temperature) at 1 A. You need to size your resistor accordingly.
But it would be far better to use an active current regulator to feed this kind of LED. Then, the current wouldn't depend on temperature. Or on your actual source voltage, for that matter.
answered 12 mins ago
Dave Tweed♦
110k9132237
According to the chart on page 17 of the datasheet, the terminal voltage of a nominal-9V LED rises to between 10.25 and 10.5 V (depending on temperature) at 1 A. You need to size your resistor accordingly.
But it would be far better to use an active current regulator to feed this kind of LED. Then, the current wouldn't depend on temperature. Or on your actual source voltage, for that matter.
answered 12 mins ago
Dave Tweed♦
110k9132237
answered 12 mins ago
Dave Tweed♦
110k9132237
answered 12 mins ago
Dave Tweed♦
110k9132237
answered 12 mins ago
Dave Tweed♦
110k9132237
110k9132237
add a comment |Â
add a comment |Â
up vote
1
down vote
Look at this characteristics. Measure the teperature as well. For example if case teperature, that means right under the diode, has a temperature of 105 C, then you should get a forward voltage 10.25. That would need a resistor of approx. 1.7 ohm.
answered 14 mins ago
Marko BurÅ¡iÄÂ
9,2262812
Can you provide an attribution for where you got this graph? How is it related to the OP's LED?
– Elliot Alderson
12 mins ago
@ElliotAlderson from the datasheet that OP linked.
– Marko BurÅ¡iÄÂ
11 mins ago
add a comment |Â
up vote
1
down vote
Look at this characteristics. Measure the teperature as well. For example if case teperature, that means right under the diode, has a temperature of 105 C, then you should get a forward voltage 10.25. That would need a resistor of approx. 1.7 ohm.
answered 14 mins ago
Marko BurÅ¡iÄÂ
9,2262812
Can you provide an attribution for where you got this graph? How is it related to the OP's LED?
– Elliot Alderson
12 mins ago
@ElliotAlderson from the datasheet that OP linked.
– Marko BurÅ¡iÄÂ
11 mins ago
add a comment |Â
up vote
1
down vote
up vote
1
down vote
Look at this characteristics. Measure the teperature as well. For example if case teperature, that means right under the diode, has a temperature of 105 C, then you should get a forward voltage 10.25. That would need a resistor of approx. 1.7 ohm.
answered 14 mins ago
Marko BurÅ¡iÄÂ
9,2262812
Look at this characteristics. Measure the teperature as well. For example if case teperature, that means right under the diode, has a temperature of 105 C, then you should get a forward voltage 10.25. That would need a resistor of approx. 1.7 ohm.
answered 14 mins ago
Marko BurÅ¡iÄÂ
9,2262812
edited 11 mins ago
answered 14 mins ago
Marko BurÅ¡iÄÂ
9,2262812
answered 14 mins ago
Marko BurÅ¡iÄÂ
9,2262812
answered 14 mins ago
Marko BurÅ¡iÄÂ
9,2262812
9,2262812
Can you provide an attribution for where you got this graph? How is it related to the OP's LED?
– Elliot Alderson
12 mins ago
@ElliotAlderson from the datasheet that OP linked.
– Marko BurÅ¡iÄÂ
11 mins ago
add a comment |Â
Can you provide an attribution for where you got this graph? How is it related to the OP's LED?
– Elliot Alderson
12 mins ago
@ElliotAlderson from the datasheet that OP linked.
– Marko BurÅ¡iÄÂ
11 mins ago
Can you provide an attribution for where you got this graph? How is it related to the OP's LED?
– Elliot Alderson
12 mins ago
Can you provide an attribution for where you got this graph? How is it related to the OP's LED?
– Elliot Alderson
12 mins ago
@ElliotAlderson from the datasheet that OP linked.
– Marko BurÅ¡iÄÂ
11 mins ago
@ElliotAlderson from the datasheet that OP linked.
– Marko BurÅ¡iÄÂ
11 mins ago
add a comment |Â
up vote
0
down vote
It could well be stray resistance. If you are only getting 640mA, then the resistance you are seeing is (12-9)/0.64 = 4.69 Ohms. That is an extra 1.7 Ohms. Your resistor is 3 Ohms. It looks like it is a 5% tolerance, which means it could be as high as 3.15.
You have the resistance in the multimeter leads, you have resistance in those white wires, and you also have resistance in your terminal blocks, where the wires connect to the breadboard, and the breadboard itself also has resistance.
The next thing to do is measure the actual voltage drop across the LED. That will have some tolerance as well, so you may find it is not exactly as the datasheet says. This will also have some significance.
Check all of this and recalculate.
answered 15 mins ago
MCG
4,82631440
add a comment |Â
up vote
0
down vote
It could well be stray resistance. If you are only getting 640mA, then the resistance you are seeing is (12-9)/0.64 = 4.69 Ohms. That is an extra 1.7 Ohms. Your resistor is 3 Ohms. It looks like it is a 5% tolerance, which means it could be as high as 3.15.
You have the resistance in the multimeter leads, you have resistance in those white wires, and you also have resistance in your terminal blocks, where the wires connect to the breadboard, and the breadboard itself also has resistance.
The next thing to do is measure the actual voltage drop across the LED. That will have some tolerance as well, so you may find it is not exactly as the datasheet says. This will also have some significance.
Check all of this and recalculate.
answered 15 mins ago
MCG
4,82631440
add a comment |Â
up vote
0
down vote
up vote
0
down vote
It could well be stray resistance. If you are only getting 640mA, then the resistance you are seeing is (12-9)/0.64 = 4.69 Ohms. That is an extra 1.7 Ohms. Your resistor is 3 Ohms. It looks like it is a 5% tolerance, which means it could be as high as 3.15.
You have the resistance in the multimeter leads, you have resistance in those white wires, and you also have resistance in your terminal blocks, where the wires connect to the breadboard, and the breadboard itself also has resistance.
The next thing to do is measure the actual voltage drop across the LED. That will have some tolerance as well, so you may find it is not exactly as the datasheet says. This will also have some significance.
Check all of this and recalculate.
answered 15 mins ago
MCG
4,82631440
It could well be stray resistance. If you are only getting 640mA, then the resistance you are seeing is (12-9)/0.64 = 4.69 Ohms. That is an extra 1.7 Ohms. Your resistor is 3 Ohms. It looks like it is a 5% tolerance, which means it could be as high as 3.15.
You have the resistance in the multimeter leads, you have resistance in those white wires, and you also have resistance in your terminal blocks, where the wires connect to the breadboard, and the breadboard itself also has resistance.
The next thing to do is measure the actual voltage drop across the LED. That will have some tolerance as well, so you may find it is not exactly as the datasheet says. This will also have some significance.
Check all of this and recalculate.
answered 15 mins ago
MCG
4,82631440
answered 15 mins ago
MCG
4,82631440
answered 15 mins ago
MCG
4,82631440
answered 15 mins ago
MCG
4,82631440
4,82631440
add a comment |Â
add a comment |Â
up vote
0
down vote
Page 17 of the datasheet shows the IV curve for the 9V version. For 1 amp, you are looking at a Vf of 10.4 volts or so, depending on the temperature of the led.
Note that 1 amp is the ABSOLUTE maximum, and without proper cooling of the led, you are almost guaranteeing a dead led, or multiple internal failures.
answered 3 mins ago
Passerby
54.4k448142
add a comment |Â
up vote
0
down vote
Page 17 of the datasheet shows the IV curve for the 9V version. For 1 amp, you are looking at a Vf of 10.4 volts or so, depending on the temperature of the led.
Note that 1 amp is the ABSOLUTE maximum, and without proper cooling of the led, you are almost guaranteeing a dead led, or multiple internal failures.
answered 3 mins ago
Passerby
54.4k448142
add a comment |Â
up vote
0
down vote
up vote
0
down vote
Page 17 of the datasheet shows the IV curve for the 9V version. For 1 amp, you are looking at a Vf of 10.4 volts or so, depending on the temperature of the led.
Note that 1 amp is the ABSOLUTE maximum, and without proper cooling of the led, you are almost guaranteeing a dead led, or multiple internal failures.
answered 3 mins ago
Passerby
54.4k448142
Page 17 of the datasheet shows the IV curve for the 9V version. For 1 amp, you are looking at a Vf of 10.4 volts or so, depending on the temperature of the led.
Note that 1 amp is the ABSOLUTE maximum, and without proper cooling of the led, you are almost guaranteeing a dead led, or multiple internal failures.
answered 3 mins ago
Passerby
54.4k448142
answered 3 mins ago
Passerby
54.4k448142
answered 3 mins ago
Passerby
54.4k448142
answered 3 mins ago
Passerby
54.4k448142
54.4k448142
add a comment |Â
add a comment |Â
up vote
0
down vote
You have to actually READ THE DATASHEET:
Depending on temperature, the LED will drop about 10.2 to 10.5 V with 1 A thru it. Conversely, with 9 V across it, the current will be about 300 to 450 mA.
The datasheet is really quite clear. I can't see how anyone would think this LED would drop 9 V at 1 A.
answered 3 mins ago
Olin Lathrop
278k28331783
add a comment |Â
up vote
0
down vote
You have to actually READ THE DATASHEET:
Depending on temperature, the LED will drop about 10.2 to 10.5 V with 1 A thru it. Conversely, with 9 V across it, the current will be about 300 to 450 mA.
The datasheet is really quite clear. I can't see how anyone would think this LED would drop 9 V at 1 A.
answered 3 mins ago
Olin Lathrop
278k28331783
add a comment |Â
up vote
0
down vote
up vote
0
down vote
You have to actually READ THE DATASHEET:
Depending on temperature, the LED will drop about 10.2 to 10.5 V with 1 A thru it. Conversely, with 9 V across it, the current will be about 300 to 450 mA.
The datasheet is really quite clear. I can't see how anyone would think this LED would drop 9 V at 1 A.
answered 3 mins ago
Olin Lathrop
278k28331783
You have to actually READ THE DATASHEET:
Depending on temperature, the LED will drop about 10.2 to 10.5 V with 1 A thru it. Conversely, with 9 V across it, the current will be about 300 to 450 mA.
The datasheet is really quite clear. I can't see how anyone would think this LED would drop 9 V at 1 A.
answered 3 mins ago
Olin Lathrop
278k28331783
answered 3 mins ago
Olin Lathrop
278k28331783
answered 3 mins ago
Olin Lathrop
278k28331783
answered 3 mins ago
Olin Lathrop
278k28331783
278k28331783
add a comment |Â
add a comment |Â
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1
And what voltage did you measure accross the LED?
– Marko BurÅ¡iÄÂ
21 mins ago
2
The datasheet shows a typical forward voltage of 9V at 400mA, not 1A.
– Finbarr
20 mins ago