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#1
August 28th 03, 04:25 AM
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LED education needed
To All, I need to understand a few things about LED's, such as amperage,
current limiting and light output.. Anyone an expert that can explain things and answer my further rising questions in terms an electronics hack (myself) can understand... Thanks Bob in phx... |
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#2
August 28th 03, 05:09 AM
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bobinphx wrote: To All, I need to understand a few things about LED's, such as amperage, current limiting and light output.. Anyone an expert that can explain things and answer my further rising questions in terms an electronics hack (myself) can understand... Thanks Bob in phx... Well, as a start it is generally assumed that an LED when under forward bias and lit up has 2V across it with 20mA flowing through it. This allows you to calculate a series resistor with any applied voltage. Does this help? Any other questions? Bob WB0POQ |
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#3
September 16th 03, 03:31 AM
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voltage / resistance = current. simple ohm's law.
E I R voltage / current = required resistance "Bob Liesenfeld" wrote in message ... bobinphx wrote: To All, I need to understand a few things about LED's, such as amperage, current limiting and light output.. Anyone an expert that can explain things and answer my further rising questions in terms an electronics hack (myself) can understand... Thanks Bob in phx... Well, as a start it is generally assumed that an LED when under forward bias and lit up has 2V across it with 20mA flowing through it. This allows you to calculate a series resistor with any applied voltage. Does this help? Any other questions? Bob WB0POQ |
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#4
September 26th 03, 04:11 AM
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One issue with calculating the required resistance is that most LED's drop
the voltage about 2 volts. So if you really wanna be accurate, use: (supply voltage - 2) / (desired current) = reccommended resistor But it shouldn't matter too much unless you are either using small voltages or are concerned about exact current draw. 73 -KG6SGY "Zombie Wolf" wrote in message ... voltage / resistance = current. simple ohm's law. E I R voltage / current = required resistance "Bob Liesenfeld" wrote in message ... bobinphx wrote: To All, I need to understand a few things about LED's, such as amperage, current limiting and light output.. Anyone an expert that can explain things and answer my further rising questions in terms an electronics hack (myself) can understand... Thanks Bob in phx... Well, as a start it is generally assumed that an LED when under forward bias and lit up has 2V across it with 20mA flowing through it. This allows you to calculate a series resistor with any applied voltage. Does this help? Any other questions? Bob WB0POQ |
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#5
September 26th 03, 04:11 AM
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One issue with calculating the required resistance is that most LED's drop
the voltage about 2 volts. So if you really wanna be accurate, use: (supply voltage - 2) / (desired current) = reccommended resistor But it shouldn't matter too much unless you are either using small voltages or are concerned about exact current draw. 73 -KG6SGY "Zombie Wolf" wrote in message ... voltage / resistance = current. simple ohm's law. E I R voltage / current = required resistance "Bob Liesenfeld" wrote in message ... bobinphx wrote: To All, I need to understand a few things about LED's, such as amperage, current limiting and light output.. Anyone an expert that can explain things and answer my further rising questions in terms an electronics hack (myself) can understand... Thanks Bob in phx... Well, as a start it is generally assumed that an LED when under forward bias and lit up has 2V across it with 20mA flowing through it. This allows you to calculate a series resistor with any applied voltage. Does this help? Any other questions? Bob WB0POQ |
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#6
September 16th 03, 03:31 AM
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voltage / resistance = current. simple ohm's law.
E I R voltage / current = required resistance "Bob Liesenfeld" wrote in message ... bobinphx wrote: To All, I need to understand a few things about LED's, such as amperage, current limiting and light output.. Anyone an expert that can explain things and answer my further rising questions in terms an electronics hack (myself) can understand... Thanks Bob in phx... Well, as a start it is generally assumed that an LED when under forward bias and lit up has 2V across it with 20mA flowing through it. This allows you to calculate a series resistor with any applied voltage. Does this help? Any other questions? Bob WB0POQ |
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#7
August 28th 03, 05:09 AM
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bobinphx wrote: To All, I need to understand a few things about LED's, such as amperage, current limiting and light output.. Anyone an expert that can explain things and answer my further rising questions in terms an electronics hack (myself) can understand... Thanks Bob in phx... Well, as a start it is generally assumed that an LED when under forward bias and lit up has 2V across it with 20mA flowing through it. This allows you to calculate a series resistor with any applied voltage. Does this help? Any other questions? Bob WB0POQ |
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#8
August 28th 03, 03:31 PM
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The best tutorials are on Agilent's website. For controllers, National Semi
and Linear Tech have very interesting articles. One thing which I will point out is that each LED (generally) needs its own current limiting resistor. Don't try to parallel LEDs with only one current limiting resistor. LED brightness is also affected by ambient temperature. Lastly, there are some good current regulation circuits out there -- LEDs can be used in densitometric (where you need 60+dB of linear performance) applications if you tightly control the current. "bobinphx" wrote in message news:3Ae3b.74955$kP.24778@fed1read03... To All, I need to understand a few things about LED's, such as amperage, current limiting and light output.. Anyone an expert that can explain things and answer my further rising questions in terms an electronics hack (myself) can understand... Thanks Bob in phx... |
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#9
September 11th 03, 05:15 AM
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.....[snip]....
One thing which I will point out is that each LED (generally) needs its own current limiting resistor. Don't try to parallel LEDs with only one current limiting resistor. .....[snip].... But, if you have a few extra volts, they CAN be placed in series. Aren't the super-bright traffic-light LEDs usually 5-6 in series? --Myron, W0PBV. -- Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) |
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#10
September 11th 03, 05:15 AM
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.....[snip]....
One thing which I will point out is that each LED (generally) needs its own current limiting resistor. Don't try to parallel LEDs with only one current limiting resistor. .....[snip].... But, if you have a few extra volts, they CAN be placed in series. Aren't the super-bright traffic-light LEDs usually 5-6 in series? --Myron, W0PBV. -- Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge PhD EE (retired). "Barbershop" tenor. CDL(PTX). W0PBV. (785) 539-4448 NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol) |
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