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LEDS are diodes and will operate correctly only when the voltage is sufficient and also the current is sufficient. So i cannot solve it correctly since i have no info on the current. Generally a led can be safely conduct if the current is around 0.020 amps or 20ma so 3-2.4=.6v .6/.02= 30 ohms.
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∙ 14y ago
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What is a protective resistor?
The protecting resistor is put in series with the LED so that you have a voltage divider - the supply voltage is split across the LED ( max 0.6v) and the remainder across the protecting resistor. So if your supply is 6volts, 5.4v will be across the resistor,
What is my Led and what resistor do I need?
Led is a light emitting diodes which can two leads .one lead is larger and the other is smaller. You did't use any resistor because it glows with the small amount of energy! Idiot. I mean't how to I find out what my LED is. I know what a Led is and without a resistor, you prick, It wouldnt last a second.
What the role of a resistor in an led circuit?
a resister is to RESIST current flow....if the LED gets the full effect of the power supply, the LED will immediately blow out.
Should a resistor go on the positive or negative side of an LED?
It does not matter. Kirchoff's Current Law states that the signed sum of the currents entering a node is zero. A consequence of that law is that the current in every part of a series circuit is the same. The only thing that resistor location affects is the potential voltage of the LED terminals with respect to the rest of the circuit. Certainly, if you are driving the LED with high voltage, such as 120VAC, you should consider the resistor location so as to reduce electrocution hazard but, the LED's performance is not affected by resistor location in the circuit.
How do you build a door sensor alarm system using a simple circuit board?
I bought: reed switch LED Buzzer Button (On/Off) Resistor (if necessary) I connected: <---Button------Reed switch------Resistor (if necessary)------LED------Buzzer---Batteries--->
How do you convert 12 volts dc to 3 volts dc for LED?
Depends on the led forward bias threashold, if its a typical led it will be .7 volts so, .7x6=4.2V, so pick a resistor that will drop around 7 volts. What is the current? Then just to V=IR, 7=IR.
What size resistor to change 12 volts to 3 volts for a led?
Assuming that you're talking about 12V DC you would use a 4 ohm resistor. If you mean AC then you would need a step-down transformer with a 4:1 ratio.
Why does a Led have a 470 resistor connected to the LED?
A: That resistor is there to limit the current to the LED it can be any value if the voltage is decreased or increased or no resistor if the voltage across the led is equal to the forward voltage drop.
Why is a resistor used to operate an LED?
To calculate the current through an LED, use the following formula Current = (Source_voltage - Led_voltage_drop)/Resistance Now if you didn't use a resistor, the you only have the resistance in the wire, which is very small (eg .001 ohm). So if you have for instance a 9V battery, and a 2.1 volt drop across the LED, the resultant current would be so high, it would destroy the LED. We put a resistor in to lower the current to an acceptable range (often 20-30ma)
The voltage drop across led is?
The voltage drop across an LED varies, but is typically around 2 volts.
Led circuit for 120 volts?
There can be no answer for this without knowing how strong a resistor is involved. (Ohms)
How is the brightness of the LED affected by different resistor values?
LED's are light emmitting diodes. diodes have a voltage threshold that must be reached for them to fully "turn on". A resistor can be used to limit that voltage. As the voltage drop across the diode is increased above the turn on voltage (typically .5 - .7 volts), the diode will emmit light. The LED will only light up so far, so by turning the voltage up significantly more will have a very limitted payback in light output.
What side of the LED should the resistor be attached to lower the 12 volts DC to the LCD?
I'm pretty sure it doen't matter, the total resistance of the circuit is what counts, the diagrams I have seen however predominantly put the resistor on the + (anode) side of the LED.
Why must an LED always have a resistor connected in series with it?
An LED usually has a resistor connected in series with it because an LED (light emitting diode) is not linear in current to voltage (like a resistor) and has to be operated within specified current and voltage conditions. In most circuits the supply voltage is higher than the forward voltage of the LED so the LED would burn up from too much current without a current limiting resistor in series. The resistor sets the voltage and current to a good operating point (voltage and current) for the LED by dropping some voltage across it. The operating point varies depending on the size, type and manufacturer of an LED so the LED's data is used to select the right resistor size for a given voltage source.
How do you connect an LED into a circuit?
A: Add the proper resistor in series with the LED. What resistor? Simple 10volts source minus the LED source divided by the 20ma current that should be flowing gives you the resistor 10-1.8=8.2/.02=900 ohms. The 1.8 can be anything it is up to the LED voltage drop. LONG LEAD IS POSITIVE SHORT IS NEGATIVE SINCE IT IS A DIODE
What size of resistor is required to operate the LED from a 9V battery?
In order to determine what size of resistor is required to operate an LED from a 9V battery, first start by knowing the current and voltage required for the LED. That information is available in the LED's specifications. For discussion purposes, lets assume a typical LED at 2.5V and 50mW. The translates to a forward current of 20mA. Build a simple series circuit containing a 9V battery, a resistor of an as yet unknown value, and the LED. By Kirchoff's current law, the current in the LED is the same as the current in the resistor, which is also the same as the current in the battery. This is 20ma. By Kirchoff's voltage law, the voltage across the LED plus the voltage across the resistor equals the voltage across the battery. This is 6.5V. (9 - 2.5) By Ohm's law, resistance is voltage divided by current, so the resistor is 6.5 / 0.02, or 325 Ohms. The nearest standard value to that is 330 Ohms. Cross check the power through the resistor. Power is voltage times current, or 6.5V times 0.02A, or 0.13W. A half watt resistor is more than adequate for this job.
What is the voltage drop per led in a 25 led series circuit with 120 volt supply and leds are 3.0 volts 20 ma with a resistor of 5000 ohms?
There is not enough information to answer this question correctly. As the current increases through a diode, the voltage dropped across it increases. This correlation is not a linear function such as a resistance, and a datasheet for the diode or a curve tracer would be necessary to obtain the correct function. To explain further, if there were 25 series LEDs all with a 3 volt drop across them, a 75 volt potential would be measured across the diodes, and 45 volts would be measured across the 5000 ohm resistor. Ohms law will show that 45 volts applied to 5K ohms will equal 9mA. This violates the 20mA criteria in the question.
