NOOB QUESTION: What kind of resistor do I need?

In summary, MikieCGY is looking to make a costume out of 500 LEDs for Burningman, but is having trouble powering them with a 9V battery. The LEDs require 65-75 mA each, meaning that 500 of them would require a total of 17A, which is not feasible with a 9V battery. Suggestions were made to use a larger power source, such as six D type cells, and to experiment with using fewer LEDs and pulsing them to save on current. A fuse is also recommended for safety.
  • #1
MikieCGY
2
0
First off.. this is my first attempt playing with this kind of stuff.. please have a bit of patience with me :)


I'm looking to make a costume out of LEDs for burningman.. bought a 1000 of them off ebay and when I connect them the 9V battery I'm guessing is too strong for it and burns the LED out.

is it possible to run say 500 LEDs off of 1 9V battery?

These are the specs of my LEDs (which is another language to me)



WLD : 465-470 NM

IV: 8000-10000 MCD

VF: 3.4 -3.6V



please advise. thanks :)
 
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  • #2
MikieCGY, Welcome to Physics Forums!

It appears you have the blue LEDs made by China Young Sun LED Technical Co., LTD. Their model (part) number is YSL-R1042B5C-D13. The specification sheet is available at:
http://www.sparkfun.com/datasheets/Components/LED/Blue-10mm.pdf

The LED’s output wavelength, intensity, and forward voltage you mentioned were measured with a current of 80 milliamperes flowing through it. The suggested operating current is 65-75 mA, which would consume 180 milliwatts of power.

Using your 9 Volt battery, to energize one LED you would use a 120 ohm resistor in series with the LED (between the battery and the LED) to limit the current to around 70 mA.

No, you cannot run 500 LEDs off one 9 battery! A typical alkaline 9 V battery has the capacity of 565 mAhr, meaning it can supply 565 milliamps for one hour. So if you connected eight circuits like the one described above in parallel they would operate for about one hour. You will have to either use bigger batteries or fewer LEDs, or both. Have a good time!

p.s. I went to Burningman in 1982 and had a fantastic experience! I wore a ball cap with a solar cell powering a tiny dc motor with a plastic propeller on top.
 
  • #3
Thanks for the quick reply Bobby! Also going to a hobby shop today in hopes of buying some resistors instead of buying them online..

does each LED need its own resistor?

How many LEDs can one 9V battery power?

Can you suggest a different power source?


Looking forward to the burn.. its definitely grown since 1982 ... been wanting to go for a fe years now and finally going this year

I'm pretty crafty but my electronic knowledge is just god awful :(


thanks!
 
  • #4
You could run LEDs in pairs, connected in series with a 30Ω resistor from 9V, that would be more efficient on your power. You would get twice the bang per buck? Each pair would take about 70mA.
250 pairs would need 17A. That represents 17X9 = 150W+, which would be totally daft and would fry you, even if you could carry all the batteries needed! You wouldn't need anything like as many as that. You could get a good show with twenty pairs, which would draw 1.4A (12w).

Actually, you would be better to experiment with just how little current you could get the LEDs to light up at all then use more. That would depend upon the exact behaviour (rather than the published spec) of the LEDs.
AS a power source, six D type cells would be better than 9V batteries and you can get holders for them. You would be well advised to use a fuse in the circuit - just next to one end of the battery pack. D type cells hold a lot of energy and you don't want to be dressed up in a potential crematorium if you get a short circuit somewhere!

To save on current drain it may be worth while pulsing the diodes and accepting the reduced brightness so that you can use more light sources all over you. But you'd need an oscillator / switching circuit, which may not be straightforward for you.
 
  • #5


Hi there, it's great that you're getting into electronics and experimenting with LEDs! To answer your question, the type of resistor you need will depend on the specific circuit and components you are using. Factors such as the voltage and current requirements of your LEDs, as well as the power source you are using, will determine the type and value of resistor needed. I recommend doing some research on LED circuits and consulting with experienced individuals to determine the best resistor for your project. As for running 500 LEDs off of 1 9V battery, it is possible but you will need to consider the voltage and current requirements of your LEDs and make sure your battery can supply enough power to run all of them. It may also be helpful to use multiple batteries or a different power source for such a large number of LEDs. I hope this helps and good luck with your project!
 

1. What is a resistor and why do I need it?

A resistor is an electronic component that limits the flow of current in a circuit. It is used to control the amount of current flowing through a circuit and to protect other components from damage. Without a resistor, the current in a circuit can become too high and cause malfunctions or even fires.

2. How do I know what type of resistor I need?

The type of resistor you need depends on the specifications of your circuit. You will need to consider factors such as the amount of current flowing through the circuit, the voltage of the circuit, and the power requirements. It is best to consult a resistor color code chart or a resistor calculator to determine the appropriate resistor for your circuit.

3. Can I use any resistor in my circuit?

No, you cannot use any resistor in your circuit. Different resistors have different resistances and power ratings, which can greatly affect the performance of your circuit. It is important to choose the correct type and value of resistor for your specific circuit to ensure proper functioning.

4. What is the difference between a fixed resistor and a variable resistor?

A fixed resistor has a set resistance value that cannot be changed. It is used in circuits where a consistent resistance is needed. On the other hand, a variable resistor, also known as a potentiometer, has a variable resistance that can be adjusted manually. It is used in circuits where the resistance needs to be changed, such as in volume controls or dimmer switches.

5. Are there any safety precautions I should take when handling resistors?

Yes, there are some safety precautions you should take when handling resistors. Always make sure to handle them with clean and dry hands to avoid any damage to the resistor. Additionally, avoid touching the leads of the resistor while it is connected to a power source, as it can cause electric shocks. It is also important to store resistors in a dry and cool place to prevent any damage or changes in their resistance values.

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