Hi
I am planning to produce a sort of computer shelving unit which will be decorated with LED lights, preferably blue. I am think of having about a maximum of 15 blue LED's which will be shun through acrylic, which will be connected to the USB port ( supplies 5volts DC). I am realy stuck on which are the best LED's suited for my project and what else i need like resistors and watt resistors. Please help. Some explanations would also be useful as I am a bit new to electronics.

Luis

 

Hello,

Keep in mind that you can normaly only draw 100 mA from a USB connection.
See the hardware book link for more information.
http://www.hardwarebook.info/Universal_Serial_Bus_(USB)

For calculating teh resistors for the leds you can use ledcalc:
http://ledcalc.com/
When you take 3.5 volt as led voltage you will be on the safe side.

Greetings,
Bertus

 

If you select one LED at a time, your USB port may be ok. If you want all 15 on bright, you will need more power. I would limit the current from a USB port to 50 mills.

 

hey thx for your guys adive it realy helped. Seeing as you guys say that the usb power is a bit too low how would i exactly plug it into the computer power supply which i think is 12volts?

 

oh sorry i forgot to mention when i did the caluclation thing with the site it said i should get a resistor with a 1/8 power rating and all the ones i have seen have a 0,6 watt power rating, what does that actually mean and will it make a difference?

 

Hello,

You can take a resistor with a higher power rating.
It will be larger by size.
See the link for more information.
http://www.interq.or.jp/japan/se-inoue/e_resistor.htm
This link comes from the EDUCYPEDIA.
http://www.educypedia.be/electronics/resistors.htm

Greetings,
Bertus

 

WOW!!! You guys are fast haha thx so much helped loads. hopefully i will later on post a picture when i finish thx a bunch

 

Hi
I am planning to produce a sort of computer shelving unit which will be decorated with LED lights, preferably blue. I am think of having about a maximum of 15 blue LED's which will be shun through acrylic, which will be connected to the USB port ( supplies 5volts DC). I am realy stuck on which are the best LED's suited for my project and what else i need like resistors and watt resistors. Please help. Some explanations would also be useful as I am a bit new to electronics.

Luis

since USB can allow the maximum output of 500mA current, your circuit should not draw more than that. for 5volts I suggest u to use 680ohms to 1kilo-ohms resistor. a 1/4Watt is enough. connect 15 LEDs each with a resistor and connect to power supply. it is wise to take (5v)power supply from the SMPS of PC not from the USB.

 

For 5volts I suggest u to use 680ohms to 1kilo-ohms resistor.

How did you arrive at those numbers?
A typical blue LED might have a rating of 3.4v to 3.8v @ 20mA.
Rlimit = (Vsupply - VfLED) / DesiredCurrent, so with the above numbers,
Rlimit = (5V - 3.4V) / 20mA = 1.6/0.02 = 80 Ohms, and
Rlimit = (5V - 3.8V) / 20mA = 1.2/0.02 = 60 Ohms.
Since Power in Watts = Voltage x Current, 1.6 x 0.02 = .032. A 1/10 Watt resistor would be more than enough.

It is wise to take (5v)power supply from the SMPS of PC not from the USB.

I do agree with your last assertion.

 

I am a beginner in electronics so this question may sound dumb. What is the simplest circuit I can create in a remote transmitter to activate a 5 or 10 watt bulb?

 

I am a beginner in electronics so this question may sound dumb. What is the simplest circuit I can create in a remote transmitter to activate a 5 or 10 watt bulb?

You hyjacked this thread. Make your own thread.

A transmitter does not activate a light bulb. A receiver with a high current output circuit does. A transmitter and receiver are neeeded. It is simple for a couple of mm but you forgot to say the distance you need.