Electronics help

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slimesquare

Well-Known Member
RPF PREMIUM MEMBER
So, I'm working on a project that will run 60 super bright blue 5 mm LEDS. I've done some reading on wiring them in a series, but instead of running all 60 in one series I thought it would be easier if I wired them in smaller series of 4 LED per group, so instead of 60 running in a series there will be 15 series of 4 LEDS with a resistor. The company I bought the LEDS from sent me resistors but I think it said they would only work if I was trying to make it 12v. I believe the LED voltage said 3-3.3 v

Can someone help me with what type of resistors I need to use if I was gonna try and make it able to plug into a wall. Or if there is a safer way to use batteries with out using a ton of them.

If I left out any info you need please ask. I'm new to custom electronics.

Thanks,
Slimesquare
 

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Kevin Gossett

Master Member
RPF PREMIUM MEMBER
Google "led calculator". It will tell you what type of resistor you need and give a diagram on how to wire everything up
 

Troy Downen

Active Member
You actually have the right idea here. Please refer to my response (#14) to a similar question in an earlier thread:

http://www.therpf.com/f9/led-electric-circuit-help-131536/

I posted some diagrams in this thread as well.

Short response (assuming a 12V power source): 4 LEDs in series without a resistor, or 3 LEDs in series with a 100 ohm resistor. I'd suggest the latter if you want maximum light emitted.

Easy as pie. :)
 

epilepticsquirl

Sr Member
I've done something similar with about 100 LED's. I have mine running from a 15 volt power supply attached to a PWM Dimmer to adjust the brightness.

This wizard helped me immensely with the project, even shows the schematic in picture form for those not too familiar with electronics.
LED series parallel array wizard
 

Delmustator

Sr Member
Based on a Phihong PSU I have spare. Looks like a small wall PSU.
Input 100-240 VAC, Output 5 VDC / 2A. This is in parallel.

Positive side ------ Negative side

Solution 0: 1 x 60 array uses 60 LEDs exactly
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms
+----|>|---/\/\/----+ R = 18 ohms

The wizard says: In solution 0:
each 18 ohm resistor dissipates 180 mW
the wizard says the color code for 18 is brown grey black
the wizard thinks ½W resistors are needed for your application
together, all resistors dissipate 10800 mW
together, the diodes dissipate 19800 mW
total power dissipated by the array is 30600 mW
the array draws current of 6000 mA from the source.
 

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Delmustator

Sr Member
Using a 20 VDC output laptop power brick.

Positive side -------- Negative side

Solution 0: 6 x 10 array uses 60 LEDs exactly
+----|>|----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 2.2 ohms
+----|>|----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 2.2 ohms
+----|>|----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 2.2 ohms
+----|>|----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 2.2 ohms
+----|>|----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 2.2 ohms
+----|>|----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 2.2 ohms
+----|>|----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 2.2 ohms
+----|>|----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 2.2 ohms
+----|>|----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 2.2 ohms
+----|>|----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 2.2 ohms

The wizard says: In solution 0:
each 2.2 ohm resistor dissipates 22 mW
the wizard says the color code for 2.2 is red red gold
the wizard thinks ¼W resistors are fine for your application
together, all resistors dissipate 220 mW
together, the diodes dissipate 19800 mW
total power dissipated by the array is 20020 mW
the array draws current of 1000 mA from the source.
 

Delmustator

Sr Member
You can get a laptop power brick off eBay for under $20.

P.S. Just make sure you get the wall cord for the power brick. For some reason, the chuckle heads on eBay will sell the power bricks without the wall cord. Which makes them basically useless. If it says (Power Brick Only),,, pass unless you have the wall cord.

Note: Most laptop power bricks DO NOT use the standard 3-prong grounded power cords like what you use with your desktop PC power supply. They use either a 2-prong power cord or some special molded 3-prong in a V shape cord.

Here's a nice 19v power brick, with cord for under $10.
http://www.ebay.com/itm/HP-COMPAQ-NOTEBOOK-POWER-BRICK-90W-LAPTOP-DV9000-DV8000-/130677720819?pt=Laptop_Adapters_Chargers&hash=item1e6cffc6f3#ht_2683wt_1396

It has a nice male mini-plug. So you could purchase the matching female plug and wire it into your project. Nice and clean...

19 VDC only slightly changes your wiring diagram.

Solution 0: 5 x 12 array uses 60 LEDs exactly
+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 33 ohms
+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 33 ohms
+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 33 ohms
+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 33 ohms
+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 33 ohms
+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 33 ohms
+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 33 ohms
+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 33 ohms
+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 33 ohms
+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 33 ohms
+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 33 ohms
+----|>|----|>|----|>|----|>|----|>|---/\/\/----+ R = 33 ohms

The wizard says: In solution 0:
each 33 ohm resistor dissipates 330 mW
the wizard says the color code for 33 is orange orange black
the wizard thinks 1W resistors are needed for your application
together, all resistors dissipate 3960 mW
together, the diodes dissipate 19200 mW
total power dissipated by the array is 23160 mW
the array draws current of 1200 mA from the source.
 
Last edited:

slimesquare

Well-Known Member
RPF PREMIUM MEMBER
now can I use something with higher voltage like the 19v brick if I use the 12v resistors that came with it? or will it fry everything?
 

slimesquare

Well-Known Member
RPF PREMIUM MEMBER
thank you Delmustator, I guess ill be scavanging ebay to find the proper parts when I got home from work....that'd be nice to make it just plug right into the power source...awesome help guys thank you!
 

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