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wiring a hobby sign with leds + el wire

Printed From: the12volt.com
Forum Name: Lights, Neon, LEDs, HIDs
Forum Discription: Under Car Lighting, Strobe Lights, Fog Lights, Headlights, HIDs, DRL, Tail Lights, Brake Lights, Dashboard Lights, WigWag, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=135478
Printed Date: May 12, 2025 at 12:26 PM


Topic: wiring a hobby sign with leds + el wire

Posted By: fcs22
Subject: wiring a hobby sign with leds + el wire
Date Posted: December 06, 2013 at 1:15 PM

hi-
i'm a total newbie to this, so all help is appreciated, and you can't tell me anything too basic.

designing a hobby project -- i am wiring a small sign.
the components are as follows:

58 x 5mm LEDs (12v)

12 x 3mm LEDs (12v)

1 x 2.3 EL wire

1 x 12v inverter to power the EL wire

1 x 12v wireless relay switch (with paired remote)

1 x 12v power supply (8 x AA batteries)


I need help designing this circuit.

from what i can tell reading these forums, my best bet is to split up the LEDs into groups of 4 to divide the 12v to the 3v needed. the EL wire has a power inverter that needs 12v input.

how do i lay it all out? where in the chain should i put the switch?






Replies:

Posted By: oldspark
Date Posted: December 06, 2013 at 5:16 PM
Welcome to the12volt!
And good onya for trying something like this - it's a pretty safe intro that covers a lot of basics - but I'll leave my praise ramble for now.


You said "12V" LEDs, but 12V LEDs involve a resistor and LED or resistor and a string (group) of LEDs.
LEDs are usually ~2V for red & green, ~3.4V for white, ~4.5V for blue, etc.   
And then - yes - wire "strings" or series LEDs where the number of LEDs per string is determined by the SUM of all LED voltages (aka VL) not exceeding the (minimum) supply voltage - eg, 12V. or maybe 11V allowing for a flat battery etc.
A resistor is then used to "drop" the remaining voltage - and also limit the maximum string current.

Typically for white LEDs, a max of 3 per string - ie, 3 x 3.2V or 3 x 3.5V = 9.6V or 10.5V which is comfortably less than 12V.
If red which were traditionally 1.7V but now 2V or 2.1V, assume 2V hence we could have 6 LEDs = 6 x 2V = 12V (especially in 12V vehicles which are usually more like 12.5V to 14.5V), but we might want to include a resistor so hence maybe only 5 (or 4 or 3) for a "12V" supply.

We need to know the LED current to calculate the resistor value (R = V/I from Ohm's Law V = IR), but your LEDs are probably rated as 20mA. (All LEDs in a string will have the same current thru them.)
NOTE - one resistor per string. The (12V) strings are then paralleled together.


Instead of me rambling, look at electronicsclub.info - Light Emitting Diodes (LEDs).
There are other good web references and LED resistor calculators.
Maybe then get back with your preliminary design - how many LEDs with what VL voltages and currents and resistor values and I or others might do a sanity check BEFORE you buy extra components or assemble it etc.

Also note that LEDs are not that critical. Many people wire strings of (say) 6 or 7 reds or 4 whites direct to 12V vehicle systems (ie, 14.4V) without resistors, but resistors should help maintain a more consistent illumination (brightness) with varying voltage as well as help ensure the LED's max current is not exceeded - though less current may not make much practical difference to brightness, and (slight) over-current usually means a shorter life (ie, less than several years) rather than any instant destruction.


As to the EL wire, I presume you mean an ElectroLuminescent display and hence the inverter.
That should simply be a case of wiring the EL to the inverter as per instructions, and the inverter's 12V to the batteries (8 x 1.5V in series = 12V).

The wireless remote I presume is the master on-off switch that sits between the batteries and the rest.

How long the batteries last depends on total current consumption, but that's another issue. However a 12VDC plugpack could be substituted, or even a car battery etc though they are ~12.7V fully charged (and higher when being charged), but the use of LED string resistors should mean that's not a problem. You'd have to check what voltage input the inverter tolerates.   




Posted By: fcs22
Date Posted: December 07, 2013 at 3:32 PM
oldspark- thanks for your help. here are the specs of the LEDs i bought on ebay. they list on ebay as 12V...
posted_image

does that mean there's already a transistor in them?

ebay link here:
https://www./itm/50-x-Warm-White-5mm-LEDs-Pre-Wired-Light-12V-20cm-Bulbs-/300516795565




Posted By: oldspark
Date Posted: December 07, 2013 at 5:11 PM
They are white LEDs (usually ~3.5V each) with a resistor.

One problem is that you will be using 3x the current necessary - ie, instead of having one string of 3 LEDs (plus resistor) at 20mA you will have 3 parallel strings of 20mA LEDs consuming 60mA.


Since they are 12V, just connect across your 12V supply.

Resistors and LED calculators are for "raw" LEDs (2V-4V etc), not 12V LED "modules".




Posted By: fcs22
Date Posted: December 07, 2013 at 7:24 PM
OK, got it. Makes sense. I didn't know the difference between a raw LED and a module. Thank you.

Next question (hopefully not too many more..) If I am wiring them all to the 12V source and not in series, then I have about 60 wires that have to connect to 1 wire. what's the best way to accomplish this?

is it a breadboard like this?
https://www.sparkfun.com/products/112




Posted By: oldspark
Date Posted: December 08, 2013 at 1:08 AM
You could provided it's in a stable environment (not vibrating etc).

Or just use any screw type cable joiners.

If they are 20mA LEDs, their total current will be 1.2A.

Though it's a bit hard to estimate, your batteries should last around 1 hour.




Posted By: fcs22
Date Posted: December 18, 2013 at 8:40 PM
OK, i'm in the process of putting it all together and had 2 follow up questions:

1. You wrote about that battery would last about an hour. What if I wanted to use as a wall plug in. Could i just wire up something like this instead of the battery packs?
https://www.amazon.com/Switching-Power-Supply-Adapter-110V-/dp/B006NTNGN0

2. I turned it on as a test, and the overall brightness of the LEDs was TOO BRIGHT. What can i do to decrease their brightness? is there something i can put in the circuit to do this?

thanks,
Sam




Posted By: fcs22
Date Posted: December 18, 2013 at 8:41 PM
Could I used this to dim the LEDs that I have?

https://www.amazon.com/Controller-Dimmer-Wireless-Control-R106/dp/B00AHU2U7O




Posted By: oldspark
Date Posted: December 19, 2013 at 12:12 AM
From what I can see, both are fine ie, they both handle your 1.2A LED current.





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