Hi guys is there anyone that can help me out here. I am tring to build a LED house number sign something like the ones below but I can't find any tutorio on how to do this, so I was wondering if anyone here can help me out or show me how to do it. Your effort will be greatly appreciated.

 

Do you want a fixed number with a fixed color?

A number with a single color is as simple as making a circuit board with LED locations chosen as needed. Likely LEDs are in series groups to prevent an unreasonable voltage requirement.

 

There are a bunch of ways to do this. Here's how I would start (on paper): Hook up several strings of LEDs, with each string having its own current-limiting resistor. Add up all the voltages of the LEDs in each string to find out how much voltage you need to drive the string. Say you have around 22 LEDs per number on the sign, and 4 numbers, and you want to power the thing from 12V. You then have 88 LEDs to drive. Let's say you also want super-bright green LEDs which have a forward voltage of 2V each and each is designed to take 20mA. You can have a maximum of 6 LEDs per string (2V per LED). . .but you should always build in a little extra because your voltage will probably not always be exactly 12V. A maximum of 5 LEDs per string will let the string work down to 10V. So (88 LEDs/5 LEDs per string) = 17 strings of 5 LEDs each, plus one string of 3 LEDs to make 88.

So now each of these 18 strings needs a current-limiting resistor. You calculate that with the formula R = (Vsupply - Vload) / I. R is the resistor value, Vsupply is the supply voltage (12V) and Vload is the sum of the forward voltages of the LEDs in the string. I is the amperes required by the string. LEDs in series don't add their ampere ratings, so while a string of 5 2V 20mA LEDs in series has a forward voltage of 10V, it still has an ampere rating of 20mA.

So for each 5-LED string: R = (12V - 10V) / 0.02A, so R = 100 Ohms. For the 3-LED string, R = (12V - 6V) / 0.02A = 300 Ohms. If you only have access to 10% resistors then use 330 Ohms instead. You need 17 100 Ohm resistors and 1 300 Ohm resistor.

Now you need to make sure your power supply can handle it. You could power this array from any 12V wall-wart which can supply 360mA. (360mA = 20mA per LED string.) However, an unregulated power supply will probably supply more than 12V if it is really overrated (say 1A or more) so try to get something closer, like a 12V 500mA adaptor.

But: what other features do you want it to have? Should it light up only when it's dark out, should it fade on and off, etc.


Good luck!

Torben

 

Ouch!

What a lot of work just for a number!

Why don't you try this:?

Get some acylic glass coloured the way you like most, yellow, red or any colour. Buy a bunch of self adhesive paper dots in a paper shop and put them nicely on the rear side of the glass. Then spray it black. When the paint is dry remove the paper dots and you have something left looking like a LED. Use an incandescent lamp inside and shade it so it will emit light not directly onto the glass.

Your friends will admire you for the lots of work youv'e done.

Saves one week of soldering and possibly fried LEDs too.

Boncuk

 

While I agree in principle (that is, it's silly and a waste of money and time), this should be doable on a Saturday afternoon at most, unless you're soldering with a banana.


Torben

 

The Source was clearing those things out for $3 about 2 months ago.

It makes sense to power your house number in a world going green

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com

 

Interesting idea, i may want to build one myself.

 

Is there a step by step tutorio online. I know since this is an easy project to build people might not put out a tutorio for this, but I'm just start over fresh in the electronics field.

 

As long as the voltage is high enough it's just a bunch of LEDs wired in series with a current limiting resistor.
http://www.theledlight.com/ledcircuits.html

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com

 

Hi Sammy,

Are you determined to use individual LEDs instead of just shining a light through some holes? What is your experience level with soldering and LEDs and such? As noted it's an expensive and labour-intensive way to do the job.


Torben

 

Right, but with bright LEDs we're talking over 100V even for the 3-digit signs, aren't we? Yow.


Torben

 

Please plan for two. My house number is short: 54

 

In my opinion it is not a great task. A few things to keep in mind about LED's are:
The luminous intensity or mcd can vary with forward current.
Different colored LED can be connected in series and the current thru each LED will be the same, but because of the individual charastics the various colors may not be the same intensity.
The LED's have a polarity so they need to be connected properly.

If I were going to make such a sign I would choose all the same color of LED.
I have used 3mm(T1 size)and 5mm(T1-3/4) size numerous times. I have selected a front panel, plastic or metal, drilled holes in the pattern I wanted and put the LED's in the panel. Glued them to the panel sometimes with hot glue or general purpose cement. Wired a small number in series, used a current limiting resistor, and had multiple strings in parallel, suppled with a DC voltage for illumination. If the LED's are mounted fairly close to each other the bent leads can be soldered together for the series connection.

As a side note you always don't need the full current for illumination. I have some high intesity blue leds that just about blind me with only 5mA of current.

__________________
The great thing about electronics is unlimited ways to do the job. The only limit is one\'s imagination. I generally think my way is best.
Show me a different way. I have an open mind.

 

I've seen LED signs with no transformer, perhaps you can run about 50 LEDs directly from 120VAC with a blocking diode and resistor. Dangerous if you're not sure what you're doing.
Or you can break them up into sets.

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com

 

Kind of late, but the cheap and easy solution would be Christmas lights. I usually check after the holidays, for the LED stings on sale. Last Christmas was a bust, only found a few red, and not much of a discount. Probably waited too long.

Anyway, cheaper then buying individual LEDs, pre-wired. Just layout your numbers, drill a bunch of holes, stuff the LEDs in.