Need some help for a volunteer

[Blitzburgh]

namely...me.

I have been asked (tasked) with making an interactive map that is to be used in a Welcome Center.

Basically, the idea is to have a plexiglass 5'x 4' plexiglass map made of our location. When a lost tourist shows up, they will be able to press a button corresponding to the location they want to go to and then have an LED light up in that area.

Could I get some pointers here of how to proceed? Any additional input that you may have would be greatly appreciated.

Sincerely, Mike

 

[solis365]

get a 5V wall wart and some 20mA LEDs in your desired color (you can find LEDs on ebay much cheaper than you can from radioshack). Choose resistors based on the forward voltage of the LED color you have chosen (red typically 1.8, blue is higher). You can use the LED resistor calculator to figure out what value of resistor you need. Then, for each LED, just hook up one series resistor and one normally-open momentary pushbutton switch. Wire the two ends to your 5V wall wart (with the LED facing the right direction). This will give you one LED. Do the same exact thing for as many LEDs as you need, and hook them all up to the 5V. Plug it in and push some buttons. Now you are free to mount the LEDs in whatever way is most convenient to the map case you have designed. Mount the buttons as well, and voila!

Sorry for being basic about things as I am not sure of your experience level in electronics.

**broken link removed**

That picture is what your circuit will look like. The value of the resistor may change based on your LED selection, of course, and Vcc will be replaced by the positive side of your 5V wall wart. If the button connection is shaky or hard to keep full contact you can put a small value capacitor in parallel with the switch.

 

[Blitzburgh]

Are you KIDDING ME?!?!?

That was GREAT!!! Thank you for the input. My level is novice at best, but I capture most of what you have written and think I can pull this off.

I am a little vague on the term "Wall Wart" (I actually thought you meant WalMart at first but then you kept repeating it)

A 5 V wall wart
50 LEDs of my choice
Resistors per the chart
Wire (I am guessing I can go pretty thin here eh?)
and attitude.

Thanks so much. Mike

 

[Blitzburgh]

Now, something just came to me here.

What if some of the kids get in there and start playing around and pushing buttons so to speak. Or someone leans up against the display and inadvertantly presses 4 or 5 buttons at the same time? Will that be enough to pop the circuit? Or will it just cause the lights to not light up?

 

[bychon]

LED's use about .01 amps each. If the wall wart is rated for 50 times .01 amp, that's about half an amp. Use a half amp wall wart and the kids can push all 50 buttons without any bad happening..

 

[solis365]

A wall wart is one of those annoying oversized plugs used for charging cell phones and the like. They are made for converting the 110V alternating wall voltage to a 5V DC voltage. (well, different ones have different voltages). You can probably buy one on ebay for not much money. websites like sparkfun.com sell them, but i think sparkfun is expensive. You can also probably salvage one from any location where electronic junk is being thrown out.

you have 50 locations to illuminate? I know each location's LED only takes 20mA or so but chances are there will be a little kid (or adult, hehe) who will try to press all the buttons at once to make all locations light up. You don't want to blow up your wall-wart if this happens, so you should get one that is rated to output up to 1A. (50 times 0.02A = 1A). Its probably overkill but it won't be that much more expensive and will keep things from breaking. I would actually get one rated to 1.25A or 1.5A for a little extra safety margin, or if you ever want to add more locations.

the wall wart should have its own wiring for your 5V and ground. If you add any extra wire for the 5V or ground rails, just make sure it is rated for 1.5A (the rating of the wall wart or a little higher). The wire for each individual "branch" can be very small indeed. 24AWG would be MORE than enough here.

quick ebay search yielded:
**broken link removed**
**broken link removed**

youll probably just want the 1A version because its way cheaper and ebay is full of them. my guess is that if something exceeds the current rating, it will just drop its output voltage, making all the LEDs dimmer. Once the buttons stop being pressed all at the same time they will go back to full brightness.

whatever you get, make sure it's not a fancy USB charger or anything. sometimes those have internal control circuitry and will only turn on for the right device, or require a minimum load, etc. A barrel jack output will guarantee you simplicity. You can buy circuit-board-mount barrel jack plugs from places like radioshack, sparkfun, and probably ebay, so you won't even have to cut the cord.

EDIT: you two posted while i was writing. byron is right; you probably dont need 20mA going through each LED. The difference in perceived brightness between using 20mA and 10mA is not very much, so just figure on using 10mA in a 20mA rated LED. if its too dim you can try a slightly lower value of resistor to increase the current until you get the brightness you like, but like i said, the perceived difference isnt much. it gets to be more detectable between 0 and 10mA.

 

[bychon]

The circuit posted with a 330 ohm resistor uses 10 milliamps. However, using 20 milliamps each will do no harm. Just lower the resistor to 160 or 180 ohms. (180 ohm resistors are easier to find and buy.)

 

[MikeMl]

Wiki Wall Wart

 

[Blitzburgh]

MAN! You guys are EXCELLENT! Seriously, thank you all for the help.

I just bought these LEDs **broken link removed**

Next will be a trip to RS to pick up some 100 ohm resistors (Using your chart gave me this rating)

Some 24 gauge wire, pushbutton switchs (any suggestions on ebay that I could use?)

and attitude - can do.

Thanks again SO VERY MUCH

 

[Blitzburgh]

BTW - I think I am correct on this. I should be able to get a pretty standard 1/2" by 20" piece of metal to drill and run the positive side of the dc voltage on, correct? i.e. I don't want to tie 50 individual strands of wire all together in a bundle. I am just trying to keep the project neat. (Will post pics hopefully when this is done.)

 

[Blitzburgh]

The circuit posted with a 330 ohm resistor uses 10 milliamps. However, using 20 milliamps each will do no harm. Just lower the resistor to 160 or 180 ohms. (180 ohm resistors are easier to find and buy.)

Thank you. Will remember that as well.

 

[bychon]

Looks good from here. Try to enjoy your work.**broken link removed**

 

[solis365]

you're right about the metal bus line, thats actually a much better idea.

those LEDs will be pretty bright at 20mA - so bright you might not want to look at em straight on.

try getting a few values of resistor to try out first - 100ohm, 150ohm, 200ohm, and maybe even a 250ohm. I think you'll find that it will be more pleasant to look at with 200ohm or so, they wont be so piercingly bright (bulbs of this brightness are the ones in LED keychain flashlights and the like. those are pretty bright).

The circuit posted with a 330 ohm resistor uses 10 milliamps. However, using 20 milliamps each will do no harm. Just lower the resistor to 160 or 180 ohms. (180 ohm resistors are easier to find and buy.)

you are right, assuming the forward voltage of that LED is only 1.8V. But for the 3V blue LEDs that he selected, the resistor will need to be 200ohms for 10mA and 100ohms for 20mA.


as far as resistors and switches, radioshack will DEFINITELY be expensive for buying 50 switches. try an online retailer, and try to get both resistors, switches, and wire from the same place to save on shipping, thats usually where they get ya with this stuff.

I use jameco but there are others.
resistors: CF1/4W201JRC: VARIOUS: Passive Components
switches: GPB001-R: JAMECO VALUEPRO: Electromechanical
Jameco Electronics - Electronic Components Distributor

the first switch link is the cheapest one i could find there. You are looking for a momentary contact, normally open switch. Just about anything will handle the 5V, in fact the lowest category they have is 12V.

sorry i dont mean to push specific websites, its just more convenient to show one, heh

 

[Blitzburgh]

Okay, so here is the resistors and wire I bought. Any red flags before I move on?

**broken link removed**

**broken link removed**

 

[Blitzburgh]

you're right about the metal bus line, thats actually a much better idea.

those LEDs will be pretty bright at 20mA - so bright you might not want to look at em straight on.

try getting a few values of resistor to try out first - 100ohm, 150ohm, 200ohm, and maybe even a 250ohm. I think you'll find that it will be more pleasant to look at with 200ohm or so, they wont be so piercingly bright (bulbs of this brightness are the ones in LED keychain flashlights and the like. those are pretty bright).

you are right, assuming the forward voltage of that LED is only 1.8V. But for the 3V blue LEDs that he selected, the resistor will need to be 200ohms for 10mA and 100ohms for 20mA.

as far as resistors and switches, radioshack will DEFINITELY be expensive for buying 50 switches. try an online retailer, and try to get both resistors, switches, and wire from the same place to save on shipping, thats usually where they get ya with this stuff.

I use jameco but there are others.
resistors: CF1/4W201JRC: VARIOUS: Passive Components
switches: GPB001-R: JAMECO VALUEPRO: Electromechanical
Jameco Electronics - Electronic Components Distributor

the first switch link is the cheapest one i could find there. You are looking for a momentary contact, normally open switch. Just about anything will handle the 5V, in fact the lowest category they have is 12V.

sorry i dont mean to push specific websites, its just more convenient to show one, heh

Please, push a website! LOL I am swimming out here, but it looks like I am going to make it to shore. Great help here. Just super.

 

[solis365]

the 180ohms should be fine.

how much of that wire did you buy? its solid silver wire so its $3.21 per foot... which is really expensive for what youre doing

 

[crutschow]

No reason to use silver wire. Plain old copper wire is fine.

 

[bychon]

You don't need 1% precision resistors, either. 5 or 10% would do.

 

[Blitzburgh]

the 180ohms should be fine.

how much of that wire did you buy? its solid silver wire so its $3.21 per foot... which is really expensive for what youre doing

Oh man, You cannot believe how my heart jumped in my chest when I realized what I did. You caught the part where it mentions per foot. I thought I was buying the spool! LOL

(Dumbo award)

So I settled on this.

**broken link removed**

Also bought the Jameco switches you recommended. They should be easy to work with. Ditto for the 5V power supply.

Thanks again to everyone for the assistance.

One last thing. A metal rail for tying the wires together with the power supply. Any suggestions on where to find something like this?

Have decided against plexiglass for the map. Think we are going to go with a cedar wood map. Goes a bit more with the location and think it would be easy to work with.

 

[crutschow]

Enameled magnet wire is for winding coils and transformers. It's bare wire with an enamel (varnish) insulation. You should use normal insulated hookup wire.