LED circuit HELP for a Guerilla/Creative Marketing Campaign

[ZigZag]

Hello everyone!

I'm ZigZag!










Guys, I could really use your technical expertize:

Executive summary:

I'm working on a currently-zero-ROI project (needs to be as cheap as possible). Basically, I need to backlight a 5"x10" "clear" (it looks white not clear, but it is called clear) Coroplast (aka corrugated plastic, aka sign board). Ideally I would like the sign to be visible from 50+ feet away (during street-lit conditions) for 7+ nights while animating in different colors (e.g. if it can turn on and flicker, like an old/cold neon sign does, and then slowly/smoothly transition through 3-4 colors before turning off and then after few seconds restarting all over again with some randomness built in) for under $ 1 USD (ha! I know! What would be more reasonable?) (would buy enough parts for 100-500 of these at once). I could live with a sign that is visible in street-lit conditions from 20 feet away for 2 nights and is backlit with a white led for under $1.65 (better estimate?) if I source 1000-2000 at once. Depending what this discussion will yield, I may do some of both (more of cheaper kind and less of the fancy kind). Price = excluding batteries. This is for outdoor use.


THE BIG A$$ THROWIE!

$ It needs to last 2-7 nights $
$ It hast to be visible 20-50 feet away in street-lit environment $
$ It cant be too heavy (sign will be held by 1-4 magnets) $
$ I would prefer to have these signs animated in multiple colors, but will deal with only white $
$ It has to be cheap, really cheap (yet satisfy the minimum requirements) $




*** I would really prefer 7 nights, but if 2 nights is 2x or more cheaper I would have to deal with only 2 days (it does not have to turn off during the day, but it will save on power)
*** I can live with the sign being visible 20-30 feet away in street-lit conditions
*** I would rather only use one magnet (cost issue) but if it can stay on for 7+ nights and/or be visible at 40-50+ feet away 4 magnets could be used
*** @$4/sign=no go! @$3/sign=will bleed me to death slowly @$2/sign=will keep my fridge empty for 2 months @$1/sign=I will loose some weight dieting, but would be an overall a really happy camper!






# I know very little about electronics and circuitry (willing to learn).

# I do not have any components yet except Coroplast and a breadboard to test circuits.

# I understand the difference between different metrics used measure light that is radiated by LEDs, but as I've never played with any high-powered LEDs I do not have personal experience as to how these numbers translate into "backlighting Coroplast and being visible at X feet away"

# I think battery can be saved, if needed, by using a sensor that can tell if it is light or dark out and turn on or off the LED ( e.g. http://www.evilmadscientist.com/article.php/nightlight )

# In the aforementioned link there are comments about how to increase the simple circuits productivity at minimal cost (adding a mosfet), but I do not know how it would apply to me (batt life vs. cost)

# I think the magnets will hold at least a pair of AAA if I chose to go with 4 of them per sign (costly, but...)

# I planned to source things from eBay and sites like Mouser, but I need at least a hundred of these already made by the second Thursday of August, so I have limited time for experimentation, if any (e.g. for visibility distance) due to shipping times.







Please let me know of my options and help me design a circuit, PLEASE!

 

[(*steve*)]

You are up against a large number of problems.

1) total energy available from batteries
2) brightness required
3) cost constraints
4) "smarts" (e.g. randomness of lighting)

You need something that turns off during the day and turns on (preferably for a limited time) at night to conserve power. Therefore a sensor and some amount of smarts.

You want high brightness and variable colours which means multiple high power LEDs or a single multi-colour LED.

The smarts imply a very cheap microcontroller (look for obsolete components on eBay -- you should be able to find stuff around $0.25 per unit. To detect day/night, an LDR is probably the best option -- you may be able to find them for around 10c each. Then you'll need transistors to turn on the LEDs and resistors to limit current. Each of those should be quite cheap.

The big cost will be the LEDs and batteries.

Oh, and you'll need a small PCB to build it all on (which you'll have to make yourself if it's going to be a reasonable cost.

Can it be done for around $1 US? I doubt it. (mostly it depends on the cost of LEDs and batteries)

The major issue is that the stuff required to program the uC and make the PCBs is likely to cost you quite a bit, and may blow your budget unless you're going to use it again.

Another thing you have to consider is how the LEDs will illuminate the sign. Will they be placed in front for reflective illumination, behind for transmissive, or attached to the edge like some bar signs (not sure what this is called)

The big risk is that since you can't really prototype before you order all the components that you're probably going to have to be creative in getting around problems as they arise.

 

[ZigZag]

Thanks Steve!

You are up against a large number of problems.

1) total energy available from batteries
2) brightness required
3) cost constraints
4) "smarts" (e.g. randomness of lighting)

You need something that turns off during the day and turns on (preferably for a limited time) at night to conserve power. Therefore a sensor and some amount of smarts.

I may be able to increase the battery life a bit if I can add some sort of timer: I only need the signs to run from dusk to 3am.

The smarts imply a very cheap microcontroller (look for obsolete components on eBay -- you should be able to find stuff around $0.25 per unit. To detect day/night, an LDR is probably the best option -- you may be able to find them for around 10c each. Then you'll need transistors to turn on the LEDs and resistors to limit current. Each of those should be quite cheap.

LDR would be THE choice for the cheaper version. LDR+timer circuit (would account for less daylight during the winter) or just a smarter timer circuit would extend battery life.

A suggestion was made to me: using a PIC10F200 may provide the control circuitry for about $0.30 USD for the fancy-shmancy animation.

tekwiz had a great idea about sticking the LEDs in the groves/tubes or Coroplast! Also gave me a good idea what a 1W led can do and how much space it needs for diffusion and how long it would last:

A member from another forum offered his take and has provided a very useful info:

Place a small white LED in the end of each channel of the sign material. Block the other ends with white material. You may only need one every 2 or 3 channels. The material's translucence will take care of diffusion. LEDs are very cheap in large quantities, especially as you won't need the brightest ones...this project can use the cheapest ones you can find. Add a battery & photo switch.

Your biggest issue will be power consumption. That much lit area at your desired brightness level will take a considerable amount of power. You will be lucky to get a single night out of a set of 3 AA batteries.

BTW: A single 1W LED will light the whole thing, but you'd need to space it 6' behind the sign to light it all. A 1W LED will get ~7 hours from 3 AA batteries.

I think this would eliminate backlighting with powerful LEDs , but it does make LEDs cheaper for this project because they would be less powerful.

The big cost will be the LEDs and batteries.

I do not count batteries in the budget.

Oh, and you'll need a small PCB to build it all on (which you'll have to make yourself if it's going to be a reasonable cost.

Good point. How do you make your PCBs? I mean materials and such...

Can it be done for around $1 US? I doubt it. (mostly it depends on the cost of LEDs and batteries)

If I go with less powerful LEDs to use with the method tekwiz suggested - I think I can get them for under $0.10 USD - I may need at least 2 for each sign.

The major issue is that the stuff required to program the uC and make the PCBs is likely to cost you quite a bit, and may blow your budget unless you're going to use it again.

Could you tell me what exactly this stuff is please. I do plan to do this again - I would see it as an investment.

You want high brightness and variable colours which means multiple high power LEDs or a single multi-colour LED.

Another thing you have to consider is how the LEDs will illuminate the sign. Will they be placed in front for reflective illumination, behind for transmissive, or attached to the edge like some bar signs (not sure what this is called)

I haven't decided as to how exactly to light up the signs yet. According to tekwiz, I will need 6" if I want to use a 1W LED and diffuse the light evenly. If I use the method where I stick few less powerful LEDs inside of the groves/channels of the Coroplast - I may have to use at least 2 LEDs and probably more.Then I can cover the back of the sign with white material (e.g. bright-white paper) to double the visibility.

Do you suggest transmissive illumination? It is hard for me to imagine how that could work unless I use UV LEDs and glow-in-the-dark lettering to charge them.

What do you mean by side illumination? Something like tekwiz's idea of inserting them inside the Coroplast material?

The big risk is that since you can't really prototype before you order all the components that you're probably going to have to be creative in getting around problems as they arise.

This is the worst part :-\ I may have to increase my time flexibility, but it will be extremely hard.I would be more likely succeed if I can make cheap - straight forward ones by the 3 week deadline and then spend extra time on the more complicated design.

 

[(*steve*)]

PCBs require copper clad board, resist and etchant. If you're using through-hole components you'll need to drill the boards. If you're making a lot of boards you'll probably want to do something other than hand-draw them (so look at toner transfer or pos/neg film methods (which in turn will require some subset of a darkroom).

You'll need a soldering iron, solder, tools, etc. If you're planning on using surface mount components you'll need some method of relowing the solder (and a method of applying the solder too)

And of course you need to design the circuit board, learn to solder, etc., etc.

For programming a uC, you'll need a programmer, the appropriate code on a PC to write/compile/burn the software, plus the skills to write the software. Cheap uCs are often only able to be programmed once, so you need to have lots of spares while you develop your code, or a special version that can be erased (you *may* be able to get away with a similar, more expensive erasable uC, but the *right* thing is a UV erasable one).

If you have 3 weeks, and you don't have the skills or the equipment, then you need to be fully motivated, unemployed, and not sleep. Oh, and you need to have suppliers who can deliver *fast*.