Battery powered LED project

[TexAvery]

Hello everyone!
I have a parking meter project that will require 40 to 60 5mm LEDs that need to be battery powered for 30 days, but only at night.
LEDs can be any color but red.
I am thinking a Joule Thief circuit with a darkness sensor (photo diode)?
The challenge is I only have two 2"x1.5"x4" space for the battery/batteries.
Yes, this would be a paying project.

 

[electroyas]

it need only 1.5V as i can remember so plenty of room if you use button type battery

 

[ronv]

Don't speed all that money yet.

Each LED will need 2 or 3 volts across it and a current of 0.01 amps (not real bright) so you could get 3 or so in series on a 12 volt battery. So if you need 60 of them that would be 20 strings in parallel for a total of .2 amps for each hour.
Times 10 hours is 2 amps a day X 30 days is 60 amp hours. That's about like a car battery. You could get it smaller with lithium batteries, but boy would it be expensive.
Here is one that is only 7.5 AH @ 11.4 volts but it is still bigger than the space you have for only one and you would need 10.

**broken link removed**
How about a solar panel so they could recharge each day?

 

[dr pepper]

OOps edit messup.

 

[dr pepper]

I've seen parking meters with solar cells to recharge them, but they have lcd's rather than leds so use much less power.
If you flashed the leds at 33% duty your power would be cut by a 1/3 while still being readable.

 

[TexAvery]

I can reduce the number of LEDs to 20.
Could there be some interaction with a user, where if someone were actually near it, the lights would become brighter, or more of them would come on?
I do not have room for a large single battery, but can fit many small (not coin) batteries.
My budget will be $500
Is it possible?

 

[dr pepper]

Yes I think its possible, maybe a pack of aa's, or aaa's could be made to fit.
You could use a passive infra red motion sensor to detect presence, you can get them on ebay cheaply.
Ultra high brightness led's can be driven at a low current and still be visible.
If you want to show time remaining for parking, maybe when noone is detected you could just show one led, green for still more than 5 mins left, orange for less than 5 mins and red for out, so an attendant can see from a distance if someone has overstayed.

 

[alec_t]

I have to ask: why so many LEDs? What do they indicate? You surely don't need to light up the whole parking area?

 

[TexAvery]

Art Project for the City of Houston

 

[ronv]

So lets narrow it down. Say 20 LED's - is that for each meter?
How many meters? Cheaper by the dozen.....
Could they blink?
Dimmer then brighter as a hand approaches or as a person walks by?

$500 each meter? If so start counting we will find a way.

 

[alec_t]

If this is an art project then are the LEDs just pretty or are they displaying specific useful data? If just pretty then can you use an animated display so that not all 20 need to be on at the same time?

 

[ronv]

Gotta love E-Bay.

Here is a $2 part that could sense motion, and turn on at dark and only draws 65 ua from the battery when in standby.

**broken link removed**

 

[dr pepper]

I've got one of them, they dont have a day/night sensor.

Me and my big mouth, yes the module has the option of having day/night, the req photoresistor isnt fitted as standard however, you need to solder an orp12 or similar to the board.

 

[ronv]

I've got one of them, they dont have a day/night sensor.

Does it work okay?

 

[kinarfi]

Hello everyone!
I have a parking meter project that will require 40 to 60 5mm LEDs that need to be battery powered for 30 days, but only at night.
LEDs can be any color but red.
I am thinking a Joule Thief circuit with a darkness sensor (photo diode)?
The challenge is I only have two 2"x1.5"x4" space for the battery/batteries.
Yes, this would be a paying project.

When you say this is a paying project, do you get paid for making it or are they going on the market, art show lead me to think you're getting paid for designing something for the show and when it's over, these may or may not stay.
If it's just for the show, what do you have so far? Maybe we can help perfect what you have.
Kinarfi

 

[TexAvery]

I now know my original plan is not possible. So here is the revised plan.
4 LEDs
I have room for PIR **broken link removed**
PIR triggers a "waking" fade up to full brightness.
Sleep mode (no movement) LEDs can be dim, maybe half brite.
LEDs only work at night.
Has to function for 30 days on 8 AA batteries, maybe 12 if circuit board is small.
No solar cell charging.
Just 4 meters, it's a prototype/art project.

 

[blueroomelectronics]

How many are you planning to build?

 

[TexAvery]

Four meters

 

[dr pepper]

Ronnie, yes it works well, no false triggers and the range is good for a few meters.
I ordered one just because I was getting something else from the same firm in china at the time, and they are well worth a quid.

 

[ronv]

You can take a look at this one. It is not real "crisp" at turning on at dusk - kinda fades on and fades off. When someone approaches it fades on and after the PIR times out it fades off. Should last 30 days.
If you use the Ebay PIR you don't need to tap into the batteries to get 5 volts you can just run it with 10 AA's.

PS we might need to play around to find the right LDR for the PIR sensor to turn it on and off, but we could ask them for a spec if you Chinese is good.