Looking for some advice on a project I will be undertaking soon. A couple weeks ago, I had a porch built, and with the left over scraps I want to build a housing for an address display. What I'd like to do is put a few small solar panels on the top of the display, and a light + battery pack inside. That's where it goes a bit beyond my know-how. I don't want a super-bright bulb (it's shining through frosted glass/plexiglass so it doesn't have to be super bright), but I know whatever bulb I do end up using will be the determining factor for the battery pack + mini solar panels. The bulb should be off during the day time, so that should help with getting the batter(y|ies) charged. The display isn't going to be too large, maybe 12in x 9in x 4in So here are my questions:
- What size bulb would you recommend?
- What specification for batteries would I need to last through the night using the recommended bulb?
- How much solar power will I need to ensure the batter(y|ies) get charged during the sun hours?
(Note: Sun hours per day for my area - low: 4.22, high: 5.22, avg: 4.99)
>>990765
>What size bulb would you recommend?
Lol man, bulbs use a lot of power, you'll need to use a far bigger battery and solar cell, just use LEDs, a fraction of a watt of LED power will be the same as a lightbulb that uses a couple of watts.
>What specification for batteries would I need to last through the night using the recommended bulb?
Assuming 12 hours of darkness per day, and given the dimensions you gave, I think the best would be to use 1 Watt of LEDs this equals to 15 standard warm 5mm LEDs, 15 LEDs use 300mA when connected in parallel to a lithium battery, this would require a 4 or 5Ah battery, and a solar cell of 5 volts, ideally it would only need 1 watt, but we all know 1 watt is the peak that cell can produce, and doesn't takes into account if it's cloudy of if it's charging in the morning of the afternoon, so at least buy one rated for 3-5 watts to ensure it charges even if the day is cloudy, if you live in a rainy place go for the 5 watts one.
This is for lithium batteries, another option is to use lead-acid batteries, like this cute one http://www.chargingchargers.com/batteries/small-sealed/UB1250-D5741.html it is rated for 5Ah, far more than what you need since you can parallel series of 3 LEDs, that for 15 LEDs would give you a current consumption of 100mA, and a total on-time of about 40 hours, giving you a good margin of error, the solar panel should then be rated for 12 volts and again, at least 3 to 5 watts.
For the charge control you'll probably want to use cheap modules, either for lithium or for lead, since homemade circuits can get a bit complex for anyone with 0 experience, make sure they come with overdischarge and overchaerge protection, they're quite simple to use, simply connect the solar cell at one side and the batteries at the other and the circuit will take care of it.
>>990930
Finally, to turn off the lights during the day you'll need an LDR sensor module, unless you're willing to learn how to use operational amplifiers as comparators and make your own circuit. This modules are quite simple and will output 5 or 0 volts depending on if light arrives to their sensor, they usually can be adjusted with a potentiometer to choose how dark you want it to be for the lights to turn on.
Since you've got 5 volts at the output you'll need a logic level MOSFET, if the signal is inverted (the MOSFET recieves 5 volts during the day) you'll need a NOT gate made out of a transistor and a couple of resistors, it's at the bottom left of the picture. You can connect 12 volts to the collector of the transistor instead of 5 to forget about using a logic level MOSFET and use a plain MOSFET like an IRF540
This are the LED connections whether you choose lithium or lead batteries, now it's up to you to decide.
Bump? Is OP gone?
>>991504
Well, anyway, I had to design a light sensor for my dad, so I made a proper one with hysteresis so it doesn't flickers when reaching the threshold, for anyone who is interested in a light sensing switch feel free to check it out:
http://www.instructables.com/id/A-Better-Light-Sensor-Switch-PCB-Included/
Schematics and board for Eagle are provided in exchange for blatant shilling
there's no need to build anything since you can get solar lights for free (from your neighbor's yard) or nearly-free from the dollar store. you just take it apart and make it fit your design.
