Solar Tracker + Servo Consumption + battery charger

Hello everyone,

Before i start my next project i'd like to plan it and see how feasable it would be.

I want to build a box, a special one.

Wooden box with a small game that, if you win, will open the lock and reveal its contents. Seems simple but i'd like to implement a solar tracking system with 2 to 3 servos, and this solar panel : http://www.sparkfun.com/products/7840

I'll need to feed 2 RGB LED's, 1 Arduino (Duemillanove), 2 / 3 servos (for solar tracking purposes), 1 servo for the lock and this LCD screen: http://www.sparkfun.com/products/709

To make the consumption as low as possible. the tracking system will have a SPST switch, only to be activated when the user wants. Keeping the servos OFF most of the time. The LCD screen displays the game, so it will only be on, whenever the box is CLOSED and when CLOSED it will have a SPST switch to active the whole system (much like an ON / OFF switch for the whole rig). The RGB LED's will power on when the LCD is on, and will power off when the LCD is off. The Lock (servo) will be always off, unless the user wins the game, and so it opens the box. Whenever the box is closed, a sensitive switch will be pressed, making the servo lock the box again.

having all this in mind... Will the solar tracking system charge a 9V battery, enough to, at least, delay the a full and healthy charge? So for example, instead of 1 week the box can last like 2 weeks without maintenance (considering someone actually opens it and activates the solar tracking system lets it on for a while).

I know it will be practically impossible to charge the whole battery (even if its a regular rechargebla 9v battery) with this rig, but im only looking for an extended period of time before charging it with a nice, heatlhy those of Voltage.

What do you guys think? :) I'd love to hear your thoughts on this.

Thank you!

Dump the 9V battery. Use 4 AA batteries. They will easily last two weeks powering the LCD for a few minutes at a time (make the Arduino shut it off if no activity for some time). Use sleep modes as much as possible.

2.5 W at 9V is 277mA. If your total current draw is less than this, the solar charger will be able to charge the batteries - provided the box is not left in a closet, it is a bright sunny day, the panel is spotlessly clean, etc. Any cloud cover or dust, dirt, fingerprints, etc. will reduce the output (considerably).

Personally, I don't see it as cost-effective. Better batteries are better.

hmmm... why should i drop the 9V rechargeable battery? It takes less space and has more voltage. (well now that i think about it, i dont really need the 9V, servos should work perfectly at 5v....)

I have four 2700mAH AA Batteries ( http://www.taosgifts.co.uk/ekmps/shops/taos/images/gp-aa-rechargeable-ni-mh-batteries-2700-mah-card-of-4--54-p.jpg ). But they are only 1.2v wich makes 4.8v 2700mAh in parallel.

Hmmm... thinks

Servos are much more dependent on current than voltage. The 4 AAs provide lower voltage, but a lot (read that as a whole lot) more current. Servos are generally tolerant of low voltage, but are not at all forgiving of low current.

Interesting.... Very well. 4x AA Battery it is.

I'll keep this topic up to date as soon as I start the project :) Thanks!

Careful with the 5V regulator you will have to connect the supply to the +5v pin. In this case thou will need no separate the arduino an the servos' supply.

yes, of course ;)