Simple Kids Science Experiment

LHERREMANS · February 2017

So I thought when I helped my daughter design her science experiment, I was doing something super simple ( always the key in a good science experiment in our house as we work hard, but not very science smart )

What we need to do is power an AUTOMATIC FISH FOOD FEEDER with solar panels.

I don't have it yet and the only info I can get online for now is that it would be normally powered with
2 x AAA 1.5V Batteries.

After trying to research I have MANY Questions.. but I sill start with just the very basic one.. and if it's any easy answer, I won't hurt my brain anymore trying to figure this out.

My first question is can I simply buy a simple solar panel and attach the leads to where the batteries would go and make it work??
( that's kind of what we were planning and thought it would be that easy.. I'm finding out it may not be that easy.. I think .. I don't know !

)

If this is actually a simple answer and can suggest what I would need to buy.. I see there are different levels of output .. etc.. SO CONFUSED... I would appreciate any economical suggestions.

If this is NOT that simple to do.. any suggestions on the most simple and economical suggestions to accomplish this would be greatly appreciated.

Estragon · February 2017

Assuming the feeder batteries are series wired, that would be 3v nominal. What we don't know is the current draw. A typical alkaline AAA battery has a capacity of about 1 amp hour or 1000 milli-amphr. A 3v 25mAH pv panel can be bought for about $5 on Amazon. If you knew the current draw on the feeder, you could hook up an appropriate number of 3v panels in parallel to supply current needed.

Potential issues:
1. 3v nominal pv may put out a higher voltage than a nominal 3v string of batteries. It shouldn't be much higher assuming room temps, maybe a few 10ths of a volt, but could be too high for the feeder. Is the feeder expensive?

2. The feeder may have a small motor to open and close a hopper door? If so, there will be a momentary surge in current needed, so the panels would need to be sized to supply the surge. You would have to experiment a bit by adding panels in parallel until it ran the feeder.

3. The panels will need direct sunlight. The fish will not get fed at night or on cloudy days.

Depending on your daughter's age, it could be an interesting project. A simple multimeter would be a useful tool to have to measure and record voltages and currents at various stages.

Photowhit · February 2017

You could likely attach it to the battery terminals, but you would need to regulate the voltage. Of course the fish feeder likely has some sort of timer which would reset when there was no power....

These will vary by your battery bank, 2 AA alkaline would have be 3 volts.

You could also consider a NiMH battery bank to maintain a current and hence the timer overnight. Some NiMH will allow a small over charge current with out damage, dissipating the current as heat, somewhat removing the need for a charge controller.

Perhaps a better idea would be to find an old panel from a motion detector light which already charges a 2.5 volt battery bank. (a 2 AAA or 2 AA battery bank) Use the battery bank from it with the charger left in place.

LHERREMANS · February 2017

OK.... all interesting information ... here's another questions... instead of this battery bank... can I just install rechargeable batteries ( even though it nullifies the feeder from being actually powered by the solar panel I know ) but our only requirement was to "use solar power" but can I attach the leads from the solar panel to directly to the ends of the battery while installed in the feeder to keep the batteries charged long term ??

Estragon · February 2017

Having a battery would avoid issues with peaking current to drive motor, timer reset, etc. You would still need to match/control voltage of the solar with the charging voltage required by the battery, which would need to be in a range acceptable to the feeder.

Estragon · February 2017

Maybe something like this:
https://www.amazon.com/Volt-Solar-Panel-Battery-Charger/dp/B001ACXY6E/ref=sr_1_4?ie=UTF8&qid=1488298221&sr=8-4&keywords=solar+battery+charger+3v

westbranch · February 2017

If you only have to feed once daily the sun coming up and shining on the panel would act as the switch, since the sun comes up once a day so you could use the amperage as the trigger , since volts rises quickly and amps follow with full sun. when the amps drop to zero that would be the reset trigger.
hth

westbranch · February 2017

Another idea might be to use a small AGM, for kid/safety reasons, from a motorcycle or garden tractor and a cheap Ebay/amazon PWM charge controller with the ability to turn a light on and off several times a day...??

bill von novak · February 2017

westbranch said:

If you only have to feed once daily the sun coming up and shining on the panel would act as the switch, since the sun comes up once a day so you could use the amperage as the trigger , since volts rises quickly and amps follow with full sun. when the amps drop to zero that would be the reset trigger.

On partly cloudy days you might end up with some VERY well fed fish.

Johann · March 2017

Why not use one of these.
https://www.amazon.com/Qualitus-Driveway-featuring-weatherproof-construction/dp/B01CIVYN6U/ref=pd_sbs_60_2?_encoding=UTF8&pd_rd_i=B01CIVYN6U&pd_rd_r=FA8V8SYZF6MWBHBAZ1T6&pd_rd_w=si6nB&pd_rd_wg=9GXC4&psc=1&refRID=FA8V8SYZF6MWBHBAZ1T6

The ones I have put out enough volts to charge 2 AA or 2 AAA or 2 C or 2 D batteries in series.
Those LED lights I have, have the right solar panel on the top of the light already, which is charging 2 AA rechargeable batteries. and all is housed at the top of the light in one piece. the battery compartment is on the underside of the top piece.

I use one of those LED solar light tops for my driveway alert motion system. I got tired of having to buy regular batteries for it. You need to jump or cut the build-in photoeye to make it work at day-time or just put black tape over the photo-eye.

Notice, I have a different model than posted. You may have to do some research on them and ask questions. Just trying to give an idea.

Seems like, per question and answer section at the amazon link, that they have 2 removable batteries at the underside.

Simple Kids Science Experiment

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