Solar retrofit for kids toy

[ADWSystems]

My daughter was gifted a toy that runs off of 2 AA batteries (1.5V each). She turns it on, then falls a sleep. The batteries are dead by morning. As this sits on a desk/table or can be hung from a wall, it is stationary but moveable. I was trying to determine what it would take to make it solar powered/solar recharged so it stops eating batteries.

From a past project, I have a method to build an adapter into the battery compartment to allow for the use of an external power source. In this case, I could mount the batteries within the solar panel/charger and then connect it to the toy.

If the knowns are 3V at 100mA. How do I figure out what size solar panel is needed to recharge the batteries? What do I need for a charging circuit (assuming NiCd or NiMh batteries)?

 

[Andrei_D12]

Hi!
From what I understood, you want to power a toy from a solar panel, but you don't know the size of the solar cells.
For an exact power, the size of the cell is highly dependent on it's quality.Higher quality results in a more compact cell. I found something that can be suitable for your application here:
https://www.aliexpress.com/wholesal...11131&origin=y&SearchText=solar+cell+for+toys
( I haven't bought from here yet, however, considering that most of the toys, including the solar ones, are made in China, the price is pretty good. The only bad thing is the delivery time that can range from 2 weeks to 2 months, 2 months is the guaranteed delivery time. You can also search on www.solarbotics.com for solar cells, but the prices are higher...)
As for the batteries, maybe some supercapacitors ( 1 Farad or more) can be the solution, because, unlike the NiCd or NiMh, they charge a lot faster and they can keep the toy on for a few minutes (it's highly dependent on the capacity). Also they can be charged and discharged more times than a normal battery. This is what I am talking about:

An example of supercapacitor.
And, finally, the circuit needed is a SOLAR ENGINE. It charges a capacitor with a solar panel, and when a certain amount of energy is present, it releases all the energy to the load. It uses few components and its easy to build. The only disadvantage is that the load receives no energy during charging. I played with circuits like this, but not using supercaps, only ordinary ones.
The supercapacitors combined with the solar cells make the ultimate combination when it comes to solar energy!

This is my idea. You can agree with me, you can diasgree... And if I said something wrong, announce me!

Andrei

(Note: the supercaps above have a Huge capacity. You don't need that much)

 

[ADWSystems]

Hi!
From what I understood, you want to power a toy from a solar panel, but you don't know the size of the solar cells.
For an exact power, the size of the cell is highly dependent on it's quality.Higher quality results in a more compact cell. I found something that can be suitable for your application here:
https://www.aliexpress.com/wholesal...11131&origin=y&SearchText=solar+cell+for+toys
( I haven't bought from here yet, however, considering that most of the toys, including the solar ones, are made in China, the price is pretty good. The only bad thing is the delivery time that can range from 2 weeks to 2 months, 2 months is the guaranteed delivery time. You can also search on www.solarbotics.com for solar cells, but the prices are higher...)
As for the batteries, maybe some supercapacitors ( 1 Farad or more) can be the solution, because, unlike the NiCd or NiMh, they charge a lot faster and they can keep the toy on for a few minutes (it's highly dependent on the capacity). Also they can be charged and discharged more times than a normal battery. This is what I am talking about:

An example of supercapacitor.
And, finally, the circuit needed is a SOLAR ENGINE. It charges a capacitor with a solar panel, and when a certain amount of energy is present, it releases all the energy to the load. It uses few components and its easy to build. The only disadvantage is that the load receives no energy during charging. I played with circuits like this, but not using supercaps, only ordinary ones.
The supercapacitors combined with the solar cells make the ultimate combination when it comes to solar energy!

This is my idea. You can agree with me, you can diasgree... And if I said something wrong, announce me!

Andrei

Super caps would be a good idea but I don't know if they would have the run time while the panel is dark. 3V at 100mA, is an equivalent resistance of 30 ohms. (I do actually need to measure the current, this is a ballpark and guesstimate).

Not supplying energy while charging is not quite what I had in mind. Is there an option to prioritize running the toy and changing with the excess?

 

[Andrei_D12]

I have a question: is your daughter playing a lot with that toy, or she's just playing occasionally with it?
I mean how many hours?

 

[Andrei_D12]

One idea is to increase the current capability of your solar cells, so that it charges faster.
Knowing that a capacitor behaves like a battery, another idea is to make a charger,with a capacitor in, so that the toy is powered by the solar cell and, at the same time, the capacitor is being charged.

 

[audioguru]

Are you going to take the toy with its new solar panel outside into the sunshine each day all day long so the battery will be charged for it to play for a couple of hours each evening? Will you blow away any clouds somehow?
The solar panels in cheap Chinese solar garden lights get sunburned within a few months and they look like the cheap ones in the ad. good so;lar

I hope you are not thinking of solar charging using ordinary light like a solar powered calculator. The calculator uses an extremely low current from the solar panel or battery. Some "solar" calculators have "a photo" of a solar panel instead of an actual solar panel and its tiny button battery powers it for a year.

 

[ADWSystems]

As for time, play time is most is in the evening when there isn't sun. It will have all day to charge.
Duration is a couple of hours. Frequency is most every night.

I definitely understand the solar cell is going to be larger (much larger) than that of a solar calculator, likely larger than a solar garden light. I'm game up to about 9" x 3" or so. Larger I would have to think about, (solar cell would be getting rather large when compared to the toy).

Just measured the current, 70mA (or just shy).

 

[audioguru]

If your daughter plays with the toy every evening then she will not be able to and will cry every evening following a cloudy day. Unless the solar panel and/or battery are/is enormous.
Why not use a Ni-MH AA cells charger that plugs into a wall electrical outlet?

 

[ADWSystems]

The only chargers I have seen require removing the cells from the load and place them in the charger. I don't want to be removing the cells everyday. blah!

I think "enormous" is relative. There is a 60mm x 60mm (2.4" x 2.4") cell that is rated at 3V @ 40mA. Three cells would be 7.2" x 2.4" and have a max output of 120mA, even at 2/3 output would be 80mA. Is there something I'm missing?

 

[audioguru]

40mA when pointing directly at the sun at noon on a sunny day. Less when not pointing and much less in the morning and afternoon. Much less on a cloudy day. Average maybe 10mA per hour. You put 3 of them to get 30mA per hour.
The toy might use 100mA for 2 hours and charging needs 1.4 times more so you need 280mAh which is 30mA for 9.3 hours. It might work.
I would simply add a charging jack and resistor to a wall wart power supply.

 

[Colin]

"so it stops eating batteries" Have you thought of removing its teeth?

3v solar panel is not going to charge 3v battery.

The idea is not feasible.

 

[Andrei_D12]

**broken link removed**
You said that she plays with the toy in the evening. And if is evening, she stays in her bedroom (well, that's my logic). I don't think she is walking in the house carrying the toy. If so, as Audioguru mentioned, this is the best solution. Of course, you must take all the safety measures for her when it comes to someting that is mains powered.

 

[large_ghostman]

Can I ask what kind of toy it is? And what does the toy do? Does your daughter interact with it?
I am asking because maybe the answer lies in knowing if its being played with or not, that way we might be able to get it to switch off after X time of not being played with.
I know its a bit outside the box but if we know what it is and how its played with then just maybe...................

 

[Andrei_D12]

Can I ask what kind of toy it is? And what does the toy do? Does your daughter interact with it?
I am asking because maybe the answer lies in knowing if its being played with or not, that way we might be able to get it to switch off after X time of not being played with.
I know its a bit outside the box but if we know what it is and how its played with then just maybe...................

In my opinion, a current consumption of 100 mA indicates that the toy has a motor (or more) and/or a musical box and/or some lights. Anyway, ADW said that the toy is STATIC, so, again, a charger like in the photo is the solution.

 

[large_ghostman]

In my opinion, a current consumption of 100 mA indicates that the toy has a motor (or more) and/or a musical box and/or some lights. Anyway, ADW said that the toy is STATIC, so, again, a charger like in the photo is the solution.

I was trying to avoid anything mains or batteries you charge, apart from the obvious 'IT's CHEAP' response I was wondering why it didnt have a wall wart anyway. My sister has lot of toys with leds and such and they are all over 100mA no motor in sight, plus the 100mA was a guess not measured.

So I would still like to know the above questions, it might be static but dosnt mean there is no interaction. A piano is static!

 

[Andrei_D12]

Where is a spring powered toy when you need it??

I agree with the fact that the mains is very, very dangerous, especially for children. So, we will exclude this solution. Solar energy, wind energy, water energy, EXCLUDED!!!
Only solution that MAY work is to find a dynamo, a large spring and other mechanical parts so that you can build a generator. Take a look at the african radios that are used without any problems. However the toy may consume more than a radio...

If this doesn't solve the problem, buy a large and beautiful Teddy bear or Barbie doll and... that's it. Problem solved!

 

[ADWSystems]

I was trying to avoid anything mains or batteries you charge, apart from the obvious 'IT's CHEAP' response I was wondering why it didnt have a wall wart anyway. My sister has lot of toys with leds and such and they are all over 100mA no motor in sight, plus the 100mA was a guess not measured.

So I would still like to know the above questions, it might be static but dosnt mean there is no interaction. A piano is static!

The 100mA was a guess, measured is 70mA. It is a puzzle game with a replay mode. It hangs on the wall. It doesn't move, hence the reason why I was considering solar recharge. The wall wart is out as there are no outlets nearby. If a wall wart was included, it would have required an extension cord to power it.

 

[audioguru]

The game hangs on the wall. I doubt it is outside so it is inside and has no sunshine so for 70mA you will need a solar panel as large as the entire wall (exaggerated a little).
Right now it is overcast outside my window and the room is bright. I measure a charging current of 0.2mA into a solar garden light with a "dead" (o.63V) Ni-MH battery cell. After charging for 15 seconds I tried it and the covered garden light lighted its LED for a couple of seconds. For 70mA for 2 hours you need 140mAh which might need 2,016,000,000 (more than two billion) little solar panels. An Energizer "9V" Ni-MH rechargeable battery produces 175mAh when its load draws 17.5mA for 10 hours or about 70mA for 2 hours.

 

[large_ghostman]

So she has to interact with it then? press button etc? So as above I am wonder if it can be tweaked to turn off after X time of no input, that way batteries last longer. YES I KNOW its more work etc etc, some of us like to make circuits and solves problems, even us ebay wh@]] sometimes dont just go buy a solution, sometimes us hobby types like over complicated feature creap riddled projects!! Everything has just about been built (ok untrue) and cheap as Chinese, but I like the smell of solder

 

[Andrei_D12]

The game hangs on the wall. I doubt it is outside so it is inside and has no sunshine so for 70mA you will need a solar panel as large as the entire wall (exaggerated a little).
Right now it is overcast outside my window and the room is bright. I measure a charging current of 0.2mA into a solar garden light with a "dead" (o.63V) Ni-MH battery cell. After charging for 15 seconds I tried it and the covered garden light lighted its LED for a couple of seconds. For 70mA for 2 hours you need 140mAh which might need 2,016,000,000 (more than two billion) little solar panels. An Energizer "9V" Ni-MH rechargeable battery produces 175mAh when its load draws 17.5mA for 10 hours or about 70mA for 2 hours.

The solar garden cells are good only for garden. What about putting the puzzle near the window and with long wires a solar panel OUTSIDE? Solar panel made with a few high quality cells (0,45v and a few hundred miliamps ) may work. I know that the entire panel surface would be as big as a laptop display, a bit inconvenient.