solar cell to replace 1.5v batt - noob

[nopuk]

Hi,
Total noob here. I have a small office desk toy that runs off a 1.5 v battery. I would like to solder battery connections to my solar cell and leave it on the window - i know it will not work all the time, and perhaps not half as well but i just like renewable energy toys.
So im guessing my plan of just connecting wires is wrong since either current/voltage will spike on a hot day and kill the toy. Any help for a circuit to make to cap the voltage ? As i said total noob so simple is better

 

[Anon_LG]

Do you know anything about the internal workings of your toy, does it involve complex processing? Does it take the voltage directly in or does it feed through a regulator? Generally, if it is something simple like a motor connected to the battery, just hook up a 1.5 volt open circuit maximum solar cell, the toy will however have to be in *very* bright sunlight, such as summer daylight however. If you like I could help you out more with the circuitry and get a system that will enable the device to operate at lower light levels as well with a few extra components.

Provide some pictures of cell and toy (preferably opened up), if you can not open it up and you decide to do this straight away ensure you connect the positive terminal of the solar cell to the positive terminal of the battery holder and likewise for negative - > negative.

I hope this helps, I am happy to provide more,

 

[nopuk]

Thanks Lavaguava, the toy ( see pic - see attached ) is a rotating globe, seems to be just a small motor hooked to a 1.5 battery.

the more circuit needing less light sounds interesting but im scared

 

[Anon_LG]

Yes, this looks absolutely fine to hook up to a 1.5 volt max photovoltaic cell. Depending on the inner workings of the motor module the globe will either stop completely or just get slower at lower light levels.

The circuitry required for globe at lower light levels may be a bit complex for a beginner but if you want I could walk you through it. The basic explanation is: A photovoltaic cell with a higher voltage (or several in series to produce the higher voltage) is fed into a voltage regulator. So the cells are producing a higher voltage (leading to higher surface area = higher power output), the regulator keeps it at 1.5 volts as long as the voltage fed into the regulator is 1.5 volts + dropout voltage (The datasheet states that this is a maximum of about 0.3 volts) = 1.8 volts. So as long as the voltage is between 1.8 and 5 volts (stated as maximum by the above datasheet) the globe will function as normal. The regulator just requires two external capacitors. If you decide to go forward with this I am willing to help. You may find the regulator here.

Someone else may post soon to help you/prove me wrong.

You seem to have a relatively good grasp of this for a "noob", everyone on this forum was once a noob, maybe you should take this up as a hobby

I will continue helping as long as you need, hope this helps,

 

[nopuk]

Hi again, thanks for the advice - my solar cell is a 12v cell I am not opposed to buying a new 1.5 v one, but no harm learning as i am here. I have a decent amount of physics background but did my best to avoid electronics, so basically I know the words but zero clue how to use them in a circuit.
I am after googling voltage regulators - those circuit diagrams seem complicated, and I honestly dont understand how they work.

 

[Anon_LG]

Hello again Nopuk

I can assure you that the voltage regulator circuits are not complex if you use a voltage regulator IC such as the one I have linked to, requiring only a few external capacitors. The ones you may have googled probably involved the discreet components (ie ones you build yourself) If you are however unsure about the circuits and are absolutely opposed to trying to use a voltage regulator you will require a 1.5 volt max solar cell.
OK, so it is up to you, you could:
buy a 1.5 volt solar cell and no regulator
OR
You can use this one with the datasheet here, note that the circuitry only requires two external capacitors, this regulator will work with your panel

It is up to you, I am happy to continue providing help ,

 

[nopuk]

Cool, I am happy to buy the one you linked to on ebay - happy to solder my first IC . Could you perhaps guide me on what capacitors I need and where to place them in the circuit and how to connect the legs of the IC ? - basically the data sheet scares me and I don't understand all the points

 

[Anon_LG]

Excellent

I am glad you went for the regulator option, this will provide you with practical experience. The datasheet here shows that a non adjustable version requires only two external capacitors. The diagram shows these should be polarised capacitors, I would use tantalum, a mimum of 22uf (microfarads) on the output and 10uf on the input. You can purchase these from maplin (I am however unsure whether you have these in Italy) here and here. If you do not have maplin in Italy, provide me with an electronics retailer and I will find the suitable ones from them. Alternatively you could purchase lucky bags (Way better value, a good option if you take up electronics as a hobby) and hope you will find two capacitors with a value of over 10uf and 22uf.

Once you have purchased these provide a photo, I will draw the connection on the picture and send it back. Even if you do not understand this project, do not be put off, this is the area of power electronics and analogue or digital electronics may be more your thing.

I hope this helps,

 

[nopuk]

Cool, ok got my stuff, I am in Ireland yup maplins here. I picked up the regulator, and the capacitors. I was trying to have a go myself so I also picked up a small breadboard, some wires, resistors and a LED's ( thought they would be handy to see when the current is flowing visually ), I also have a multimeter myself - familiar how to read dc voltages and resistances from it. The pic is what I am looking at now. The 12 volt solar cell I have is kinda fragile so I was experimenting with 2x.15v batteries since it also has a red and black wire and provides a voltage - but I can use the solar cell whenever.
I tried looking at the data sheet, and think i can follow it except what does ground mean in terms of the breadboard - or is the breadboard of no use for this project ?
Anyways - do your thing

 

[Anon_LG]

Wow! That was fast!

And sorry, I thought it was Italy , how embarrassing. Having Maplins will make your life a *lot* easier if you take this up as a hobby.

Excellent that you picked up a multimeter, first I think you should connect one of your 1.5 volt AA cells across the globe module as you would with normal use. Follow this diagram, instead of the bulb however use the module, this will output how much current your module draws. I suggest you do this to gain experience with your multimeter (also I am curious).

The breadboard will help a lot.

Oh, oh no. I have just looked at the voltage regulator they have supplied you with, it is wrong, false advertising, the link I sent you was suitable. Have you noticed that the packages are completely different?, I just read the datasheet for the one you have pictured and this has an *absolute* maximum rating of twelve volts, an operating voltage of seven volts. This is no good (in a worst case scenario), an absolute maximum rating is not the amount you go up to for extended periods of time, if you are to use this regulator we will have to incorporate something called a voltage divider as well as the regulator, a voltage divider incorporates the use of two resistors, more components, more complexity for a beginner. Is the voltage regulator you have pictured definitely the correct one? If it is the you will either require two resistors to form the voltage divider or purchase the correct regulator, I could provide another source.

That being said, the regulator may still be suitable for use with the solar cell as it may never reach 12 volts in such a northern country. On top of this you can still practise using the regulator with the AA cells. Insert the regulator into the breadboard with the tantalum capacitors either side (with the side with text on facing the camera) and insert the red battery lead into the red power rail and the black lead into the black power rail. Does the globe have leads? If so, put them in the breadboard as well. I can draw the wires for you to position the jumpers.

I hope to see this through

Hope this helps,

 

[nopuk]

Hi again,
May I just ask a question to get my bearings straight here, I built the attached circuit to test my understanding of how the regulator circuit should work - I left out the capacitors since they seem to be non vital for DC steady voltages.
From the left, black to black of 6v power supply, red to red of the same 6v bench supply unit ( it works fine checked ). Pin 1 ( input ) of regulator connected to red power line ( i think ), middle pin of regulator connected back to the black line.
Lastly pin 3 connected to volt meter from yellow cable, and other end of volt meter connected to the black power line. I tried this set up, the regulator started to smell and was red hot to touch and I barley measured a 1.0 V from the yellow/blue wires. Also the bench supply unit maxed out on current which also seems very odd.

I would like to understand the above before moving on.

 

[Anon_LG]

Ah

Understandably, you have attached the regulator pins incorrectly, you have assumed that the regulator uses the layout of input->ground->output for it's pin out This one however has the layout Ground -> output -> input

See the top of the datasheet Re-arrange your connection accordingly, hopefully you have not damaged the IC. I will continue and will not stop until the project is successful.

I hope this helps,

.

 

[nopuk]

thanks! simple explanation!! Turns out I had damaged it, but I had got two at the time, second one works fine. 0-6V gives out 2.4 ish V, past 6 it gives out 3 and a bit V.
The solar cell I plan on using tops out at 12V on the best day of the summer outside , I would plan to have it next to a window indoors, so the current regulator should be ok.
I was unable to measure the current you asked for, since there is no open wire/joints to touch to place the multimeter leads. I

Do I need the capacitors at all then ? Since its all DC and small variations dont seem to be an issue what is the point ? I think I should be ok to solder the above and hook it up and see what happens ?

 

[Anon_LG]

Excellent

I am glad you have this working. The current measuring should be fine, it is not essential. As for the capacitors it is up to you, personally I would hook up the capacitors to see the effect (if any), before connecting the regulator output to your globe. However if you would like to hook it up now I see no problem (I have no idea what the effect of the raised voltage will have on the globe though)

I would advise you test the effects of the capacitors, if this gives you a lower voltage than you are currently reading, use the capacitors. To hook up the capacitors: Look at the side with text on, to one side will be a + sign, the lead nearest to this should be connected to the output and the other to ground, the same for the input.

Keep bouncing messages to me and I will carry on providing advice. Do you have any previous experience in electronics? You seem to have a very good understanding for a beginner.

I hope all goes as planned,