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Solar Cell Prove monitoring project

Ødemark

Jun 25, 2015
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Hello lads!, I need help for a personal project, I explain myself:
- I wondered how much sollar energy I could harvest in the roofs of my house to see if that would be a good investment (I live in Norway, and since the sun is quite peculiar here, I want some empirical results.
-after much thinking, i got the folowing idea: I have a small USB keyboard with the numbers and math symbols, some small solar powered mini lamps for the garden and some random components from a broken radio, and of course , a paper clip ;)
well, My idea is the little solar cell will charge the capacitor, and when this is full, would send the signal to the center pin of the transistor and this will allow the 2 conectors of the keyboardto be en contact, which would send a digit to my computer. in this way, I would know how much energy each digit represents, and I can program a software that monitors all the digits (Up to 10 solar cells in different parts of the roof) each second and records the data and show it in a graph etc..
well the software writing aint the problem, the electronics are, I Am as new to this as I can be, so here is how far I got.
1-Solar cell
2-capacitor
3-transistor
4-both sides of the keyboard plates (when this sides get in contact a digit is sendt to the computer)
zumgxf.jpg

This is a test, as soon as i fin how to make it work, Ill make all the proves
2s0bcjd.jpg

Questions:
Where do I connect the other end of the power cell?
or basically, how can I make this work?, things I shoud know like witch capacitor/transistor should I use etc... Im really lost.
Thanks of forehand guys!
 
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Colin Mitchell

Aug 31, 2014
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" I wandered how much solar energy I could harvest in the roofs of my house to see if that would be a good investment"
You can get anything up to 1kw per metre in thermal energy. It's always a good investment because it is free energy.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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hi, your idea has some merit, however it would only provide an estimate since the charging of the capacitor does not represent an ideal load for the panel.

what I would probably do is make a circuit with a 555 where to timing capacitor I'd charged by the solar panel and discharged by the 555.

depending on the panel and the size of the capacitor you could either measure the pulses output as a measure of total energy or the frequency ac a measure of instantaneous power. it may be possible to interface the former to a keyboard if the pulse rate is low enough
 

davenn

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Sep 5, 2009
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you need to totally rework the circuit you have shown
it isn't going to work in its current state ... apart from your Q about where the other wire from the dollar cell goes,
DC power doesnt flow through a capacitor as you notice from the capacitor, there is a gap in the middle
for DC this represents an open circuit

The transistor as it is isn't going to do anything either.
Not sure where the USB keyboard fits into all of this
 

Ødemark

Jun 25, 2015
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you need to totally rework the circuit you have shown
it isn't going to work in its current state ... apart from your Q about where the other wire from the dollar cell goes,
DC power doesnt flow through a capacitor as you notice from the capacitor, there is a gap in the middle
for DC this represents an open circuit

The transistor as it is isn't going to do anything either.
Not sure where the USB keyboard fits into all of this
So between the cell and the capacitor, should be a DC to AC converter? And then the capacitor will work as expected?
 

Ødemark

Jun 25, 2015
5
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Jun 25, 2015
Messages
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hi, your idea has some merit, however it would only provide an estimate since the charging of the capacitor does not represent an ideal load for the panel.

what I would probably do is make a circuit with a 555 where to timing capacitor I'd charged by the solar panel and discharged by the 555.

depending on the panel and the size of the capacitor you could either measure the pulses output as a measure of total energy or the frequency ac a measure of instantaneous power. it may be possible to interface the former to a keyboard if the pulse rate is low enough
What is a 555?
 

Ødemark

Jun 25, 2015
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Now I got it!, I gotta find a way to discharge the capacitor once full, ain't it?
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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yeah, a 555 provides a way to do that.

it can sense the charge on a capacitor, discharging it once it reaches a certain level. Because the discharge time is fixed, the total cycle time is determined largely by the rate of charge ( assuming the discharge time is short). If the capacitor is being charged by a solar panel, the charge time is thus determined by solar irradiation. Therefore the output frequency is determined by the power available from the panel (which is what I think you're after)
 

BobK

Jan 5, 2010
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yeah, a 555 provides a way to do that.

it can sense the charge on a capacitor, discharging it once it reaches a certain level. Because the discharge time is fixed, the total cycle time is determined largely by the rate of charge ( assuming the discharge time is short). If the capacitor is being charged by a solar panel, the charge time is thus determined by solar irradiation. Therefore the output frequency is determined by the power available from the panel (which is what I think you're after)
This sounds like a good idea, but the capacitor has to be charged to 2/3 of the supply voltage to the '555. I think a garden light solar cell will not produce much more than 2V, so it might not be doable without using multiple cells in series.

Bob
 
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