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Topic: question on solar and transistors (Read 361 times) previous topic - next topic

tjones9163

Hello, I have recently been experimenting with very small solar cells. I have hooked up 2 solar cells in series and with bright light shined upon the solar panel, i am able to light up and LED. now I also tried hooking the positive terminal of my solar panel to the base of an NPN transistor with a 10k resistor also on base and also used my solar panel to provide positive and negative for my transistor. this circuit did work but not work as well as when I just used the panel and led. Is this because NPN transistors work with current and not voltage, so there is not much to amplify?? and my second question--Could the reason the transistor circuit did not work as well is that I am dealing with low voltage to begin with and because of the voltage drop from the transistor?? would a mosfet be better?
Thanks
pic of the solar cells below

jremington

Draw a circuit diagram and post it. If you don't know how to do that, now is the time to start learning.

Here is a great place to start.

tjones9163

My best attempt at circuit diagram attached below
thanks for response

tjones9163

Draw a circuit diagram and post it. If you don't know how to do that, now is the time to start learning.

Here is a great place to start.
thanks for the response. I replied below with a diagram, I wasn't sure how to attach a pic to your quote but thanks again

jremington

#4
Aug 11, 2018, 05:15 am Last Edit: Aug 11, 2018, 05:15 am by jremington
OP's pic (which is fine):


What transistor is that? To saturate the transistor you may need a lower value base resistor. You are assuming current gain = 100 or roughly, 10K/100 Ohms, which is probably too high. Try 2K.

tjones9163

thanks for response, the transistor is an NPN Transistor(8050) , I have tried with a 3.3k resistor on the base but it still doesn't work as well as when i just use the solar panel and led, could this be because of the voltage drop of Transistor, and also i heard that these type of transistor work with current not voltage, could that be a factor?
Thanks

jremington

#6
Aug 11, 2018, 05:27 am Last Edit: Aug 11, 2018, 05:28 am by jremington
Quote
when i just use the solar panel and led
What does that mean? Did you have a 100 Ohm resistor in series with the LED? If not, don't you think that would have an effect?

Always post a circuit diagram, so we know what you are talking about.

Hint: buy a multimeter, so you can measure currents and voltages. Very, very informative!

tjones9163

#7
Aug 11, 2018, 05:33 am Last Edit: Aug 11, 2018, 05:33 am by tjones9163
This is a circuit with just Solar panel and LED-resistor, which works better work than transistor circuit.

tjones9163

What does that mean? Did you have a 100 Ohm resistor in series with the LED? If not, don't you think that would have an effect?

Always post a circuit diagram, so we know what you are talking about.

Hint: buy a multimeter, so you can measure currents and voltages. Very, very informative!
I know my old cen-tech DMM stopped working but is also very old. I need to save up for a new one. Hopefully soon lol

mauried

What is it that you are expecting the transistor to do?
It wont make the led any brighter, and because there will a small voltage drop across the transistor, the led will be dimmer.


tjones9163

What is it that you are expecting the transistor to do?
It wont make the led any brighter, and because there will a small voltage drop across the transistor, the led will be dimmer.


I'm actually not sure lol, just experimenting. But let's say I connected even more together in series, couldn't I do the same setup with the transistor and able to handle devices that require higher current. I'm not sure because I am new to solar panels but will it hurt or damage my solar cells if I hook them directly up to what I am trying to power without a transistor in between? would a mosfet perhaps be a better choice? I do not know. I do also realize that there are manufacture made inverters and charge controllers for solar but I want to learn with basic electronic components.
Thanks for response.

jremington

Quote
will it hurt or damage my solar cells if I hook them directly up to what I am trying to power without a transistor in between?
No.

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