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### Topic: question on solar and transistors (Read 368 times)previous topic - next topic

#### tjones9163

##### Aug 11, 2018, 04:32 am
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

#1
##### Aug 11, 2018, 04:43 am
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

#2
##### Aug 11, 2018, 05:04 am
My best attempt at circuit diagram attached below
thanks for response

#### tjones9163

#3
##### Aug 11, 2018, 05:06 am
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 amLast 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

#5
##### Aug 11, 2018, 05:23 am
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 amLast 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 amLast 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

#8
##### Aug 11, 2018, 05:36 am
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

#9
##### Aug 11, 2018, 08:14 am
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

#10
##### Aug 11, 2018, 05:05 pm
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

#11
##### Aug 11, 2018, 05:19 pm
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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