# connecting a motor directly with solar cell. Motor not working.

#### ashokraj

Joined Feb 1, 2018
133
Hi, I want to rotate the motor directly with solar. My aim is to change the speed of motor depending on amount of light on the solar. I do not wish to use any other power supply. I want the motor to rotate solely with Solar only. this is a very small project for high school students. What I have noticed is if I supply the motor with 1.5v battery it rotates but not when i connected with solar!! Even though It generates 1.5V it doesnt rotate.

to test the solar cell I have connected LED and came to conclusion that nothing is wrong with Solar cell.

When I have connected just battery with solar, I noticed the current is 45mA.

I am with a suspicion that solar cell doesnt provide the necessary current required by the motor. as per the specifications of solar the current generated by it is 100mAh. but in reality it is not supplying that much. so how can I make the motor rotate with solar ?
or
do I have to go with a voltage to current converter ?
or
Any basic circuit of current amplifiers which I can build with opamp or transistors with the supply voltage of 3V or 1.5V ?
any insights are much appreciated.

Solar panel used
Motor used

#### djsfantasi

Joined Apr 11, 2010
9,081
MAh is not mA. Just saying. And 100mAh is a battery rating. I’ve never seen it used in a solar panel (?)

Second, a motor requires much more current to start. If you spin the motor, does it continue to run while connected to the solar panel under bright light? In fact, if you just put the panel directly under a bright light, does the motor run?

The current rating can be calculated from the wattage rating. W=VI or I=W/V. Hence, the current output is 0.8/6 or 133mA.

But, that’s its maximum rating. If the light on the panel is not bright enough, the output will not be 133mA.

#### Ya’akov

Joined Jan 27, 2019
8,176
Hi, I want to rotate the motor directly with solar. My aim is to change the speed of motor depending on amount of light on the solar. I do not wish to use any other power supply. I want the motor to rotate solely with Solar only. this is a very small project for high school students. What I have noticed is if I supply the motor with 1.5v battery it rotates but not when i connected with solar!! Even though It generates 1.5V it doesnt rotate.

to test the solar cell I have connected LED and came to conclusion that nothing is wrong with Solar cell.

When I have connected just battery with solar, I noticed the current is 45mA.

I am with a suspicion that solar cell doesnt provide the necessary current required by the motor. as per the specifications of solar the current generated by it is 100mAh. but in reality it is not supplying that much. so how can I make the motor rotate with solar ?
or
do I have to go with a voltage to current converter ?
or
Any basic circuit of current amplifiers which I can build with opamp or transistors with the supply voltage of 3V or 1.5V ?
any insights are much appreciated.

Solar panel used
Motor used

View attachment 234465
Unfortunately, there is no way that solar cell will power that motor. The no load current rating of the motor is 350mA, the solar cell, in the brightest possible sunlight, might produce 100mA.

You will need a different motor or ~5 of the solar cells.

#### Audioguru again

Joined Oct 21, 2019
6,168
1) Measure the voltage at the motor when it is running and is powered by the battery.
2) Measure the voltage at the motor when it is powered by the solar panel.
Are both motor voltages the same?

#### BobaMosfet

Joined Jul 1, 2009
2,082
Watt's Law: P = IE

In your case I = P/E.

I = 0.8W / 6VDC
I = 133mA.

Your motor requires 350mA to get it to start turning (that charges the coils and overcomes inertial resistance).

You are 0.350 - 0.133 = 0.217A (217mA) shy of doing that on an incredibly bright day. Add 3 more (or even more, depending on average brightness in your area) panels in parallel to up your current.

#### DickCappels

Joined Aug 21, 2008
10,068
In my experimenting with motors and solar cells nearly 60 years ago I found that very few motors could be driven my a small solar cell. Try smaller motors and don't expect too much in the way of torque.

You wrote:
What I have noticed is if I supply the motor with 1.5v battery it rotates but not when i connected with solar!! Even though It generates 1.5V it doesnt rotate

This suggests that there is a problem with measurement. The first thing I would do is to remove the 10 ohm resistor then look at it (try it) again.

#### sagor

Joined Mar 10, 2019
861
And remember that the 350mA is "no load". Once you put any load on the motor, even a small fan, the current requirement goes way up.