Using a solar cell I managed to control the speed of the motor.
I used a solar panel from an old solar lamp. It has a 1.7V voltage drop in medium-light conditions but a very low current, being unable to power the motor. For this purpose I used 2 2N2222A NPNtransistors to amplify the current.
The motor has a minimum current of 70mA and a maximum current of 250mA. So the desired current will be somewhere in between. For this to happen we have to size the base resistor properly.
Step 1: Parts Needed
- Toy motor
- Clip connector
- 9V battery
- 2 NPN 2N2222A transistors
- 4.2K resistor
- Solar cell
Step 2: Schematic and Calculation of the Base Resistor
Our motor will work just fine if we use a resistor with a value less than 11.8k and more than 3.32k.
I used an 4.2k resistor for this project.
The first transistor amplify the signal(current) from the solar panel(but not enough)
Second amplify too but the base resistor will limit the maxim current through the motor (Ic) to 250mA ( the base current will be Ic/β)
- The resistor is calculated for 9V but will be some voltage drop on Q1 too which I ignored in this instructable.
Step 3: Final
I'm looking forward to hear your opinions! :)