Battery, Light sensor and a mini motor?

Thread Starter

ShortCircuitJ5

Joined May 26, 2022
5
First the picture, because a picture is worth a thousand words.

ElectronicQuestion1 (1).png

Is this possible?

If the light is OFF, then the motor stops.

Low light brigthness = low motor speed.
High light brigthness = high motor speed.

Thanks.
 
Sort of... what you will need is a photoresistor. Chances are to find one that will handle the current of the motor may take some digging. You will more likely either need a transistor with the base current determined by the photoresistor, maybe a 555 timer PWM type circuit, or some other form of circuit. Personally I would use a microcontroller to monitor the photoresistor which then activates and adjusts the duty cycle of a PWM signal to change the motor speed.
 

Reloadron

Joined Jan 15, 2015
6,584
Yes, it is very possible and very doable. That said you will need some specifications before you even start. It's about the numbers. Numbers like battery and motor voltage. The motor voltage and current will determine what battery will run it and how long. The numbers will also determine what the mystery black box will be. In a nutshell yes, it's doable and doable starts with a pile. albeit a small pile of numbers. I also agree with geekoftheweek above:
Personally I would use a microcontroller to monitor the photoresistor which then activates and adjusts the duty cycle of a PWM signal to change the motor speed.
Some effort to program a a small dimple uC (micro-controller) and that is your Black Box. There are also other ways to do it. It all starts with a pencil (large eraser preferred) and a blank sheet of paper and defining exactly what your project is and numbers. :)

Ron
 

MisterBill2

Joined Jan 23, 2018
11,877
Certainly the control described is possible, BUT the light sensor will need to be one like is used in the photo control switches for higher powered lighting. And it will be a simple series circuit with only one battery lead connected to the light sensor, which will be a photo-resistor, not a photocell or photodiode or solar cell. But while it will work, it will not be useful.
 

Reloadron

Joined Jan 15, 2015
6,584
When light is striking the LDR (Light Dependent Resistor) the resistance is low resulting the transistor to be turned on. The motor runs. Removing light the transistor is biased off and the motor stops. The circuit is as basic as it can be. The motor is just a small DC motor requiring low current. Yes, there are other solutions for DC motor speed control like using PWM (Pulse Width Modulation) but they become more complex. What you see in the video is very crude basic and simple. The delay response of the motor is the LDR is not a fast response.

When you have questions please start a new thread of your own.

Ron
 

Marley

Joined Apr 4, 2016
475
I'm tempted to say a photoresistor and a 555 (and a few other components).
PWM drive to the motor.
But what voltage is the motor?
 

MisterBill2

Joined Jan 23, 2018
11,877
The very simplest is still the series circuit with the large diameter higher power handling resistive device from one of the higher powered light controls. The resistor is over ten Kilohms in the dark and under 100 ohms in bright light. Yo will need a higher voltage battery, but it is the simplest circuit. A photo transistor can do it better but it will take a few more parts, I think.
 

MisterBill2

Joined Jan 23, 2018
11,877
My bad. Sorry about that. Plenty of ways to control a small DC motor. Depends on what you want and the motor type.

Ron
Given the picture in post #1, the motor is a fairly small hobby type DC brushed motor, probably operating on about 3 volts, or one lithium cell. My suggestion will require a higher supply voltage because of the resistance of the light sensor.
 

Reloadron

Joined Jan 15, 2015
6,584
Given the picture in post #1, the motor is a fairly small hobby type DC brushed motor, probably operating on about 3 volts, or one lithium cell. My suggestion will require a higher supply voltage because of the resistance of the light sensor.
Post #7 shows a circuit and calls out a 2N3904 pretty common NPN transistor with a max collector current of 200 mA. While the link points to a 9 volt supply which only needs be enough to turn the motor. It's a pretty common hobby circuit and the current is handled by the transistor. Pretty much as I described. Also in the linked video the motor runs or doesn't. The LDR and 10K form a basic voltage divider to bias the 2N3904 base using a 1K base resistor. Crude and simple. Would I suggest it? No, but I still haven't a clue what the thread starter has in mind. :)

Clueless in Cleveland
Ron
 

MisterBill2

Joined Jan 23, 2018
11,877
Certainly that circuit with the transistor will work, and probably a lower current photo-resistor will be simpler to find and cost less as well.
 
Top