Creating a solar battery charger attach to a small dc motor

Thread Starter

neowebmedia

Joined Feb 25, 2019
7
Hello!

My project is super small. Recently I bought a solar AA battery charger. I would like to add a small DC motor to this device. Also, would like to add a on/off switch to the motor. I attached a photo of the charger to this ticket. Do you think it could be easy to add a small DC motor to this device?

The objective is simple. I want to make a flag rotating during the sunny day and moving to the batteries during cloudy days and nights.

Thank you!
 

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ericgibbs

Joined Jan 29, 2010
9,360
hi neo,
Welcome to AAC.
I have marked up your image showing a 2Vdc Motor and switch.
With such low capacity batteries and a low power output Solar panel, I would say the motor will only run for a few ten's of minutes, on a full charge.
Let us know the details of the motor and it maybe possible to calculate the running time.
E
 

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pmd34

Joined Feb 22, 2014
503
You could have a look at using a mobile phone vibrator motor, which should be very low power, but as ericgibbs mentions, it is likely to completely flatten the batteries. You could consider making a circuit that only switches the motor on if there is too much voltage from the solar cells (but thats more complicated!) I understand that with such simple solar chargers, the batteries have a very limited lifetime, as there is nothing to prevent the batteries being over charged on very sunny days.
 

wayneh

Joined Sep 9, 2010
16,162
Your plan might work if you could step the flag around in short bursts instead of having the motor running continuously like a clock. That would require a much larger panel and battery pack. But how about having it move 60 degrees say, every two minutes? There are many suitable circuits online. I forget what they’re called but I’m sure someone here knows what I’m talking about. Lord knows it isn’t me! :D
 

pmd34

Joined Feb 22, 2014
503
Ah I see, the sort of motor you are looking at will run very fast (hundreds of RPM), so you would need to look at a geared one, but still I guess it will be taking maybe >40mA which does not give you much running time with the batteries. Such a small solar cell will also not provide much power, and may not even power such a motor directly.
A very good PV module (20% efficient) in very bright sunlight will give you 200W / m^2 (ish) so your 9cmx9cm would very optimistically give you about 0.36W or 72mA @ 5V so maaaaybe in the brightest of days it could run the motor alone, but with no power to charge the batteries.
 

BobTPH

Joined Jun 5, 2013
2,205
I used a small gear motor to rotate a doll on top of a music box prop for a dance routine. It drew only about 20mA @ 3.7V and had plenty of torque to rotate 7 in. tall barbie type doll.

Bob
 

wayneh

Joined Sep 9, 2010
16,162
I used a small gear motor to rotate a doll on top of a music box prop for a dance routine. It drew only about 20mA @ 3.7V and had plenty of torque to rotate 7 in. tall barbie type doll.

Bob
Cheap electric clocks take a single AA battery and run for months. Maybe you could spin a flag using the drive for the second hand.
 

Bernard

Joined Aug 7, 2008
5,360
A small solar panel from flag illuminator, 7.5 X 6.5 cm, 6V OC, 105 mA SC, 2-20- 2019.
Vibrating bug SP 1.3 X 2.5cm in sunlight drives a vibrator motor.
Just checked a look alike motor, RF-300CA-11440, 5V, draws 15 mA @ 1.5V.
Small vibrator motor 95 mA @ 1.5 V.
 
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Thread Starter

neowebmedia

Joined Feb 25, 2019
7
Ah I see, the sort of motor you are looking at will run very fast (hundreds of RPM), so you would need to look at a geared one, but still I guess it will be taking maybe >40mA which does not give you much running time with the batteries. Such a small solar cell will also not provide much power, and may not even power such a motor directly.
A very good PV module (20% efficient) in very bright sunlight will give you 200W / m^2 (ish) so your 9cmx9cm would very optimistically give you about 0.36W or 72mA @ 5V so maaaaybe in the brightest of days it could run the motor alone, but with no power to charge the batteries.
Exactly. This kind of motor is running fast. I just something making a full 360 every 3 seconds.
 
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