Continue to Site

# Designing a joule thief for a motor

Status
Not open for further replies.

#### zemanekj

##### New Member
I'm working on creating a joule thief to power my DC electric motor. Can I replace the LED with an electric motor? Or would that ruin the circuit?
Here is the video I'm going off of:
Would I need to add a diode do convert the electricity from A/C to DC?

Thank you!

A joule thief circuit takes a low voltage and low current from an almost dead battery cell and boosts the voltage high enough in pulses to dimly light an LED. Since power= voltage times current then by boosting the voltage then the output current is less than the weak battery current.

The output from a joule thief is DC pulses, not AC.

An electric motor needs a certain voltage and uses a certain amount of current but you did not say them. The current used by the motor is probably much too high for a joule thief circuit, use a battery with a high enough voltage and enough current capacity to power the motor for as long as you want.
You can make a different, much more powerful circuit to boost voltage to drive your motor, but you need to know the voltage and current specifications of the motor.

For a motor you need a high current charge pump ... This is a design I did and little over kill for your motor, but the idea is the same.

Look up "Dickson Charge Pump" this works really well for DC motor applications.

Last edited:
Building a joule thief without any calculations is kinda random, so theres no way to say for sure if it'd work or not.
The only thing to do is try it, though you'd only be able to power a tiny motor, say something meant for a solar powered display.

A joule thief circuit takes a low voltage and low current from an almost dead battery cell and boosts the voltage high enough in pulses to dimly light an LED. Since power= voltage times current then by boosting the voltage then the output current is less than the weak battery current.

The output from a joule thief is DC pulses, not AC.

An electric motor needs a certain voltage and uses a certain amount of current but you did not say them. The current used by the motor is probably much too high for a joule thief circuit, use a battery with a high enough voltage and enough current capacity to power the motor for as long as you want.
You can make a different, much more powerful circuit to boost voltage to drive your motor, but you need to know the voltage and current specifications of the motor.

Building a joule thief without any calculations is kinda random, so theres no way to say for sure if it'd work or not.
The only thing to do is try it, though you'd only be able to power a tiny motor, say something meant for a solar powered display.
I'm learning all of this on my own. would you recommend any books or educational content to help me figure out what calculations I need, etc..?

A book called, "The Art Of Electronics" is pretty good. I got the 2nd edition for free online and now there is a 3rd edition that I have never seen and do not need. Calculations are mostly simple Ohm's Law:

#### Attachments

• Ohm's Law.png
42.2 KB · Views: 132

both of them are available at archive.org

If you want to know more about joule thief's in particular google 'blocking oscillator', that is the proper name, they've been around for decades in various applications.

If you want to know more about joule thief's in particular google 'blocking oscillator', that is the proper name, they've been around for decades in various applications.

Not 'really' the same thing, while a 'joule thief' is a type of blocking oscillator, a blocking oscillator is rarely a 'joule thief'.

But throughout all this, the OP has never mentioned what motor he's wanting to run, and what he's wanting it to do, never mind explaining why he thought a joule thief might be a good idea?.

Ok

and what he's wanting it to do, never mind explaining why he thought a joule thief might be a good idea?.

Willing to bet it's an on going thing with his wanting to run a motor from RF energy in the atmosphere. He just keeps asking the same question in different ways, on different forums.

both of them are available at archive.org
Thank you!

A Joule Thief is designed to extract the tiny bit of energy left in a nearly dead batter to generate low current pulses to light an LED.
It's not magic, it cannot increase the energy above that available from the battery/source.

Its possible to light an Led off Rf from an ant, just so you can see a tiny bit of light, probably a few uA or so, getting a motor to turn would require you to be under the transmitter.

Status
Not open for further replies.