**The Joule Thief Circuit: A Simple yet Effective Solution**

In this video, I will show you how to build and master the popular Joule Thief circuit, a simple yet effective solution for utilizing stored energy from a supercapacitor.

**Components Needed**

To create the Joule Thief circuit, you will need the following components:

* One generic NPN BJT (in my case, the BC547)

* A 1 kilohm base resistor

* A hand-wound transformer with two lengths of 0.65 millimeter enamel copper wire around a ferrite toroid core (inner diameter: 8.4 mm, outer diameter: 14.7 mm)

* The LED (power: 0.5 watts, voltage: 3.2 volts)

**Schematic and Parts List**

The schematic for the Joule Thief circuit is simple to create, with only 5 solder joints connecting the components together. If you'd like to try building it yourself, you can find a parts list and the schematic in the video description.

**Testing the Circuit**

After powering the circuit with my lab bench power supply, I was pleased to see that it worked pretty well for such a hastily constructed circuit (created in under 15 minutes!). However, I soon realized that the supply voltage of around 2.3 volts caused only heat to be generated by the transistor, without illuminating the LED.

**Analyzing the Circuit's Working Behavior**

Let's take a closer look at how the Joule Thief circuit works:

* A small amount of base current initially flows, allowing a small amount of collector current to flow.

* This collector current induces a voltage into the secondary coil of the transformer (which is in series with the voltage source due to its reverse wiring direction).

* The induced voltage increases the base current, which in turn increases the collector current.

* This process repeats until the transistor reaches saturation, at which point the collector current rises linearly.

**The Oscillator's Frequency**

Once the magnetic flux density of the toroid core is reached, the induced voltage decreases, causing the base current to decrease as well. As a result, the transistor is no longer in saturation, and practically no collector current flows.

However, the energy stored in the primary coil's magnetic field still needs to dissipate, leading to an overvoltage of around 94 volts at the collector (if no load is connected). When this occurs, the forward voltage drop across the LED will cause it to illuminate between the collector and emitter.

**Solving the Oscillator's Frequency Issue**

To solve this issue, we could create another transformer with more windings and a larger toroid core to increase the inductance and slow down the charging and discharging process. Alternatively, we could simply increase the value of the base resistor, which would decrease the overall base current.

**The Circuit's Efficiency**

While the efficiency of the Joule Thief circuit can be as good as 94% for voltages around 1.5 volts, it can also drop to as low as 24% for higher input voltages.

**Conclusion**

In conclusion, while the Joule Thief circuit may seem simple to create for beginners, it can be quite challenging to properly understand its function principle and dimension the components correctly.

WEBVTTKind: captionsLanguage: enI recently got myself those 22 farad super capacitors which are indeed quite super because after charging them up to the maximum rated voltage of 2.5 volts they are capable of delivering up to 69 joules of energy which is around 140 times more than your average electrolytic capacitor at the same size of course my eneloop double-a battery still can hold up to 150 times more energy than my super cap but on the other hand due to its lower internal resistance the super cap can supply more current than your common double-a a common field of application for those are emergency flashlights like this so called shaking torch after a couple of ummm playing shakes the 0.33 part super cap is charged up to four point eight volts which is around 3.8 joules of stored energy there can be used to illuminate a white LED year for roughly a 5 minutes but even after the LED Catterick the super cap is still charged to 2 point 7 volts which basically means that 32% of the initial energy is unusable for us due to the high power voltage of the LED thankfully though there exists a rather popular and simple circuits the Joule thief that can solve this problem and in this video I will show you how easy it can be to build one of those and how hard it actually is to master its circuit design let's get started first off let's gather the components that we need one generic NPN BJT year in my case the bcs 637 / 1 kilo ohm base resistor a hand wine transformer which I created by winding two lengths of 0.65 millimeter enamel copper wire around a ferrite toroid core with an inner diameter of eight point four millimeters and an outer diameter of fourteen point seven millimeters and soldering the opposing inputs and output wire together and finally the LED i1 power in this case is 0.5 watts power they deal with a probable tidge of 3.2 volts according to the rather simple schematic I then created 5 solder joints in order to connect the components to one another and if you want to give the circuit a try as well you can find a parts list and the schematic in the video description after powering the circuits with my lab bench power supply this circuit actually seems to work pretty well for the fact that was created in less than 15 minutes but it is still not suitable for my application because supply voltage is above 2 point 2 volts only heat up the transistor and not illuminate the LED so let's analyze the working behavior of the circuits to find a possible solution in the beginning a small amount of base current only lets a small amount of collector current flow this collector current then induces a voltage into the secondary coil of the transformer which is in series to the voltage source due to its reverse wiring direction and thus increases the base current which therefore increases the collector currents this process repeats until the transistor reaches the saturation states in which the collector current Rises in a linear fashion the primary coil builds up with magnetic fields and the induced voltage into the secondary is at its maximum but once the magnetic flux density of the toroid core is reached the induced voltage decreases the base current decreases as well and the transistor is no longer in its saturation States practically no collector current can flow any more but the energy of the primary coils magnetic field needs to dissipate the result is an over voltage of around 94 volts at the collector if no load is connected all around the forward voltage of my idea if I connected between the collector and emitter this cycle then repeats all over again so in a nutshell it is an oscillator which acts as a crude boost converter and if we take a look at the voltages near the 2.3 volt mark we can see that the frequency increases rapidly until the oscillation disappears completely to solve that we could either create another transformer with more windings and a bigger toilet core in order to increase the inductance and the slow down the charging and discharging process and decrease the overall frequency of the oscillator or we just keep it simple by increasing the value of the base resistor and thus decreasing the overall base current in both cases the circuit finally does work pretty well with my fully charged shop super capacitor and illuminates mataji up to 20 minutes continuously but don't think this circuit is perfect not even close even though the efficiency can be as good as 94% for voltages around 1.5 volts it can also be as full year as 24% for voltages needs upper and lower input limits in conclusion I can say that this circuit is pretty easy to create for beginners but it can get quite difficult to properly understand the function principle and dimension the components I hope you like this video if so don't forget to Like share and subscribe that would be awesome consider supporting your through patreon that is what keeps the show going stay creative and I will see you next timeI recently got myself those 22 farad super capacitors which are indeed quite super because after charging them up to the maximum rated voltage of 2.5 volts they are capable of delivering up to 69 joules of energy which is around 140 times more than your average electrolytic capacitor at the same size of course my eneloop double-a battery still can hold up to 150 times more energy than my super cap but on the other hand due to its lower internal resistance the super cap can supply more current than your common double-a a common field of application for those are emergency flashlights like this so called shaking torch after a couple of ummm playing shakes the 0.33 part super cap is charged up to four point eight volts which is around 3.8 joules of stored energy there can be used to illuminate a white LED year for roughly a 5 minutes but even after the LED Catterick the super cap is still charged to 2 point 7 volts which basically means that 32% of the initial energy is unusable for us due to the high power voltage of the LED thankfully though there exists a rather popular and simple circuits the Joule thief that can solve this problem and in this video I will show you how easy it can be to build one of those and how hard it actually is to master its circuit design let's get started first off let's gather the components that we need one generic NPN BJT year in my case the bcs 637 / 1 kilo ohm base resistor a hand wine transformer which I created by winding two lengths of 0.65 millimeter enamel copper wire around a ferrite toroid core with an inner diameter of eight point four millimeters and an outer diameter of fourteen point seven millimeters and soldering the opposing inputs and output wire together and finally the LED i1 power in this case is 0.5 watts power they deal with a probable tidge of 3.2 volts according to the rather simple schematic I then created 5 solder joints in order to connect the components to one another and if you want to give the circuit a try as well you can find a parts list and the schematic in the video description after powering the circuits with my lab bench power supply this circuit actually seems to work pretty well for the fact that was created in less than 15 minutes but it is still not suitable for my application because supply voltage is above 2 point 2 volts only heat up the transistor and not illuminate the LED so let's analyze the working behavior of the circuits to find a possible solution in the beginning a small amount of base current only lets a small amount of collector current flow this collector current then induces a voltage into the secondary coil of the transformer which is in series to the voltage source due to its reverse wiring direction and thus increases the base current which therefore increases the collector currents this process repeats until the transistor reaches the saturation states in which the collector current Rises in a linear fashion the primary coil builds up with magnetic fields and the induced voltage into the secondary is at its maximum but once the magnetic flux density of the toroid core is reached the induced voltage decreases the base current decreases as well and the transistor is no longer in its saturation States practically no collector current can flow any more but the energy of the primary coils magnetic field needs to dissipate the result is an over voltage of around 94 volts at the collector if no load is connected all around the forward voltage of my idea if I connected between the collector and emitter this cycle then repeats all over again so in a nutshell it is an oscillator which acts as a crude boost converter and if we take a look at the voltages near the 2.3 volt mark we can see that the frequency increases rapidly until the oscillation disappears completely to solve that we could either create another transformer with more windings and a bigger toilet core in order to increase the inductance and the slow down the charging and discharging process and decrease the overall frequency of the oscillator or we just keep it simple by increasing the value of the base resistor and thus decreasing the overall base current in both cases the circuit finally does work pretty well with my fully charged shop super capacitor and illuminates mataji up to 20 minutes continuously but don't think this circuit is perfect not even close even though the efficiency can be as good as 94% for voltages around 1.5 volts it can also be as full year as 24% for voltages needs upper and lower input limits in conclusion I can say that this circuit is pretty easy to create for beginners but it can get quite difficult to properly understand the function principle and dimension the components I hope you like this video if so don't forget to Like share and subscribe that would be awesome consider supporting your through patreon that is what keeps the show going stay creative and I will see you next time