Close or Esc Key

Arduino Projects   |   Raspberry Pi   |   Electronic Circuits   |   AVR   |   PIC   |   8051   |   Electronic Projects

Insight - How Piezoelectric Gas Lighter/Igniter works

Written By: 

Abhimanyu Mathur


Even though several breakthroughs in Chemistry were achieved by them, the Curie’s are known to majority of the world for their revolutionary work on radioactivity. However, it is amazing to know that one of their discoveries has given one of the most common accessories any kitchen has. Not related to radioactivity, this is the Gas Lighter. Based on the principle of piezoelectricity, which is one of the discoveries made by Jacques Curie and Pierre Curie. Piezoelectric lighters are an economic solution to light gas stoves. Ever wondered how does a small force of thumb produces a spark of the order of kilo volts (kV)? Let’s have a look on the insides and working of the lighter in this device dissection article.

A piezoelectric crystal is the heart of the gas igniter. When a strong force is applied on it by means of a spring loaded hammer it produces an electric spark. Certain dielectric materials have an internal crystalline structure which when subjected to mechanical stress produces an electric field and vice versa. The degree of electric field produced is directly proportional to the magnitude of force applied.
These materials are termed as piezoelectric crystals and this principle is termed as piezoelectricity.
Fig. 1: Piezoelectric Gas Lighter

Outer Structure

Encased in a steel structure, piezoelectric gas lighters are usually in a tubular form as shown in the image above. At the top is a push button made up of steel inside which is present  a spring loaded hammer.  When pressed it produces the necessary force needed to generate electric potential in the piezoelectric crystal. Two small handles are provided which helps in gripping the lighter when pressing the hammer with the thumb. The internal view of the tubular rod will clear the mechanism of spark production.
Fig. 2: Ignition Head Comprising Thin Metal Rod in Plastic Casing
The image above shows the bottom part of the gas lighter. This part is known as ignition head.  The ignition head contains a thin metal rod covered with the plastic casing. When the hammer is pressed, a spark is produced at the corner of the metal rod. Interestingly the position of the produced spark varies each time hammer is pushed down.


Fig. 3: Inner Components Showing Plastic Tubular Structure that Contains Hammer and Spring Assembly
On opening the steel casing structure from near the top handle a plastic tubular structure comes out  which contains the hammer and spring assembly.
Fig. 4: Close View of Tubular Structure and Hammer--Spring Assembly
The image above shows a better view of the tubular plastic structure. It holds the spring hammer assembly inside it. There are immediate radius transitions in the plastic structure that taper it down giving the structure a telescopic appearance.
Fig. 5: Internal Structure of Plastic Casing
This telescopic structure plays a very important role in generating the high force needed to hit the piezo crystal. The internal structure of the plastic casing is shown in the image above. At the radii transactions, there are two small walls like barriers all across the periphery.
Fig. 6: Image Indicating Hammer-Spring Assembly
The above image shows the spring and hammer assembly which is responsible for generating the high force. There are two springs, and a strong metal rod at the end of which is present a hammer. The outer spring is used to operate the push button and bring it back to its normal state. The inner spring is used to load the metal rod so that the small hammer can strike the crystal for generating the spark. The inner spring is relatively strong and stiff and therefore when loaded generates a high force. The exact working is explained later in this article.


Fig. 7: Safety Latch
Fig. 8: Position of Latch and Plastic Casing before they Collide to give Click Sound
Shown in the image above is the safety latch of the lighter. Casted upon the upper section of the hammer assembly, the latch holds in the internal spring assembly.When push button of the lighter is pressed to its maximum extent, the collision of latch with the plastic assembly produces a click sound. A strong metal ring which is placed just above the plastic casing protects it from potential damage when the spring loaded metal rod strikes the impact pad.

Piezo Assembly

Fig. 9: Piezo Assembly and its Various Parts
Tightly packed inside lower part of the steel tube is the piezo assembly. It consists of the following parts in hierarchical order:
       1.      Impact Pad
       2.      Piezoelectric crystal
       3.      Ignition Head.
Impact Pad
Fig. 10: Impact Pad
Impact Pad bears the hammer blows from the upper part and passes the force on the piezoelectric crystal causing it to deform and produce a spark. It is made of brass and has a shape of a cone. The part with less radius impacts on the crystal while the upper part receives the hammer blow.
Piezoelectric crystal
Fig. 11: Lead Zirconate Titanite Piezoelectric Crystal
Shown above is the magnified image of the lead zirconate titanate piezoelectric crystal.  A bit distorted, this crystal is in a cylindrical shape and is responsible for voltage production when pressure is put on it. Other extensively used piezoelectric crystals are quartz, sodium potassium tartrate and tourmaline.  The crystal acts as a battery for the lighter and when it ends, the lighter either requires refilling or is useless. The lighter shown in this article cannot be refilled after once the crystal deteriorates.
Ignition Head
Fig. 12: Ignition Head Parts and Anvil
The ignition head is the part from where the spark reaches the gas stove. When the piezoelectric crystal is pressurized mechanically, it generates voltage pulses of the order of kV and ultimately, it is this high voltage that discharges a spark. The upper part of the ignition head acts as an anvil for the piezoelectric crystal. Made of steel or aluminum, the anvil provides inertia that aids in magnifying the impact of the impact pad.


Working of Piezoelectric gas lighter

Fig. 13: Spring Loaded Hammer Assembly at Rest
The push button behaves like a linear actuator. In the normal state the outer spring rests against the internal wall present all across the periphery of the first radius.  When we start pushing the push button, it presses the hammer and spring assembly to move in the telescopic shaped plastic casing. Since the outer spring is blocked by the internal wall, it starts getting loaded. This force is used to send the push button back to its normal state.
Fig. 14: Figure Showing Extended Part of Hammer when Spring is Pressed
The metal rod along with the inner spring keeps moving in the plastic structure till the hammer encounters the second internal wall which blocks it partially.
Fig. 15: Image Showing Metal Rod Inside Plastic Casing
The movement of the hammer is not straight and it is held at the second radius transition point. As we keep the pressing the push button and since the hammer is blocked from moving further in, the inner spring gets loaded. At a certain point the spring force is enough to overcome the internal wall force and forces the hammer to move further in and strike the impact pad with a huge force of the inner spring. The moment the impact is created the inner spring pulls the metal rod back to its normal position and the outer spring in turn pulls the push button back to its normal state. Hence the complete assembly is back to its normal state. 

This mechanical force generated by pressing the hammer assembly causes the crystal to generate voltage which is carried by the electrodes at the ignition head to generate a spark. This entire process gets completed in a second or two and the momentum generated by the thumb is strong enough to create a 7kV voltage spark that lights the air-gas mixture near the burner. 




how to make a digital thermometer with a 8051 microcontroller?

Very useful article

Very useful compared to other websites I found