Simple Neon Tube Flasher Circuit

Neon lights are cool, but they usually need a lot of power to work.

This article shows you how to build a special circuit that lets you use a small battery pack low voltage DC power supply to make a neon light flash on and off.

WARNING: Building circuits with high voltage can be dangerous.

Only do this with adult supervision.

What is a Neon Tube Flasher Circuit:

A neon tube flasher circuit is an electronic circuit designed to flash a neon tube ON or OFF at a certain specified rate.

Neon tube flashers are commonly used for decorative lighting purposes, signage, or artistic displays

Circuit Working:

Parts List:

The essential voltage required to initiate the neon tube is attained through the deployment of a conventional step down transformer with a rating of 240 to 6.3V strategically connected in reverse order to achieve the desired voltage configuration.

To ensure efficient operation, the circuit boasts a remarkably low battery drain ranging between 1 to 2 milliamps when powered by a 9V battery supply.

At the core of the circuit is Q1 a unijunction transistor meticulously configured to function as a relaxation oscillator.

The operational frequency is finely tuned through the interplay of the R2 and C1 network.

The pulses generated by the UJT Q1 are channeled to transistor Q2 orchestrating the subsequent switching of transistor Q3 into saturation mode.

This transition induces a rapid surge in current through the 6.3V transformer winding.

As Q3 attains saturation a significant voltage is imparted to the secondary winding of the transformer, effectively triggering the neon tube to emit a distinctive flash.

To fortify, the circuit against potential damage diode D1 is strategically positioned to shield the transistors from high voltage spikes arising from the inductive switching of the transformer.

Formulas:

Calculating the approximate oscillation frequency of a relaxation oscillator circuit using a UJT:

f = 1 / ( η * R * C)

• f is the approximate frequency, in hertz (Hz).
• The intrinsic stand off ratio of the UJT is represented by η (eta), which usually ranges from 0.4 to 0.7, however it may differ according on the particular UJT device.
• R is the resistance in ohms Ω that is attached to the UJT emitter 47k.
• The timing capacitor value, C in farads F is 47µF.

Applying the Formula:

Determine η (eta): The inherent stand off ratio (η) may have a typical or range provided by the datasheets for particular UJT types.

For the particular UJT you are using, you can guess a value between 0.4 and 0.7 if you do not have a datasheet.

But doing so will make the estimated frequency less certain.

Enter the values: You may use the formula to obtain an approximate frequency after you know the values of the resistor R and capacitor C, as well as an estimated value for η.

Crucial Information:

Due to changes in η, component tolerances and other factors, the estimated frequency may not match the real circuit behavior.

To get more precise results, think about: analyzing the circuit and figuring out the oscillation frequency with the use of SPICE simulation tools.

looking for application notes or design processes for UJT relaxation oscillators.

These resources may offer frequency estimation techniques and design guidelines based on particular UJT models.

How it is Build:

Lets follow the steps to connect the components parts to build this described circuit:

• Begin by placing the unijunction transistor Q1 on the PCB and connect it in relaxation oscillator configuration with resistors R1 and R2, as well as capacitor C1 to establish the desired operational frequency.
• Integrate transistor Q2 into the circuit to receive, pulses from Q1 ensuring proper connectivity with the relaxation oscillator.
• Connect transistor Q3 to Q2, facilitating the saturation mode transition based on the pulses received.
• Incorporate the step down transformer in reverse order connecting it to the circuit to achieve the requisite voltage for neon tube activation.
• Integrate diode D1 strategically to safeguard the transistors from high voltage spikes generated during transformer switching.
• Position the neon tube appropriately in the circuit to receive the triggered flashes.
• Connect the entire circuit to a 9V battery supply, ensuring the proper flow of current.

Conclusion

You can construct a state of the art simple neon tube flasher circuit that operates seamlessly with a low voltage DC power supply, unlocking a myriad of potential applications.

References

Neon lamp

Datasheet2N2646