Although neon lights are fantastic they often require a lot of electricity to operate.
This article explains how to construct a special circuit that enables you to turn ON and OFF a neon light using a little battery pack low voltage DC power source.
WARNING: Designing high voltage circuits might be dangerous.
Do this only under an adults 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, advertisement or innovative displays
Circuit Working:
Parts List:
| Category | Description | Quantity |
|---|---|---|
| Resistors | 47k CFR 1/4 W | 1 |
| 330Ω CFR 1/4 W | 1 | |
| Capacitors | Ceramic 470nF | 1 |
| Electrolytic 47µF 25V | 1 | |
| Semiconductors | Transistors BC547 | 2 |
| UJT 2N2646 | 1 | |
| Diode 1N4007 | 1 | |
| Transformer 0-6V 500mA 220V | 1 | |
| Neon Tube 220V | 1 | |
| Battery 9V | 1 |
To generate the required voltage to start the neon tube a standard step down transformer rated at 240 to 6.3V is carefully connected in reverse order to provide the right voltage for the configuration.
When supplied by a 9V battery source the circuit has an extremely low battery drain of 1 to 2 milliamperes allowing efficient operation.
The unijunction transistor Q1 which is carefully positioned to operate as a relaxation oscillator is at the center of the circuit.
The R2 and C1 networks operate together to fine tune the operating frequency.
Transistor Q3 is after that switched into saturation mode by means of the pulses produced by the UJT Q1 that are sent to transistor Q2.
The 6.3V transformer winding sees a sharp increase in current as a result of this change.
When Q3 reaches saturation a considerable amount of voltage is applied to the transformers secondary winding which in turn causes the neon tube to flash rapidly.
In order to strengthen the circuit against any damage diode D1 is positioned carefully to protect the transistors from high voltage spikes caused by the transformers inductive switching.
Formulas:
Using a UJT to figure out a relaxation oscillator circuits calculated oscillation frequency:
f = 1 / ( η * R * C)
- f is the rough frequency in hertz (Hz).
- η (eta) which represents the basic standoff ratio of the UJT usually ranges between 0.4 and 0.7 however it can differ based on the specific UJT device.
- R is the resistance in ohms Ω that is connected to the UJT emitter 47k.
- The timing capacitor value C in farads F is 47µF.
Applying the Formula:
Determine η (eta):
The datasheets for specific UJT types can provide a usual or range for the basic standoff ratio (η).
If one is not having a datasheet for the specific UJT than one can estimate a value between 0.4 and 0.7.
By doing so however, the expected frequency will become less sure.
Enter the values:
After knowing the resistor R and capacitor C values and a rough figure for η one can use the formula to get the estimated frequency.
Crucial Information:
Because of component tolerances, differences in η and other variables the actual circuit performance may not match the desired frequency.
To achieve more accurate results think about examining the circuit and calculating the oscillation frequency using SPICE simulation tools.
Look for application notes or design processes for UJT relaxation oscillators.
Based on certain UJT models these websites can offer design guidelines and techniques for frequency calculation.
How it is Build:
To build a Simple Neon Tube Flasher Circuit follow the below steps for connections:
- Connect the PCBs unijunction transistor Q1 first followed by resistors R1 and R2 and capacitor C1 to create a relaxation oscillator.
- This will provide you with the proper frequency of operation.
- When receiving pulses from Q1 add transistor Q2 to the circuit to ensure a proper connection with the relaxation oscillator.
- Based on the received pulses connect transistor Q3 to Q2 to enable the saturation mode transition.
- For the circuit to have the necessary voltage for neon tube activation connect the step down transformer in reverse order.
- To protect the transistors from high voltage spikes produced during transformer switching carefully add diode D1.
- To get the triggered flashes place the neon tube in the circuit at the correct position.
- Find out the correct current flow by connecting the complete circuit to a 9V battery source.
Conclusion:
One may build an innovative simple neon tube flasher circuit that runs smoothly on a low voltage DC power source offering us a wide range of possible uses.