Advanced Dimming Capabilities:
Electronic ballasts (EBs) or electronic control gear (ECG) for fluorescent lamps have revolutionized the lighting industry, offering remarkable advantages over their traditional counterparts. These modern devices come with higher efficiency, flicker-free start-up, absence of 50 Hz (60 Hz) flicker, and significantly prolonged tube lifespan. Additionally, they provide an innovative feature – dimming options, which further enrich the lighting experience.
Wide Range of Options:
Reputable manufacturers like Osram and Philips produce EBs equipped with a 1–10 V analog control interface, enabling seamless integration into various setups. Prospective buyers interested in these dimmable EBs can easily locate them through numerous online retail outlets with a simple internet search using the term ‘dimmable EB.’ It is crucial to note that, for the specific circuit discussed here, EBs with a digital interface (known as DALI, or Digital Addressable Lighting Interface) are not applicable.
Understanding the 1–10 V Interface:
The 1–10 V interface functions by delivering an interference-proof DC voltage of up to 10 V. Under load, it maintains a consistent current of 0.6 mA, effectively acting as a constant current source with an open-circuit voltage of 10 V. Dimming of the connected lamp is regulated by a resistor linked across the interface. The lamp’s brightness decreases as the resistor’s value decreases, lowering the voltage across it. At its maximum brightness (100% of nominal power), the lamp operates when the control input is open circuit and the voltage across it reaches 10 V. Conversely, shorting the control input diminishes the lamp’s brightness to 3% of its nominal power.
Tailored Lighting Solution for Aquariums:
In the context of aquarium lighting, a straightforward circuit has been developed. This circuit connects across the control input of the EB, allowing the control voltage to manifest across it. By employing the variable resistor P1, the brightness of the fluorescent tube can be precisely adjusted. This customization offers aquarium owners a tailored lighting solution, perfectly suited to their specific requirements.
Simulated Sunrise Operation:
The circuit operates by connecting electrolytic capacitor C1 across P1, allowing a minute charge current of 0.6 mA to pass through. Due to the large capacitance of C1 (10000 μF), the charging process is very slow, taking approximately 12 minutes to achieve the desired brightness for the fluorescent tube. The gradual increase in voltage across C1 results in a slow rise in the brightness of the tube, simulating a natural sunrise. Notably, the circuit functions without the need for its own power supply.
Simulated Sunset Operation:
When the EB is switched off, C1 discharges into P1, ensuring a gradual dimming effect when the circuit is next switched on. An optional feature involves the integration of relay RE1 and resistor R1 into the circuit. Upon closing the contacts of RE1, C1 discharges slowly into R1, causing the control voltage to decrease gradually. Consequently, the tube dims slowly, imitating a sunset. The rate of the simulated sunset can be controlled by adjusting the value of R1; a higher value results in a slower dimming process.
Adjusting Brightness and Sunset Duration:
The brightness of the tube can be further controlled by adjusting P1. Additionally, the maximum achievable brightness is influenced by the value of R1; a higher R1 value results in a brighter output. By strategically timing the closure of the relay contacts using timeswitches, the simulated sunset effect can be synchronized with the aquarium light operation. For instance, the aquarium light can be plugged into one timeswitch, while a mains adaptor driving RE1 is plugged into another. The relay contact can be set to close 30 minutes before the first timeswitch turns off the aquarium light. After the simulated sunset is complete, the relay contact can be allowed to open, concluding the gradual dimming process.