Efficient Relay Operation with Reduced Heat Dissipation
In situations where relays are prone to warming up when continuously energized, this circuit offers an efficient solution. While the relay is initially actuated as usual, this circuit subsequently decreases the ‘hold’ current flowing through the relay coil by approximately 50%. This reduction significantly minimizes heat dissipation and reduces wasted power, enhancing the relay’s efficiency. It’s important to note that this circuit is suitable only for relays that remain activated for prolonged durations.
Dimensioning the Circuit for Specific Relays
To tailor the circuit to a specific relay, specific equations come into play. The resistance value of R3 is determined using the formula R3 = 0.7 / I, where I represents the relay coil current. Additionally, the charge time for the circuit is calculated as Charge time = 0.5 × R2 × C1. After the relay is deactivated, it’s crucial to allow a short delay for the relay current to return to its maximum level before it can be fully energized again. To minimize this delay, it’s advisable to keep C1 as small as possible, ensuring swift reactivation of the relay at full power.
Optimizing Delay and Relay Activation
For practical applications, it’s advisable to incorporate a minimum delay of approximately 5 seconds, although this duration can be fine-tuned through experimentation. C2’s action ensures a momentary application of the full supply voltage across the relay coil, expediting the relay’s activation. T2, in conjunction with the delay network formed by C1 and R2, regulates the current flowing through the relay coil via T1 and R3. This setup effectively reduces the current to half of the ‘pull in’ current. D2 discharges C1 when the control voltage is Low, taking roughly one second to completely discharge C1. Once the delay elapses, T2 shunts T1’s bias current. D1 aids in rapid discharge of C1. The relay specified in the circuit operates at 12 V / 400 ohms, but it’s important to note that all component values provided are for reference and can be adjusted based on specific requirements.
Understanding the Ohm as a Unit of Electrical Resistance
The ohm, a fundamental unit in the International System of Units, signifies electrical resistance. It’s named in honor of the renowned German physicist Georg Ohm. The ohm is precisely defined as the electrical resistance between two points of a conductor where applying a constant potential difference of one volt induces a current of one ampere in the conductor. Notably, this occurs when the conductor doesn’t exhibit any electromotive force within itself.