DC Power Supply/Resistor Power Rating (Circuits For Beginners #3)

Summary

This video introduces the workings of a laboratory DC power supply, explaining its key components, such as channels, ports, and knobs for controlling voltage and current. It covers the difference between floating and grounded power supplies, highlighting safety implications. The video also demonstrates how to use the current limit feature to protect components, like resistors, from damage. Practical examples show how to set up a circuit, adjust settings, and prevent overheating by controlling power dissipation. This tutorial is essential for anyone learning to use DC power supplies safely and effectively.

Takeaways

• 😀 Laboratory DC power supplies have multiple ports with color-coded terminals for different functions, such as red, black, and green cables.
• 😀 The power supply typically has knobs for controlling voltage and current, with separate settings for each channel.
• 😀 Channel 1 and Channel 2 can be independently adjusted for voltage, while Channel 3 is a fixed 5V output.
• 😀 A floating power supply means its voltage is not referenced to an external ground, unlike grounded power supplies.
• 😀 Grounding the power supply via the green pin allows you to set voltages relative to earth, which is important for safety.
• 😀 The power supply’s current limit feature prevents damage to components by restricting the maximum current that can flow through the circuit.
• 😀 Voltage and current settings can be used to calculate the power dissipated by resistors, helping avoid damage to components.
• 😀 For example, a 10 Ohm resistor can only safely dissipate a certain amount of power. Exceeding this limit can cause the resistor to overheat or burn out.
• 😀 The current limit feature can be set in advance to protect devices from excessive current, thus preventing potential damage during testing.
• 😀 A simple test using a 10 Ohm resistor and current limit settings demonstrates how the power supply regulates current and voltage to ensure safe operation.
• 😀 By understanding the relationship between voltage, current, and power, users can safely test circuits and avoid overloading components, like resistors.

Q & A

What is a laboratory DC power supply and what are its main features?

A laboratory DC power supply is a device used to supply a controlled direct current (DC) voltage to an electronic circuit. It typically features multiple channels, with knobs to control both voltage and current. The power supply also has various ports, usually color-coded, for connecting wires.

How does the channel system in a DC power supply work?

In the DC power supply, there are multiple channels, typically labeled as Channel 1, Channel 2, and Channel 3. Each channel has its own voltage and current controls. For example, Channel 1 is on the right, Channel 2 on the left, and Channel 3 provides a fixed 5V output.

What does it mean when a DC power supply is described as 'floating'?

A floating DC power supply means that the voltage is not referenced to the earth or ground. In other words, the voltage between the output terminals is independent of ground potential, making it safer to handle under certain conditions compared to grounded power supplies.

Why is it important to know the difference between the red, black, and green cables on a DC power supply?

The red, black, and green cables indicate different purposes in the power supply. Red is typically used for positive connections, black for negative connections, and green for ground connections. Understanding their roles helps in correctly setting up circuits and ensures safety, especially when grounding is involved.

What is the role of the 'current limit' feature on a DC power supply?

The current limit feature on a DC power supply allows the user to set a maximum current that the supply will output. This helps prevent damage to sensitive components in the circuit by limiting the current to a safe value, even if the voltage is increased.

How does setting a current limit affect the voltage output in a DC power supply?

When a current limit is set, the power supply will adjust its voltage to ensure that the current does not exceed the limit. If the voltage required to achieve a certain current is too high, the power supply will not output the desired voltage, effectively 'clamping' the voltage to a lower value to stay within the current limit.

What could happen if the current limit is not set properly and a component is exposed to too much current?

If the current limit is not set properly, the component could be exposed to excessive current, potentially causing overheating, component failure, or damage to the circuit. For example, a resistor rated for only 0.25 watts could burn out if too much current is allowed to flow through it.

How can you prevent a resistor from burning out when using a DC power supply?

To prevent a resistor from burning out, you can use the current limit feature on the DC power supply. By setting the current limit to a value that ensures the power dissipated by the resistor stays below its rated wattage, you can avoid overheating and damaging the resistor.

What is the significance of the green grounding pin on a DC power supply?

The green grounding pin on a DC power supply provides a reference to earth ground, ensuring safety when the circuit is connected. If the red or black terminals are tied to this ground, it allows the voltage to be referenced as positive or negative with respect to ground.

What happens when you increase the voltage on a DC power supply beyond the set current limit?

When the voltage is increased beyond the current limit, the power supply will not allow the current to exceed the set limit. The voltage will be 'clamped' at a lower value, and the display will show a red indicator to indicate that the current limit has been reached.