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How to limit 12v dc at 5 amps?

How to limit 12v dc at 5 amps

If you need to limit a 12V DC power supply to 5 amps, there are several methods to achieve this safely and effectively. Below, we will explore some solutions and considerations to help you regulate the current flow.

Using a 5 Amp Fuse

One straightforward method to limit the current is by using a 5 amp fuse. Fuses are designed to break the circuit when the current exceeds a specific threshold, in this case, 5 amps. Using a fuse can help protect your circuit from damage due to excessive current.

Maintaining a 2.4 Ohm Resistance

Another approach is to ensure that the resistance of the components connected to the 12 volts stays at around 2.4 ohms. Ohm’s law (V = I * R) indicates that for a given voltage (V), the current (I) flowing through a circuit is inversely proportional to the resistance (R). By keeping the resistance at a specific value, you can limit the current to 5 amps (I = V / R).

Utilizing Power Supplies

If you prefer a more controlled and adjustable solution, you can use power supplies specifically designed for your requirements. These power supplies come in various types, such as buck/boost or up/down converters, and allow you to regulate the voltage and current output.

Constant Current Regulators

A suitable choice for your needs is a constant current regulator. These regulators are available online and are generally priced around $10 for a 5-10 amp model. Some models come with an LCD display, making it easy to adjust and monitor voltage and current values.

When purchasing a constant current regulator, ensure that it can supply more than 5 amperes and that it is adjustable or pre-set to your desired 5-amp limit. If you approach the maximum amperage limit of the regulator, it may get hot. To address this, consider using a heatsink or larger fan to maintain optimal operating temperatures. Alternatively, you can opt for a regulator with a higher maximum amp rating to provide additional headroom.

Adjusting Voltage and Amperage

Once you have your constant current regulator, you can adjust the voltage and amperage to match your requirements. Most regulators feature potentiometers for adjustment, while more advanced models may have pushbutton controls.

To set the voltage, connect a voltmeter directly to the regulator’s output and adjust the voltage potentiometer until it reads 12 volts. To set the amperage, connect an ammeter in series with a device capable of drawing at least 5 amperes (preferably more to ensure safety). Adjust the amperage potentiometer until you reach the desired 5-amp limit.


By using a 5 amp fuse, maintaining a 2.4 ohm resistance, or employing a constant current regulator, you can effectively limit a 12V DC power supply to 5 amps. Choose the method that best suits your requirements and technical expertise. Implementing these solutions will ensure your circuit operates within the desired current range, protecting your devices and enhancing overall system safety.

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