Design DC Circuit for 15V Battery: +10V, +5V & -5V, Max Power 1mA

In summary, the goal is to design a DC circuit with a 15V battery that can provide node voltages of +10V, +5V, and -5V with a maximum power demand of 1mA. The solution involves using 4 equal resistors in series, resulting in node voltages of +7.5V, +3.75V, and -3.75V. However, there is difficulty achieving the desired node voltages and guidance is needed.
  • #1
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Homework Statement


Design a DC cct having a 15V battery to provide the following node voltages: +10V, +5V, and -5V with respect to a circuit ground node. Select your resistors such that the max power demand on the battery does not exceed 1mA.

The Attempt at a Solution



I made a cct with 4 series resistors. 15V source is in series with R1, which is in series with R2, which is in series with R3, which is in series with R4. Since in the question the voltage drops are all equal (5V), I selected 4 equal resistors of 4k. With this design I can node voltages of +7.5, +3.75 and -3.75 with respect to a circuit ground. (I chose the cct ground to be the node connecting R3 and R4)

For the life of me, I don't see a way to get the node voltages specified in the question. Can somebody PLEASE guide me in the right direction??
 
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  • #2
Try sketching down the outputs you want in order, starting with -5V, 0V (ground), 5V and 10V. How many gaps are there between the nodes?
 
  • #3


I would suggest approaching this problem by first determining the total resistance needed in the circuit to achieve the specified node voltages. This can be done by using Ohm's Law, V=IR, where V is the voltage drop, I is the current, and R is the resistance. In this case, we know the voltage drops (+10V, +5V, and -5V) and the maximum current allowed (1mA), so we can solve for the total resistance needed.

Once we have the total resistance, we can then determine the individual resistances needed for each branch of the circuit. This can be done by using voltage dividers, where the voltage drop across each resistor is proportional to its resistance compared to the total resistance. In this case, we would need to select resistors with specific values to achieve the desired node voltages.

It's also important to consider the power demand on the battery. We want to minimize this demand to ensure the battery lasts as long as possible. This can be done by selecting resistors with higher values, which will result in lower power dissipation.

Once the individual resistors are selected, the circuit can be constructed by connecting them in series and connecting the appropriate nodes to the battery to achieve the desired node voltages.

Overall, the key to designing this circuit is to use Ohm's Law and voltage dividers to determine the necessary resistances and then carefully select resistors to achieve the desired node voltages while minimizing power demand on the battery.
 

1. How do I design a DC circuit for a 15V battery with specific voltage outputs and maximum power?

To design a DC circuit for a 15V battery with specific voltage outputs and maximum power, you will need to use a combination of resistors, capacitors, and diodes to create a voltage divider circuit. This circuit will divide the incoming 15V from the battery into the desired +10V, +5V and -5V outputs while also limiting the current to a maximum of 1mA.

2. What components do I need to create a voltage divider circuit?

To create a voltage divider circuit, you will need resistors, capacitors, and diodes. The specific values and types of these components will depend on the desired output voltages and maximum power. It is important to choose high-quality components that can handle the input voltage and current without overheating or failing.

3. How do I calculate the required resistor values for the voltage divider circuit?

To calculate the required resistor values for the voltage divider circuit, you will need to use Ohm's law (V=IR) and the voltage divider formula (Vout=Vin*R2/(R1+R2)). First, determine the output voltage (Vout) for each output using the voltage divider formula. Then, use Ohm's law to calculate the resistance values (R1 and R2) needed to achieve the desired output voltages. Keep in mind that the total resistance of the circuit (R1+R2) should be kept as high as possible to limit the current to 1mA.

4. How can I ensure that the circuit will not exceed the maximum power of 1mA?

To ensure that the circuit will not exceed the maximum power of 1mA, you can use a current-limiting resistor in series with the circuit. This resistor will limit the amount of current flowing through the circuit and prevent it from exceeding the maximum power. The value of this resistor can be calculated using Ohm's law (R=V/I) and should be placed on the positive side of the circuit before the voltage divider.

5. Can I use this circuit for other battery voltages and maximum power requirements?

Yes, you can use this circuit for other battery voltages and maximum power requirements. However, you will need to recalculate the resistor values and possibly adjust the types of components used to match the new specifications. It is important to carefully design and test the circuit to ensure it can handle the input voltage and current without any issues.

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