Is My Pull Up Resistor Calculation Correct?

In summary, the conversation discusses the process of calculating resistance when using a current source and voltage reader. The calculations result in a voltage drop of close to 5V, but when using the voltage reader, a reading of 9.83V is obtained. This suggests that the current source may not be precise and requires a voltage drop of a couple of volts to operate correctly. Therefore, the resistance calculation of 9.83/.0006 is not accurate.
  • #1
ee1215
29
0
http://i.imgur.com/TbYIHnb.png?1

So, if I have a pull up and apply a current source. How would I need to read/calculate resistance?

V=IR
I = 5V/8k = .0006A would result in a voltage drop of close to 5V

Using a current source/Voltage reader I supply .0006A which should equate to ~5V drop

But when I read my voltage reader I get 9.83V. Is this correct?

Then my resistance would be 9.83/.0006 ~ 16.4k ?

These calculations do not seem correct.
 
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  • #2
ee1215 said:
http://i.imgur.com/TbYIHnb.png?1

So, if I have a pull up and apply a current source. How would I need to read/calculate resistance?

V=IR
I = 5V/8k = .0006A would result in a voltage drop of close to 5V

Using a current source/Voltage reader I supply .0006A which should equate to ~5V drop

But when I read my voltage reader I get 9.83V. Is this correct?

Then my resistance would be 9.83/.0006 ~ 16.4k ?

These calculations do not seem correct.

Sounds like your current source is not very precise. Keep in mind that real-world current sources need to have some voltage drop across them in order to operate correctly. Typically you need a couple of volts across a current source in order for it to say "in compliance".
 

FAQ: Is My Pull Up Resistor Calculation Correct?

What is a pull up resistor and why is it used?

A pull up resistor is a resistor connected between a signal line and a positive power supply. It is used to ensure that the signal line is at a known state when no input signal is present. This prevents the signal line from floating and producing unreliable results.

How do I calculate the value of a pull up resistor?

The value of a pull up resistor can be calculated using Ohm's law, which states that resistance (R) is equal to voltage (V) divided by current (I). The ideal value of a pull up resistor should be high enough to provide adequate current to the signal line, but low enough to prevent excessive power consumption. A commonly used value is between 1-10kΩ.

What factors should be considered when selecting a pull up resistor?

When selecting a pull up resistor, it is important to consider the voltage level of the signal line, the current required by the circuit, the power supply voltage, and the type of integrated circuit used. Additionally, the noise immunity and speed of the circuit should also be taken into account.

Can I use a pull up resistor for both inputs and outputs?

It is not recommended to use a pull up resistor for both inputs and outputs. This is because the resistor may interfere with the proper functioning of the inputs and outputs, and can cause issues such as signal distortion or reduced voltage levels.

How can I test the effectiveness of a pull up resistor?

The effectiveness of a pull up resistor can be tested by measuring the voltage at the signal line with and without the resistor connected. If the voltage is stable at the desired level with the resistor connected, then it is working effectively. Additionally, testing the circuit with and without the pull up resistor can also help determine if it is necessary for proper functioning.

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