MullOverThings

Useful tips for everyday

# Can you use a pull down resistor on an analog input?

## How does a pull up resistor affect the input pin?

With a pull-up resistor, the input pin will read a high state when the button is not pressed. In other words, a small amount of current is flowing between VCC and the input pin (not to ground), thus the input pin reads close to VCC.

## What is the maximum pull up resistor for a logic gate?

By knowing the information above, we can calculate the maximum pull-up resistor value required for a single TTL 74LS series logic gate as: Then using Ohms Law, the maximum pull-up resistance required to drop 3 volts for a single TTL 74LS series logic gate would be 150kΩ.

## How does the pull up resistor work on a VCC?

When the button is pressed, the input pin is pulled low. The value of resistor R1 controls how much current you want to flow from VCC, through the button, and then to ground. When the button is not pressed, the input pin is pulled high. The value of the pull-up resistor controls the voltage on the input pin.

Most analog input control loops are connected in a 2-wire configuration which requires a DC Power Supply. In some cases, the power supply is external, and in other cases, the power supply is part of the PLC or DCS. The transmitter signal is usually 4 to 20 mA.

If you are curious to know more about the Analog Input module, do a google search for 1769-IF8. Okay, let’s look at another example and see if we can find the transmitter, power supply, and controller.

This equation can be used to scale the analog input to the engineering value: Engineering Value = (Raw Value / 27648) * 300 Of course the easiest option here is to use structured text.

## When to use a pull up resistor in a sensor?

A pull-up resistor is used in a sensor or switch circuit in which the ECU can not determine the value that the sensor or switch is inputting. The resistor is used in conjunction with a 5-volt supply and restricts the flow of current to allow the circuit to have very low amps within it.

## Where is the pull up resistor on an ECU?

In this diagram, the pull-up resistor is represented by the yellow line and has been wired externally, but most aftermarket ECUs will have the resistor built in, which we’ll be able to select different resistance values for, via the ECU software — in that case no wiring would be required.

## How are 5 volts connected to a pull up resistor?

If the ECU header plug side of the pull-up resistor is connected to 5 volts, when the switch is open, 5 volts will also be present at our digital input pin. When we close the switch, this completes the circuit and we’ll end up with zero volts at the digital input pin.