What is the value of resistor for pull-up for LDR sensor interfacing?

What is the value of resistor for pull-up for LDR sensor interfacing?

For logic devices that operate at 5V, the typical pull-up resistor value should be between 1-5 kΩ. On the other hand, for switch and resistive sensor applications, the typical pull-up resistor value should be between 1-10 kΩ.

What size pull-up resistor do I need?

A rule of thumb is to use a resistor that is at least 10 times smaller than the value of the input pin impedance. In bipolar logic families which operate at operating at 5 V, the typical pull-up resistor value is 1-5 kΩ. For switch and resistive sensor applications, the typical pull-up resistor value is 1-10 kΩ.

What is the point of a pull-up resistor?

In electronic logic circuits, a pull-up resistor or pull-down resistor is a resistor used to ensure a known state for a signal. It is typically used in combination with components such as switches and transistors, which physically interrupt the connection of subsequent components to ground or to VCC.

How do you calculate pull-down resistance?

To calculate the pull-down resistor value, it’s slightly different from the pull-up resistor value. Knowing that current is 100uA, we’ll take 0.5v as our pull-down voltage since the input is 0.8v. Thus, applying our R = V/I once again, but this time we don’t have to minus, so our formula remains constant.

How are the pull up and pull down resistors connected?

By using these two pull-up resistors, one for each input, when switch “A” or “B” is open (OFF), the input is effectively connected to the +5V supply rail via the pull-up resistor.

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 is a pull up resistor connected to a Vcc supply?

This condition means that their output is either grounded when LOW, or floating when HIGH, so an external pull-up resistor, (Rp) needs to be connected from the open-collector terminal of the pull-down transistor to the Vcc supply.

Can a TTL gate be connected to a pull up resistor?

Two or more open-collector outputs of TTL gates can be directly connected together and tied through a single external pull-up resistor. The result is that the outputs are effectively AND’ed together as the combination behaves as if the gates were connected to an AND gate. This type of configuration is called wired AND logic.