How do pull up /down resistors work? (details with voltage, current, impedance, etc)?

Answer 1

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Answer 2

It is a path to either VCC or ground.

You can switch a light bulb on, by either connecting the ground, or the positive if the other end is already connected.

A transistor is a switch.
It switches either ground or VCC to a circuit.

If it used used with a pull up resistor, then when the switch is open, then the path is to VCC. When the Switch is closed, the path goes to ground.

Vise Versa if Pull down.

Answer 3

Pull up and pull down resistors are halfway a figure of speech.

Used in Logic circuits....

A pull down resister lowers the voltage going into a Integrated circuit chip to bring it down to ground....

A pull up resister raises the voltage to bring it up to VCC (the positive voltage of the logic circuit...Be warned, that doesn't mean that that's the voltage of the ENTIRE circuit... the logic circuit could be running on 5vdc while the rest runs on 24vdc... if you pull up the IC to the 24VDC you could blow it out...

(I'm sorry I can't give you EXACT sizes but, it's determined by the volatages you use & monitor. Also by the IC itself..ie. how far off of zero or VCC it needs to be to trigger.)

If you're monitoring part of the 24vdc circuit then you will have to adjust your resistance accordingly to avoid damaging the lower voltage components....

Impedance is used with inductors nor resistance circuits so that doesn't apply here.... as to the value of the resistor...It's determined by the maximum amt of current you want to flow thru the data point...

for example....

#1>>you've got a IC that turns on a fan when pin 5 raised above ground..... connected to pin5 is a red wire (connected to nothing) & a high (say 500Kohm) value resistor (connected to ground).
As long as the red wire has no voltage on it at all...pin5 is grounded by the resistor...add a little voltage to red wire and pin5 is no longer grounded and your fan turns on.

#2>> same circuit as #1 but you use a smaller resistor.... say.. (100Kohm) now you need to use more voltage to bring pin5 up off ground...(This is because the smaller resistor will draw more current to ground before you can raise the voltage high enough to trigger the fan )

#3>>if you connect the resistor to VCC or the positive voltage of the IC.. you've set the chip to keep the fan on....Now you have to use a ground signal to shut off the fan...Be warned, you'll have to select a resistance that wont FRY when you ground it. use your VCC to determine the max current. Remember as long as there's no ground attached you can use a VERY high resistance to keep the current down and still pull pin5 high.

WIKI has the data for you too..I tried to laymanize it from my own experience...

Here's a working example for a compter communications circuit
http://en.wikipedia.org/wiki/Pull-up_resistor#I.C2.B2C

Hope I helped you....
-Dawgy

Answer 4

Ohm's regulation states that : V=IR in case you connect 9V battery for the length of a resistor say of one thousand ohm, then which means you've outfitted a circuit, then the present I is the bypass of electrons contained in the circuit, it flows from the constructive terminal of the battery operating by the resistor decrease back to the unfavourable port of the battery, the cost of the present which flows merely may be calculated from the above equation I=V/R= 9/one thousand amp= 9ma in case you position a resistor of say ten thousand ohm's or 10 kohms then the present will be 0.9ma, or in case even as R=100 ohm's I= 90ma

Answer 5

i dunno