Converting

daba said:

I'm going to ask if anyone on the forum actually knows what "NPN" and "PNP" are acronyms for, both the "real" ones, and the "colloquial" ones.

Don't give it away just say "Yeah" or "Nay"

Once you understand the terminology, you can quickly ascertain where your "sources" and "sinks" are, as the acronyms are nearly always applied to the configuration of the output stage of the device....

Click to expand...

Yes, but it is more fun to say
PNP is PuttiNg out Positive - switched voltage
NPN is Not Pointing iN - emitter diode direction

I also use it as a reference for what I want to use in my systems.

PNP = Permitted
NPN = Not Permitted

daba said:

I'm going to ask if anyone on the forum actually knows what "NPN" and "PNP" are acronyms for, both the "real" ones, and the "colloquial" ones.

Don't give it away just say "Yeah" or "Nay"

Once you understand the terminology, you can quickly ascertain where your "sources" and "sinks" are, as the acronyms are nearly always applied to the configuration of the output stage of the device....

Click to expand...

I definitely know the colloquial terms, however I'm not sure if the ones I think are the real ones are actually the official real ones.

I give up..

PNP = Positive Negative Positive (Positive switched - Negative is common)
NPN = Negative Positive Negative (Negative switched - Positive is common)

PNP = "Pack 'N Play" (we have a 7mo at home...)

PNP = Positive Negative Positive (sourcing)
NPN = Negative Positive Negative (sinking)

Tell your instructor to get a sensor that can do both next time, then he won't need a special card to convert them.

Use an SCP instruction to scale your conversions.

And like the rest said, open up your software and your book and try it yourself for a bit first. You might realize that you could answer your questions faster on your own than waiting for one of us smart mouths to miss the fact that you're just trying to get out of homework

no offense.

I "literally" "lol('d?)" when I saw this from the OP's last post looking for help about a homework question on the difference between inductive and capacitive sensors

"Please don't send me boring google links, I am looking for passionate and interesting answers!!"

^ Future of our society right there. Hope you're ready!

Adeline said:

Hi there, Does anyone know how a NPN sensor can be converted into a sourcing sensor? Can you describe in detailed lament terms how a PNP sensor can be converted to sinking. Are there any drawbacks to these techniques?

Anyone know what equations to write that could be programmed into a controller for the following conversions:

a) 4-20 mA to 0 to 100 gallons
b) 0-10V to 0 to 100 gallons
c) 4-20mA to 50 to 500 pounds
d) 4-20mA to 13 cfm to 26cfm (gas flow)

Click to expand...

x-x1 divided by x2-x1 is equal to y-y1 divided by y2-y1 is the formula

x is input value
x1 input low
x2 input high
y output scale value
y1 output low
y2 output high

LoganB said:

PNP = Positive Negative Positive (sourcing)
NPN = Negative Positive Negative (sinking)

Click to expand...

I'm not convinced that PNP == Sourcing and NPN == Sinking.

Are you talking about the output stage of the device, or the input stage of the input module ????

That's where it gets confusing for many people...

A PLC Input could be "Sourcing" which requires the field device to be "Sinking". Generally the PLC Input will be "pulled-high" by internal components, and the field device pulls it "low". This could be achieved with an NPN or PNP transistor output stage in the external device....

A PLC Input could be "Sinking" which requires the field device to be "Sourcing". Generally the field device will be "pulled low" by internal components, and the field device pulls it "high". This could also be achieved with an NPN or PNP transistor output stage in the external device....

Take the external device out of the equation, a "Sinking" PLC Input needs a positive voltage applied to it by a "Sourcing" device (e.g. a switch to +ve).... And a "Sourcing" PLC Input needs the input to be connected to Input Common (e.g. a switch to 0V or common.).

Basic transistor structure

The transistor is a three terminal device and consists of three distinct layers. Two of them are doped to give one type of semiconductor and the there is the opposite type, i.e. two may be n-type and one p-type, or two may be p-type and one may be n-type.. They are arranged so that the two similar layers of the transistor sandwich the layer of the opposite type. As a result transistor are designated either P-N-P (PNP) types of N-P-N (NPN) types according to the way they are made up.
Transistor basic structure and circuit symbols The names for the three electrodes widely used but their meanings are not always understood:

• Base: The base of the transistor gains its name from the fact that in early transistors, this electrode formed the base for the whole device. The earliest point contact transistors had two point contacts placed onto the base material. This base material formed the base connection . . . and the name stuck.
• Emitter: The emitter gains its name from the fact that it emits the charge carriers.
• Collector: The collector gains its name from the fact that it collects the charge carriers.

For the operation of the transistor, it is essential that the base region is very thin. In today's transistors the base may typically be only about 1µm across. It is the fact that the base region of the transistor is thin that is the key to the operation of the device

Referring to the above, the transistor is in the output stage of the device (photo eye, prox, etc..) you are connecting to the PLC. So PNP is Sourcing and NPN is Sinking current.