This is probably a Duhhhh question for anyone who knows anything about electronics, but I'm not someone who knows anything about electronics. If I've got a bunch of wires hooked up to PNP inputs, and the I/O label says the input is sinking and the output is sourcing, how do I toggle them on and off? They're on (I believe) right now, when I have them hanging out in space not touching anything else. Touching them to ground produces all these errors that seem to indicate I shorted the circuit. Go easy on me, I know virtually nothing about electronics.
2006-12-29 05:43:55 · 4 answers · asked by manuelriliz 3 in Science & Mathematics ➔ Engineering
It would help to know what you are connecting to...
Because you mention I/O labels Sinking and Sourcing you may be dealing with A PLC (Programmable Logic Controller) .
PNP and NPN besides referring to transistor type, also mean the following in the PLC control world:
NPN (Sinking) - A PLC output that acts as an open circuit OR a connection to Ground.
PNP(Sourcing) - A PLC output acts as an open circuit OR a connection to a Power Supply.
Think of completing a circuit by SOURCING power from the power supply to a circuit OR SINKING by completing a power path to ground from the circuit.
To further confuse you, an input sensor may either SINK or SOURCE Its output which is connected to the complimentary input of the PLC (SINKING sensor output to a SOURCING PLC input)
To turn on/off a SINKING or SOURCING PLC output you must do one of the following:
1.) Have a program loading and running in the PLC AND satisfy the program logic to control the output. This means if you want to start a pump when you press a button the PLC is looking for a button press on the input and it will examine the program logic and activate the Output accordingly. If you have an input sensor connected to the PLC you will have to trigger the sensor.
2.) Use PLC programming software to communicate with the PLC and FORCE the output ON/OFF
2006-12-29 05:52:07 · answer #1 · answered by MarkG 7 · 1⤊ 0⤋
You don't mention what the rest of the circuit is or what an error is. PNP just means a transistor. If it is in a system with a negative ground and a positive supply then grounding the input should turn the transistor on. Then the output will source current from the positive rail that you can use to drive something, like a lamp or a relay with the other end at ground.
2006-12-29 13:50:10 · answer #2 · answered by Anonymous · 0⤊ 0⤋
I assume you are referring to PNP inputs on logic circuits (some variant of TTL). If so, the inputs will see a logic high if floated and a low if connected to ground. Allowing the inputs to float with wires connected make them susceptible to noise pickup. They should be pulled to VCC by a resistor, 2200 Ohms will work OK. In any case, long loose wires connected to logic inputs are prone to errors from noise pickup and ringing. For an excellent overview of designing with TTL logic see http://www.fairchildsemi.com/an/AN/AN-363.pdf .
2006-12-29 14:02:07 · answer #3 · answered by Joe 5 · 1⤊ 0⤋
If you could give a part number for the device in question, I might be able to help. The question is a bit vague.
Knowing what the device is that you are working with will really help. Email if you wish.
2006-12-29 14:41:50 · answer #4 · answered by Deirdre H 7 · 1⤊ 0⤋