Hello makers, if i run an outside +5 v lead into an analog input that is not powered or grounded to arduino, will it fry the pin? If so how can i work around the extra power?
No, but you'll get unpredictable results.
As a general rule, the external ground should be connected to the Arduino ground.
Without a common ground the 5V has no reference and no current path. So as far as the Arduino is concerned the 5V does not exist!
If you've ever used a voltmeter you know that you need two connections to measure the voltage difference between two points. Frequently, the negative/black meter probe is connected to ground but you can measure the voltage between any two points.
Power Linemen can touch a 500,000 DC volt power line as long as their feet are not on the ground.
LarryD:
Power Linemen can touch a 500,000 DC volt power line as long as their feet are not on the ground.
Have you seen the videos of linesmen getting from helicopter to the high voltage line? Quite spectacular arcing to the helicopter.
Weedpharma
I worked for a utility.
You have to wonder what's going through their minds.
About 500,000V
Weedpharma
Need clean pants.
new_rigger:
Hello makers, if i run an outside +5 v lead into an analog input that is not powered or grounded to arduino, will it fry the pin? If so how can i work around the extra power?
If a ground is connected as well it will parasitically power the Arduino and could cause latch up.
Never connect a signal into any unpowered electronics unless you have especially designed the electronics to cope. This normally involves some sort of isolation like an opto coupler.
What are you trying to do with this 5V?
Im running the ps_on wire from an atx mobo to the arduino to recognize when the comp is powered on or off.
I think we need a schematic you are not describing your setup nor what you want to do with it correctly.
The arduino would be recording when the comp powers on or off. While the comp is off, the ps_on wire from the psu is sending a constant +5v signal (high) when the comp comes on it sinks to a lower voltage. I was trying to use this wire and voltage change as a trigger, (like from a sensor)to signal the arduino to click its counter.the psu already has its ground to complete its circuit. The arduino has its powercoming from a 9v wall plug.
Im guessing i just need to create a common ground by running the psu ground to the arduino.
Did you know when the computer power comes back on and the computer connects to the Arduino's com port, the Arduino will reset?
Measure Power Good rather than PS ON. The latter only tells you whether something is trying to start the power supply, not if it actually started.
@grumpy the arduino will run independent not connecting to serial while comp is on and off.
@ syntax the pinout diagram i recieved said ps on was the on line and pwr_ok was the ready state. Once i figure out the ground issue ill try both to see if we are talking about the same wires.
Grumpy_Mike:
Did you know when the computer power comes back on and the computer connects to the Arduino's com port, the Arduino will reset?
That is if the Arduino is indeed connected to the USB port.
If it is, this is a good application for a Pro Mini and one of the really cheap USB adapters that does not include the RTS or DTR line!
Well, it is a perfect application for a Pro Mini anyway!
new_rigger:
@ syntax the pinout diagram i recieved said ps on was the on line and pwr_ok was the ready state. Once i figure out the ground issue ill try both to see if we are talking about the same wires.
PS_ON is the line that needs to be pulled low for the PSU to start; an input to the power supply. Power Good (or PWR_OK as you call it) is an output from the power supply, which will be pulled to 5 volts if and when all power supply lines are stable and within limits - this is basically what tells the motherboard that it's safe to boot.
syntaxterror:
PS_ON is the line that needs to be pulled low for the PSU to start; an input to the power supply. Power Good (or PWR_OK as you call it) is an output from the power supply, which will be pulled to 5 volts if and when all power supply lines are stable and within limits - this is basically what tells the motherboard that it's safe to boot.
As i understand it the ps_on will stay low until the power is off. It basically would be to show when the power button was pressed instead of stating the whole comp had booted. This allows me to put the arduino in a stasis loop before the entire boot process begins. Then when ps_on goes high again th arduino can resume its function. So arduino runs while comp is off, then arduino '"sleeps" while comp is on. Eventually i want to connect multiple mobo in this fashion, so the arduino can manage a network. This is also why i am trying to run it individually instead of just sourcing power from the psu +5vsb line.
Paul__B:
That is if the Arduino is indeed connected to the USB port.If it is, this is a good application for a Pro Mini and one of the really cheap USB adapters that does not include the RTS or DTR line!
Well, it is a perfect application for a Pro Mini anyway!
This is my first arduino. I havent actually researched all the different boards yet. I just jumped in and said this will be fun!
new_rigger:
As i understand it the ps_on will stay low until the power is off. It basically would be to show when the power button was pressed instead of stating the whole comp had booted.
It will stay low until the power is off, yes. It will not directly reflect the button presses though; the motherboard has some circuitry in between. It's perfectly viable to detect this way and under normal circumstances there shouldn't be a difference between PS_ON and Power Good except for inverted logic levels and maybe a few hundred milliseconds of delay.
I just thought it preferable to sense the actual function of the power supply rather than the intended function of it.