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Author Topic: Arduino Powers on With Power Applied to Input Pin  (Read 2810 times)
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This is what I have in place now (I redid the whole thing with new resistors and new transistors to make sure I hadn't screwed it up). It now just constantly stays white (which means that all of the inputs are on)
Jay


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All the inputs will be hgh if you do not connect anything to the base of the transistor, if the points marked as 12V actually go to 12V and the inputs still read high then you have either failed to connect the grounds together, or you have miss identified the connections on the transistor.
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All of the bases are connected to the 12v source through a 10K resistor and also the ground through a 10k resistor. The emitter is connected to the same ground as the arduino. I will take voltage measurements later tonight.
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I'm getting 4.83 at all inputs... And even with a very solid ground it doesn't change. As far as I can tell, the voltage from the 5V feed is just going right into the signal pins because the arduino is offering it a convenient ground.
Jay
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If that is the case then it is not wired up like you think it is. If it is wired like you say the collector and thus the arduino input must be low, that is less than 1V.
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Mike,
I have triple checked the specs for the 2n2222 Transistors to make sure I'm on the right legs. I checked this morning and the voltage is going from the 5V feed directly into the input pins even when there is no feed from the 12V side. Even when I turn the switch on in one of the 5 12v lines, it doesn't change anything. I understand the logic and that what you described and instructed me to do should work, but it isn't and I can't figure out why.
Jay
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Mike,
The 5V output from the arduino. In your diagram the wire coming from the arduino doesn't just connect to the 3.3K resistor. What else does it connect to? I'm not familiar with reading these diagrams, as the saying goes, I know enough to be dangerous (obviously).
Jay
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Even when I turn the switch on in one of the 5 12v lines, it doesn't change anything.
How do you switch the switch ON?? Show it to us in the schematics..
« Last Edit: May 17, 2013, 06:30:27 am by pito » Logged

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The 5V output from the arduino. In your diagram the wire coming from the arduino doesn't just connect to the 3.3K resistor.
Yes it is just connected to the 3K3 resistor. The other end of the resistor is connected to one of the inputs and the collector of the transistor.

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I checked this morning and the voltage is going from the 5V feed directly into the input pins even when there is no feed from the 12V side.
Yes that is how it works. When you connect the 12V then this will cause the input pin to go low.

Have you connected up the grounds of the 12V and arduino?
http://www.thebox.myzen.co.uk/Tutorial/Power_Supplies.html

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but it isn't and I can't figure out why.
It is because somewhere down the line you are not doing what you think you are doing.
Can you post a clear photograph of your wiring?
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I got the best picture I could for this. Please understand that I am a complete novice to this.  smiley-red smiley-roll-sweat I know that it looks like they are close together, they are, but I know that no wires are touching that should not be and before the picture they were all separated by electrical tape to ensure they did not contact each other.

This is an automotive application so the 12V feeds are coming from the brake lights, the license plate bulbs, the turn signals and the reverse bulbs (5 inputs total, 1 for each type, left turn, right turn, brake, license plate, and reverse). The arduino is also grounded to the chassis (as are all other electronics) so I am assuming that this is sufficient for a common ground. The emitter is also connected to the chassis (a piece of sheet metal). The 5V from the arduino is coming from an output pin.

Thank you all for your help so far.

Jay


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Those transistors are the wrong way round. With the flat facing towards you the collector is on the left hand side.
I have attached the data sheet.

* 2N2222.pdf (241.62 KB - downloaded 9 times.)
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Lovely. At least its something stupid. I will correct that issue tonight and get back to you.  smiley-red
Jay
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I turned the transistors around with the same results.
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Bit of feedback on that photo: that's just a recipe for a short between some of those connections to develop.
Do yourself a favour and get a breadboard to test circuits, and some protoboard / blank PCB so you can lay it out on a bit of board.

Have you got 12V going in on your input? What's the arduino reading the pin state as (i.e. are you expecting high as On, instead of Low as On?)
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Due to the way that I had it set up originally I was expecting high to be on (ie: analog read is above 1000) will trigger the light to turn on. I should have posted my code as that would help clarify my confusion. I will correct the code and get back to you.

Also, a bread board is next on my list. I did enjoy the practice soldering but it was a bit too time consuming and wasted a few parts, but I chalk that up to the price of learning something new.

Jay
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