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Author Topic: IC that takes HIGH in and outputs GND  (Read 764 times)
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NEWBIE WARNING: THIS IS PROBABLY REALLY SIMPLE AND OBVIOUS, BUT I AM STILL A BEGINNER AND DONT KNOW WHAT TO DO

I can't seem to find an IC that will do this. I have found stuff on open collectors and low side switching, but I don't fully understand what these are so I am not sure if they are what I am looking for.

Basically, I have a button that when pressed connects to ground on a seperate IC (specifically the PIC18LF2550). This GND signal is registered as a pushed button, and an action is performed. I wish to emulate this button with the arduino, but when I use the GND on the arduino, the IC does not register the input as  GND and does not perform the desired action. Also, the way I am using the PIC requires that I do this weird ground switching thing, so there is no designing a whole simpler solution (if I could do that, this wouldn't be so hard).

So what I am looking for is an IC that I can provide a relative GND to from the PIC18LF2550 and will output GND signals for every high input I give it. I don't care what it does with other inputs. I just want it to take high inputs and take them to the PIC's GND. Something like this, where the green is high, black is low, and red/pink is GND relative to the PIC.


(sorry for the crappy picture)

Any help would be greatly appreciated =)
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IC that takes HIGH in and outputs GND
That would be an inverter, such as the 74xx04.

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but when I use the GND on the arduino, the IC does not register the input as  GND and does not perform the desired action.
This I don't understand.

Do you have a button that you want to work with both the PIC and the Arduino at the same time? Are you replacing the PIC with an Arduino?

Do you want a logic HIGH on the Arduino input to be transferred to a logic LOW on one of its outputs?

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Rob
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The way I read your question you are simply having trouble detecting a SPST (the simplest switch) button push "event".  To use a SPST button you need to connect the Arduino's internal pull-up resistor to the input, put the swtich between ground and that input, and detect when the input goes LOW.  When it is HIGH it is in the unpushed state.  A full tutorial is here:

http://www.arduino.cc/en/Tutorial/button

If this is indeed what you want to do an inverter will not help, it will invert your problem but you will still have the problem.
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but when I use the GND on the arduino, the IC does not register the input as  GND and does not perform the desired action. Also, the way I am using the PIC requires that I do this weird ground switching thing,
You need to connect the ground on the arduino to the ground on your PIC and the you can get an arduino output to act as the input for the PIC.
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Put another way if you don't common the grounds you are trying to use one circuit as a radio-antenna for the other!!  The word "circuit" means just that.  Every signal wire needs a return path, by convention we keep things simple and share that path for all signals and call it "ground".
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As I have come to expect from Grumpy_Mike. Your solution works perfectly. Mind explaining to me how this magic works?
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Yeah well done, how you deciphered dirtshell's original post I have no idea smiley You must have done a lot of teaching.

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Rob
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Mind explaining to me how this magic works?

How about a quick answer without much elaboration.

It is the magic of a closed circuit versus an open circuit and voltages with a common point of reference.


* circuit.jpg (94.64 KB, 818x902 - viewed 13 times.)
« Last Edit: November 09, 2012, 01:32:50 pm by pwillard » Logged

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Mind explaining to me how this magic works?
Try this:-
http://www.thebox.myzen.co.uk/Tutorial/Power_Supplies.html

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You must have done a lot of teaching.
Well only 21 years of it at University.  smiley
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