# Multiple Button w/ Resistors

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• 03-04-2011, 12:09 AM
2k1Toaster
You need a pulldown to ground. You are basically floating an input which is an electrical no-no. So take a couple hundred Kohm resistor and tie it between the analogue input and ground.
• 03-04-2011, 12:14 AM
SKiTLz
Quote:

Originally Posted by 2k1Toaster
You need a pulldown to ground. You are basically floating an input which is an electrical no-no. So take a couple hundred Kohm resistor and tie it between the analogue input and ground.

Thanks for chiming in. You mean literally from the ground pin to the input pin?

I'm googling what you said so I can understand it, but just wanted to confirm that's what you meant.
• 03-04-2011, 12:21 AM
2k1Toaster
Quote:

Originally Posted by SKiTLz
Thanks for chiming in. You mean literally from the ground pin to the input pin?

I'm googling what you said so I can understand it, but just wanted to confirm that's what you meant.

Indeed I do.

Basically the FB's input is an empty bucket when you power it on. Then you press your button and it fills the bucket up to the level specified by your resistor divider combo. The FB reads the level of this bucket by skimming a bit off the top. (A very very very small amount, like a couple drops). When you disconnect your button that bucket is still full. What you need to do is poke a hole in the bucket. So when the button dumps in its goo, it can drain away when disconnected. Now if you make this hole too small, it won't drain. If you make this hole too big, the button has to put more current (more pressure) to maintain the same level.

So pulldowns are a common occurance.

Alternatively, you can connect the input to power and ground the button through a resistor.
• 03-04-2011, 01:28 AM
SKiTLz
Well, I think I killed my brain. I can't get MDX to read any voltage now. Make you a deal. I'll buy another one if you can give me a diagram so I don't kill the next one.. :)
• 03-04-2011, 01:34 AM
2k1Toaster
Quote:

Originally Posted by SKiTLz
Well, I think I killed my brain. I can't get MDX to read any voltage now. Make you a deal. I'll buy another one if you can give me a diagram so I don't kill the next one.. :)

How EXACTLY did you hook it up and what values of what did you use.

Also, there is a thermal fuse on there. If the board looks dead, give it a few minutes to cool down and try again. You may have killed that output, but the brain should come back to life.

---------- Post added at 11:34 PM ---------- Previous post was at 11:33 PM ----------

And please tell me you were messing around with bare leaded components with a live device... :)
• 03-04-2011, 01:49 AM
SKiTLz
Ok the board appears to have come back to life. Looks like you called it..

Left side of Button -> 100ohm resistor -> +5V
Right side of Button -> Input
+5V -> 100k ohm resistor -> input

I see it lowers the voltage when the button isn't pressed, but pushing the button still does nothing.

I know i'm in over my head, but I will get it... Eventually.
• 03-04-2011, 01:52 AM
2k1Toaster
Quote:

Originally Posted by SKiTLz
Ok the board appears to have come back to life. Looks like you called it..

Left side of Button -> 100ohm resistor -> +5V
Right side of Button -> Input
+5V -> 100k ohm resistor -> input

I see it lowers the voltage when the button isn't pressed, but pushing the button still does nothing.

I know i'm in over my head, but I will get it... Eventually.

Are you sure you meant +5v on both of those?

When it goes dead like that, you shorted it. VERY bad. But protected against slightly.
• 03-04-2011, 02:04 AM
SKiTLz
Quote:

Are you sure you meant +5v on both of those?

When it goes dead like that, you shorted it. VERY bad. But protected against slightly.
Sorry.. I made a mistake. This is what I meant.

Left side of Button -> 100ohm resistor -> +5V
Right side of Button -> Input
+5V -> 100k ohm resistor -> Ground

That is how I interupted your bucket analogy. But that doesn't mean I got it right.
• 03-04-2011, 02:09 AM
dscustoms
You were supposed to hook the ground through the 100k ohm resistor to the input.

---------- Post added at 11:09 PM ---------- Previous post was at 11:06 PM ----------

The input has three pins. V+, input, Ground. Connect V+ to one side of your button, from the other side of your button connect your 100ohm resistor in series to your input pin. Then connect the input pin to the ground pin with a 100K ohm resistor (since its what you have).

right?
• 03-04-2011, 02:10 AM
2k1Toaster
Code:

``` +5v ---  |  |   > <    1Kohm to 250Kohm   > <  |  |  |--- Input  |  | ------ BUTTON ------  |  | --- GND```
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