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  #1  
Old 04-13-2012, 07:45 PM
DiodeTech DiodeTech is offline
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Bumper switch info error

On the vex product page: http://www.vexrobotics.com/products/.../276-2159.html
it states in switch info that the switch is normally open, but states next in the signal behavior:

"When the switch is not being pushed in, the sensor maintains a digital HIGH signal on its sensor port. This High signal is coming from the Microcontroller. When an external force (like a collision or being pressed up against a wall) pushes the switch in, it changes its signal to a digital LOW until the switch is released. An unpressed switch is indistinguishable from an open port."

Are HIGH and LOW switched in this part? My understanding of high and low is that high is powered and low is off. Is this my understanding or a typo?
Thanks
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Old 04-13-2012, 08:01 PM
DiodeTech DiodeTech is offline
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Re: Bumper switch info error

Or is it high impedance and low impedance?
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Old 04-13-2012, 08:02 PM
jgraber jgraber is offline
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Re: Bumper switch info error

This thread is in the wrong forum, I'll flag it to ask that it be moved to community technical support.

The switch is normally open: true;
The cpu provides a pullup resistor: True;
The digital input value of an empty input port is 1 (due to pullup): true;
The digital input value of an input port with a switch (not pressed) is 1: true;
The digital input value of an input port with a PRESSED switch is 0: true;

Quote:
Are HIGH and LOW switched in this part?
No.

Quote:
My understanding of high and low is that high is powered and low is off. Is this my understanding or a typo?
The piece you might be missing is that the switch is connected between the input and Ground, so when the switch is closed/pressed, it shorts the input to ground = 0, to override the pullup resistor default power = high = 1.

This is common in electronics, sometimes called "active low", because it is easier for some electronic technologies to short to ground than to provide power.
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Old 04-13-2012, 08:03 PM
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MetalJacket325 MetalJacket325 is offline
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Re: Bumper switch info error

I'm not sure about high and low but, in easyC a pressed bumper reads 0 and an unpressed one reads 1
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Old 04-13-2012, 08:10 PM
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RoboDesigners RoboDesigners is offline
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Re: Bumper switch info error

Quote:
Originally Posted by jgraber View Post
The digital input value of an input port with a switch (not pressed) is 1: true;
The digital input value of an input port with a PRESSED switch is 0: true;
In ROBOTC, this is reversed...
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Old 04-13-2012, 08:24 PM
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MetalJacket325 MetalJacket325 is offline
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Re: Bumper switch info error

Quote:
Originally Posted by RoboDesigners View Post
In ROBOTC, this is reversed...
The reversed way (1=pressed, 0=not) makes more sense, that's one thing in easyC that bugs me
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Old 04-13-2012, 08:43 PM
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jpearman jpearman is offline
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Re: Bumper switch info error

Quote:
Originally Posted by RoboDesigners View Post
In ROBOTC, this is reversed...
Yes, it depends if you set the sensor as a "Touch" sensor or a "digital in" sensor. Digital in works the same as EasyC, 0 = pressed. The touch sensor reverses this and 1 = pressed. I find it sort of annoying to be honest but guess it makes sense.
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Old 04-13-2012, 08:44 PM
DiodeTech DiodeTech is offline
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Re: Bumper switch info error

Quote:
Originally Posted by jgraber View Post
This thread is in the wrong forum, I'll flag it to ask that it be moved to community technical support.

The piece you might be missing is that the switch is connected between the input and Ground, so when the switch is closed/pressed, it shorts the input to ground = 0, to override the pullup resistor default power = high = 1.

This is common in electronics, sometimes called "active low", because it is easier for some electronic technologies to short to ground than to provide power.
Thanks for the quick replies. It appears the confusion lies in the fact it is not solely a basic switch circuit. I think I understand now, but pulling resistors is a little beyond by electrical engineering knowledge. Sorry about the wrong forum, I was debating if it was a question about the website or the switch itself.
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