Electronics help plz


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k, I need some help in the picture below is a schematic diagram of a logic probe.

"High" = Logic 1

"Low" = Logic 0

"high indicator" and "Low indicator" are LEDs

The problem is that I don't know how the "low indicator" LED light up without having the "high indicator" LED light up at the same time if the logic chip sends a "Logic 0" or "low" signal.

Please help

Thnax in advance :)

BTW, it's really hard to find a big electronics forum around the net. :pinch:

post-7-1073533956.jpg

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First off, the circuit should not be mixing the 5V for the LEDs with the 5V battery you have shown. If they are not the same voltage source (or at least have the same reference to ground) then the circuit will not work as intended.

As for the question, if the switch is set to High, as shown, you have a current path through the High Indicator LED's ground to the battery. The positive

When the switch is in the Low position, the voltage potential is from the Low Indicator LED's voltage source to the ground.

Actually, now that I look at it, there will also be a current flow on the right-hand side of your circuit during the transition times when the switch is neither High nor Low. Once contact is established, however, it forces the junction between the resistors to be the same potential as either the 5V or ground, and NO current will flow on half of the circuit (only on the side with the potential.

Hope This Helps,

Mark

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When the switch is in the Low position, the voltage potential is from the Low Indicator LED's voltage source to the ground.

Thanks for your reply, but the current can only go in one direction.(From High indicator to Low indicator) Because the LED is a diode, which controls the direction of the current. The direction that the triangle is pointed at in the diagram means that the current cannot flow to same direction as the triangle is pointing at.

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Thanks for your reply, but the current can only go in one direction.(From High indicator to Low indicator) Because the LED is a diode, which controls the direction of the current. The direction that the triangle is pointed at in the diagram means that the current cannot flow to same direction as the triangle is pointing at.

I'll come up with diagrams that show what I am talking about....

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Hey... How do I post the images nice and in-line like you have your original post?

The IMG tag seems to want to use a URL, and I don't want to have to upload these to some cheesy website, just to link to them. I want them included in the post... Maybe I am missing something... :wacko:

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Screw it... :crazy:

Here they are... one at a freaking time...

Switch in "High" position...

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Switch in transition (Open). No voltage supplied by switch. In this case, current will flow from ground to +5 on the right side, through BOTH resistors, cutting current way down...

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