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Logic signal conditioning question? Answered

I a robot i am building, i need to condition the signal as follows with any Microcontroller, only logic gates
If 1 is high then  A & C should be high
If 2 is high then  B & D should be high
If 3 is high then  A & D should be high
If 4 is high then  B & C should be high
Where 1,2,3&4 are inputs and A,B,C,D are outputs
No two inputs will be high a t the same time

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Quercus austrina (author)2011-11-09

Sounds like control for a H-bridge, and what you are running into is how to control A through D (in pairs) with 1 through 4. You have found that you cannot just tie the outputs together as they will activate the wrong outputs along with the right outputs. Try this:

For each number, split the signal and place a diode in line with each split signal. then connect the other ends of the diodes to the appropriate lettered output. For example:

       diode-A
1-<
       diode-C

So forth and so on. This will isolate the outputs from each other while still being controlled in the required pairs.

Remember, diodes will drop a small amount of voltage Si(licon) will drop between 0.6 and 0.7 volts, Ge(rmanium) will drop between 0.3 and 0.4 volts. If this affects the output adversely, you may need an additional driver before each control line "split". That (additional driver) is a solution for another day...

Qa

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user

Yeah thanks i am testing this now, i had thought of theis earlier as well

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user

Here's a sketch of what I was trying to convey. The diodes block reverse flow (backfeeding) to the other relays (A through D) connected through common pins (1 through 4), allowing each output to control the correct relays.

Qa

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lemonie (author)2011-11-08


I think it's more like you have decided to do something (what?) in a particular way (what?) and you're asking about some component that you've imagined, that you don't know how to make?
How does the logic fit into the rest of the machine?
I'll guess that this is a motor-control function.

L

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qwerty156 (author)lemonie2011-11-10

Basically i want to connect the out puts a cheap rc car to a relay h bridge.
The problem is that the rc car uses rack and pinion while i want the h bridge ot work in differential drive.

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lemonie (author)qwerty1562011-11-10


OK, so you want a left-centre-right function for the steering.
And you want forward-stop-reverse.
Or you want to convert one of those to the other?

How do the outputs a cheap RC car function in terms of +/- off and how do they normally control the RC car (so I understand what you've got already)?

L

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Jack A Lopez (author)2011-11-08

This question sounds a lot like one of those Karnaugh map exercises.
http://en.wikipedia.org/wiki/Karnaugh_map

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qwerty156 (author)Jack A Lopez2011-11-10

Never heard of it , i am gonna read up on it
Basically i want to connect the out puts a cheap rc car to a relay h bridge.
The problem is that the rc car uses rack and pinion while i want the h bridge ot work in differential drive.

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iceng (author)2011-11-08

I don't understand the question.

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qwerty156 (author)iceng2011-11-10

Basically i want to connect the out puts a cheap rc car to a relay h bridge.
The problem is that the rc car uses rack and pinion while i want the h bridge ot work in differential drive.

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Jack A Lopez (author)2011-11-08

A = 1 OR 3
B = 2 OR 4
C = 1 OR 4
D = 2 OR 3

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iceng (author)Jack A Lopez2011-11-09

That is why I'm confused. That, your reassertion table, is So Obvious.
You think that's what was his question ?
I was thinking he wanted a flow chart or a bunch of gates.
You have a good thought with the Karnaugh map.
As he is a member over 2 yrs.  I truly want to help if I can.

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frollard (author)Jack A Lopez2011-11-09

+1

If this is a motor controller, a relay or transistor h-bridge of dpdt switches can easily control most scenarios.

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