# Logic signal conditioning question?

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 austrina5 years ago
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
qwerty156 (author)  Quercus austrina5 years ago
Yeah thanks i am testing this now, i had thought of theis earlier as well
5 years ago
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
lemonie5 years ago

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.

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qwerty156 (author)  lemonie5 years ago
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.
5 years ago

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)?

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Jack A Lopez5 years ago
This question sounds a lot like one of those Karnaugh map exercises.
http://en.wikipedia.org/wiki/Karnaugh_map
qwerty156 (author)  Jack A Lopez5 years ago
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.
iceng5 years ago
I don't understand the question.
qwerty156 (author)  iceng5 years ago
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.
Jack A Lopez5 years ago
A = 1 OR 3
B = 2 OR 4
C = 1 OR 4
D = 2 OR 3
5 years ago
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.
5 years ago
+1

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