2 for 1 outputs?

D n T

Senior Member
Im having a mental currently trying to build a solid state circuit that works like a change over relay but my brain is having a bad day.

I would like to use one output to control my H bridge.
I have a PWM on the low side of the H bridge.
The H bridge has 2 controlling inputs ( forward and backwards)
The PWM will control speed and stop.

I would like to have one on only when my chip output is high and the other on only when my chip output is low. (Like a flip flop I think, working like a changeover relay anyway)

I know it can be done but I can't work it out, Im stuck in a loop.
What is the circuit called?
 

Dippy

Moderator
Why don't you draw a rough diagram with the components as blocks.
A block schematic.
I nearly understand the description... but some bits are ambiguous.

"I would like to have one on only when my chip output is high...."
One what?

The student earns extra points for clarity.
.... bloomin' teachers :)
 

pete20r2

Senior Member
The output goes directly to 1 side, and goes to the other side through this.


This makes the two pins on the H bridge the opposite of each other, all the time.
 

KTarke

Senior Member
Usually, exact information is needed to give a exact advice...
That is why, "not-detailed" questions are not liked in the forum.

Fortunately (or UNfortunately) I think the same way as the one who asked: creative solutions could be given, without knowing everything:)

To the case: I understand, that the thing is to switch to different things from one output, and ensure, that "levels" do not matter (the other is "on" when Picaxe output is 1, the other, when output is 0. No matter of the exact voltages on the output line)

I suggest a simple (transistor driven, ofcourse) switching relay! When Picaxe output is 0, the relay is in "resting" state, and relays secondary contacs are in one position. When Picaxe's output is "1", relay is driven, and it's secondary contacs are in the other position!
This is a foolproof way to get information to switch further circuits on and off!

I don't need to know, what kind the application is ,to give this advice.
(if I understood the need rightly, to have a flip-flop -effect from a single output, to two different actions.) Usually the most simple (=relay) way is the best.
 

D n T

Senior Member
H bridge driver

I am still considering using a changeover relay, that was my original idea but I thought that there had to be a way to do what I had asked.

I was considering using relays for the whole H bridge but I want to learn how to use transistors to do it, so this was it.

But yes K.I.S.S. is the best way
By the way, the contol transistor should be a BC 548 not a TIP36
 

pete20r2

Senior Member
You want to use a npn as the controller, you've got a pnp with the emitter connected to ground, I don't believe it will work like that.
 

vttom

Senior Member
I think your circuit diagram is a little more complicated than need be. I think the following is equivalent but uses fewer components...

Code:
                       ___
                        |
                    +---+---+
                    |       |
                    /       \
                  |<         >|
        +---/\/---|           |---/\/---+
        |         |\         /|         |
        |           |       |           |
DIR >---+           +-(   )-+           +---< /DIR
        |           |       |           |
        |         |/         \|         |
        +---/\/---|           |---/\/---+
                  |\         /|
                    >       <
                    |       |
                    +---+---+
                        |
                      |/
        PWM >---/\/---|
                      |\
                        >
                        |
                      -----
                       ---
                        -

               ___
                |
                /
                \
                /
                |
                +---> /DIR
                |
              |/
DIR >---/\/---|
              |\
                >
                |
              -----
               ---
                -
 

pete20r2

Senior Member
Haha, although it is incredibly cool that you did a schematic in ascii art (by hand?), It does make it a bit difficult to read, can you give us a clearer diagram, please.
 
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