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Does an SN754410NE H Brdige need a microcontroller?

  1. Oct 28, 2015 #1
    A few months ago I asked about diodes for a basic low voltage H-Bridge. So I got the parts together. The first thing I did was to build a 5V voltage regulator, getting power from a 9V battery. I managed to build the regulator with no issues, it puts out 5mA and about 5V. I went ahead with the H-Bridge, the enable line for the side of the chip I'm using is tied to 5V power through a 1k resister, IC power and the motor power are also 5V but directly connected. The other enable line is tied to ground, as are all ground pins. The motor is connected to the motor pins, the main logic pin is tied to power. I connect the regulator to the circuit.....nothing happens. I break out my multimeter and found that there's no voltage to be found anywhere in either the H-Bridge circuit or the regulator, almost like there's some kind of broken circuit. I used the multimeter to check the connections, never found a broken one.

    All this makes me wonder if I'm missing something, should I have used a microcontroller or some kind of logic gate instead of connecting the logic directly to power? Or is there something else going on?
     
  2. jcsd
  3. Oct 28, 2015 #2

    Hesch

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    Gold Member

    The SN754410NE is just a 4 channel amplifier with some enable feature:

    http://pdf1.alldatasheet.com/datasheet-pdf/view/28616/TI/SN754410NE.html

    So you must connect some logical signals to the inputs 1A, 2A, 3A, 4A to be amplified. These signals can be made by some TTL-circuit or a μ-controller.

    You have not mentioned if you are using a stepper motor? but if you are, you can see some signals here

    http://www.ni.com/white-paper/14892/en/ [Broken]

    to be provided.

    At some instances the output signal is shown ( Fig. 6-19 ) to be 0V ( no current ). That's when you disable two channels.

    If you are using a DC-motor, you must provide some PWM-signal ( Pulse-Width-modulated signal ). The SN754410NE cannot distinguish between a 4V or a 5V signal, only between a high or low signal.
     
    Last edited by a moderator: May 7, 2017
  4. Oct 28, 2015 #3

    meBigGuy

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    First off, 5V at 5ma is not going to drive any motor I know of.

    Can you attach a schematic of the regulator and driver/motor? Also the motor specification.

    As Hesch said, an H bridge driver is just that. A driver. You need to supply non overlapping control signals to turn on the legs in the proper sequence without shorting.
    Depending on what motor you are using we can help with the motor control part.

    Need to know that you are trying to do, from a top level. Need variable speed? Stop/Go only, how fast, how slow, etc etc.
     
  5. Oct 30, 2015 #4
    Ok, so I am missing something. I think it might be a stepper, but I'm not totally sure because it doesn't say specifically, just gives a voltage range. So do all 4 channels need to be active or just the two for the side I'm using? Also, any recommendations for a simple micro controller?

    I don't have anything like that on computer, it's really just a 7805 with a couple small capacitors on pins 1 and 3. That amount of power is enough to run the motor, I plugged it directly in (yeah, bad practice) to the output and it spun like a top. It doesn't have any load and I currently don't intend for there to be any. All I'm looking to do with the motor is make it go forward and if I change the input in the right way make it go backward, that's it. I'm not looking for variable speed This is the motor I'm using.

    It's been a really really long time I've been in electronics, I'm doing this because I'm looking to get back into it and the best to learn is to do it. Thanks guys, I appreciate whatever help can be provided.
     
    Last edited by a moderator: May 7, 2017
  6. Oct 30, 2015 #5

    meBigGuy

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    This is a simple DC motor, but there is no information regarding the performance and current requirements. That is load and winding resistance dependent.

    You need to understand what the motor is actually drawing from the 7805. Does the 7805 get hot?

    It will pretty easy to drive it one direction, then in the other direction with the H bridge.

    if you connect the motor between 1Y and 2Y the following will control the motor

    Code (Text):
                 1A    2A
    Stopped      0      0
    forward      1      0
    reverse      0      1
     
  7. Nov 1, 2015 #6

    It doesn't seem that warm, I can't really tell if it's putting off that much heat, surely a good sign. On the other hand I didn't leave it plugged in for that long so maybe there wasn't enough time. Anyway, thanks for the truth table, looking into microcontrollers I think right now I'll go with making a TTL circuit. Thanks for your help, I'll give an update on the thread if it still doesn't work.
     
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