Hi all,

I'm using an SN754410 H-Bridge and an Arduino to push an actuator.

To understand how they worked I read chapter 4 of the Exploring Arduino book, link: http://www.exploringarduino.com/content/ch4/

I put the circuitry together like the image below:


It worked perfectly, I also used the Arduino code from the book to push it forward and backward.

I recently had to use the bread board for another circuit and so I removed the circuit for the SN754410.

Now when I put it back, it no longer seems to work. It no longer pushes the Actuator.

These are some of the things I have tried and some of the observations:

• I tried changing the SN754410 chip for another, did not fix it
• I tried using pull down resistors for the INPUTS of the SN754410 (1_2EN, 1A, 2A) did not work either
• I have tried changing the pins of the Arduino, nothing

• I took out the actuator and measured the INPUTS(1_2EN, 1A, 2A) and OUTPUTS(1Y, 2Y) of the SN754410 with a volt-meter
  • 1_2EN works fine, it goes HIGH and LOW when the code tells it to
  • 1A and 1Y also work fine, they go HIGH and LOW when the code tells them to
  • 2A and 2Y are the ones that behave really weird
    • 2A only stays low and when the code asks for HIGH it only goes to 1.1V (This is with a pulldown resistor) when it should be going for 5V
    • 2Y always stays around 0.60V not matter at what 2A is at (This might be working fine since 2A never really goes HIGH)

I don't understand why it suddenly it stopped working, I've been looking around but haven't found anything that could help me solve it.

Here is the datasheet for the SN754410: http://www.exploringarduino.com/wp-content/uploads/2013/06/SN754410-datasheet.pdf

I am looking for any help on what I could be doing wrong or what is wrong, I am happy to answer any questions to clarify anything!/

Thank You!

 

I recently had to use the bread board for another circuit and so I removed the circuit for the SN754410.

Some times 'breadboards' don't have good contact with the components. If you used the same hole that your using now with a larger diameter lead on the second circuit build, it could have spread the clip enough that it doesn't make contact now. The inexpensive breadboards are more prone to this, the spring contacts inside them just aren't as "springy" as a better board.

 

2A only stays low and when the code asks for HIGH it only goes to 1.1V (This is with a pulldown resistor)

You shouldn't need a pull down on the arduino pin. It is possible that the resistor is too low a value and the arduino cannot drive it. Try this without the resistor.

 

Some times 'breadboards' don't have good contact with the components. If you used the same hole that your using now with a larger diameter lead on the second circuit build, it could have spread the clip enough that it doesn't make contact now. The inexpensive breadboards are more prone to this, the spring contacts inside them just aren't as "springy" as a better board.

Ok, I will try it on another breadboard and see how it goes.

I did try and make a pcb with this IC and still gave me the same problem, I though my pcb was wrong

 

You shouldn't need a pull down on the arduino pin. It is possible that the resistor is too low a value and the arduino cannot drive it. Try this without the resistor.

The resistor is 10k Ohm, I did try it without the resistor and the pin never went low, could the pin be broken?

 

The resistor is 10k Ohm, I did try it without the resistor and the pin never went low, could the pin be broken?

What voltages did you get without the resistor?

 

What voltages did you get without the resistor?

On 2A ~5.40V and on 2Y ~12.3V

 

On 2A ~5.40V and on 2Y ~12.3V

What voltage did you get on 2A when it was supposed be low?

 

What voltage did you get on 2A when it was supposed be low?

Sorry for the delay, when 2A is supposed to be LOW i am reading 2.10V I believe this is where my problem is

 

I think there are two possibilities.
1. That pin on the arduino is faulty.
2. The code driving that pin is setting the pin to float when it should be setting it to output a low level. Can you run the example code for flashing an LED and change the pin number in it to drive the pin that is connected to 2A and see what voltage levels you get. If this also fails to go low properly then it indicates the problem is the pin. However, if it does low properly this indicates the problem is with the software.

 

I tried switching the pin to different ones but no luck.

I've made another observation, 2A reads 2.10V only when I supply voltage to Vcc2 on the H-Bridge.

When there is no Vcc2 supply, pin 2A goes LOW and HIGH like a champ, the moment I put power on Vcc2, 2A has problems going low