# Stepper-motor-driver

Hello! I recently bought a SN754410 h-bridge to control a dc-motor in both directions. It works fine, however the power of the motor is a bit to weak. The h-bridge can drive up 1 amp current between 4.5 and 36 volts, so in order to get more power I could use a battery with higher voltage, now I use 8.4 V or I could buy an h-bridge with a higher drive-current.

Do you know any better solution, maybe one where I can keep the current h-bridge?
If I need a new h-bridge, which 1 would you recommend? (I need about 4 volt current, and I control it with the Arduino pins => 5 V)?

Your title says stepper motor but your text says DC motor - which is it.

I am assuming it is a DC motor and NOT a stepper motor.

sinatra39:
The h-bridge can drive up 1 amp current between 4.5 and 36 volts, so in order to get more power I could use a battery with higher voltage, now I use 8.4 V or I could buy an h-bridge with a higher drive-current.

Are you getting 1 amp of current in the motor with your existing power supply? You don't say if 1 amp is sufficient.

If 1 amp would be sufficient but you are not getting that much then the only answer is to increase the voltage.

If you are getting 1 amp but it is not sufficient you will need a driver that can supply more current.

...R

Oh yeah, sorry, I was a bit unprecise with this one : ) , it´s an h-bridge for a DC-motor control but it´s apparently also possible to control a stepper-motor with it, since stepper-motor-driver is written onto the wrapping, haha.....but yeah. yeah, I measured the current and it´s 1 amp, I´d say from the perspective of performance the motor would need about 4-6 times more performance than it has now and since the electrical performance is proportional to the current, I´d say I need about 6 amps of current, so now I´m searching for a fitting h-bridge with operates at around 8.4 volts with a current of 6 amps and is controlable via the 5v Arduino logical pins via puls-width-modulation. Any suggestions?

I don't have any suggestions about a suitable H-bridge but Google should find plenty for you.

Don't be tempted to use a h-bridge to drive a stepper motor. It can be made to work but it is a poor alternative to a proper stepper motor driver.

...R

Describe what you need the motor to do. The applications rpm, torque and power needs and the motor ratings. A dc motor can be overloaded for short periods of time so increasing voltage beyond the rating is possible. And also driving a motor with rated voltage with too high mechanical load can damage it

Robin2:
I don't have any suggestions about a suitable H-bridge but Google should find plenty for you.

Don't be tempted to use a h-bridge to drive a stepper motor. It can be made to work but it is a poor alternative to a proper stepper motor driver.

...R

can you define a "proper stepper motor driver"

I think we all should agree upon that a current controlling microstepping controller with a high enough supply voltage is the proper way to drive a stepper motor. Of course there are other ways but they often are problem prone

The problem is that I basically don´t know anything about the motor-specifications, since the whole project is a completely rebuilt toy car, only with the "old" DC-motor still in it, but normally I drive it with a 8.4 volts batter at about 5 amps (if the maximum current through the h-bridge is too high for the motor, it´s no problem since I control the current-flow anyways via puls-width-modulation). I know this all sounds pretty nooby, which fits to me : ) but I need an h-bridge where I have a good documentation, like the SN754410 and which I can easily build onto the Arduino bread-board and which can drive a bit more currrent than the SN754410 (documentation here: http://www.ti.com/lit/ds/symlink/sn754410.pdf)

The whole purpose is basically just to drive with the moded car backwards and forwards => run the motor in different directions. As mentioned it would work perfectly with the SN754410, if it wasn´t too weak, haha

Changing the bridge alone won't help much. The current is determined by kvoltagetorque needpwm ratio(0..1) where k is a konstant unique to your system. And it is the current that causes losses in the form of heat since they are caused by i^2r. If you motor stays resonably cool its ok to increase voltage, if not, get a bigger motor.

driving the motor with PWM allows you to reduce the power, not increase it. once you get to 100% you cannot deliver more power.

if the old motor drove the car well, then your goal is to get that power out of that motor. if your circuit does not deliver the same performance, then the driving circuit or the software needs to be looked at.

dave-in-nj:
can you define a "proper stepper motor driver"

Easily. It's a driver specially designed for driving stepper motors.

...R

sinatra39:
but I need an h-bridge where I have a good documentation, like the SN754410 and which I can easily build onto the Arduino bread-board and which can drive a bit more currrent than the SN754410

What have you found with Google?

Pololu and Sparkfun each sell several different models.

...R

Thanks in advance for your answers, but there´s still one question remaining. In the datasheets of h-bridges is always a certain voltage-range and current-range. Let´s say in the data-sheet there is written that the h-bridge operates between 4.5 and 36 volts with currents until 1 amp. Does this mean that I get the maximum current of 1 amp only when the logical pins are completely switched and the voltage of the circuit is fully 36 volts or can I get 1 amp also with a lower voltage?

No, the H-bridge can withstand 1 amp at ANY voltage less than the maximum. If the motor was drawing 1 amp from 8.6v and you are PWM-ing 1 amp from a 32v supply then it should all be good.

The problem is that I have basically no clue about the motor, it´s basically an old rc-car which I disassembled completely, except for the motor and I use the chassis for a new project. Before I used the Arduino to control it, I used a pre-built modelmaking controller, which stands up to 30 amps and this worked perfectly.

But can someone explain me the basic concept of it. If there´s a volt and current range given in the datasheet of an h-bridge when does the given maximum current flow, do I have to put resistors on my own into the circuit or does the h-bridge do the complete job, if I´m in the voltage-range. For instance, if the datasheet describes an operation voltage of 4.5 - 36 volts and a current of up to 1 amp, do I get 1 amp with no resistors and JUST the h-bridge with a 36 volts supply or do I have to constrain the current to 1 amp in order to not damage the h-bridge like morgan described it? Thanks a lot by the way morgan for the quick answer.

The current drawn by the circuit will be determined by your motor and the voltage you apply to it. The H bridge just gives you the means to turn the power on or off.

If your motor draws more than the rated current for the h bridge at the voltage you supply, your H bridge will pop.

If your motor draws more than it's rated current at the voltage you supply, your motor will go pop.

If your power supply isn't capable of providing the current that your motor draws, at the voltage you are supplying, then, chances are, the voltage will drop accordingly. The power supply may then introduce some current limiting or, just possibly, pop.

But with my DC-motor and my 8.4 volts supply I obviously draw more than 1 amp without h-bridge but when I connect it to the h-bridge it works, without popping but it´s just damn weak even when I open the bases 100% , so there has to be some resistor in it, right?

Okay, I think I found the fitting motor driver for my purpose: Is this driver possible to be used by the Arduino board alone => ( Pololu - ST VNH3SP30 30A Motor Driver ) p.s. This is hopefully my last post on this topic, haha. Thanks for all the help!

From what I gather you only have a single motor? So you only need two outputs from the bridge.

Since the SN754410 has four channels you could double the output by using two channels in parallel for each side of your motor. This may be enough to get your project useable without having to pay out more money.