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Battery for stepper motors and controller

balearicdynamics

Hi to all. The scenario is the following: by one side there is a couple of stepper motors (running on 4.5 Vcc.) and by the other there is the 5 Vcc needed to power the controller board (consuming very few current, i.e. 150 mA). So, there will be two different power lines. To get them from a single battery (e.g. 2A LiIon rechargeable battery), is it sufficient splitting the battery power supply, one to the motors and one to a 5V power regulator to power the controller?

 

Thank you in advance image Enrico

  • 0

    Hi Enrico!

    That does work, but sometimes people do have issues with it because of noise or volt drop. Motor power varies a lot too since they are so diverse. An electrolytic cap very close to the motors will help during the motor stepping. Also a 100nF capacitor in parallel there.

    Plus, separate wires from as close to the battery as possible to the motor circuitry, and separate to the microcontroller circuitry.

    Finally, loop the supply wires close to the circuitries a few times with ferrite to present an impedance to high frequency noise.

    You can see similar techniques used in the Infineon DC motor control shield, which uses a large electrolytic across the H-bridge.

    The XMP-2 design here ran on 6xAAA batteries in a similar method as you describe.

  • 0 in reply to shabaz

    Hi Shabaz image Thank you for your answer and precious support. Your blog post is one that I followed during a period that from here was impossible to like and bookmark. In this project I will use camera batteries for various reasons, including that are more compact, reliable and cheap with good rechargeable options. The power section is not included with the boards, first because the user can decide to manage these controllers as he want (you will see a specific post soon) and second because the power unit should be an independent component in the project. Do you think that a classic circuit based on LM7805 may fit well or something more sophisticated should be used ?

     

    Enrico

  • 0 in reply to balearicdynamics

    Hi Enrico,

    What is the battery voltage? The '7805 needs around 7V from memory. Anything much higher will likely need a heatsink given typical SBC current requirements, but should work fine. For my scenario, I had 6xAAA i.e. 9V, so I just used a DC-DC converterDC-DC converter to get the 5V for the circuitry (the motors H-bridge was powered directly from 9V, the rest needed 5V), since for my scenario the linear regulator would have resulted in having to change the 6xAAA primary cells too often!

  • 0 in reply to shabaz

    Shabaz, I attach three images of the kind of batteries that I mean. Not super powerful but I know them very well and are very realiable. Voltage is 7.2 V that is ideal for 5V (or 3V) based devices and has a form-factor that is easy to make 3D printer cases and connect two or more of them (but in this case it is not need to add so much batteries) in series. Just like Canon do to power the cameras. What do you think of this solution ?

     

    BTW did you released the circuit of the power secion of your robot ?

     

    Thank you. Enrico

    image

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  • 0 in reply to balearicdynamics

    Hi

     

    That's a very great idea for batteries!! : ) I've not thought about using camera batteries before. How do you connect to it, pogo pin type solution, or 3D-print some holder for it?

    The 7805 should work fine I think, provided cell voltage under load is around 7V or more for a reasonable length of time for your use-case (I'm guessing it will be).

  • 0 in reply to balearicdynamics

    I didn't have a schematic for the XMP-2 supply section, but I've added some more detail at that page showing close-up photos of it - not a lot to it, just the DC-DC converter mentioned earlier and a few bits and pieces.

  • 0 in reply to shabaz

    I think that using 2 1800 mA camera batteries (that is the pack that is sold on Amazon for just 15$) is a good choice for a reasonable period of time. Instead for the 7805 I already have used and provided circuits for power regulators, also with something more sophisticated with less thermal dissipation than the 7805. Anyway I though to this component as to the other side there are few LEDs and a low power PSoC 4 so the real power consumption is low. But I am not an expert (less less than expert) on battery power supplies.

  • 0

    I know I am of a minority opinion on this, around here, but I recommend establishing an isolation boundary between your logic circuit and your motor circuit, such as optoisolatorors.  This way you can worry less about spikes.  Who knows the future?

  • 0 in reply to D_Hersey

    This sounds good. To be honest I also though to this option but the entire project will be supported with relatively low power motors, i.e. 5 V 1A max steppers Nema 17 1.8 Deg 200 steps per rotation with a torque of about 2 Kg. The main board will be PSoC4 that hss a reasonable number of well designed protections so I am not sure if adopting optocouplers maybe worthy or not.

     

    Where do you suggest to put the optoisolators ?

     

    Enrico