Increasing Voltage to Adafruit V1 Motor Shield

Discussion in 'Embedded Systems and Microcontrollers' started by Mpowley66, Jan 21, 2016.

  1. Mpowley66

    Thread Starter New Member

    Jan 7, 2016
    5
    0
    Hi all, I'm working on a robot that uses a V1 adafruit motor shield as its base. The shield uses 2 L293D dual H bridge drivers to drive the motors, and they are rated to handle currents of 0.6 A continuous. It has an internal mechanism to protect it by shutting down when it overheats. Here is a link to the datasheet. We are using a 7.2 V Nimh battery as a power source.
    http://www.ti.com/lit/ds/symlink/l293.pdf

    From the datasheet I found that the chip will drop 1.4 to 1.8 V at 0.6A so from that I would say that the resistance is 1.6V / 0.6A = "2.7" ohms
    So clearly this chip is not very efficient, but our competition mandates that we use it and that we can not hook it up to another H bridge so that we can handle more current.

    My idea was in order to provide more power to the motor without losing more power in the chip we would use a step up Dc-Dc converter to increase the voltage. Theoretically, lets say that we doubled the voltage to 14.4V. We want to buy metal gear motors from Pololu, so by doubling the voltage we could use the 12V series of motors instead of the 6V series. If we look at the 12V there is a High, medium and low power version with stall currents of 5.6A, 2.1A and 1.1A respectively. I was thinking of using the medium power 2.1 A series of motors, and then using chilled metal heat sink on the day of the competition to dissipate heat.

    Does my plan of increasing the voltage actually give me any advantage in terms of how much motor I can use?
    Do you think I can get away with using the 2.1A medium power motors if I run them off of different chips (1 motor per chip), they are not heavily loaded most of the time and I do some heavy duty heat sinking?
    Any other advice is always welcome!
    Thank you for your help and expertise!
     
  2. Mpowley66

    Thread Starter New Member

    Jan 7, 2016
    5
    0
    Would it make more sense to use the motors with the 2.1A or the 1.1 A stall?
    The robot will be quite light, so I don't think I will stall it much, but from what I understand of electric motors I may actually get better performance from the 1.1A version because I'll be able to push it harder without overloading the L293D.
     
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