VNH5019 Motor Driver Vin

Support Motor controllers/drivers and motors
1

Product: pololu.com/product/1451
The product page shows Vin 5.5-24V as the motor power supply and the operating voltage.

  1. Does this mean that this Vin also provide power to the motor carrier board itself?
  2. My understanding is that the motor power supply voltage depends on the motor. If that’s correct, does it mean that this board can only be used for motors that have the voltage operating range of 5.5V – 24V?
    Thanks.
2

Hello.

On that motor driver, VIN is the power supply for the motor and also the logic portion of the chip. The VDD line shown in the minimal wiring diagram on the product page pulls the ENA and ENB pins high (via resistors), which enables the chip. If you are using something like an Arduino to control the driver, there is generally a logic level supply (typically 5V or 3.3V) on the board that you can use to power VDD on the motor driver carrier.

This motor controller effectively lowers the voltage that the motor sees by controlling the PWM duty cycle. It is possible to use a higher voltage power supply than the motor’s maximum voltage rating and limit the maximum duty cycle to effectively limit the voltage seen by the motor.

-Nathan

3

Hi Nathan,
Thanks for the reply.

  1. Do I need to connect both VIN and VDD to power the motor driver board? Can I use only VIN without using VDD, as you pointed out that VIN also powers the logic portion of the chip?

  2. I have a DC motor with a voltage range of 1.5V – 6V. Can I use any voltage between 1.5V and 5V on VIN (i.e. less than 5.5V, the minimum listed in the product spec)? Or VIN has to be between 5.5V – 24V?
    Thanks.

4

You will need to power VDD for the chip to drive a motor. VDD is connected to the two enable pins on the chip, which are used for fault protection and will disable the driver if left disconnected. The minimum input voltage for VIN is 5.5V and I would not expect this board to operate if VIN is less than 5V. In general, you should not expect electronics to work if they are supplied with a voltage outside of their operating range.

The speed of a motor rated to run between 1.5V and 6V will vary with the voltage over that range. Typically, a motor driver like the VNH5019 would be used because it allows you vary the effective motor voltage (and the speed) over a range like that by varying the duty cycle of the signal on the input pins. A typical application might use a 6V power supply on VIN and a 50% duty cycle square wave on the PWM pin to run the motor at a 3V.

If you tell me more about how you plan to use the driver, I might be able to help you out more specifically with your connections and tell you if what you are planning sounds reasonable.

-Nathan

5

Project: use a motion sensor (sparkfun.com/products/11113).

I understand the VDD now.

My questions are about VIN:
I have 8 x AA rechargeable batteries (approx. 9.6V).

  1. Can I connect VIN to this 9.6V without damaging the vibration motor? My guess is yes as long as the OUTA and OUTB is less than 6V, which means the PWM duty cycle is less than approx. 62.5% (6V/9.6V), correct?
  2. In general, how do I determine what voltage to use on VIN?

Thanks.

6

Hello.

You are correct. Connecting the 6V maximum motor with 9.6V on VIN and limiting the duty cycle to about 62.5% should work. In general there is some flexibility in choosing the voltage for VIN on these drivers. Typically, you would use the highest voltage you wish to run your motors at for VIN, but if other components in your system make that inconvenient, limiting the maximum duty cycle of the motor driver is a safe option.

-Nathan

7

Thank you, Nathan.