Line Follower and Voltage Regulators

Other Hardware Motors, Mechanics, Power and CNC
1

Hello,

I’m somewhat new to the whole microcontroller-electronics area and as a first project I decided to work on a line following robot and I’m facing some difficulties on deciding how many regulators will I use and if it’s necessary to use one or two. The parts that I’m definately going to use are the following:

Arduino UNO with a proto shiled on top with a mini breadboard attached
QTR-8RC IR sensors using all 8 of them
An ultrasonic sensor for obstacle detection
TB6612FNG Dual Motor Driver
2 HP Micro Gearmotor 900RPM
A 7,4 2S LiPo battery
Pololu 9V Step-Up Voltage Regulator U3V70F9
A 12V DC rocker switch to power on and off the robot
Pololu S7V7F5 5V regulator (not sure about that)

My question is the following. Is it possible-advisable to use only the 9V step up regulator to power the arduino UNO through the Vin pin using the onboard 5V regulator as well as the motor driver? So I will be having two outputs from the same regulator. This particular regulator has built-in reverse voltage protection so I think that there is no danger of back EMF and the motor driver has capacitor filters so there wouldn’t be a noise problem with the system. Or it would be better if solder two wires at the accessories prong of the switch one to power the 9V regulator and the other to power the Pololu S7V7F5 5V regulator? Then, I would power the motors from the 9V regulator and the arduino UNO from the 5V regulator through the 5V pin. I know that it’s not advisable to power the arduino UNO through the 5V pin, because it bypasses the onboard regulator but I would be using and external 5V regulator adding reverse voltage protection too using a P type MOSFET transistor so I don’t image that it would be a problem. I’m a bit confused about which approach to take and what are the benefits of the one over the other. I would like to add that the robot will only run for a couple of minutes every time, so could I just use a linear 5V voltage regulator with additional reverse voltage protection?

Thanks a lot in advance.

2

I can't say I understand your description. Perhaps you can post a diagram of what you propose. See this Simple Image Guide

Have you considered using a 3S LiPo as then you would not need a step-up circuit.

I think my own approach would be to use a 7805 voltage regulator to drop the 2S LiPo to 5v and feed that to the Arduino 5v pin.

If energy consumption is a concern then maybe you would be better powering the Arduino from a separate pack of 3 x AA cells (4.5v) connected to the 5v pin. That way there is no energy loss in voltage change.

...R

3

The step-up regulator will be used not only to step up the voltage but to keep the voltage always at a constant level...The behavior of the line follower will change as the battery keeps discharging, so I need the regulator to keep the voltage for the motors always at 9V to keep the performance the same at all times. Additionally, I want to keep the weight and the size of the line follower as small as possible and adding one more power source would be a step at the wrong direction. So using a 7,4V LiPo battery with a 9V step-up regulator seems to be the best solution. What I don't know is if it is possible and advisable to have two outputs from the same regulator, as long as that the motor driver filters out the noises that might occur from the motors and the regulator itself has reverse voltage protection to keep the arduino safe from a possible EMF from the rotation of the motors. One output powering the motors and the other powering the arduino through the Vin pin. The other option-scenario that I'm thinking is to have two voltage regulators, the same 9V regulator, but this time powering only the motors using it and one additional 5V regulator to power the arduino through the 5V pin. According to the official arduino uno manual, powering the arduino through the 5V pin is not advisable because it bypasses the onboard regulator, but I would be using an external with some additional reverse voltage protection with a P type MOSFET transistor, so I don't that it would cause any problem.I can't conclude on what is the best approach to take and what are the benefits of the one method over the other. I will draw a diagram of both the proposals and post it asap.

4

alexis_droso:
The step-up regulator will be used not only to step up the voltage but to keep the voltage always at a constant level...The behavior of the line follower will change as the battery keeps discharging, so I need the regulator to keep the voltage for the motors always at 9V to keep the performance the same at all times.

I suspect you will find it difficult to get a step-up regulator that can provide enough current for motors. And, in any case, I don't think you can rely on the motor speed being constant even if the voltage is.

Apart from that, please don't post long unreadable paragraphs with lots of different thoughts in them. Break up your text into paragraphs that each deal with the different thoughts. Like this ...

The step-up regulator will be used not only to step up the voltage but to keep the voltage always at a constant level...The behavior of the line follower will change as the battery keeps discharging, so I need the regulator to keep the voltage for the motors always at 9V to keep the performance the same at all times.

Additionally, I want to keep the weight and the size of the line follower as small as possible and adding one more power source would be a step at the wrong direction.

So using a 7,4V LiPo battery with a 9V step-up regulator seems to be the best solution.

What I don't know is if it is possible and advisable to have two outputs from the same regulator, as long as that the motor driver filters out the noises that might occur from the motors and the regulator itself has reverse voltage protection to keep the arduino safe from a possible EMF from the rotation of the motors. One output powering the motors and the other powering the arduino through the Vin pin.

The other option-scenario that I'm thinking is to have two voltage regulators, the same 9V regulator, but this time powering only the motors using it and one additional 5V regulator to power the arduino through the 5V pin.

According to the official arduino uno manual, powering the arduino through the 5V pin is not advisable because it bypasses the onboard regulator, but I would be using an external with some additional reverse voltage protection with a P type MOSFET transistor, so I don't that it would cause any problem.

I can't conclude on what is the best approach to take and what are the benefits of the one method over the other. I will draw a diagram of both the proposals and post it asap.

That way the reader gets a chance to draw a breath and allow his/her brain to pause and ponder. It is a good practice to read a text to yourself out loud to get a sense of how it will seem to others.

...R