Design power supplies question

Go To Last Post
5 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Hello everyone.

I am designing a wireless remote control robot. The goal of the project is to send a wireless signal to a robot which will intern give left,right,forward, backward and speed control to the bot. There are going to be two robots that are going to be control. The first( alpha) is going to control the second robot.So the second bot is a duplicate of the second.

Here is my question: I am going to have a Xbee wireless module, motor control and control circuit. what will be a good advice for power distribution. should I give each or two module a separate power supplies?

question arise because I am designing a PCB board and is considering to run the motor controller, control circuit and the X bee all built on the same board. so power sharing and distribution( power rating for each module is different). I have two chargeable 7.2 v 7400mAH batteries.
Here are my power sharing ideas: Xbee and control circuit on same power supply. Motor controller on a separate motor controller

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I think that you may give them all the same (for logic), lets say 5VCC, but for motors, another, additional supply (many motor controllers use 5V for logic and other supply fo control). Possibly the same solution could be for Xbee.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

All from the same power supply??? are you serious? how long will the circuit run on 5v? at least motor controller will be power from an independence source motor.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

All on the same circuit - not a good idea. If your motor is being run with PWM then you'll have a lot of noise on the power lines, and if the grounds for the motor controller and XBee/other digital devices are connected you'll have noise problems which can lead to random hard-to-determine failures. The supplies should be isolated - the motor and XBee should both have their own and their grounds should only be connected at the battery terminals. Make sure you use big wide ground traces.

I'm making a robot as well and my powering scheme runs like this:
12V batteries run a 5V regulated supply that runs all of the digital electronics. The motor is powered by the batteries through an H-bridge, and the motor power path only interacts with the 5V power path at the battery negative terminal. This couples less noise into the 5V supply lines.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I'd suggest to use one switched-mode PS to generate to motor voltage out of your 7.2V batteries, and another, completely separate one (switched-mode as well) to generate the logic supply. This way you squeeze out much more AmpereHours out of your batteries than with linear regulators, and the ripple generated from the motor(s) would have to go backwards thru the first SMPS and forwards thru the 2nd SMPS before it could do any harm to your digital electronics.

That's how my robot is fed... (5V logic, 35V for the steppers, which are rated for 5 Volts, btw)

-- Thilo

Einstein was right: "Two things are unlimited: the universe and the human stupidity. But i'm not quite sure about the former..."