Ultrasonic vs Infrared for Collision Avoidance

[Shipton]

So I'm looking to buy a sensor for a robot that's going to incorporate collision avoidance. At first I was looking at the Sharp GP2D12 IR rangefinder to use for input, but truth is, I'm not sure that IR would be better or ultrasonic.

Anyone have any suggestions? And if you don't mind, if you could explain why one is better vs another?

By 'collision avoidance' I mean the robot will have to avoid other robots as well as obstacles.

 

[dknguyen]

So I'm looking to buy a sensor for a robot that's going to incorporate collision avoidance. At first I was looking at the Sharp GP2D12 IR rangefinder to use for input, but truth is, I'm not sure that IR would be better or ultrasonic.

Anyone have any suggestions? And if you don't mind, if you could explain why one is better vs another?

By 'collision avoidance' I mean the robot will have to avoid other robots as well as obstacles.

Personally, I prefer ultrasonic. Longer range and lower minimum range than sharp IR and you can do more with with ultrasonics (well, you can if you build your own fancy ultrasonic ranger with fancy signal processing and all that). It's downfall is when there is wind though.

Also a preference thing due to time-of-flight for ultrasonic vs parallax triangulation for IR.

 

[Shipton]

Thanks for the speedy reply. Any specific models in mind (please nothing too expensive - I was aiming for about $30/sensor max!)?

I plan to order off of RobotShop - Personal and Professional Robots, Robot Parts, Robot Kits, Robot Repair.

 

[ParkingLotLust]

Ive heard good things about these, but Ive never personally used them:

SparkFun Electronics - Ultrasonic Range Finder - Maxbotix LV-EZ1

 

[dknguyen]

Ive heard good things about these, but Ive never personally used them:

SparkFun Electronics - Ultrasonic Range Finder - Maxbotix LV-EZ1

Sensors

Devantech also has good ones here too.

 

[Shipton]

Question regarding using serial sensors;
I'd like to use 2 sensors on my robot, but I'm using a single PIC24HJ32GP202 to drive it.

I noticed, forinstance, the Maxbotix component up there is RS232. Does that mean I have to hook it up to the UART, or can I drive serial data, such as RS232, to an input pin?
If it does have to go to the UART, does that mean I can only have one sensor per pic?

And when it refers to the outputs being either "serial or TTL," does the TTL mean it only puts out HI/LO if it detects something in range, or can it encode bits?

 

[Shipton]

Additionally, where would I find information on using these sensors, i.e. hook up and implementation, as well as PWM and the ilk?

 

[Shipton]

Can anyone help with this please?

 

[joemcder]

I use the popular Devantech SRF08 Ultasonic Rangefinder. It detects up to 8 targets (echo returns). Of course it only provides distance, not angle. Some people mount them on a servo to scan the environment like radar. The interface is I2C which is supported by almost all microcontrollers. By the way serial & usb interfaces are intended for connecting to your computer. Most microcontroller projects use I2C or SPI, including your PIC chip.

I have used both Ultasound & IR reflectance. Which is better depends on the application. IR is basically on/off but has advantage of a wide angle. Using two IR emitters & sensors gives a pretty good idea of location. Ultrasound is a narrow beam & often requires servo scanning but can return distance info.

A good eample of the IR approach: **broken link removed**

 

[scott@maxbotix.com]

Question regarding using serial sensors;
I'd like to use 2 sensors on my robot, but I'm using a single PIC24HJ32GP202 to drive it.

I noticed, forinstance, the Maxbotix component up there is RS232. Does that mean I have to hook it up to the UART, or can I drive serial data, such as RS232, to an input pin?
If it does have to go to the UART, does that mean I can only have one sensor per pic?

And when it refers to the outputs being either "serial or TTL," does the TTL mean it only puts out HI/LO if it detects something in range, or can it encode bits?

Thank you for your interest in our MaxSonar products. The MaxSonar sensor have RS232 output for direct interfacing with a PC and most RS232 devices. TTL output can be achieved by inverting the RX pin output with an RS232 converter like the MAX232. Many users have run multiple sensors per PIC, it depends on the number of inputs the PIC has.

You may click this link to view view the downloads page. There is multiple sensor configuration, data sheets and other documentation available. https://www.maxbotix.com/downloads.html

Serial vs. TTL
Serial output is the general term for the output. The two common formates are RS232 format or TTL format.

Did this information help? If you have any other questions, please send an email to scott@maxbotix.com.

Best regards,

Scott Wielenberg
Technical Support & Sales
of MaxBotix Inc.
Phone: (218) 454-0766 Ext. 2
Fax: (218) 454-0768
Email: scott@maxbotix.com
Web: Maxbotix Home- MaxBotix Inc., High Performance Ultrasonic Range Finders and Industrial Grade Ultrasonic Sensors