go_away

Author Topic: Transmitter questions  (Read 1011 times)

0 Members and 1 Guest are viewing this topic.

Offline macadameaneTopic starter

  • Beginner
  • *
  • Posts: 3
  • Helpful? 0
Transmitter questions
« on: July 01, 2010, 01:18:25 PM »
I recently found the item below for cheap:
http://www.vexrobotics.com/products/accessories/control/276-2153.html

It includes a 75 Mhz transmitter.  I  am looking for a simple robotics solution for some older teen scouts that would like to build some basic robots, and we have a limited budget.  We would probably be building two robots.  My understanding is that the receiver included only works with vex's microcontroller, so I would probably have to buy separate receivers to control the servos.  But these transmitters are cheap (in both senses of the word).

Will some standard 75 Mhz receivers work fine with this?  Such as this:
http://h1071118.hobbyshopnow.com/products/description.asp?prod=HRC22175

I'm not sure exactly how it all works as far as pairing (or getting) the two to work together.  Any help at all would be appreciated.  Thanks ahead of time.

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Transmitter questions
« Reply #1 on: July 03, 2010, 07:02:45 AM »
Hi,

It includes a 75 Mhz transmitter.
Well, it IS a transmitter, so it should  ;D


My understanding is that the receiver included only works with vex's microcontroller, so I would probably have to buy separate receivers to control the servos.  But these transmitters are cheap (in both senses of the word).
I'm not sure whether you mean transmitters or receivers here. Do you have a receiver for the VEX allready or what?


Will some standard 75 Mhz receivers work fine with this?  Such as this:
As far as I know, the VEX uses standard R/C signals, so it ought to work.
But if you have VEX receivers...Just let the signals into whatever microcontroller you'll be using and let it control servos through that.
Lots of pages dedicated to the signals from a VEX can be found on the net.


I'm not sure exactly how it all works as far as pairing (or getting) the two to work together. 
"Pairing" is by using the same color coded crystal in each (in a pair, one is for TX and one for RX - don't get them mixed up, or it won't work).
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline vinito

  • Full Member
  • ***
  • Posts: 101
  • Helpful? 6
Re: Transmitter questions
« Reply #2 on: July 03, 2010, 08:37:51 AM »
Quote
It includes a 75 Mhz transmitter.  My understanding is that the receiver included only works with vex's microcontroller, so I would probably have to buy separate receivers to control the servos.  But these transmitters are cheap (in both senses of the word).

Compared to the dozens-o'-channels transmitters available for RC today, yea the Vex ones are fairly basic, but it's a decent product. Not terribly cheapified.

The receiver included has a pinout which can be found on the net easily. Not as easy to find, but also out there is an explanation of how to take the signal streamed out of the receiver and run it through a circuit to control servos. It's not a badly complex project, but it does take a little to figure out. So no, the receiver WILL work with other microcontrollers. You just need to write code read the data pulses (it's just PWM) and make it do what you want with it. A worthy and educational project for sure.

In fact, the Vex receiver signal is all broken out and ripe for a robotics project, while a standard RC receiver would have to be hacked to get a microcontroller to be used with it somehow. It's a standard PWM signal for servos and your sharp scouts should be able to work together and figure it all out, especially if there is some experienced help.

Here's a basic explanation and maybe some simple Arduino code to start with:
http://profmason.com/?p=602

You'll want to read this (click on "Vex radio interface" and maybe other links there)
http://www.kronosrobotics.com/Projects/vexradio.shtml
A while back I wrote code (well... edited someone else's code to function anyway) and built a circuit to read the Vex receiver and control servos with an Arduino. The code was a little bit tricky - timing must be spot-on. The circuit was pretty simple. I think it's long gone now, but IF I can find it I'll post it here.

This is most useful and informative too:
Link

ANd here's one somebody did up with a pic:
http://profmason.com/?p=602

Quote
Will some standard 75 Mhz receivers work fine with this?


It's reported that most Futaba receivers will work with the Vex transmitter, but not all of them and I'm sure other brands will work with it as well. Best to search the web and find out specifically which ones will work with it. You could take the Vex to a hobby shop and get them to help you mix & match things to see which receiver(s) will work.

But again, if you use a standard RC receiver, then you might as well just call it an RC project to begin with and not a "robot". By decoding the Vex receiver, you could make the wiggling of the transmitter knobs do whatever you wanted to do besides making servos change positions.
« Last Edit: July 03, 2010, 09:09:10 AM by vinito »

Offline macadameaneTopic starter

  • Beginner
  • *
  • Posts: 3
  • Helpful? 0
Re: Transmitter questions
« Reply #3 on: July 06, 2010, 09:41:34 AM »
This is a lot of great information, thanks.

Sadly, it IS more of an RC project.  My friend that is working with them competed at Robot Wars a few times, but has forgotten most of that with the passage of time.  I referred him here as a refresher course.  The other two leaders (which includes myself) are software engineers and would love to actually code some stuff up, but I really don't think our boys could get that technical.

They are driven by sports and won't get into the actual robotics.  We plan on covering it though.

If anyone is interested in the VEX transmitter and receiver at a really cheap price:
http://www.fcsurplus.ca/shopping/shopexd.asp?id=308003 ($39 for 6 channel transmitter and receiver)

I think we'll probably just get these.  Hopefully they don't break too easily:
http://www.robotmarketplace.com/products/0-GWS24TR.html


 


Get Your Ad Here

data_list