Subject:
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Lego R/C etc
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Newsgroups:
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lugnet.robotics
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Date:
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Mon, 12 Mar 2001 21:26:33 GMT
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Original-From:
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John Barnes <[barnes@sensors.]IHateSpam[com]>
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I'm sorry for the delay in being able to post on this subject.
I've been out of town for a couple of weeks, and will be away for
a few days this week as well. It's the busy season for me!
Here is the current state of the game;
I have built a few prototype devices, one of which appeared at the
Cheshire Legofest in the UK - thanks Jennifer for fielding the questions
for the last week or so.
This is the plan.
1. Build RF based motor controller with RS232 feature on the controller.
2. Build RF based sensor controller with RS232 feature on the readout
device.
3. Build combo RF unit with both motor control and sensor control.
4. Build "mega interface" for hardwired connection to host PC with perhaps
12 - 16 motor channels and 24 - 32 sensor channels.
(I have also built a "remote control sensor brick". It connects to the sensor
input of the RCX, running in the same way as a light sensor - taking its
power from the RCX. The receiver only draws 2mA. The remote control has
a number of buttons. Each button causes the receiver to signal the RCX with
a different current. This means you can command the RCX by wireless. Why
you ask? Because if you ever build a multi-RCX robot, you can't use the
IR remote!)
At the moment, the individual RF devices have 8 channels, while the
combo unit has 6 + 6. They all have non-volatile memory so it is possible
to program them remotely and have them act autonomously if necessary.
The mega device is on the drawing board still, although I have a potential
user who is looking at a large train control project. The autonomous
operation I am currently working on is NOT compatible with the RCX byte
code system because the Lego byte codes cannot easily be extended to
handle more resources. There is no reason why, for compatibility, this
could not be done however. I am using the new PIC16F877 devices which
are easy to reprogram.
The current combo unit uses a single frequency and thus has to switch
between transmit and receive all the time. The cheap RF modules I am using
take about 200mS to go from transmit to receive so the maximum message
rate is very very low. Not good for PC controlled remote control robotics.
At the moment, I am using RF modules which operate at 418 or 433 MHz.
Output power of about 1mW provides good range (~50' - 100') even with
very inefficient antennas. What I am intending to do, when I get some time
at home, is to investigate making a device which runs in full duplex, so it
can transmit and receive at the same time. I will try to take advantage of the
availability of both 418 and 433 MHz modules. If it works, it will speed up the
message transfer rate a lot.
The cheap RF modules do not have any kind of channel selection and thus
multiple simultaneous operation of different communications links at the same
time is not possible, unless you want to use the half duplex system and some
kind of media sharing protocol which would be very very slow. So these devices
will not play well in a Legofest type situation.
Please let me have your comments. I am hoping that the overall response to
making a range of products like this available would result in a level of
sales to
justify the investment in time and energy to build them. And I would like to
believe I am building something that would appeal to typical subscribers to
this
news group.
JB
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Message has 2 Replies:
 | | Re: Lego R/C etc
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| WOW ! Sounds like someone answered my prayers. #3 appeals to me. It sounds like just the thing to run the AI on a PC and remotely control the LEGO(R) Chassis. Would it be too much to ask for pics of the prototypes ? -Xanthra47 "John Barnes" (...) (24 years ago, 13-Mar-01, to lugnet.robotics)
| | | Re: Lego R/C etc
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| (...) Your experiments are similar to one I am attempting, albeit for a different purpose. Currently, I'm leaning toward local oscillator and I.F. stage with a double balanced mixer from Mini Circuits to place me in the 144Mhz region (although (...) (24 years ago, 22-Mar-01, to lugnet.robotics)
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