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Hi !
As some of you have noticed, Ms. Jennifer Clark showed off her beautiful
new truck model at the Cheshire Legofest recently. The truck was equipped
with a prototype radio control system which she has been kind enough to
test for me.
The prototype system has 8 control channels each providing a fairly basic
forward/off/reverse type function. Both the transmitter and receiver used
small UHF radio modules which operate in the 418 - 433 MHz band.
It is not permitted to build radio transmitting equipment for sale without
going through lengthy regulatory agency compliance testing, and for the
possible sales volume for a product like this, the cost of such testing would
dominate the price.
I have therefor been actively looking for an alternate strategy and I have
found
one which I think may help.
Digikey, a large supplier to industry and hobbyist alike here in the US has
recently taken on the Linx company's product line. This product line includes
an 8 button 418 MHz remote control and a 5 button keyfob remote control.
Although they list 315/418/433 MHz as options, they only carry the 418 MHz
version. I have successfully built a 4 channel system for use with either
of these
two devices. Using the 8 button control, the four channels are all off by
default.
Pressing one of a pair makes the channel drive the motor forward, pressing the
other makes the motor go in reverse. Buttons may be pressed simultaneously
to run more than one motor at once. Using the 5 button keyfob, which has four
oval buttons surrounding a central round one, I am decoding the round one as
a "shift key" allowing the four buttons to be switched from one pair of motor
outputs to the other.
Please investigate www.linxtechnologies.com - linx - oem. This will show you
some of the radio modules. Then consult www.digikey.com and look up;
CMD-KEY5-418
CMD-HHTX-418
RXM-418-LC-S
Ok. Here's the scoop. I am looking for a couple of volunteers who are
interested
in trying out this technology.
You must buy either of the first two items from Digikey if you live in the
US* and
pay me for the receiver module. I plan on building a few prototype systems to
see how acceptable they to are to use. Apart from paying for the two principle
radio components, there will be no other charges.
The receiver will be constructed in a 4 x 6 stud x 2 2/3 brick high lego
enclosure.
It will have electric plating on top for the motor connections and a
pigtail wire with
a Lego 2 x 2 electric connector on the end to go to a Lego battery pack (6
x AA or
1 x 9v). The antenna is internal.
This is not a Mindstorms/RCX add-on, this a remote control for a model of some
kind. I cannot legally modify a transmitter to add RS232 capability.
However;
I have also built a handy little RCX add-on which is a receiver-sensor.
Basically
this enables you to signal an RCX via on of its sensor ports from a handheld
transmitter as described above. In this case, I convert the receiver's digital
output to an analog value for input to the RCX so it can "measure" which
combination of buttons have been pressed - a la the touch sensor mux idea.
This is really only of benefit in situations where you want supervisory control
over a multiple RCX project. (You cannot easily use the IR remote with multiple
RCXs in my experience. This is more expensive than the IR remote!)
Please feel free to contact me about this project, if you are interested.
John Barnes
ps:
*If you do not live in the US;
Please investigate whatever may be locally available as far as
transmitters. The
receiver system I am using uses the Linx module as listed above and a PIC
microcontroller to decode the commands. The Linx transmitters use a Holtek
HT640 chip but I am sure that other commonly available devices would be
equally easy to decode. If you live in the UK, please check out Radiometrix. I
noticed their logo on the some of the Linx modules, so they must be tied
together
somehow. Perhaps the little transmitters are available legally in the UK.
If you
live elsewhere in the world and there are no suppliers of this kind of
stuff, check
out your national frequency allocation to see if the 418 MHz band is free for
low power telemetry and remote control function use. We may be able to come
up with some kind of plan to get you equipped.
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Message has 2 Replies:
 | | Re: Lego Remote Control - Here's The Scoop
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| John Barnes <barnes@sensors.com> wrote in message news:4.2.0.58.200103...lserver... [Snip] Thanks for the info, John. Just going to check out Australian remote control stuff.... (...) control (...) multiple (...) It can be done using LegOS - but it (...) (24 years ago, 26-Mar-01, to lugnet.technic, lugnet.robotics)
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