[Robotgroup] VEX RF remote control on allelectronics surplus

[vkonradi]

Looks like an awesome deal.  I had mapped RC radio input into a robot in the past using a standard RC transmitter and receiver, gating (ANDing or ORing I forget) the individual channel PWMs together to get a composite, then putting that into the micro timer input.  So here it all is for $30, wow!

So this radio is otherwise standard RC frequency and power level?  And channel 89 (75.970MHz) would be a terrestrial-allocated (not airplane) frequency, right?

----- Original Message ----
From: Paul Atkinson <pma32904 at yahoo.com>
To: The Robot Group Mailing List <robotgroup at puremagic.com>
Sent: Wednesday, February 7, 2007 9:04:44 AM
Subject: Re: [Robotgroup] VEX RF remote control on allelectronics surplus


I expect Gray can answer this more specifically, but here goes.

The receiver in the Vex system outputs the data for all channels on one pin. Most radio control systems (hobby type) separate the signals so each channel gets it's own pin. I believe there is a common CMOS IC that does this, but can't recall the part number off the top of my head. So best case, you have to provide one of these IC's, a bypass capacitor, and a few more header pins for the outputs to the servos. (If you really want the gory details, look at the data sheet for the National Semicinductor LM1872, there is an explanation of decoding the R/C signal about half way through, figure 12.) www.ortodoxism.ro/datasheets/nationalsemiconductor/DS007912.PDF

I suspect Vex simplified this since they are using a microprocessor in the controller of their robot system. This way they only consume one pin on the micro to receive all 6 channels. Doing the decode in a micro allows them to do mixing and other common functions like setting end points, non-linear ramping, etc prior to driving the servo signals out of the micro.

Paul

----- Original Message ----
From: Evan Harris <eharris at puremagic.com>
To: The Robot Group Mailing List <robotgroup at puremagic.com>
Sent: Tuesday, February 6, 2007 7:31:56 PM
Subject: Re: [Robotgroup] VEX RF remote control on allelectronics surplus


I'm not familiar with the VEX kits, but the remote looks cool.  What all 
(cost wise) would be necessary to make this remote control work as a 
standalone input for a non-VEX system with all the channels?

Evan


On Tue, 6 Feb 2007, Vern Graner wrote:

> For those of you with VEX kits, the RF remote control showed up on
> allelectronics recently for $30.00:
>
> http://www.allelectronics.com/cgi-bin/item/JS-6/search/6-CHANNEL_TRANSMITTER_AND_RECEIVER_.html
>
> tiny version of the above link:
>
> http://tinyurl.com/29s8cd
>
> and here's the text from the page:
>
> ---------------------------- CLIP --------------------------
> 6-CHANNEL TRANSMITTER AND RECEIVER
>
> Vex # 276-2153. Transmitter and receiver for remote control of robotics
> servos. Designed as an add-on kit to allow two human operators to
> control different aspects of the same robot, it can also be used as the
> primary control (see note below). 6 channels (4 analog and 2 digital).
> Two joysticks, each with an X and Y axis, control the analog channels
> 1-4. Momentary switches on the front and back operate the two digital
> channels. Operates on Channel 89 (75.970MHz). Includes transmitter and
> receiver with crystals for Channel 89, receiver antenna and sleeve
> holder for antenna and interconnect cable between RF receiver module and
> microcontroller. Transmitter operates on eight AA batteries or one 9.6V
> battery pack. Batteries not included.
>
> Note: We have been told recently that in order to use this transmitter
> as a primary control, it is necessary to use a micro controller module
> to split and amplify the received signal into six individual channels.
> CAT# JS-6
>
> Your Price: $29.95 each
> ----------------------------/CLIP --------------------------
>
> :)
>
> Vern
>
> -- 
> Vern Graner CNE/CNA/SSE    | "If the network is down, then you're
> Senior Systems Engineer    | obviously incompetent so why are we
> Texas Information Services | paying you? Of course, if the network
> http://www.txis.com        | is up, then we obviously don't need
> Austin Office 512 328-8947 | you, so why are we paying you?" ©VLG
> _______________________________________________
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>
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