VEX RC Controller Decoded

Just read this really cool blog post on decoding the VEX RC signal for use on Arduino or similarly cheap micro-controllers.

Check it out. Looks very straightforward and is probably very similar to what Scott is doing on the Jedi system to decode the signal.

But for those on a budget and want to try their own hand at connecting the VexTX/RX to a microcontroller without having to hope thru an intermediate RX this could be a good solution.

From the post:

The nice this about this, is that all of the channels are on a single line. This makes it very easy to interface with a microprocessor. A quick review of the PPM format:

  • 20 ms total before repeat.
  • Each channel is sent as a high signal followed by a 1 ms low. The width of the high signal determines the value sent. A zeroed channel has a width of 1ms. A full positive channel is 1.5ms and a full negative channel is 0.5 ms.
  • On the Vex there are six channel (The six peaks that you see) for a total of about 12ms buffered by approximately 8 ms.

To interface with a microprocessor, simply plug the output of the receiver into your microprocessor. Send 5V to Vdd and Ground to Vss. Tie the output of the receiver to 5V over about a 10K resistor. Start measuring pulses on that channel. If you measure at least a 6ms low(The buffer) start recording pulses. (These are your data pulses.) Record all six channels and then decode the length of each pulse.

Update: I just got a message from fellow builder Jamie who has also worked on something similar. Here’s a thread over on the Arduino forum.

Posted by Chris on August 26th, 2008 in Electronics | No Comments

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Cutting Out Skins Quickly

I’ve been very busy the last few days and a bit tardy posting to the blog. However, I’ve made a lot of progress on the skins and legs, and will hopefully catch up with all the blog entries over the holiday weekend.

In the meantime here’s a quick tip for those of you cutting out your skins.

This may not be to everyone’s liking and my old my woodwork teacher would hate me for this, but I used a sharp wood chisel to punch out the pieces. I didn’t use a hammer or anything, I just had to push hard to break the tabs. Even on the super thin laser lines there was no marks left on the skin to speak of. I just lined up the chisel on the inside and pressed down on the little tabs.

I’d tried a bunch of different methods, from using a small saw blade on the wider cut-outs, to a Stanley knife on the thiner lines, I even tried a thin Dremel disc, but none worked as well or as quickly as the chisel. I found that the dremel would easily mark the skins or cut a wider undesirable lines and the knife blade would dull too quickly.

Cutting Skins

Posted by Chris on November 20th, 2007 in Body | 2 Comments

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Quick Tip – Right Bolts for the Job

Do yourself a huge favor and throw away the bolts that come with most of the ankle detail parts. It’s virtually impossible to quickly assemble the ankle with them. I have small hands, but even I had a problem getting in there. Instead use hex head cap bolts in place of the Philip heads.

Right Screws for the Job

Like an idiot late one night I suffered through putting my ankles together before C4 with the original bolts. I even bought one of those fancy right angled screwdrivers – it did the job but it’s still incredible frustrating to use. It’s funny how sometimes you’re so close to a problem that you’ll go down the totally wrong and longer path for a solution. In this case the right bolts and a small wrench did the job so much better.

I’ve also swapped out a bunch of bolts that came with the JAG drive system. The originals work fine, but again it’s hard to get into the tight space to adjust things.

Posted by Chris on November 18th, 2007 in Legs | No Comments

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R2 Garage Buddy

Here’s a quick tip for the collector/builder who wants to use their pristine Kotobukiya R2-D2 in the workshop without damaging it.

Since starting on the skins and details I’d really wanted to have a good 3D model to ponder over. The Koto R2 is probably the most accurate in my collection, but being the paranoid/obsessive collector that I am, I knew he’d eventually get damaged or at best dusty in the shop – so I never took him down.

Then over the weekend while cleaning up my office I realized that he’d fit perfectly in one of those 50X CD-R cases. Problem solved!

R2 Garage Buddy

Posted by Chris on November 14th, 2007 in General | No Comments

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Quick Tip – Masking Parts

Here’s a quick tip when painting those hard to mask parts like the groves on the Booster Covers and inside surfaces of Power Couplers.

I wanted to use rubber latex to mask of my parts but for the life of me I couldn’t find any in local stores. Short of time and rushing for C4 I came up with an alternative – Elmers Rubber Cement – which is made from mostly Latex. It’s readily available at most craft stores. It’s goes on clear so somewhat hard to apply as it’s hard to see where you’ve already covered.

If you can get Liquid Latex then I’d recommend using it – but in a pinch the Rubber Cement worked for me.

Masking Hard to Paint Parts with Rubber Cement

Posted by Chris on August 5th, 2007 in Finish/Paint | 2 Comments

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