Poor Man's Hexapod

erco

Senior Member
Actually an 8-legged spider, but Hexapod sounds cooler. :)

I took this $8 spider kit, which is motorized but only walks in a straight line: http://www.ebay.com/itm/200955719259 and http://www.youtube.com/watch?v=uV1XLjSkpug


Then added two Hobby King HXT900 servos modified for continuous rotation and hacked them into place. A 20M2 controller and sensors will be added next, but for this first chassis test, I used a simple servo tester. Servos are driven in opposite directions, so it just turns in place. More to come. http://www.youtube.com/watch?v=zHmrUZENFhI

 

erco

Senior Member
I finally built my 20M2 controller board for this bot over Christmas break. Here's the first test, walking in circle. S-l-o-w-l-y. Bottle is just for visual reference. Later, the bot will use an ultrasonic sensor to track around a center cylinder. http://www.youtube.com/watch?v=oVVGr6kQuHA

 

erco

Senior Member
Some specific info on modifying Hobby King HXT900 servos for continuous rotation. Having modified numerous types of 9-gram servos, this one is my favorite in terms of cost, strength, speed control, and ease of use. I like to use fixed resistors instead of a pot for stability, even though the null (stopped) pulsewidth may be slightly different than 1.5 ms, or SERVO n,125. That's easily calibrated in software. Alternatively, the three pot wires could be routed through a hole in the servo case to a small external multiturn 5K trimpot and adjusted accordingly.

Part1: http://www.youtube.com/watch?v=wfmM3cuihJI
Part2: http://www.youtube.com/watch?v=7pxRhxBPSUM

 
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Paix

Senior Member
That seems spookily spider like. The big ones that seem very confident that they can take on their prey . . . Stalker Bot . . . eek! The behaviour of those advancing and retreating legs seems very realistic.
 

erco

Senior Member
I got to meet Theo Jansen, the Strandbeest inventor. He gave a talk at JPL tonight. We chatted afterward and he played with my Picaxe-controlled "TheoBot".

 
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