17 Servo Biped (formerly Robonova)


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Finally got the hardware going, 16 Hitec HSR-8498NB servos with seperate aux power via two external servo boards (at the bottom of the pict). And the 17th for the camera of course. Draws 0.38 amps @ 6V with all servos holding !

Built out matching 1500 MAH NiMH packs (one per foot) also aux power from either battery back to run the EZB. Should run for a bit between charges.

Well on to building frames for actions.

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Thanks, this should be a lot of fun. Need to figure out a good support to keep him upright while I work on frames and adjust for his CG. He really needs to be supporting his weight to get the positioning right with so many DOF.
Nice, Please upload a video when he starts moving.
Very awesome! I'm really excited to see videos also!

The Auto Position control with movement is perfect. Take a look at the example robophilo project as a start:)
Well that was interesting, just set the speed down real slow, and started a nice smooth motion to stand on one leg. Fortunately I am running him off a bench power supply. Watched the current go to almost 2 amps, with all the weight on the left leg!

Looking at the servo spec, it says they will take up to 7.4v at 1.4 amps each at stall !
I am not sure I believe that spec. The original batteries were 6v, and he would run for about 15 mins on a 1000 mAH battery just walking. I am a bit nervous since Hitec does not make these servos any more, and they are hard to find if I toast one.

The knee took the weight but got more than a bit warm to the touch.

Am I just being paranoid?
I can't tell from the pic but is there a fan on the ez-b?
Not yet, I have one, but I need to find a way to get it installed without impacting the wiring.
Thought about making another plastic plate to go across the top and using that to mount the fan.

Also noticed one of the transistors is a bit loose on the center pin that holds it to the board. Not the tabs the round center pin. It allows it to wiggle (like a loose tooth).

Turns out there is a new servo from Hitec that replaces this one. It is a bit beefier. Just ordered a a pair to replace both knee joints.
I hope the new servos get him on his feet soon!
Just looking at the specs and multiply the load. I'm not gonna get all mathematical but I believe your knee servo went because its underpowered for the weight of your robot. There are some higher torque servos you may want to try. The web store has some and I forgot their oz. In. Rating , 200 oz in I believe and the others I use are Power HD 1501mg which are 240 oz in torque @ 6v and cost 20 bucks. So far for me they have been worth every penny.
Oh I noticed your in the USA! What part? I'm in Tennessee
HI jstarne, mcsdaver:

Sorry it took so long to get back to this. I got bogged down with work, and my free time suffered quite a bit. Thank you for the help !

A while ago I ordered him some new knees http://www.servocity.com/html/hsr-5498sg_servo.html
They are 187 once/in. Not quite upto your Power HD. I need to go check those out for sure.
These were the replacements for the stock ones I was using and fit in without any mods.

Not sure why the change, other than age. This was a stock config, and worked fine with the old controller. I suspect the old controller had some form of current limiter circuit to prevent this from happening.

The new ones seem to be working fine so far, keep my finger crossed :-)

Also picked up a MMA7455 to play around with I2C, but have not been able to get a stable connection. Cables are all short lengths less than 2 inches no real joy so far.

Have a couple heli accelerometers on order to improve his balance. I pulled one out of a heli to test it and it seems to work well. Nice to have the realtime feedback into the hip joints.

Almost forgot I am in Maryland.

Thank you