View Full Version : Parallax Propeller Servo controller

12-29-2008, 02:23 AM
This is my current project.

A couple months in the making. The video explains it all.

YouTube - Demo 0001

Let me know what you think. This is just the starting phase.


12-29-2008, 10:59 AM
Dude! This looks way cool, lotta work went into this. Looks like some of the newer hex designs from Micromagic and I think Lynxmotion now too, but not with the good use of carbon fiber. I've wondered about the Propeller some, interesting to see it moving something pretty involved. Good demo, and hope you are enjoying working with it at this stage. Be interesting to hear of your component choices and why, or even a build log of what you went through in putting it together.

12-29-2008, 12:44 PM
Awesome stuff!
I could go on and on about every aspect of the fit and finish! Truly impressive:)
Keep the videos coming!

12-29-2008, 03:17 PM
Is the RCA for composite video from the Prop?

Nicely done! Pretty CF! :)

12-29-2008, 04:00 PM
Very cool Quantum, I like your ajustable servo discs, were they CNC machined? Also nice to see another person using carbon for the overall construction, Light and very strong.

12-29-2008, 04:19 PM
Hi Paul,

Very nice design of your hexapod. Any pictures too? ;)
Have you experienced any problem by using only one power connector for both servos and the prop.chip?

Great video!


12-29-2008, 07:39 PM
Hi Paul, love this creature, it is coming alive. I cracked up seeing you holding it back and it just kept coming like a little puppy that wants to lick its master!:veryhappy:

Thanks for the explanation of the IK for the legs, makes a lot of sense. I look forward to seeing your code when you think it is ready to let go, specially since I plan to experiment with the Propeller next.

Great design job.

12-30-2008, 01:14 AM

To answer some of the question above.

The RCA is for composite video out from the prop. There is no way that Id be able to develop any graphic software since Ive have never done anything like that. But there are objects available for graphics and text version. I plan on using the text version since it takes a fraction of the space of the graphic version.

The adjustments for the servos were CNC cut. I had to use a 5/64 endmill and slowly cut thru the aluminum. About 1.5 hrs for all six legs. That's just the adjustment slots. I need to rebuild the mill for higher RPM's some regearing is in order for the future. And cutting the carbon fiber was a pain. Such a mess and it still needed to be hand filled because of all the uncut fibers. It looked like ripped canvas.

Zenta the power issue worked out perfect. I currently feed the bot from a power supply that is 6V at 30amps. I have run it off a battery a NiMH which I belive is something like 7.4V. It goes thru the voltage monitor and drops it to 6v. 6V goes straight to the servos then is splits to the 5v LDO regulator than to a 3.3V LDO regulator which the Prop runs on 3.3v. The voltage monitor would have issues first and the bot would go limp when the batterys ran out of juice. I have yet to have it reset on its own due to a brown out condition. Which I believe is built into the Prop I have to double check this. So I have not had an issue with using servo power for logic. I did make a small circuit that helps with decoupling caps.

I will post some pics as well since the camera is a little clearer than the camcorder. And will post more as I go stuff done.

Thanks again

12-30-2008, 01:31 AM
Is it a voltage monitor? I think the Turnigy I saw was a switching uBEC. At one point, you called it a BEC (Battery Elimination Circuit, technically), then you called it a voltage monitor. So I was a bit confused. I looked and only see ESCs and BECs from Turnigy, so again, I suspect it's a switching regulator.

12-30-2008, 01:38 AM
I am sorry it is a uBEC 15A version. It has a built in voltage monitor just a mix up on my end of the desctiption.

12-30-2008, 02:10 AM
Nod. Several lights. They're really only useful against a lithium battery since their "cutoffs" for each led on based on lithium voltages.

The heavy lifting's getting done by the uBEC - the switching regulator.

I tried to buy a couple of those, and I didn't care for the manufacturers support. I elected instead for the more expensive Castle uBEC. Great support from those guys. Designed and supported in the US.

12-30-2008, 11:30 AM
Ah, I thought I saw the Turnigy's. I used two of them on my Phoenix and Felix.

http://forums.trossenrobotics.com/gallery/files/1/5/3/5/phoenixlm011_thumb.jpg (http://forums.trossenrobotics.com/gallery/showimage.php?i=372&c=member&imageuser=1535)

As Adrenalynn pointed out they are switching regulators for LiPo's. I'm very satisfied with them and have not had any problems.

01-02-2009, 09:24 AM
This is a very nice design! I especially like the legs with the mechanical adjustment feature that will allow much more exact calibration of the leg joints. I had never thought of doing this sort of thing, but am not going to implement this in my leg designs. Bravo and +rep for the excellent design work on this!

Are you planning to make all of your design files for this public, including any CAD files?


01-27-2009, 01:16 AM
just some pics I know there a little late. i have some more work to do on some code but will post a new vid.


01-27-2009, 05:25 AM
Hi Paul,

Nice pictures! May I ask why you used 645 for the coxa and 475 for the femur and tibia? I would suggest using the 645's for the femur to be the best solution. ;)


01-27-2009, 11:24 AM
I thought I would need the stronger servo there since I wanted it to walk on carpet as well.
Its actually ok but I should upgrade the servos.

But on a hard surface its pretty good. No problems.


01-28-2009, 06:37 PM
That Hexapod is looking awesome :] Great job Quantum! :]

sorry to go offtopic, but how do you estimate what servo would do fine. Cant spend too much on servos now, but have some "modelcraft" (chinese i guess ;) ) 40g, ~32.5Ncm lieing around.

Do you think those Hitec 645, 475 are more power then needed for your bot or is more tourqe desired?


01-28-2009, 08:57 PM
Basiclly from trying it out. Trial nd error.

But for the most part whats working for other people.

Not sure the values are right but 32.5Ncm servo comes out to something like 371 oz/in.

1N/cm ~ 9.8oz/in


01-29-2009, 03:38 PM
Good job, very nice hexapod. :veryhappy: