Thread: My 3 axis skull...in progress

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I just made my extensions and it all works just fine.

I started by getting a really nice plastic project box to mount the SSC-32 controller board in. I got the box (2 of them actually) for free from this website:

http://www.pactecenclosures.com/New-...-Products.html

In hopes that you will mass produce a product and use their boxes, they offer you 2 free samples. Good deal.

Here is a pic of the box opened up after I mounted the SSC-32 board in it. I used 1/2" standoffs.



I cut 4 square holes in the top of the box at my friends machine shop, cut out a hole where the serial port is, and mounted a small terminal block on top.

Here's what that looks like with all the hardware in:



By the way, I got the plugs and jacks for the extensions here: http://www.mouser.com/catalog/630/1117.pdf. They were pretty cheap. Under $4.00 each.

here's what it looks like from underneith where I will be doing all the wiring:



Then I had to hook up the internal wiring. First, I connected the power for the board to the terminal block being careful to pay attention to polarity.



then I wired the power that will go to the servos. What I did, was send the power for the servos directly out to the servos using 2 pins on each of the extension jacks. This way, to hook up 5 servos, I only need 7 wires. Two power wires that get distributed to all the servos at the skull end, and a control wire for each servo.

I started like this:



Then I ran wires in parallel to the last two connectors on all 4 jacks. I also started hooking up the control wires for the servos here. You can also see that I labeled what all the jacks were, where the + and - wires go, and the pin numbers on the underside so I don't get confused. (I did anyway, but I fixed it later)



Every servo has 3 wires going to it. A Black one (Which is Ground), A Red one (Which is your DC Voltage (Typically 5 or 6 VDC....I'm using 5VDC) and a yellow one (Which is the Pulse or Signal wire)

Since the DC Voltage is constantly on for all the servos, I decided to run two wires out of each jack to supply voltage for all the servos in that skull. I connect all the ground wires and all the Positive wires to these two at the other end, so all the servos have power. then All I have to worry about is the control wires (Pulse Wires)

I discovered, that even though I was sending the voltage directly to the servos, and was not using the voltage wires off the SSC-32 board, I still had to feed the DC voltage for the servos into the board in order for it to work.

I just tapped off the terminal block wires and sent that to the board, again being careful to get the polarity right.

You can see that here:



Anyway, to hook up the outputs from the board to my jacks, I did the easy thing. I bought a bunch of 3 foot servo extensions and cut them in half. For some reason, the colors are different on the servo extentions. They are Brown, Red and Orange. Red is the same. It is the positive voltage wire. Brown is the ground and the orange wire is the pulse wire.

I took the end of the extension that plugs into the board and cut off the brown and red wires, leaving just the Pulse wire (The one closest to the center of the SSC-32 board) connected. Then I soldered the control wires to each of the appropriate connectos on the jacks that I mounted, making a chart of where every wire is hooked up and what it does.

I labled my four jacks L (for Lead Vocal) 1,2 and 3 for my three backup singers.

The "L" jack has 5 control wires. one for the Jaw, three for the 3 axis motion and one more for the eyelid action.

Jacks 1 and 3 each have just 4 control wires. The Jaw and the 3 for the 3 axis movement, and number 2 has 2 additional wires. One is an extra jaw wire, because the guy in the center will be lifting up a skull that he holds in his hand, and the jaw on that skull will move. The other extra is for a high torque servo I have hooked up to a pulley system that will raise his arms so he can hold up the skull. I'll post pictures of that when I get to it.

Anyway, here's what I mean by separating the pulse wire and only hooking that up. Heres a pic just before I cut off the Brown and Red Wires:



Here's what it looks like all wired up:



And here's the finished product all closed up and ready to hook up:

Then I made the extensions themselves. This was pretty simple.

I used servo extension wire that I bought at ServoCity.com. (2 50ft lengths)



I'm sure you could use cat5 cable, but I had already bought this stuff, so I decided to use it. My only concern with Cat5 cable would be that you double up on the DC voltage wires. In some cases, those two wires need to carry the current for 6 servos all at once. Cat5 cable strikes me as a bit thin for that. Fine for the Pulse wires, however.

Since I had the wire, I doubled up the voltage wires on these extensions even with the thicker wire. I figured it can't hurt, and it might help.

Here is the plug end:



At the other end, I reconnected the remaining end of the short servo extensions I bought from ServoCity.com. I had used the other ends on the SSC-32 board earlier.

I connected all the brown wires together and soldered them to the ground wire that I ran out. I attached all the Red wires together and soldered them to the Positive DC voltage wire that I ran out. Then I connected the pulse wires to the right mini servo sockets and numbered them all for eaiser reference.

Here's the other end:



I just taped up the area where I made all the splices, and taped up other spots every foot or so just to keep the wires all together and easier to handle.

That was it! Just hooked it back up and everything worked fine. Each extension is about 12 feet long. They would have been longer if I had more wire, but 12 feet will be fine for what I'm doing. That means that one skull can be 20 feet away from the others if I want to set it up that way.

This will be long enough for me to run the cables down the back of each character where it won't be seen, and then connect them all to the controller board.

Now to hook up the whole 20 servos, I just need to plug in one plug for each skull and I'm done!

Cooooool! I ordered my boxes today...Gonna copy ya!

So yesterday I finally broke down and decided to build a 3 axis skull. I had a partial sheeet of 1/4" lexan and a miniSSC laying around so I shot over to my local hobby shop and luckily they had some large ball links for the gimbal.

I'm using 1/4" x 6" carriage bolt with a hand drilled and tapped 4-40 hole in the end (my local hobby shop rocks and they are going to drill and tap a couple bolts on the lathe this week for me so I can replace the hand done ones). For the spacers I'm using 9/32 brass tubing over the threads and it works well, I think it may even give me more motion than the conical spacers do.

I made the supporting bracket out of 1/8" aluminum stock and it seems to be beefy enough.

I'm so close to being done it hurts. The only real problem I have now is that the ball link uses something like a 1/4"-28 thread and I don't have a nut for it and I need to put a little more thought into the servo links.

So my questions to you HalloweenBob;

1) Do you have any pictures of the new metal mounting bracket installed in a skull that wasn't modified with the heat gun? I'm hesitant to dremel out more material than I have to from the base of the skull. I'd like to see how your gimbal is seated in the opening. I actually have to re-do my metal bracket since I somehow cut it offset. I started actually assembling at 11pm and by the time I got to this bracket it was 3am, and I had to cut everything with a 4" hacksaw or a dremel (I would have woken everyone up if I went to dig out the jigsaw)

2) Do the servos chatter alot at rest since they are in tension supporting much of the weight (using the neck location as the mounting spot rather than the point the kit stand uses )?

3) Did you have to take a lot of material out of the inside of the skull to make room for the servo links? I haven't started canibalizing the inside since I need to redo the bracket and find a couple 1/4-28 nuts. Would there be room to use ball cups and studs on the end of the servo arm as linkages (they provide great range of motion compared to the ball links).

Hopefully tonight I'll try putting it together using the ball links on both ends of the servo connecting rods.

Provided I get one working right I'm going for the duet (I got you babe!) thing. Some other ideas were to add shrugging shoulders to it, it's easier to raise the shoulders than to raise the hold skull assembly without adding lots of slop.

To answer your questions....

1. I did have to cut away some of the skull where I had modified it with the heat gun. basically, I just had to make the opening larger so that the center rod had enough clearance all the way around. This is because by attaching the rod end to the bracket, it is a little higher up inside the skull, making the rod need more room to move at the skull's base. To make the hole larger, just use a dremel tool or just about anything, really. I used a hacksaw blade that I just held in my hand. The skull plastic cuts very easily.

2. No, my servos don't chatter at all. I set them up so they are all in the center position when the skull is looking straight forward and all servo arms are at 90 degrees. I have no trouble with chattering or with the servos fighting each other. I did have that problem before when they were not properly aligned.

3. I did not have to cut anything out of the skull with the exception of making the neck hole larger. All the parts were designed to fit in the skull as is without any modifications to the skull. (Again other than the bottom opening)

I use the following ball linkages from ServoCity.com:

http://www.servocity.com/html/2-56x3_16__mini.html

they take a 2-56 screw, so that is the size I tapped into the top of my threaded rod. They are small so they don't bump into anything else inside the skull.

Perhaps you are running into trouble because you have chosen larger parts, and they take up too much space. Without pictures, it's hard for me to tell.

I hope that is helpful.

To the good doctor...Please post some pics of your finished extension box, and let me know if you find any improvements!

I already enlarged the hole a bit using the dremel and a sanding barrel, I guess I need to get everything together and see the clearances first. I just don't want to take too much away. It actually seems like the little bit I did before pitting everything together (basically just rounded the hole a little bit) is giving me some decent clearance).


As far as chatter, I haven't even turned on the servos yet, I just know that unless you're using heavy duty servos that when there is a static load on them, even if they are centered, sometimes they tend to chatter as they try to stay at a specific position (usually a sign of a servo getting old, but this thing isn't exactly featherweight)


As far as clearances for the linkages, I think I'm ok, I have enough clearance that I can mount one between the servo and the arm and then the other on the outside of the arm (like normal) so that I won't have as much stagger (keeping the linkages as close to perpendicular to the rod as possible)

I'm using 4-40 ball ends which are pretty tiny to begin with, I'll know a little later if I'm in trouble or not.

As far as the alignments to the main supporting rod, I used your template as a guide, but as I'm looking at it, I think I need to flip the nod servo around and it'll line up better (I don't know if it's even a problem yet).


Here are some pictures I took to show the 9/32 tubing as spacers. Don't laugh at the condition of my cuts, it was late and I really thought I was going to have to build this thing twice so I just basically hacked away at parts of it. The lexan looks particularly crappy, but it'll be concealed.


Grrrr, I don't have enough posts yet pics in next post.

Also note that I don't have nuts for the ball link acting as the gimbal, so it's slopping all over the place. By eye it actually looks like it's lined up fairly ok.

Lookin pretty good! You may find that you need a largger hole in your bracket to accomodate the rotate armature once you put it on. I don't see it attached to the rod yet. Those spacers look fine. They are thin enough not to get in the way, but thick enough to hold the rod end in place.

Nice work.

Thanks!

The hole in the mounting bracket is for the nod servo linkage from the back of the skull (did I do something different from your design?) and you are correct it's definitely not big enough for the linkage to smoothly move through, I ran out of sanding bands for my small barrel last night and just decided to test fit everything. At that point I was mostly concerned about the spacing form the gimbal to the point where the nod and tilt linkages attach.

Speaking of which... I know your machined rod is 2" from the top of the bevel to the top of the rod (before the screw in the top), would you increase the distance from the gimbal to the linkages or decrease it if you could do it over again? Basically I figure I want to keep it as long as possible for the sake of smoothness (want to use as much servo travel as possible), but at the same time I want to make sure it's short enough that the swing of the servo arm will be enough give me full range of motion.

I do think I need to swap the nod servo orientation, it doesn't come off perpendicular to the support rod the way the tilt servo does, I have to go back downstairs and look at it again to see if that's the problem.

If rotating the servo doesn't make it line up beter I'm going to just connect it and see if it works. I need to get a couple flat nuts to secure the pan arm, those standard hex nuts are too thick and waste too much space.

Once you add the rotate armature onto the central shaft, it will stick out towards the bracket you made. It needs a big clearance area because of the way it moves around when you use the nod servo at the same time as the rotate servo.

If you don't enlarge that hole, you will find several areas where the rotate armature hits the bracket while the skull is in different positions.

It will become obvious once you add the armature.

I am glad so many people are following this thread and getting this project done! It is very gratifying to see others come out with successful projects based on my input here.

If there are more people out there building these, please post and let us know. You can see that as this group gets together, they find easier ways to get this done that does not require as much custom machining as I had in my original design.

The more who post here, the better refined the design becomes.