Elmo Live Dissected

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RetroPlayer
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Elmo Live Dissected

First let me warn you, if you have small children that love Elmo with all their heart, you may not want to let them view this thread. :)

For all the help Sevik has given me while working on reverse-engineering the Elvis bust, I decided I needed to send him a thank you gift. I was originally going to send him a bust since he didn't even have one, but he isn't so much into that anyway. So I stumbled on the Elmo Live (which actually JUST hit the stores...) After showing him some videos he decided he must have one. So, I pre-ordered two of them and one will be shipped off to the Ukraine to meet its new happy owner.

 HI, SEVA!

But... one of them had to be opened up. And this is the story...

First of all, let's go over his movements.

Elmo Live can stand or sit, and can cross his right leg in the sitting position.

Each of his arms move up and down. His right arm also is also articulated at the elbow to allow him to bring his hand to his mouth.

His neck moves back and forth and his head can rotate upwards

Finally his mouth opens and closes

There are only 3 motors and 3 encoders to provide all of the movements. There is some trickery in how the movements are done and what must be some very interesting cams and clutches inside the two gearboxes within the torso. Obviously, I was a little disappointed about this, but it still has some potential, I think.

Unbelievably, as much as I find Elmo annoying, this toy is actually pretty entertaining (he is just a little too loud, though.) He has some cute stories, games, and animations. This generated a small amount of sympathy while I was skinning the fella.

Elmo has four switches that allow you to interact with him.

Left foot, back, belly, and his nose.

He also has a tilt switch in his left foot, which is weighted by the batteries.

While fully fur-clad, it really looks like he has a ton of articulation and his movements are very fast, springy, and life-like. The illusion is well done and all of the stories, etc... are programmed to make great use of his limited movements. Overall, a very well engineered toy that looks hard to break.

I will be "toying" around with this for a bit to see what kind of mayhem I can wrought. This thread will detail my adventures.

So far, I have managed to remove all of his fur without damaging it and will be posting the pictures and a how-to soon. I took 22 pictures just for the process of removing the fur, so it might be a little long for a forum thread.

For now, I present:

Elmo Live Dissected

RetroPlayer
RetroPlayer's picture
Just a warning before anyone

Just a warning before anyone runs out and buys this from my description above. I just got into the electronics and there are only three motors, three encoders, and some engenious mechanics. Might be very difficult to hack.

Grandlarseny37
Grandlarseny37's picture
That's pretty sweet,

That's pretty sweet, RetroPlayer. The thing that has impressed me the most about elmo live is how fast he can move (especially his mouth).

RetroPlayer
RetroPlayer's picture
Agreed. It really is what

Agreed. It really is what makes him seem so alive. Even if it will be tough to hack, this is some awesome engineering, programming, and animation work.

milw
milw's picture
Egad, it's the Elmo-nator!

Egad, it's the Elmo-nator!

MrScott
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murmured in my best, thick,

murmured in my best, thick, Austrian accent....

"Come with me if you want to laugh."

RetroPlayer
RetroPlayer's picture
MrScott... HAHAHAHAHA! Thanks

MrScott... HAHAHAHAHA! Thanks!

If I hack him, THAT will have to be one of his phrases.

Peter Redmer
Peter Redmer's picture
Thanks for posting this... I

Thanks for posting this... I love how he looks skinless with his eyes kinda popping out the top :)

Looking forward to the full gallery and maybe a hack too, it sounds like!

Have fun, Pete

Evans Digregorio
Evans  Digregorio's picture
RetroPlayer, After seeing the

RetroPlayer, After seeing the movements of Elmo Live on an ad, I was curious to see what this new Elmo looks like without the fur. Now seeing it, It looks like a good chassis for a robot. Thanks for sharing your pics.

idrum289
idrum289's picture
"Come with me if you want to

"Come with me if you want to laugh."

Great MrScott, very funny but you beat me to it!

RetroPlayer
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I have started to do a more

I have started to do a more in-depth tear-down. As mentioned, Elmo Live consists of three motors, three encoders, 4 pushbutton switches, a tilt switch, and a main controller PCB.

There are 3 gearboxes each with a motor and a mechanical encoder. The three gearboxes are: Head, legs, and arms. The way he works is that movement through a certain range will perform one action, while moving beyond that range, it performs a different action. I started working with the head a little and will describe that. But first, let's look at some pictures:

All the main pieces of Elmo separated.

Head Mechanism

Arm Mechanism

Leg Mechanism

Main PCB top

Main PCB bottom

RetroPlayer
RetroPlayer's picture
Alright, I am going to try to

Alright, I am going to try to explain how the head mechanism works. This might be tough to put into words. I will try to get some video after I breadboard a simple controller.

There are xxxx ranges of movement. Normal position is with the neck centered and mouth closed.

To make Elmo talk, it moves the neck forward and back with a small range very quickly.

If the neck is extended past the "talking" range, Elmo's mouth opens all the way very quickly in kind of a snap motion. It looks like he is screaming or yelling.

If the neck is extended backward beyond the normal centered position, it hits a stop and converts the movement to rotating his head upwards (looking straight up. The mouth opesn during this movement as well. Like the other way, his mouth snaps open all the way once it reaches a certain point in the motion and it looks like he is screaming, yelling, or jaw agape in awe. He uses this motion during a story about a giant where he is looking up at the giant and screaming.

Since all of these ranges open and close his mouth, he can basically "talk" in all of these positions except the most extreme where his mouth snaps open all the way. All you need to do is switch directions of the motor very quickly and move it within the desired range.

The encoders tell the CPU which range of movement the gear box is in.

RetroPlayer
RetroPlayer's picture
I am currently looking a

I am currently looking a little closer at the electronics and found some interesting things I will be working with:

First up is the ROM daughterboard. As you can see, the connections are labeled. It should be possible to get a dump of this.

Next up is the top-side in the logic area of the board. There is an interesting jumper labeled Rx. It is connected by a trace on the board to the other side of the jumper and this goes to one of the speaker pins. The other speaker pin goes to a via directly under the CPU blob. Just a theory here, but this configuration looks like it is meant to cut the trace and use the line for serial, maybe? And then the connection could be replaced by filling the jumper.

Between the CPU and the IO Extender (educated guesses) there are two test points. If these are sunplus chips, then these test points are probably the I2C interface between the two chips. My logic analyzer should answer that question.

Also, near what appears to be an IO Extender, are four unpopulated jumpers. If filled, each one would be pulled to VSS (ground.)

The function of those jumpers are unknown. But not for long.... :)

RetroPlayer
RetroPlayer's picture
One possibility of hacking

One possibility of hacking this Elmo is that it should be pretty simple to put this inside of any of the numberous stuffed hand puppets you can find at the toy stores and give it your own personality.

RetroPlayer
RetroPlayer's picture
Anyone want to place bets on

Anyone want to place bets on how quickly Fisher-Price contacts me after I dump the ROM and show how to make your own messages? I know this information will be used for evil.

sevik
sevik's picture
Heh :))

Heh :))

I think we will have something like this weird thread if nobody will stop us early :))

MrScott
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It would be some sort of

It would be some sort of kharmic cycle completion if Elmo's mechanicals were spliced into a RoboSapien carcass.

Why, you ask?
Because of this earlier effort.

http://www.robotsrule.com/html/elmosapien.php

sevik
sevik's picture
:))) Think about black and

:))) Think about black and white colored short-wooled elmo :))

RetroPlayer
RetroPlayer's picture
First attempts to capture the

First attempts to capture the ROM activity have not been successful. It looks like maybe he needs to be completely hooked up first. Right now, I have the PCB on my desk and powering it from a bench supply. No sound on the speaker either.

So, I just spent an hour in the workshop doing a few mods to make testing possible while he is put back together. I have a cable coming out which is connected to all of the ROM signals. I cut the trace on the Rx/Speaker jumper and connected a switch and a "look wire". This will also allow me to shut off his voice during testing.

Finally, I connected wires to all of the jumpers (J1-J4) and these will go to a DIP switch on a separate PCB.

These connections should allow me to access all of the signals that I am interested in. Now I just need to get him all back together (minus fur), but I have run out of time for today.

Shel
Shel's picture
What a delightful exploration

What a delightful exploration. Do you know about a very early project by the Barbie Liberation Front that took numerous talking Barbies and G.I. Joes and switched their voice mechanisms? The translarynxed dolls were put back in their boxes and returned to the shelves of Toys 'R Us and many unhappy returns ensued.
Apparently Joe was heard to pipe (well above his usual bloodthirsty growl) "I love to shop!"

RetroPlayer
RetroPlayer's picture
Yes, I was aware of that

Yes, I was aware of that story, Shel. :) That was what I meant by 'evil.' I actually appeared in a Boston Globe article about hacking toys that mentioned the same story. That was around 2002, I think.

Roboman
Roboman's picture
Hmm, wondering if l shouldnt

Hmm, wondering if l shouldnt simply rip the skin of my sons Elmo (keep it secret please) and use the robot base to finish my Chucky robot project as seen in http://mbah.net/mbahnet/robotics/main.htm

RetroPlayer
RetroPlayer's picture
Looks like this hit all the

Looks like this hit all the blogs already. :) Guess the pressure is on to perform.

I am getting data from the ROM right now and Sevik and I are analyzing the interface.

RetroPlayer
RetroPlayer's picture
Here's what we have

Here's what we have determined so far:

DATA is a serial input/output for the data or address
CLK is the Data Strobe
ADDR is the Address strobe
DS appears to be a bank select

So far we have not been able to find a standard ROM interface that matches these signals. Usually, there is only one strobe for both data and address.

If anyone has seen this before, please give us a hand. Here's a LA capture of the bus transactions:

I'll upload it to the gallery so it can be seen at full scale

RetroPlayer
RetroPlayer's picture
Not extremely important as we

Not extremely important as we know enough to get a microcontroller to dump the ROM for us. But, that is going to take some time. If it is some known standard interface, I might have the tools to dump it more quickly.

milw
milw's picture
Can you post an expansion of

Can you post an expansion of one data/clock/address burst? Hard to see what's going on in the gallery version...
ps how much $$ are these Elmos?

RetroPlayer
RetroPlayer's picture
milw said: Can you post an

milw said: Can you post an expansion of one data/clock/address burst? Hard to see what's going on in the gallery version... ps how much $$ are these Elmos?

Done. Added zoomed in traces to the gallery.

I paid $60 each from toysrus.com

RetroPlayer
RetroPlayer's picture
Shorting the jumpers (J1-J4)

Shorting the jumpers (J1-J4) makes no visible difference. Still playing with the ROM signals.

It seems that the ROM only contains the animations and sounds. There must be firmware in the CPU. There is only activity on the lines when he is moving and speaking.

I will post some video of Elmo animating without the fur sometime tonight or tomorrow. Seems more than a few people want to see that. :) His Kiss-Kiss routine just cracks me up. So cute. I mean... in a 34yo grown up, serious, engineer kinda way. Hehe

My little niece is going to be here this weekend (tonight actually) and she is getting one of these for Christmas, so it might be a chance to see how she reacts without her catching on.

Shel
Shel's picture
RetroPlayer said: Yes, I was

RetroPlayer said: Yes, I was aware of that story, Shel. :) That was what I meant by 'evil.' I actually appeared in a Boston Globe article about hacking toys that mentioned the same story. That was around 2002, I think.

Yeah, someone told me about it a number of years ago, mainly because I knew people who worked at Mattel.

MrScott
MrScott's picture
Regarding that voice box swap

Regarding that voice box swap deal, as a GIJoe collector, my subset of the toy market were split between amusement and outrage....

Which way a person went usually was related to whether they could find a non-sullied copy to replace the tinkered toy. Some collecting completists get bent out of shape when they cannot find a mint in box sample. MIB is not my concern, so I was the amused side of the group.

RetroPlayer
RetroPlayer's picture
I would think that a modded,

I would think that a modded, but sealed copy would be a collectors item all by itself. A piece of history.

RetroPlayer
RetroPlayer's picture
I should have said, I was

I should have said, I was interviewed in the Boston Globe article "Hackers in toyland"

http://www.rtmark.com/more/articles/furby20001223.html

RetroPlayer
RetroPlayer's picture
BTW, I have no connection

BTW, I have no connection with RTMARK (the leftist organization) but it looks like the only copy of the article left on the internet.

I was a minor part of the hacking Barney scene way back when, too.

MrScott
MrScott's picture
RetroPlayer said:

RetroPlayer said:
I would think that a modded, but sealed copy would be a collectors item all by itself. A piece of history.

The collectors covet manufacturing variations and misprints. They're not so excited about products that were purchased, altered, and returned to be recirculated.

Believe it or not, there's a subset of the toy tribe that will buy a figure, open it, strip it of anything of interest, and substitute much cheaper content for a store return.  The unaware gramma buying something for her grandkids ends up buying junk, and dissapointing the wee folk. It's not unsual to buy a high end figure and find it swapped for a $5 one.

RetroPlayer
RetroPlayer's picture
Roboman said: Hmm, wondering

Roboman said: Hmm, wondering if l shouldnt simply rip the skin of my sons Elmo (keep it secret please) and use the robot base to finish my Chucky robot project as seen in http://mbah.net/mbahnet/robotics/main.htm

Hey, Roboman. I missed your post before. Have you gotten any further with the chucky doll? Any of the mechanics already done?

RetroPlayer
RetroPlayer's picture
Update: Sevik and I have

Update: Sevik and I have decided that he will reconfigure his FPGA ROM emulator that he is using for the Robopanda hacking to dump the ROM and go that route. I will be focusing on creating an entirely custom controller. I would like to add some more movements anyway and will need a new controller to do that.

I haven't decided exactly what I want to do with him yet, but when I look at him, I see "Daffy Duck" or just about any of the warner bros. cartoon characters. A "Marvin the martian" would be awesome, except you can't see his mouth, so it might not be so interesting to watch. My favorite WB character is Michigan J. Frog. But That doesn't really fit the body type at all.

I am open to suggestions, if anyone has any.

I owe some videos of Elmo in his current state and will get those up before I retire the Elmo personality for good.

I also owe an article on disassembling him and some details on how the mechanisms and encoders work.

RetroPlayer
RetroPlayer's picture
I shot a ton of video this

I shot a ton of video this morning before I realized that Elmo wasn't moving his legs at all. A wire had broken on his leg motors. So, instead of re-shooting everything, I am just going to record one routine where he sits and crosses his legs. I have a rough storyboard in my head to reduce the footage down to just enough to see all his features and will try my hand at splicing something interesting together.

That pretty much complete's Elmo's life as "Elmo." Starting tomorrow I will be breaking him down and making some molds of useful pieces and looking at what I might want to do with him.

Right off the bat, a few mods I have been thinking about are copying his right arm to his left arm, and modding his shoulders to allow them to move up and down. Right now, the shoulders have a ramp in them that move his arms away from his body as they rotate up. I also removed his springy hands which are just silly looking and useless. I will try to build something to replace them, perhaps with a simple cartoon like hand. Not sure yet. His legs would be very difficult to mod, I think. And his head really can't be modded much other than maybe some moving eyes.

As far as hacking his electronics, this looks to be pretty difficult to do for such a limited reward. The ROM is not a standard memory interface that we have found so far. We already know how it works and we will still be dumping the ROM. Sevik will most likely create a ROM emulator, but coming up with something for the average hobbyist will not be easy. Depending on how much of his movements I will be able to mod to be more generic, I might design a replacement controller.

The problem is that Elmo was designed specifically for the movements used in his routines. It seems they started with the content first, and then reduced it down to re-using similar movements, and then designed the hardware to do only these movements.

I really like the overall design, shape, size, etc... so I am likely to do something with it, but to make a generic robot base is going to require some pretty extensive modding. Definitely not impossible, but it will probably end up being hard for others to follow. Regardless, I will make the best effort to describe whatever I do as I do with most of my projects. Half the fun is in sharing information.

We'll see. The initial excitement of this toy has wore off a little (my 6yo niece found him more boring than I did, BTW) but this is certainly not the end of the story...

RetroPlayer
RetroPlayer's picture
I started the full tear-down

I started the full tear-down a little early and got a shot in the arm with what I have found. The arms are completely cable-driven. The mechanism is very simple. There are two pulleys. One for the shoulder rotation, and one for the elbow. There is a clutch between the two pulleys which allow the arms to rotate up and down freely. If the motor is moved beyond the fully up or down position, this engages the second pulley which lifts the elbow mechanism.

The arms themselves have joints capable of the full range of motion of a human arm (up to the forearm.) The shoulder sockets have the ramps in them that I mentioned before which limits the "side out" arm movement. But this can be machined down to allow the shoulders to move the full range.

Further, it looks like it should be fairly simple to make a copy of the right arm and install it on the left arm for two fully articulated arms. The only trouble is that there is one extra spring in the right elbow mechanism. But a piece of thin piano wire should be enough to take care of that.

If the rest of the assemblies are this simple, the modding possibility of this chassis just skyrocketed.

I uploaded several images of the arm sub-assembly tear-down to the gallery. The next to be done will be the head.

RetroPlayer
RetroPlayer's picture
I've got some ideas for

I've got some ideas for replacement hands. Remember those mechanical hand toys you had when you were a kid? If not, look here:

http://store.rebeccas.com/store/merchant.mvc?Screen=PROD&Product_Code=NV...

Something like this would work fine, but in the typical cartoon (3 fingers and a thumb) style and would be cable driven as well. I think a corkscrew type mechanism might even allow me to twist the wrist. Hard to describe, so I will draw something up to explain it. If all movements are, or can be converted to, cable-driven then all motors could be put in the torso (or even feet.) I know, at least, that part of his legs are cable driven. His hips probably are not since they need to handle his weight. The head appears to be all mechanical linkages and cams.

RetroPlayer
RetroPlayer's picture
I got into Elmo's head (scary

I got into Elmo's head (scary place, that) a little last night and found that it was all linkages and cams as I had suspected. To convert the movements it is going to take some planning since many of the cams and levers are very dependent on the gearbox casing. I have decided that there are enough mods that I want to do with the arms that I will be focusing on them first. I am not even sure that I would want to keep the head the way it is, so I'll save it for later when it has my full attention.

Back to the arms. I keep mentioning how great they are, but they really are. They are modular enough that they would be useful for full robotic arms of just about anything at this scale. This is the second reason I am planning to make molds of them.

There is one movement that these are not capable of, however. And that is rotation at the shoulder. Imagine if you place your arm down at your side. You are able to cross your forearm across your stomach. This is the movement that these arms are not capable of. This could be done at the elbow/forearm junction however.

I am not clear enough on my plans for these yet, so I am just going to show some closeup pictures of the arms to give you an idea of what they are capable of.

This is the shoulder of the right arm. The end of the shoulder has a pulley around which the string was wrapped to allow it to rotate. Inside is a place for a compression spring which would rotate it back. The two white knobs are currently just being used as stops to limit the side to side motion, but the white plastic pieces are actually rollers which slid along the ramps in the shoulder sockets to move the arms away from the body when the shoulder is rotated. It should be possible to machine out the ramps so these can just move around freely and a string attatched to these knobs to actuate them. Maybe a spring around the center axle to return them so only one string is needed?

To get the strings (or cables) through to the rest of the joints, the shoulder has a tube through the center of it.

Sorry for the dark pictures. The tube is big enough that several thin cables could fit in there. But if you put more than one cable in there, the cables should have shealths, so they don't bind each other. I usually make my own cables when I need something this small and just use insulated electrical wire. I pull the wire out to use the insulation for a shealth. It should be possible to buy capillary tubing small enough to use, but this is what I seem to always have on hand when I need to do something like this.

A diagonal hole would need to be drilled to guide a cable up to the shoulder knobs, since the tube just goes straight through right now.

The cable that went through the shoulder went over this elbow piece and looped around a piece that was screwed into the hole above in the forearm. The jagged points are meant to bite into the cable and secure it. When the cable was pulled through the shoulder, it would bend the elbow. There are compression springs at each end of this elbow piece to straighten it back out.

All of these joints are using rivets which will need to be removed to take the arm apart for molding and casting. I tried knocking them out with a small hammer and tap, but haven't been successful yet. I might need to make a tool out of a C-Clamp (like a gear puller) to push them out. They seem to be glued in. Not a big deal, but I am taking it slow so that I don't break anything.

This is the end of the arms. Elmo's hands were just long springs with paddles on the end. One end of the spring just looped over this post and a second piece (not shown) screwed down to hold the spring in place.

And finally, let's take a look at the movements:

This is the right arm, which has the elbow. The forearm can actually lay flat against the upper arm.

This is the left arm, which is missing the elbow. Looking at the mechanisms closely, the elbow piece from the right arm should fit in place of this forearm to make both arms articulated. The shoulder in this arm also has a tube through it just like the right, which means cables can already be run through it without modding it. The shoulder itself is a little different in that this one is a solid piece while the right side is machined to allow the cables some room.

Here's a video of the arm mechanisms (as-is) using cable control. All that I have done here is separated the arms to move independently and threaded new cords. It is ot so easy to move with just my fingers and I didn't think to create finger loops at the time. :)

 

Update: Wrong video linked

 

RetroPlayer
RetroPlayer's picture
Something like this is
Kmac
Kmac's picture
Hi Guys

Hi Guys

My 9 month old sons elmo's mouth has stopped moving (only when he is talking) after one day and some heavy handed nephews, it was purchased from ebay so has no warrenty, is there a spring that could of come off that controls the jaw mechanism?

Any ideas guys please

RetroPlayer
RetroPlayer's picture
Kmac said: Hi Guys My 9 month

Kmac said: Hi Guys My 9 month old sons elmo's mouth has stopped moving (only when he is talking) after one day and some heavy handed nephews, it was purchased from ebay so has no warrenty, is there a spring that could of come off that controls the jaw mechanism? Any ideas guys please

Kmac,

There are lots of springs, levers, and cams in the head that could have broke. His mechanisms are pretty sturdy, though and are designed to give way to forcing movement. They would difficult to break.

Let me ask a couple of questions to help you figure out what is wrong:

1. Is the jaw just hanging open and loose?

note: The upper jaw an lower jaw both move like a pair of scissors. So, a broken jaw should still show movement in the other jaw.

2. When he should be talking, do you hear alot of rapid motor noise?

note: It should sound very rapid, like a motor switching directions very quickly

3. Does his head still move when he talks?

note: the head itself should still move back and forth or rotate up and down, even with a broken jaw. A good test is to push the button on his foot. The first story he tells is about the giant and he rotates his head up and down during this story. 

I found that with not-so-rough treatment during my disassembly, a wire had broke off his leg motor and I noticed that they were not soldered on very well. Probably this is all that happened to your son's toy.

Regardless; opening him is pretty easy, but putting him back together again is going to be a little more difficult. You are going to need some heavy red thread and two large zip-ties, small needlenose pliers and some patience.

If you are willing to try, I am willing to try to help you, but let's get a "test plan" going first by answering those questions above.

Kmac
Kmac's picture
Hi Retroplayer

Hi Retroplayer

1 The jaw dosn't hang loose.
2 No exessive motor.
3 His head still moves.

On the test you asked me to carry out Elmo moves his mouth on the actions of the story but not when narrating.
I have also realised that when he is scared he should shake but he remains still even though the motor is running.

Any idea's

RetroPlayer
RetroPlayer's picture
Sounds like either the

Sounds like either the encoder has been knocked loose or only the bottom jaw is broken. When his head tips back, the mouth opens, but you would notice the upper jaw moving and not the bottom, so it would look like his mouth was opening.

There is a plastic guide pin that moves inside one of the slots in the cams (I'll get a picture of it in a little bit.) Perhaps this was busted off.

Any rattling noise in the head if you shake it?

RetroPlayer
RetroPlayer's picture
To get inside the head, you

To get inside the head, you will need to locate the neckline in the back. The threads of the fur are concealing it, but if you push them around right where you feel a big ring, you will find it. Near the very center of the back of the neck, you should feel two hard plastic bumps. These are the ends of the zip-ties that are holding the fur to the torso and the head. You will need to try to locate in the seam and pull it apart a little, then clip the zip-tie off. Rip the threads holding the seam together along the back of the head and you should be able to fold the fur back enough to see that the eyeballs are holding the rest of the fur to the head. Pop the eyes out of the upper jaw bracket and you should be able to pull the fur all the way off the head.

Above you can see where the eyes clip into the upper jaw bracket.

This is what Elmo looks like while you are removing the fur. You shouldn't need to undo the fur on the torso, though.

Once the head is free, it should look like this.

There are three screws holding on the head shell. The other two screws that are exposed hold the mechanism together, so don't remove those yet.

Four screws hold the head mechanism together and a spring is slid onto one of the shafts. Remove the screws, then hold the pieces together while sliding off the spring. Inside the mechanism is another spring under alot of tension, so, before pulling the brackets apart, hold the upper jaw in place and be somewhere where you can find the spring if it goes flying.

This shows the mechanism related to the lower jaw. The circles marked "Post" have guide pins that fit into the cams. The upper one is connected to the lever for the upper jaw. "Spring" marks the location of the spring I mentioned above which is under high tension. One end is connected to the upper jaw and it wraps around the shaft in the picture above. There is a little hole there where one end of the spring pushes into.

Putting the head back together is not so simple mostly because of that spring. But, it is possible as these pictures were actually taken in reverse order, so you can see that I managed to get it back together.

Looking at the mechanism, it seems that it might be possible that one of the guide pins popped out of the slots. The whole mechanism is designed to have alot of give, but if someone were forcing the mouth open AND holding the neck straight at the same time, it would be possible to snap something. If they did, you will definitely hear some rattling inside the head.

Hopefully, if you get inside the head, these pictures will help you locate anything that is out of place.

 

RetroPlayer
RetroPlayer's picture
Here you can see the spring

Here you can see the spring that will probably go flying out when you open the mechanism. This spring holds the mouth closed, so even if it popped off the track (possible) the jaws should still move. His mouth will just hang open a little more than usual.

You can move the head to all of the positions manually. Like I said, they are meant to have alot of give. Push the head forward at the back of the neck and the jaws should open up. Push his head his all the way back and rotate it up (it will only move a little.) Hmm... this movement seems like it could be forced quite a bit and break something or pop something off track. The rest of the movements should give only little resistance and feel smooth and controlled. If it just flops around, then something is broke.

Also, take a look at this:

As you can see, the wires are breaking off. This is a little board with current limiting resistors for the motor. But, if his head seems to be rotating up (again, his eyes are connected to the upper jaw, so if he looks like he is looking up, then his upper jaw is moving) then the motor must be working.

RetroPlayer
RetroPlayer's picture
Well, since I was playing

Well, since I was playing around with Elmo again anyway to help out Kmac, I thought I would show you guys the encoders. I have removed the wiper so that you can see the actual contacts.

It's difficult to describe exactly how this works in words, I think, but I'll give it a try.

This is the head encoder, first of all. Pin one is the red wire.

As you can see, there is a common track, which is the ring around the center. This is connected to ground on the controller PCB. I will reference pin numbers according to this.

When the wiper is over pin 1, the head is in the normal, idle state (mouth closed, head back) Rotating clockwise from this position rotates the head upwards and counterclockwise moves the neck forward.

To talk, Elmo rapidly just moves his neck back and forward. It senses how much to move by rolling the wiper off the pin1 contact in either direction. Moving as far as the contacts for pin 2 or pin 6, he begins to look like he is yelling. Pin 6 and his neck is forward, beginning to yell. Pin 2 and he is looking up and yelling. Moving on and off these tracks allows him to talk while in these positions.

Pins 5 and 3 are the extreme positions both neck all the way forward (Pin 5) or neck back, and head rotated upward (Pin 3.)

The actual wiper is connected to the shaft and looks like a spring loaded roller skate:

The head encoder has 5 regions, while the arms and legs have only 3 regions.

Kmac
Kmac's picture
WOW Thanks Retro player.

WOW Thanks Retro player.
Im amazed by your effort to help us fix our Elmo!!
Im an Engineer but maybe not as talented as yourself in this field!! I will give it a go and let you know how I get on....once again thanks for your help.

DJ_Resistor
DJ_Resistor's picture
Wow RetroPlayer, thats

Wow RetroPlayer, thats amazing! What role do you think the limiting resistors have for the motor?

What's your background?

RetroPlayer
RetroPlayer's picture
DJ, after looking at them a

DJ, after looking at them a little closer, they appear to be chokes, not resistors. Probably meant for noise & spike suppression to prevent the controller from resetting, due to the fact that the motor switches directions very rapidly. And due to the PWM, they probably also provide some resistance during a stall or short condition to prevent the toy from bursting into flames.

I haven't actually looked at the PWM output to the motors yet, so I am just making some educated guesses here that can be easily tested. The controller is currently disassembled for other research at the moment.

I am an electronics technician in the aerospace & defense industry.

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