Adventure of Adding Sound to a Monsters Inc Bobbing Head Car

I've added mounting "brackets" to hold the mini commander ACC and the MP3 board. I've made them out of bits of brass sheet.  I really like to use brass for this because it is relatively easy to cut and bend.  These brackets may need further tweaking when i actually attach the boards to them.  I plan to use double sided foam tape to attach the boards to the brass.  I attached the brass "brackets" with small a nut and bolt to the teter-totter fixture.

The teter-totter fixture from the car is easy to remove; just one screw on the bottom center of the car will do the job.  It also makes for a nice place to mount things.  Below are 2 brass pieces, one mounted inside the teter-totter and one mounted outside.  You can see I drilled the holes low on the teter-totter to attach the brass.  I did this intentionally so the bolt and nut would not obstruct the movement of the teter-totter.

Note: for anyone not to familiar, it is easier to drill the brass and plastic separately.  I held the brass on the teter-totter with my hand where it needed to go, then marked the brass.  Then I drilled the hole though the brass by itselt, not near the plastic.  Be sure to have the brass clamped down for drilling, it can catch the bit otherwise and spin and be quite dangerous for any nearby skin (ask me how I know).  Then I held the brass and the teter-totter together by hand and used the brass hole as my guide for drilling through the plastic.

An aerial view of the teter-totter and brass mounting pieces attached.  You can see the bolts are off set of each other so they didn't have any problems tightening or touching in the middle.  You can also see how the 2 brass mounting pieces are bent differently.  I'm not sure either way will be a better bend, I'm testing as I a go a bit.  The benefit of brass is I can always remove it and re-bend to a better fit.

At this point you might be wondering, why not just attach the boards to the shell of the car?  it would be fast and easy.

two reasons:

1. attaching them to the shell makes doing any adjustments or repairs harder as I will have wires attached to both the base of the car and the shell of the car. 

2. If everything is attached to the base of the car, I can use this same base for many different bobbing head cars.  I could swap the shell for Peter Pan bobbing head car and change the sounds, or any other bobbing head car.

I placed the boards by the brackets I made to see how they will fit.  Modified the brackets so they are both the same style now.  As you can see below, I think it is going to work pretty well.

I also spent some time making a simple map of how I will trigger the sounds.  I plan to use the Mini Commander HC1 and HC2 outputs to act like push buttons to control 2 different sounds.  I plan to use LC1 input on the mini commander to trigger 2 more sounds.  The LC1 will go to 2 different switches (likely reed switches) that will be meant to trigger the sound when each character is in their up position.  Lastly, I could use LC2 for the final sound on the MP3 board.  I'm pretty excited to be able to effectively use all the sound options.

As for sounds, I've used a MacBook, Apple TV, and QuickTime to record several bits of audio from the movie.  I've edited these into various clips in Audacity and have more than 5 to choose from. 

Nice project, keep up the good work and keep us posted as you go!  Where did you get the MP3 board?

@JD2035RR posted:

Nice project, keep up the good work and keep us posted as you go!  Where did you get the MP3 board?

thank you!  Forum member @gunrunnerjohn developed the MP3 board.  He had a few early ones for sale, I think he is working on getting more. 

A lot of progress made.  I soldered wires to the pickup roller that needs to go on the car.  My local train store had the correct roller needed in stock.  Thankfully they knew which one it was that was needed (thanks Sommerfelds).  I soldered full lengths of wire to the roller.  I cut it shorter after I attached the roller to car and I know how much wire I actually need (try not to waste my good wire).

These pickup rollers just snap in place.  Very easy task.

After soldering the pickup wires, I did some more soldering for the connections between the MiniCommander Acc and the MP3 board.  I only started with the connections I knew I needed.  Below you can see the HC1 and HC2 are fully soldered and ready to test.  LC1 only has 1 wire soldered from the mini commander to 2 wires from the MP3 board.  This is because I plan to use a reed switch to activate these 2 sounds, so I will need to get reed switches in line off the black wire from the mini commander acc.  These sounds will trigger one a time, based on which character is at its peak.

Below you can see both boards are connected to track power from my pickup roller.  The HC1 and HC2 connectors are plugged into the mini commander.  I programmed the mini commander prior to this.  Aux 1 played the first sound, Aux 2 played the second sound.  A successful first test; I am very happy!

Below I temporarily added a reed switch to the black wire from the LC1 connection.  I tested this and was able to hear the 3rd sound when running a magnet past the reed switch.  Another successful test.

Looking great, love to see the MP3 board getting used with multiple sounds.

If you only have one power pickup, I recommend adding another to the second truck.

I think I am stuck with only one pickup cause the other truck has the gear mechanism that helps make the car a bobbing head car.

You might be able to do something custom, I suspect that you'll have some cutting out of the sounds with only one pickup, especially over any switch.

Yep, two or three of the sound clips will be very short and cut outs won’t much of a risk. At least 2 it will be an issue. I wonder if a capacitor could help?

A cap wouldn't do much.  What I'd consider is perhaps an AC<->DC power module set to 10V and a couple of 1.5F supercaps in series to make a 10V cap.  That would give you some hold-up time, my experience would suggest probably 4-5 seconds before the power supply on the sound board dropped out from low voltage.

thanks Gunrunner, I'll need to consider this.  I'm not sure how much room something like that would take up inside the car. It may need to be a phase 2 enhancement. 

A lot of progress was made over the weekend, as well as some setbacks.

First, I took the magnets that came with my reed switches and put two of them on a piece of electrical tape as seen below.

Then I wrapped that tape onto the part of hte car that causes the bobbing action.  I figured by using tape I could adjust the "timing" by moving the magnets more or less off center from peak height.  I could also adjust what is needed from a magnet standpoint very easy by just using the tape.

Next I soldered 2 reed switches to the MP3 board.  You can see them below (the two black things off the end of the white wires).

Then I soldered those 2 switches to the mini commander LC1 output.  The one magnet pair is intended to trip each reed switch at different times.  Thus, I'll get 2 sounds triggered from one output on the Mini Commander.

I hot glued the reed switches in place as a test to see how they would trigger with the car in movement.   This is where I ran into setbacks.  One of the reed switches would not trigger at all, the other reed switch would trigger very inconsistently.  I do not believe my concept is flawed, but it certainly isn't working as I would have hoped. I tried moving the magnets and changing to a different sized magnet and many other different magnet combinations, but nothing proved to very successful.

As a next step, I ordered some different reed switches that I am hoping prove to be a solution.

troubleshooting continues.  Sometimes even a nice map and well thought out plans don't lead to success on the first try.

I've disconnected the mini commander and put all the jumpers back in place on the MP3 module.  I verified sounds all trigger with included remote of the MP3 module.  I then removed all the jumpers and reconnected the minicommander.  I verified the HC1 and HC2 output are still working.

I received new reed switches and connected one to one of the sound outputs and LC1, held the magnet to the switch and no sound. 

My next step for troubleshooting is connecting the LC1 output to each remaining sound individually without any reed switch in the middle.  This should help point in a direction on what to explore next.  I have sneaking suspicion there is some sort of connection issue with one of the MP3 inputs; one of the sounds wouldn't trigger ever with the old reed switches, the other sound wouldn't trigger consistently.  I should've marked the more troublesome reed switch connection before starting my troubleshooting steps.  Always fun to tinker and learn

Remember, the sound module needs about 2V to 18V on the individual trigger inputs, and each input is totally optically isolated.  If the module sees AC or DC voltage in that range, it should play the associated sound.

Thanks John. I’ll check the voltage from LC1 too.

I plan to attach a light to LC1 to make sure I can visibly see the output turn on and off. Then add the reed switch back in to watch the light. Then finally add the mp3 module back in.  

Well, after some careful troubleshooting I've determined 2 issues to my original setup.

Issue #1 - the reed switches.  Below you can see a red switch floating above the grass.  This is one of my new reed switches and so far these are triggering with far more reliability than my first ones.  I haven't yet mounted them to the car, that will be coming soon.  However, even just floating and manually passing the magnet by I'm getting the sounds to trigger consistently, something that was not happening with the other reed switches.

Issue #2 - I believe to be the wiring harness for triggering the sounds.  I tested each sound trigger one by one.  Below you can see some of my wiring mess in testing.  Eventually, to test each sound trigger I had a light and multimeter hooked up.  I could see the light turn on, see the volts go up, see the MP3 board light up, hear the sound play.  This worked for all sound triggers except one.  For the one trigger that did not work, I tried touching the solder joints on the bottom side of the MP3 board that correspond to that trigger, then I heard the sound.  This is why I'm pretty sure it is wiring harness related.

I've decided to just ignore this sound input and just have 4 sounds.

up next, I plan to re-tape my magnet to the car, and glue the new reed switches down and test the trigger of the sounds as it rolls.  Then it will be on to final assembly!

The adventure continues...  The new reed switches were working better than the old ones, but still not as reliable as I would like.  I'm not sure why they aren't working as I expected but I've decide to go with a more crude approach.  I've turned the teter-totter mechanism itself into a pair of switches to trigger the sounds.

The first step was to bend some copper into a contact point.  This piece will get attached to the teter-totter.  Two of them will be made, one for each side of the teter-totter.

I soldered a wire lead off of the end.

As a quick way to test, i just attached the first copper contact plate using electrical tape.  Later I added hotglue to hold it in place better.  I attached a plate on each side of center after I proved the concept on this one side.

Below is my quick proof of concept rig.  All I had to do was push down on the teter-totter and it would close the circuit.  The sound did not trigger 100% of the time, but it was far more reliable then my experience with the reed switches.  After this successful testing, I attached copper plates on either side.

I also mounted my speaker.

Below, you can see how LC1 output from the mini commander is split into 2; one goes to a copper plate on the bottom left and one on the bottom right.  you can also see how the copper plates mounted to the teter-totter mechanism each go to separate sound triggers on the MP3 board.

Below, the MP3 and Mini Commander boards are finally mounted their brass brackets using double sided tape.

Next phase is more testing with the shell off.  I imagine I will need to clean up wire paths a bit when putting the shell on, and I may have some clearance issues with the MP3 board and Sully, but all should be manageable.  I will take it out for a few laps before putting the shell on.  I also need to work my sound files further as I've noticed a few small things I do not like about them.

I'm at a loss why the reed switches don't work, those would have been what I turned to for this task.

I have no idea John, but I'm sure it is user error somehow.  I adjust the magnets, and positioning, and just wouldn't get better than about 15% success rate on the sounds going off.  Even my current method is less successful than I would have guessed, but far better than what I was experiencing with the reed switches.   Either way, it has been a fun project so far!

The project continues, mostly in troubleshooting mode right now.  The first issue I had with the shell on was that Sully could not go all the way down.  He bumped into the MP3 board, stopping his travel.  The cause was the MP3 board wires were pushing against the shell, pushing the board 2 close to Sully. 

I also decided not using the 5th sound was a waste of a cool MP3 board.  Since I had to take the car apart a bit to fix my first issue, I decided to solder 2 wires directly to the board.  These line up with the one sound I could not trigger via the wiring harness.  These wires go directly to LC2 on the MiniCommander Acc.  I also ordered some Red LEDs that will get connected to this output.  This will be my one output that has both lights and sound. 

Below you can see 2 wires coming off the board for triggering the sound.

Below you can see an attempt at cleaning up some of the wire mess that goes into this car with zipties.

Below is a brass piece bent into a sort of L shape.  This specific piece has 2 jobs.  Job 1 - is to push back against the MP3 board, that way it should not stop Sully on his descent.  Job 2 - is to hold one of 2 red LEDs.

Here you can see the brass piece mounted.  I expect/hope the MP3 board will push on it, and it will stop it from caving in so far as to impede sully.  Eventually a RED LED will mounted on top as well.

A second brass bracket was made and hot glued at the other end of the car.  This one only has one job, hold a red LED.

I will continue testing while I wait for my LEDs to arrive.  This project has been a lot of fun and nearing completion.  I've also continued to modify my sound files in preparation for completeness.  I now have to consider how I plan to manage sound 5.

I hope that brass is insulated from the MP3 board, though I could just sell you another one...

I do hope to buy another (probably a few), but not because I damage this one.  I did wrap the brass where it touches the MP3 board in electrical tape to insulate it.  I forgot to mention that!

Just checking!

Lionel's employees would have to make the larger O scale 60' box cars with moving figures and sounds, in order to have enough room for all of the complicated components.

The newest oddity of this project.  I hooked up LC2 directly to the remaining sound on the MP3 board.  The sound will not trigger when turning that output off/on.  I tested the LC2 output with an LED I had and it turns on and off correctly.  I tested triggering the sound from track power and the sound plays as desired.

I think I will test LC2 triggering a relay to send track power to the MP3 input and see if it works that way.  I'm not sure what I'm not understanding correctly but fun either way.  Nearing completion.

Note that those outputs use triacs, so try a .01uf capacitor across the output and then see if it properly turns on and off.

thank you John, I'll give that a try!

The finish line is within reach.  Adding a capacitor helped with LC2 (thanks GunrunnerJohn).   Below is the final assembly of the internals.  You can see the LED's placed on the mounting brackets.   I think a few more zip ties were added to organize the wires a bit more after.  The shell has since been placed back on and shortly I'll shoot a video of the final results. 

The cars always seem so huge at the start of a project, and by the end, it is a jumble of wires.  However, with the shell on, it looks the same as it always did.

Video upcoming, right?

Video upcoming indeed!  Really happy with this one!  I'm not sure of my now 6 cars I've modified which is my favorite but this one is near the top of the list for sure

Link to video. The car is complete!

https://m.youtube.com/watch?v=vU1HfC20gWU

What's that four channels of sound?  You need to use the last channel for something cool.

No, no. I used all 5. LC1 uses up two. One for Sully, one for Mike.

Don’t worry GRJ I took full advantage of your board . Ready to buy another!

Cool, glad that you finally beat it into submission.  I guess you sorted out the reed switches?

Nope, never did. Stuck with my more crude approach of making the teter-totter into the switch with copper contacts. Was much more reliable. For now the reed switches live in my parts drawer for another project.

ive got a the rhino bobbing head car that I’ve long wanted to add Indiana Jones sounds too (the third Indiana Jones movie was a favorite of mine growing up). I may attempt reed switch use for that one in the future (after buying another sound board from you ).