Big Mouth Billy Bass

Big Mouth Billy Bass

While visiting the local op-shop (charity store) just before Christmas I came across an original Big Mouth Billy Bass. For $2 you cannot go wrong so I gave it a new home.

Checking the battery compartment there was no sign of corrosion from leaking batteries so I put in some batteries and turned it on. On pressing the red button on the name plate the fish wiggled and the repertoire of 2 songs played alternatively each press. It appeared to be working.

The sensor in the name plate also triggered a song when a shadow passed across it.

After half an hour the annoyance caused by the 2 song repertoire playing over and over again emerged, so I had to turn it off. Not knowing anyone I disliked enough to give this annoying device to as a gift I decided I would pull it apart to see what was inside.

Big Moth Billy Bass Dissembled

Opening up the base I found a through hole component PCB and a tangle of wires . The PCB had a number of engineering changed – components not installed and the spare solder pads used to add jumpers or additional components. Looking at the poor soldered connections on the wires from the PCB to the peripheral components it was obvious that the device must have been assembled in Asia. A label on the back confirmed “Made in China”. This emphasised to me that Chinese assembly has come a long way since 1999, the copyright date on the unit. These days even the cheap items from Ebay or Banggood have a reasonable quality of construction.

Six wires from the PCB went into the fish. Two of the wires could be seen to go to a small motor and I assumed that the remainder went to other motors in the mechanism. PCB markings confirmed that there were 3 motors.

On triggering the fish the tail and the mouth moved but the head did not. I checked with a meter and it appeared each of the 3 motors were energising during a song cycle but only 2 planes of movement were occurring. By removing a number of screws and disconnecting the fish’s cloth skirt from the baseplate the fish itself could be removed. After a bit of inspection and judicious keyhole disassembly I discovered that the motor that made the head move did not have a drive pinion on its shaft so could not provide motion even though the motor ran. Eventually the broken pinion was shaken out of its gearbox. After going through some other junked toys I found a suitable replacement pinion and the motion was restored.

Motions are created by the motors driving the head, tail, or mouth mechanisms until mechanical stops are encountered. A motor may continue to be run for a short time stalled. When a motor is de-energised a return spring restores the fish’s position to its starting location. Motors are energised and de-energised at appropriate points in the song so that the motions appear to match the song.

Stalling the motor may be the reason why drive pinions fail. Broken drive pinions have been reported by others on the internet.

Turning to the PCB, what it contained intrigued me. Although the COB assemble at the right end of the board was obviously the sound generator it had 10 PCB connections so must be doing something more complex than just generating the music. In all probability it was a microcontroller so would also control the motions etc. But then why did the PCB need 10 additional transistors? What were they doing? I would need to trace the circuit to find out.

Big Mouth Billy Bass PCB

With the circuit traced I found that 3 transistors created a simple 3.5V linear regulator, 3 transistors were used for the light triggered circuit, 3 transistors were divers for the motors, and the final transistor drove the speaker. I also found the ON-OFF switch on the back of the unit was not to switch the battery power to the unit, rather it turned the light triggered function ON-OFF.

Except for the voltage regulator the circuit topology was relative uncomplicated. The regulator arrangement provided a reasonable regulation although it used no reference. The whole circuit drew a quiescent current of around 10uA hence there was no need for a power switch.

Big Mouth Billy Bass Schematic

Now that I had identified the internal circuity was there anything that this circuitry could be used for to make the fish’s antics more interesting?

Over 10 years ago there were numbers of article on the internet on modifying these units to allow them to play additional tunes. In later years people replaced all the original electronics with Arduinos so as to play alternate sounds and to add additional functionality. In 2017 modifications using Arduinos and integrated with the Amazon Echo were describe by various people, while in late 2018 a Big Mouth Billy Bass with Amazon Alexa functionality built in became commercially available in the USA.

It would appear that newer versions are somewhat different externally to the original that I have. Also the internal mechanical mechanism has been significantly redesigned and the new PCB circuitry is much more integrated and smaller.

So what to do with my original?

My plan is to just remove the COB assembly and reuse the motor drivers and the light detector on the existing PCB. A micro with Ethernet connectivity to obtain NTP time would then be added. Sounds can be created by using a sound module playing files from a SD card. The sound module would directly drive the speaker. Perhaps the 3.5V regulator should be used to power the sound module as a micro module’s regulator generally has limited current capacity.

To dispense with the problem of tunes or witty saying quickly getting boring I propose to change the functionality to that of a talking clock. This would give the current time whenever the button is pressed or when someone moved past the fish. In this way utterances will be both useful and a little different each time.

If I want to take modifications even further then integration with Google Assistant, which I have had some experience with, would be undertaken but then the project would mainly involve that other programming language – software, which is not in the scope of this blog.

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