The tail gets a brain transplant

Over the summer, I designed an easy to use general purpose animatronics controller. I just got the chance to finish writing the firmware for it last weekend and it got put into the tail today. The board is fully user programmable and can be programmed anywhere without the use of a computer. You can see a size comparison between the new board and an early prototype in the bottom left corner.

I also made a few changes to the tail itself, I replaced the steel wire I was using with steel cable, which is more flexible and should last much longer.

The enclosure had to be very large to accommodate the old prototype board, so one of the next steps is going to be to make it smaller. As far as prototypes go, this one is pretty much done. Just add some buttons, some fur and it’s good to go.

There is no feeling quite like the one you get from a prototype working for the first time.


I have my latest design prototyped on a bread board. It has two independently controllable channels (one for each servo) and is fully user programmable. It does not require the use of a computer to program it, all programing is done using the four buttons on the right. When it is complete you will be able to store up to three programs in the device. It is possible to define a start position, end position and oscillation speed for each servo. It is also possible to have the servo move to a specific position and stay there by making the start and end positions equal.

I got a pleasant surprise in the mail this morning. Looks like I’ll have to start coding soon. I think I might also be looking for a costume designer that uses LEDs in their costumes to give my LED mounting boards (top) too.

How to hack LEDs for a wider viewing angle. This is a good technique to use if you cannot find diffuse or wide viewing angle LEDs in your desired color and brightness.

I’m working on some easy to use LED mounting boards at the moment. They can be glued, mounted using screws, or sewn onto fabrics and accept any 5mm LED. They measure bout 3.5cm by 1.5cm. I have the first few prototypes on order and they will probably arrive in the second week of August.

$5 Soft Object Detector


I have more or less finalized my servo controller design and I am ready to start prototyping, but I still have to wait for parts to arrive. So, in the mean time I decided to experiment with a few Ideas I have had, like this soft object detector. Those of you that have been following this blog will probably already have some idea of what those soft objects might be :).

This project uses parts totalling less then $5, not including the Arduino used for testing.

I used a HC-SR04 Ultrasonic range finder ($2.00 on eBay), a 950nm IR LED ( and a matching IR receiver module (


So what is this black magic and how does it work? The operation of this sensor is based on the fact that soft objects have a tendency to absorb sound. The ultrasonic range finder works like a bat’s echolocation, it emits a pulse of high frequency sound and times how long it takes for it to return. If the speed of sound is known, the distance from an object can be determined from the amount of time it takes for the sound to reflect off of an object and return to the receiver. Soft objects are ‘invisible’ to the ultrasonic range finder because they absorb, rather than reflect the pulses of high frequency sound that the range finder emits.

The infrared sensor works by shining an infrared light onto an object and checking whether it reflects back into a receiver. The simple infrared sensor that I have made here cannot determine the distance from an object, but it can determine the presence of an object. This is sufficient for my purposes. Since it relies on light rather then sound, it will still usually reflect off of soft objects (and detect them).

When the infrared sensor detects the presence of an object, but the ultrasonic sensor does not, we can infer that there is a soft object in front of the sensor.

I have tested this with a black fluffy blanket, and the range seems to be limited about 1m, it does improve with objects that have a higher albedo, but only to about 2m.

This sensor would be great for doing things like detecting pets or people wearing fursuits. In the case of a fursuit, one could hide the range finder inside of the nostrils of the head and cover the silver bits with a black permanent marker. A sensor like this could be used to control animatronics automatically, and do things like make ears perk up and a tail start to wag when a fursuiter is nearby.

I came to the conclusion that I needed a new power supply. I had some extra board space, so I decided to offer the people who will be using it a piece of advice.

It Lives!

For those of you that have been following this project on Reddit, Thank you. I will now be posting project updates here and linking to them on Reddit occasionally.

I thought I would share my first working prototype because I am about to make some major changes to the design. This prototype can control a single servo granting movement in a single axis of the tail (left - right or up - down). It is powered by 4 standard “AA” batteries and only uses components that are easy to find, making it very easy for anyone to build.

It was also designed to be easy to use. You simply put batteries in it and it makes the servo motor oscillate from left to right. Adjustments are made by adjusting the connection to the tail itself.

I have not tested it under load but, battery life seems to be very good. I got 2+ hours out of it on some (very cheap) 800mAh cells, it probably would have run even longer, but I got sick of measuring the battery voltage after two hours.

I have decided to improve on this original design. I will be replacing the microcontroller with a smaller, more capable one. I have added a low battery indicator LED, additional circuit protection and the ability to control two servos. Allowing you to control both up-down movement and left-right movement.

Of course, a controller like this is not just limited to tails, you could, for example, have ears that wiggle. There is a lot of simple animation that this controller could be used for.

All of the components are still easy to find, or can be substituted, and I have made an effort to retain the simplicity of my previous design. The idea is to create something anyone can use to add animation their costume pieces, even if they have no knowledge of electronics. I am really looking forward to seeing what this controller is used to make.