DIY

Sphero R2-D2 Teardown

The Star Wars series has garnered attention for multiple generations. The revolutionary special effects, dramatic storyline, and personable characters have made it a staple in the sci-fi community. Connected toymaker, Sphero, set out to replicate one of Star Wars’ fan-favorite characters – R2-D2.

Sphero’s inclusion of realistic sound effects and interactive motion controls give this toy a personal experience for users of all ages to enjoy. Their custom application enables users to control R2-D2, driving home Sphero’s mission to revolutionize connected play.

After “toying” around with R2-D2 in the office, we wanted to get an inside look at the electronics that made R2-D2 possible. While our partner, Fictiv, did a great job detailing the mechanics, we took an electrical view and analyzed the electronics, architecture, and “smarts” that made R2-D2 a reality. Take a look!

The Teardown

Opening the body and exposing the circuit boards and cabling.

 

We started by removing the body’s snap mechanisms. This immediately exposed two circuit boards and a fairly sizeable 250mAh LiPo battery. Sphero’s choice of this battery comes as no surprise as the size is reasonable for this specific application – most smartphones, medical devices, and cameras typically use a similar battery.

The battery was affixed just beneath one of the circuit boards. At first glance, we saw that there was a ton of cabling linking the two circuit boards together, and the boards fit perfectly within R2-D2’s smallish form factor.

A frontal look at R2-D2 – exposing the circuit boards, cabling, and battery

 

One board was secured on the front of the unit, and the other was adjacent to the leg. We were surprised that Sphero chose to integrate standard circuit boards rather than flex boards, but we assume they went this route to keep the costs low. Additionally, the wiring harnesses in between the circuits boards and the motors give greater flexibility and more degrees of freedom than a flex circuit would.

The two main circuit boards: (Left) power board with nRF52 Bluetooth, memory and audio (Right) motion control board and MCU

 

After further examination, we noted that the larger board affixed to the top of R2-D2’s body is the motion control and MCU board. This board gathers the information from the communication/power board and controls all of R2-D2’s motors. The motion control chip and microcontroller unit (MCU) are both on the same circuit board with multiple motor driver chips surrounding it. It’s worth noting that the MCU is an STM32F which is a low-power workhorse for consumer electronics.

The smaller board adjacent to the leg controls R2-D2’s power, using the USB connector as a charging port. There is a battery charging circuit and a fuel gauge for monitoring the charge status of the battery and the power is distributed from this board to the rest of the unit. Additionally, this board holds the NRF Bluetooth system on chip (SoC) which interfaces with the memory for pre-recorded audio and a class D amplifier to drive the speaker.

Speaker enclosed within custom unit

 

The speaker itself is nestled within a separate custom acoustic cavity unit – this gives R2-D2 it’s nice full sound.

Cable-connected head LEDs

 

Once the body electronics were removed and analyzed, we turned our attention to what was inside R2-D2’s head. The head contains three cable-connected LED boards. These LEDs provide lights to the head that send out varying colors some are only a single color like white or red, but there are also a couple of RGB LEDs that allow for a wide range of colors indicating R2-D2’s ‘mood’ or preset animation. This LED combination allows communicative detail and gives R2-D2 a more realistic look and feel.

As we were testing out R2-D2 around the office, one command really stuck out to us – the extension and retraction of the third leg. This fascination made us dive a bit deeper into how this mechanism worked.

Exterior leg with hall effects sensor and gears

 

The exterior legs are connected to their motor boards via six conductor wiring harnesses. There is also a magnet wheel mounted to the back of each motor with hall effects sensors underneath to determine motor position, direction, or velocity. The sensors, used as encoders, are necessary in applications like this where the motor speed control is critical since the overall direction is determined by both motors running in tandem.

Additionally, R2-D2 has a gearbox that controls the collapse and extension of the third leg. After tearing open the gearbox, we found a potentiometer – this is used to determine the absolute position of the motor.

Like hall effects sensors, the potentiometer is used as an encoder to determine the motor’s absolute position which enables R2-D2’s head and third leg to stop in specific positions. Unlike the motors with hall effects sensor encoders, the potentiometer encoders have a limited range of motion which is OK since both the head and third leg also have a limited range of motion.

FINAL THOUGHTS

With many other competing replicas on the market, Sphero took a unique approach to their model. R2-D2’s mannerisms, controls, and feedback are spot on – every “beep” and “whistle” added to its authenticity. While Sphero’s model is a bit pricier than others, the experience is worth it.

Most toys don’t incorporate sophisticated feedback. However, in a world where IoT and smart devices have reshaped many industries, it’s evident that Sphero put a lot of thought into the finished product. Their inclusion of R2-D2’s communicative detail and app-connected controls give it a hyper realistic look and feel, and make the experience a full generation ahead of similar toys in the genre.