Speed Jenga

An augmented version of JENGA® utilizing a kitchen scale and game software

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Speed Jenga is a digital scale designed to make JENGA® fast and fun for the whole family. Each game consists of 120 seconds divided among players. When the tower falls, the player with the most remaining time wins! Pause blocks and data analytics add an additional level of fun to this timeless classic.

KiCAD, BOM, and Gerber Files

x-zip-compressed - 154.87 kB - 02/04/2020 at 01:10



Adobe Portable Document Format - 65.93 kB - 02/04/2020 at 01:06


ScaleJenga Development Hardware Guide.pdf

Adobe Portable Document Format - 222.06 kB - 01/13/2020 at 23:59


Speed Jenga Rules.pdf

Rules of the game.

Adobe Portable Document Format - 64.20 kB - 01/11/2020 at 23:27


  • 1 × SparkFun OpenScale SEN-13261
  • 1 × Cheap Kitchen Scale Strain Gauge with platform
  • 1 × Jenga Tower 54 blocks. 51 used in tower, remaining three used to supplement pause block. Pause block can be painted a unique color to differentiate.
  • 6 × Spare Jenga Blocks Platform for supporting OpenScale, strain gauge, and tower

  • Previous Hardware Explorations

    Andrew02/04/2020 at 00:44 0 comments

    The OpenScale turned out to be exactly the off-the-shelf product we needed to quickly make a connected Jenga game. It's had some downsides to it, though,  that we've been wanting to bypass for a little while now.

    These are:

    • It requires a physical USB connection for power and data
    • It requires a full-sized PC or laptop (or equivalent) to play a game
    • It offers no feedback at the tower, all feedback comes from the terminal or PC speakers
    • The total response time of the game + hardware can sometimes be laggy or slow

    With these problems in mind, I started to make a new development board that would replace the OpenScale. I wanted to run the game code either A) on a Bluetooth connected phone nearby the tower or B) the development board itself. I had little to no familiarity with implementing Bluetooth on micro-controllers and wanted an integrated option to cut down on future BOM size. So, I decided to try out the CC2650 Launchpad and make a booster-pack for it. The booster pack would have some user feedback (piezo-buzzer and LED bar), step-up voltage regulator to run everything off of 3.3V batteries, and a configurable strain gauge amplifier to interface with the scale.

    I was mostly familiar with the MSP430 launchpads and thought this would be a good first step. The CC2650 had integrated Bluetooth functionality, is an ARM processor, and utilizes TI-RTOS for real-time applications. Seemed like the perfect fit to cut down on lag.

    I made a schematic, laid out a board and assembled. I decided to call it the blueblox (pay no attention to the silkscreen...this is not the constantly evolving project name you're looking for). 

    First Blueblox assembly
    Build In Process...the strain gauge amplifier was trickier than I thought it'd be to hand-solder

    Before I tried out the first board (I haven't even powered it up and checked the step-up regulator), I wanted to get familiar with the CC2650 and it's Bluetooth and RTOS features. This is where I stalled out. And, with it, the first custom hardware for Speed Jenga. The TI-RTOS documentation indicated to me that this was a larger departure than expected from the basic embedded C-code I was already familiar with via the MSP430 launchpads. I just got stuck in the mud.

    This is not the end for this hardware excursion, but I might take a step back and reconsider how I proceed. I've purchased a Bluetooth serial replacement (BlueSMiRF) and will try that out with the OpenScale first (along with a simple LDO and 9V battery). With the USB cable eliminated, we'll see if setup is any easier. Then, maybe, I'll come back around to the blueblox. For the time being, please check out the hardware documents and the picture below. Hope to get back to it soon!

    -- Andrew

    Assembled booster-pack and launchpad
    blueblox rev. 0 out in the wild

  • Software Beginnings

    Zac12/21/2019 at 15:07 0 comments

    Future software updates will be posted in upcoming log entries, but here is a quick summary of how the code base has evolved into what it is now. 

    Tower State:

    The pyserial library  made Python an easy choice for reading serial data from a kitchen scale. The core of the gameplay is based on reading the 'state' of the tower at any given moment. There are four different states depending on how many blocks are on the tower: on, off, pause, two off (disqualification), and collapse (see snippet from 

            #set scale status variables
            self.on_max = self.tower_wt + (self.avg_block_wt * self.block_variance)
            self.on_min = self.tower_wt - (self.avg_block_wt * self.block_variance)
            self.off_max = self.tower_wt - self.min_block_wt
            self.off_min = self.tower_wt - self.max_block_wt
            self.pause = self.tower_wt + self.min_block_wt
            self.two_off = self.tower_wt - self.min_block_wt * 2
            self.collapse = self.tower_wt - self.min_block_wt * 6


    Determining the tower state was challenging since each block varies in weight and the weight of the tower fluctuates as players touch and pull out blocks. 

    See block weight distribution below in kg:

    Changing state:

    Matplotlib was helpful for visualizing change in state. To trigger a change in state the tower weight (blue) must fall within a range of state (grey and yellow). Simultaneously, the standard deviation (red) of the most recent data points must fall below the std trigger (black). Adjusting the std trigger changes the responsiveness. Currently it takes about about a half second to confirm a valid change it state. 

     Below is snapshot of a block being pulled off and placed back on to the tower (

  • Project Genesis

    Andrew12/21/2019 at 13:38 0 comments

    This project has been a work in progress, off and on, for the past few years. It's seen short bursts of work and interest and changed over time. As an attempt to summarize this work and push it forward, Zac and I have decided to publish this project to the community.

    Zac enjoyed the pacing and challenge of speed chess. He also enjoyed Jenga. When he took the same time keeping pacing and format of speed chess and applied it to the game of Jenga he found it to be an improvement on the original game. It was just fun. And, it seemed we weren't the only ones that thought so! A brief search online (check out YouTube for some ideas) shows that this is a known and fun way to play Jenga!

    Zac started tinkering around in Python and built some game code. His first version managed the turns, kept track of time, and allowed for more than two players at a time. I added a big rocker switch to a Raspberry Pi and we were up and running. It was still fun. 

    We liked this even more, but hitting the switch every time took away from the fun of the game and was easy to forget. We wanted something more natural. We wanted some intelligence in the tower itself to know when we took a block off and when we placed it back on. We threw around ideas, like RFID tags in each block, individual electrical contacts running up and through the tower. Those ideas seemed too complex and not really feasible. Then we added the OpenScale.

    With the OpenScale, we had easily readable data of the tower weight. Zac explains in his software log post how we translate that reliably into gameplay data. It worked, was fun, and was the best gameplay experience yet! He added the gameplay mechanic of a pause block to allow more control over tower construction for each player. With multiple players and a time and turn element, each game now had a winner, not only losers.

    So, that's where we are now. It's been a bit of a slow burn of a project, but a fun one. Moving forward, we want to make this game more portable, more reliable, easier to use, and more accessible. We'll be posting project updates, logs, past work, gameplay videos, and rules.

    Hopefully, there's some others here on this site that also like to game, and can enjoy this particular project as much as we have!

View all 3 project logs

  • 1
    Kitchen Scale modification

    The first step is to modify a cheap kitchen scale. Really, any load cell should do, but it is likely easiest to buy a pre-built kitchen and use the internals.

    A pre-built scale is cheap (<$10), has a platform to build the jenga tower on, and already includes the aluminum block load cell.

    We used the scale below, most are the same.

    Disassemble to remove all of the electronics. 

    Just keep the platform, strain gauge, and base.

  • 2
    Connect load cell to OpenScale

    The Sparkfun OpenScale is a great tool for connecting any load cell or scale to a serial port. It has a strain gauge amplifier (HX711), microcontroller, and USB circuitry. It also has 5V power over USB to power the bridge of the load cell connected to the HX711.

    Colors may vary for the load cell you purchase, but we're connecting the wheatstone bridge of the load cell to the OpenScale in this step.

    Connect the load cell to the following terminals of the OpenScale header. For our scale, the :

    Load Cell Wire ColorOpenScale TerminalCircuit Terminology
  • 3
    Build Jenga Block Base

    To support the load cell and the OpenScale, we've gone with a themed platform.

    Glue together 6 standard Jenga blocks, pre-drill holes and mount the load cell base and OpenScale directly to the block platform with screws.

View all 5 instructions

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marblypup wrote 06/24/2021 at 13:04 point

I've been building a bipedal robot for the past 2 years :-/ It has load cells for toes, so hopefully it'll know where its centre of mass is above.

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fx2 wrote 03/19/2020 at 08:35 point

Thanks for idea. I build a modification of it - to play without PC or smartphone (scale only).

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Giulio Pons wrote 01/28/2020 at 23:07 point

very nice job!

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Andrew wrote 01/30/2020 at 16:20 point


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