B.04 Plinko

To begin planning how my random colour picker machine will work, I first must choose a randomising method. This week I’m looking at the game Plinko: popularised in the 70’s by TV game show ‘The Price is Right’ and later revived in this decade by hipsters with a surplus of bottle caps.

How it works: the user puts the token into the top of the Plinko then on its way down the token hits the pegs, changing direction as it falls and yielding a (relatively) random outcome.

Most plinkos have an open top where the user can choose where to place the token, this affects the outcome but doesn’t give the user full control. In the diagrams, I have drawn up a version of plinko that takes the power of suggestion away from the user.

I want my machine to be almost automatic, requiring minimal input from the user. It should be able to create a randomised yet constrained output by itself.


The biggest challenge here is figuring out how to ensure that the same colour is not picked twice. I’ve looked at a number of different mechanisms (pictured above) that involve a rotation of either one or two balls.

C4d Mockup 

Preparing to make the machine out of MDF, I decided to make a digital mockup in Cinema 4D so I could use the measurements.


Soon after I made this mockup, I realised that the chance of landing in the two edge spaces was slimmer than landing in the middle. This was confirmed in this article which features the following excerpt:


What now?

This presents me with a pretty hefty challenge. Can I adapt plinko to produce a truly random result?

– I could open the top of the plinko and add a spinning top or dice to decide for the user where to put the ball. However, this is pretty pointless as the spinning top would produce a more random output than both methods combined.

– Then again, I do need the ball to drop in this because the machine needs a downward force to print (stamp) the colours onto the paper. Even if I had straight falling tubes, having a spinning top that tells the user where to place the ball is hardly automated at all.

– One other idea is to add a the spinning top mechanism to the bottom of the plinko machine and utilising the first idea in the sketch where the holding segment is 2/3 the height of the ball. I’ll investigate this further in a follow up post.