Gravity Assisted Blinking Coin Cell Christmas Tree

If making this project again there are several things we might try differently:

• Design a uniform end return that would slow and redirect the coin cell at the end of each ramp.  The end return being used now is a bit of a hack
• Catch the coin at the bottom and have it do something instead of just roll out (e.g. light and hold the top LED)
• Look at adding a motorized coin cell return to the top of the tree
• Consider other features - like nails used similar to a Pachinko machine or a display to count trips

Credit to Adrian for the idea of a rolling coin cell.  In fact, credit to Adrian for all the real thinking....

I have a six year old to pick up the coin cell at the bottom of the tree and return it to the top.  If you don't have one yourself, you might consider a mechanical return mechanism.  We considered several approaches but did not pursue them to completion due to said six year old and laziness but are confident you could do it.

Each approach used a motor removed from a small camera.  The motor was attached to a salvaged gear mechanism from an old inkjet printer.  In each case the coin cell was able to move the cell the required height but the number of repetitions was limited and the mechanisms add complications that require further engineering.

Approach One - Winch

A spool was glued to one of the gears and heavy thread used to move the battery up and down.  A completed mechanism might look something like this:

Approach Two - Pulley

Similar to above but use a pulley so the motor can be offset with possible geometry advantages.

Approach Three - Belt

Approach Four - Mechanical Linkage

Something like this:

As expected, there is a lot of bounce as the coin cell rolls down a track.  I was curious to see how much.  Here is an oscilloscope trace from one such experiment.

Fortunately, the LEDs couldn't care less about this.  I did try putting a rather large cap between the rails which removed the bounce entirely.