Three-Pendulum Harmonograph (#1)- an automatic drawing machine


Ladies and Gentlemen, you will like this. Here is a harmonograph in MS Excel 2003 which models a real one build by Karl Sims. Watch the video first to know what to expect. I could have built it from the bare drawing equations but that would have been too easy and no fun at all so I tried to model the real mechanism with 3 pendulums and the linkage rods. It…


A basic 3-body Planetary System


Hi folks, as a continuation to the previous tutorial here is a 3-body planetary model where the solution to the equations is contained in a static form, as a lookup table (I previously called it a “pure spreadsheet solution”). The model is static in the sense that after any parameter is changed, the solution data remains unchanged in a table until a new parameter is updated by the user. The display is dynamic however since an “Offset()” function…


How to Model a Basic 2-body Planetary System


Here is a tutorial explaining how to model a two dimensional  2-body planetary system in Excel. It uses the Euler method of integration. The tutorial starts with explaining the simple newtonial laws acting on the two planets. There are essentially just two forces acting on each body at any time: the inertia and the gravitational attraction. During each small time step, from the distance between bodies we can calculate the gravitational…


Day and Night Over the Atlantic – an example of sprite animation


Hi guys, here is an animation I made yesterday by downloading 120 pictures of the Earth taken 12 minutes apart by satelites above the equator at 30 degrees longitude west on 10/01/2010. The pictures are 500 x 500 pixels and they are pasted as a background of a chart by a slimmed down VBA macro. You can change the speed of the model. The time increment is fixed however at 12 minutes…


A Speedometer in Excel


Here is a speedometer in Excel 2003. It’s an old file and the charting wasn’t done in the most economic fashion. I used too many series while I could have consolidated a lot of the dial curves. It is still a good example of animation and displaying custom numbers on a chart. There are two VBA macros involved, one for changing the speed value and the other for randomly changing the…


A Realistic Looking Digital Clock Model


Hi guys, here is a dynamic digital clock model in Excel I made today. The display looks very realistic. I studied for this all the clocks in the house including the stove, microwave oven and washing machine clocks, plus some pictures on Google. It will display your local computer time. It uses “sprites” as a method of creating the digits. I learned a lot while making it and I need to prepare a…


Time in VBA Part#1 – Japanese Clocks


Hi guys, here is a simple file with a bunch of clocks. The code is very basic and the whole workbook is fully open so you can see how it’s done. All the spread sheet calculations are contained in the upper left corner and the VBA code is just few lines long. Click the “Run-Pause Clock” button to start or pause the VBA clocks. All the of them will display your local…