Help Writing an Excel VBA Script

      No Comments on Help Writing an Excel VBA Script

UPDATE: I have satisfied this need.


Greetings to my dear amateur radio aficionados and other friendly geeks with too much time on their hands. 🙂

I have written a paper for submission to the ARRL QEX magazine describing a fuse model and characterization protocol for conserved computer simulation (i.e. Saber, Ansys Simplorer, LTSpice, etc.). It is nearly ready for submission, and I am relatively certain that it will be selected for publication. Please see the abstract below.

AbstractThis paper presents a behavioral model for the electric fuse which can be realized for conserved[MP1]  computer simulation with applications such as LTSpice. The model simplifies simulation by translating the traditional time integral square of instantaneous current (i2t) into the thermal domain (R𝜃i2R). This approach is unique in that the primary modeling consideration is given to the device as a low-current self-heating resistor given a unity ζ current order coefficient. At unity ζ values, the device is able to dissipate thermal energy as fast as it comes in. At a crossover current, a ζ order coefficient increases from unity for a fusing effect where the device is no longer able to dissipate thermal energy as fast as it comes in. The net result is a translation of the published i2t profile into the thermal domain. The model has a thermal network to the ambient with a user-defined simulation precision of the published characterization i2t profile and a transient voltage response in the low current region that accurately duplicates published behavior. Owing to its low numerical overhead, the model is highly productive within LTSpice and various qualified analog conserved circuit solvers [MP2] for whole systems simulations.

The model’s heart relies on a Zeta order coefficient (ζ) having numerous dependencies. There is no explicit equation for ζ, it is transcendental. Any fuse characterization will have a lookup table matching the current with ζ.


The model is only an approximation for transient analysis as far as computer integration limitations. Accuracy is primarily a function of simulation environmental variables such as a Local Truncation Error and maximum time step. I developed it several years ago so it has well proven itself for ultra-reliability and ease of use. We have used it at Ford several times when the proprietary Synopsys fuse model would not accommodate requirements.


I have written an Excel VBA script that solves for ζ, populating an entire lookup table for a given characterization. It works but I would like something professional that I need not be ashamed of when published in a magazine such as the QEX getting global distribution.

The script iteratively solves for each ζ but does not always solve to an optimal conclusion and gives no warning that more iterations are required. I spent a lot of time several years ago developing the script that I am using and have no interest in refining it since it works but is very rudimentary.


Would somebody please develop a truly professional VBA script that dependably solves for any given ζ? I will give you the script that I have so that you can refine it if you like or develop something all new


For the winning VBA script I will credit the author with writing the VBA script. You will get your name in the QEX magazine.

This could be a club effort. A given amateur radio club could have any number of contestants or work together to develop one VBA script.

Leave a Reply