http://www.jacques-laporte.org/forum/viewtopic.php?id=180

Project VTQ-13c – Part 1 – Introduction

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### 1 horst2013-07-09 14:18:53 (edited by horst 2013-11-07 17:10:10)

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##### 1. Introduction

By the end of april 2013, the VTQ-13 project came to a sussessful end: The new calculator is now in use with it’s full functionality. The first conceptual works begun in september 2011, so the project lasted for 20 months. Removing holiday times and phases, when I got no time to work on that project, there remains a net-working-time of about 11 months, one month for hardware issues, 10 months implementing the calculator’s operating system.
1.1  VTQ-13 Model description

Originally planned to be calculator similar to the beloved HP-45, it turned out to be more like a HP-27++.

The image below shows a HP-27 (image is courtesy of The HP-Museum), the shining example of my calculator in concerns of functionality.
The VTQ-13c’s catalog of features reads like this:

• Transcendental functions as known from the HP-35
• Statistics: Summations with 2 variables, standard deviation, linear regression and linear guess as implemented on the HP-45. Instead of featuring a simple factorial-function, the VTQ-13c provides Gamma(x+1), but has no normal distribution as it can be found on the HP-27.
• Business functions (time value of money, net present value, internal rate of return) as implemented on the HP-27. In contrast to the woodstock model, the VTQ-13c provides a more modern set of formulas for a full 5-variable evaluation of compound interest problems, as it appeared on the HP-92 for the first time.
• Calculations with hours, minutes and seconds; Coordinate-transformations (as on the HP-45). Modulus, full store- and recall arithmetics on all 31 registers. Numeric range from 10e-1000 to 10e+1000 with a precision of 12 decimal figures.
• Hexadecimal calculator with wordsize up to 32 bits. Signed, unsigned. Bitmasking operations (features like this are found on
HP-41 extensions, HP-16c or HP-42s). This section the “++” stands for 😉

While most of the older HP calculators were designed as portrait models, the VTQ-13c comes in landscape format with it’s keyboard layed out similar to a mixture of an HP-97 an a voyager machine:

I went for this decision primarily in order to be able to place the display module optimally. But it looks nice this way doesn’t it?
There are more differences to the predecessor VTQ-9 concerning the layout: Instead of the clumsy computer’s keyboard switches I used small micro-switches and homemade key caps that give a look-and-feel similar to original HP-calculators and recuded dimensions of the case dramatically.

### One Response to “DYI impressing VTQ-13c calculator”

1. Oh, I didn’t expect to meet a post of my good old calculator again, since Jacques Laporte died and took his forum with him.

This little pal is still working but has undergone some modifications: it’s now programmable…

horst