Nothing important (my first little hw mod)


Never done any hardware mods before - I'm a software guy. But after visiting Diego around NewYear, I got some inspiration :-)

I now have a "light module" - when I plug it into my 41, a LED on two stiff wires lights up the LCD screen. Nothing big, but useful.


Ahhh...must be like AME's Port-X-Light module they built and sold in 1982 in addition to their more popular Port-X-Tender. They had a very busy vendor table at the Philadelphia HP Handhelds Conference in the Spring of that year.


Richard Nelson showed me one still in it's box. Slick idea but what is the power drain. Also, not a hard item to assemble as I was thinking of doing it.

You could make it from existing supplies at Circuit city. Must look into it. Geir, how about a picture?

Here is a shot by Richard Nelson of light module system:

Edited: 19 Apr 2009, 2:11 p.m.


Mine has a socket at the light's end so that I can easily swap the LED - to choose between white, red or green light (being an amateur astronomer, these things are important).

Picture = later.


Swap the LED? Why didn't you use an RGB LED so that the HP-41 could control the color?

[Of course, I know the reason. While doing what I suggest would be possible, it would be *much* more work than what you've done. Consider it a tongue-in-cheek suggestion.]


Yeah, I thought about that myself - and also a simpler little thing (maybe?) to have the light only go on when I turn the calc on. Now it's always on when the module is plugged in.

But as you might suspect, I'm nowhere near even envisioning how any of that could be done (yet).


That is simple, just use the PWO signal to control power to the LED. PWO is high when the calc is running. You could also make a wired OR (with two diodes) to have the LED on when running and when in STANDBY.
To control power make a simple FET switch or transistor, or drive a LED directly if it does not draw too much power.
Drive a multicoloured LED would really require more complicated stuff. My MLDL2000 can drive LED's by choice with access to reserved memory locations. Cheapest solution would be a Novram like device with some spare I/O. It would be fun for amateur astronomers to read the current time and date to check if the sun has set already and then drive the red LED ...


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