Texas Instruments TI-5020

[Michael GilliganParticipant @michaelgilligan61133]

[Michael GilliganParticipant @michaelgilligan61133]

I believe we have some TI calculator aficionados here, so I thought it worth posting this:

I bought the calculator out of curiosity but then found that it displayed a lot of ‘broken’ digits whenever it turned on

It is totally ‘light powered’ so there is no battery to replace, and I assumed it was a dud.

Yesterday, I found the User Manual : **LINK**

http://www.datamath.net/Manuals/TI-5020_US.pdf

… which makes interesting reading as an historical document AND confirms [see p3] that such behaviour is anticipated !

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Text from p3

.

.

This must have been operating at the edge of what was commercially viable at the time.

More info. here : **LINK**

http://www.datamath.org/Desktop/ti-5020.htm

MichaelG.

[Brian WoodParticipant @brianwood45127]

Michael,

I have the TI-30SLR model of Texas Instruments light powered calculator which has served me faithfully in almost daily use from 1982. The turning on procedure is the same as you describe but there is no mention of random bits and pieces in the display on first awakening, nor do they appear. Clearly an improvement on the earlier version.

I am pleased to report that it still has a lot of numbers left in it after all these years!

Regards

Brian

[Brian WoodParticipant @brianwood45127]

Oops,

I didn't read the link you posted until just now, it seems mine predates the TI-5020 by a year and to my mind it is a much better designed device.

Brian

[Michael GilliganParticipant @michaelgilligan61133]

For anyone who might be interested … This is probably the most convenient ‘landing page’ for the DataMath collection:

**LINK**

http://www.datamath.org/Leaflets.htm#CL-823A

MichaelG.

[Iain DownsParticipant @iaindowns78295]

The first significant purchase of my young life was a Sinclair calculator. I blew something like 80 quid on it (which was a VAST sum of money in the 70's) and 3 weeks later they reduced the price to 25 pounds.

Those of a certain age will know that it was a deeply unreliable beast and I had to fix the on off switch with a dab of solder if I remember. Probably the most use was in clever stories which ended up spelling Shell Oil upside down…

Iain

[Nick Clarke 3Participant @nickclarke3]

and 5407708

[John OlsenParticipant @johnolsen79199]

Any sort of processor with registers in it is liable to wake up with them in a random state. The usual way of dealing with this is to apply a power on reset. Typically this involves holding a reset line low until there has been enough time for the power line to become stable, eg switches have finished bouncing and so on. A common way of doing this is for the reset pin to have a capacitor to ground and a suitable resistor to the power rail. Once the capacitor has charged enough the system comes out of reset in a known state. This sort of scheme is much harder to apply to a solar powered device, where the power may come up very slowly. So it becomes easier just to rely on the user to press reset.

John

[Gary WoodingParticipant @garywooding25363]

Your TI-5020 beats my EL-545 by 2 years. It too is a totally solar powered 10-digit scientific calculator. I've never experienced the fragmented digit problem, but maybe that's because it's 2 years younger.

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