$1 scientific calculators

[jhallen]

I just got Ocean State Job Lot's new "10+2 56 function scientific calculator":



It's now $3.99, the old one was $2.99.

https://www.oceanstatejoblot.com/school-...uct/220211

This is the latest in a long line of Chinese calculators using the same Sharp chip. Don't poo-poo these too much- remember that the world's median income is $850 / year.

Here it is for $0.95 each for 50,000:

https://lecount.en.made-in-china.com/pro...C710-.html

The older versions were from Kenko:

Kenko-105:

https://shopee.ph/Kenko-KK-105-Scientifi...5758937082

Kenko-105B, with clock!

https://kazanexpress.ru/product/Kalkulya...05B-295249

Anyway, so here is my review:

The buttons on the new version are _much_ better. The older ones often got stuck under the frame when you pressed them.

But what is going on with the layout? Notice that SIN, COS and TAN are randomly positioned, not all right next to each other! Same thing for the A-F hexadecimal keys.

The plastic cover is held in place with the rubbery sides- but it doesn't really work. It takes the slightest force for it to fall off.

Replacing the battery is difficult. The calculator is powered by a single LR1130 battery: so yes, this calculator is cheaper than what you can buy the battery for at Walmart:

https://www.walmart.com/ip/LR1130-189-Al...erId=10455

Here are some large photos of the construction and manual. Notice that the battery comes pre-corroded.
The traces on the white plastic keyboard sheet are made from all carbon tracks. It's interesting that they have carbon track vias.
Annoyingly that sheet is held in by heat-stakes.
As cheap as this thing is, the keyboard action really is improved- I think it's the "advanced" honeycomb in the calculator's back.
The Kenko ones used a cardboard(!) sheet as the back of the keyboard sheet.

Notice the high level of craftsmanship of the insides of the plastic :-)

The calculator did not survive my taking it apart. I don't know why. Edit: actually it's OK (whew), the battery cover has to be place for it to work.

[brouhaha]

Perhaps ten years ago, I bought a few of those (or a very similar model) at a Dollar Tree store where they were in fact $1 each. I think it was the one seen here:

https://www.eevblog.com/forum/reviews/qu...r-a-dolar/

Of course, now days Dollar Tree sells stuff for $1.25.

I love how the Ocean State Job Lot has scattered the trig functions around the keyboard randomly.

[toml_12953]

Does STAT mode work? I bought a bagful of Jot calculators (very similar to the one pictured) for $1.00 each and it does work on those but a few months later, the ones in the store did nothing when STAT was pressed. Also the company stopped including the press-on cover.

[jhallen]

(12-19-2022 04:57 AM)toml_12953 Wrote:  Does STAT mode work? I bought a bagful of Jot calculators (very similar to the one pictured) for $1.00 each and it does work on those but a few months later, the ones in the store did nothing when STAT was pressed. Also the company stopped including the press-on cover.

It works for me. I maybe spoke too soon about the keyboard quality: the 2nd key sometimes doesn't register when I press it, but I didn't notice until after taking the calculator apart, so I could have ruined it. Maybe this was the issue for you?

Here is another version that's getting some popularity. It has an LCD writing pad:

https://www.amazon.com/gp/product/B097RDC834

[Rick314]

Here is another thread in this forum on the same subject. It includes some detailed usage notes, and that they were available for $1 since at least 2009. I teach Digital Logic at a local community college and give one of these to each student at the final exam.

[rprosperi]

(08-10-2023 02:32 PM)Rick314 Wrote:  Here is another thread in this forum on the same subject. It includes some detailed usage notes, and that they were available for $1 since at least 2009. I teach Digital Logic at a local community college and give one of these to each student at the final exam.

Classy move, well-played sir, I salute you!

[NicolaB]

It could be modded to have two cells and therefore double the runtime. If the keyboard keeps working this is absurd value for money.