You may have seen the ads for The Dollar Store. How much is this flower arrangement? One Dollar. How much is this tea kettle? One Dollar. How much is this package of light bulbs? ONE DOLLAR. How much is this 56 function, 10 digit scientific calculator? ONE DOLLAR. EVERYTHING IN THE STORE IS ONE DOLLAR.
I'm dating myself to say my first "real calculator" was a Texas Instruments SR-50A, slightly newer than the SR-50 shown here. It had a price tag of around $170 35 years ago. Nice red LED display, many functions and a rechargeable battery that would last all day provided I remembered to plug it in. i had a few moments of panic in college when I had forgetten to recharge the night before a test!
So what do you get at the Dollar Store for a buck? A decent looking calculator with a ten digit LC display that seems to have all the functions of an SR-50 for a tiny fraction of the price.
Comparing the dollar calculator to the TI SR-50, all the functions seem to be included. I spot checked a few calculations and everything seemed spot-on.
How can a scientific calculator be built? Taking a look inside is pretty interesting.
A couple LP1130 button cells power the show. There's a small circuit board of about 0.75" x 2" with a blobbed chip for a brain. The LCD readout is on the back side of this tiny circuit board. The keyboard is the white area to the right in the above picture. Typically, this would be a circuit board with contacts for conductive buttons. But what is the white material? Obviously, costs have to be cut some place, and this is it.
The conductive traces are printed on a piece of polyester film! Awesome. Admittedly, the buttons do have a rigid feel to them and take a fair bit of pressure to press. I understand that keypad failures are common after these things have had some use.