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6
votes
2answers
133 views

LEDs inside of solar-powered calculators

Why do a lot of solar-powered calculators contain red or infrared LEDs that are hidden from the user? So far I have only seen this in Texas Instruments calculators. Here are some examples of this in ...
2
votes
3answers
177 views

“High Voltage” Logic levels why they are rare

I'm continuing to dissect and learn from this old (1974) calculator. One thing that surprised my was that the pins of the main IC have both negative and positive voltages 0 to ±28V. Having worked ...
13
votes
1answer
383 views

Studying the PCB of a 70s calculator. What were they thinking?

I've been studying the PCB from an ELSI 8002 calculator from 1974. I'm thinking of repurposing the case for a project, though now that I've fixed it (by re soldering the battery connectors) I don't ...
0
votes
1answer
55 views

How to claculate LM-723 regulator circuit headroom above the intended output voltage

I need to calculate the transformer VA for bipolar regulator circuit using LM723 so I need the voltage drop or may be a headroom for LM723 under load. The data sheet is silent about it. Is there ...
-2
votes
1answer
211 views

Calculator with MSP430 in Assembly Language

I am programming a calculator in assembly language with the MSP430g2553. I have a 4x4 membrane keypad and an 2x16 LCD. I already can display numbers in the LCD with the keypad. The issue is that the ...
1
vote
3answers
108 views

Antenna feed line calculator

I'm working on designing a board with the RFM22B-S2 SMD Wireless Transceiver - 915MHz. The board module requires a 50 ohm feed line to the antenna. I've been looking at trace impedance calculators and ...
7
votes
2answers
1k views

What type of processor in usual 8-digits pocket calculator?

There are a lot of +,-,*,/,CE,MC,M+,M-,MR buttons 8-digits calculators on market with keyboard layout like: ...
1
vote
1answer
53 views

Problem in a boost calculator circuit

In order to get an output of 100V-300v (for the ultrasound piezo drive ) from a 3.3V output of the microcontroller. I have built the boost circuit according to this circuit: But there is one point ...
15
votes
5answers
4k views

Breadboard computer [closed]

Is it possible to make a simple computer entirely with breadboards and basic electronic components? Is it feasible to, for example construct a scientific calculator in this way?
10
votes
3answers
2k views

Where did these Ohms come from?

I am new to electronics and am tyring to figure out something that is a bit disturbing to me. I am trying to figure out the amount of resistance I need to put in series before an LED, and the equation ...
2
votes
1answer
692 views

PCB Crosstalk calculators… Center line distance or trace separation

I am still a beginner in this field, and recently I've learned about Crosstalk and Crosstalk calculators. I've tried the one on EEweb, Saturn, Ultracad and some others. Some of these calculators ask ...
-1
votes
1answer
242 views

How to make a Calculator? [closed]

I am new to electronics programming. I am currently using C#. Can you please tell me how to programme a Calculator, what programming language should I use? Can I use C/C++? And what components ...
-2
votes
2answers
274 views

Why do TI (Texas Instruments) graphing calculators not use TI chips? [closed]

Most semiconductor manufacturers seem particular about using their own products when possible. For example, the Analog Devices Blackfin development board uses another Blackfin processor for the JTAG ...
2
votes
1answer
331 views

What IC is in this particular black blob on my pocket calculator? [duplicate]

I've taken apart my pocket calculator, and I'd like to know what IC is inside the black blob. Is there an IC commonly used in such applications?
0
votes
1answer
2k views

Simple calculator problem [closed]

So I am trying to create a calculator program in arduino using this codes. ...
2
votes
1answer
221 views

Trying to read calculator key presses into PC via parallax propeller chip

I am trying to do read the key presses from a calculator via a parallax propeller board (it's actually a DefCon 20 badge) into my computer via USB. I want the calculator to remain fully functional as ...
-5
votes
2answers
379 views

Calculator with phone keypad question [closed]

I am not an electronic person and found this site in a my quest for the perfect calculator. I use both a phone and calculator for calculations and find the back and forth to cause me to make errors ...
0
votes
2answers
438 views

Calculating “useable amps”

We use a 1650 mAh capacity LiPo battery. It has a 2.5volt undercurrent protection cutoff set. Our device uses a CONSTANT 5mA of draw UNTIL the battery drops down to 3.2V, at which time the system ...
-2
votes
2answers
631 views

how can i connect my usb port to ATmega16

I have a calculator circuit and i want to be connected to pc with a USB port,this circuit contains a ATmega16 micro,my question is how can i see dats that keypad sends in both calculator lcd an pc ...
0
votes
2answers
310 views

How to design voltage ladder on ADC for non linear purposes

I'm designing a 4-bit ADC for a project that receives a reference voltage that ranges from 1.0 to 1.25. The problem is, it's not a linear variation, as in 0001 can be 1.05V, 0010 1.1V but 0011 could ...
-3
votes
2answers
735 views

Arduino 3 digit LCD calculator

We would like to build a calculator using Arduino which uses 3 digit LCD and a keypad similar to digital phones. (# for plus , * for minus) Which components and way is good enough to not to run out of ...
1
vote
0answers
189 views

Impedance calculators differ pretty much?

As you can see here to calculators I found show huge difference or didn't I set it up correctly? I didn't found hints on possible validity limits. Can someone say if one of those given out results is ...
8
votes
3answers
2k views

Designing a simple ALU

I need to design an ALU with two 8-bit inputs A and B and control inputs x, y, and z that supports the following operations: ...
3
votes
2answers
950 views

What exactly is happening when a graphing calculator LCD malfunctions when batteries are weak or overloaded?

I'm a beginner in electrical engineering, and I have limited knowledge of how electronics work internally. I'm trying to understand some odd LCD behavior when the batteries are weak or subjected to a ...
1
vote
1answer
1k views

How to calculate Vout in this resistors network?

How do I calculate Vout in terms of Vin and R1,...R5? Vin----+-------+ | | R4 R1 | | +--R5---+--Vout | | R3 R2 | | ...
15
votes
12answers
47k views

How to build a calculator?

I'm a newbie in electronics. I'm trying to build a calculator from scratch as a simple project and side hobby to keep me busy. My goal is to build a simple calculator, not a scientific or graphing ...