Electr Gem Version

Interactive language for electronic formulas.

Rationale

  • I have not found an open source language or calculator at the command line, specialized in electronic formulas
  • I'm always confused with milli, micro, pico, nano, etc
  • I prefer to type 100k rather than 100000, or 100M rather than 100000000
  • If, for any reason, I want to write 100000000, then I should be able to write 100_000_000 or 100,000,000

I don't want a big monster but a tiny specialized language.

What do you think?

I started to write this tiny language. First, a quick prototype in Ruby, as a proof of concept. And then, maybe, a more portable version in C.

Tell me what you think on twitter or better, open an issue here on Github. In any cases feel free to start a discussion.

The current version is an early one:

  1. Don't expect too much
  2. Expect a lot of bugs
  3. Please be kind enough to report any bugs here in Github

Installation

Install it with:

$ gem install electr

Examples of what Electr can do right now

Start Electr

Just type electr:

$ electr

And you'll see the prompt waiting for you:

E>

To compute an expression without entering the interactive mode, use the -e switch:

$ electr -e "3V / 25mA"
120

To display the AST instead of doing the computation, use the --ast switch (this is intended only for the developers):

$ electr --ast -e "3V / 25mA"
ast
  root
    operator (/)
      value ::= 3V
      value ::= 25mA

Resistors in serie

Start simple to illustrate the addition. We have a 10,000 Ohm resistor (10k) and a 200 Ohm resistor (200R):

E> 10k + 200R
10200

Should it be K, k, kΩ or the three is still open to debate.

Ohm's law

Divide Volts (V) by milliamps (mA) to get some Ohms:

E> 3V / 25mA
120

There is no symbol for the multiplication. Simply put values side by side:

E> 1mA 3k
3

Frequency of an oscillator

A little bit more complex is the computation of a frequency for an oscillator. We've got two constants (2 and pi), a value in micro Farad (0.5uF) and a square root (sqrt) of the product of two resistors (11k 22k). The result is in Hertz.

E> 1 / (2 pi 0.5uF sqrt(11k 22k))
20.4617344581

Units

Currently Electr knows the following units:

Prefix and/or Symbol Name
k K kΩ kilo ohm
Ω R ohm
A ampere
V volt
W watt
mA milli ampere
mV milli volt
mW milli watt
μ u μF uF micro farad
p pF pico farad

What is missing?

Electr is at a very early stage and it miss a lot of (basic) things! You can expect that the following features will be implemented in the next couple of days/weeks:

  • [x] Negative numbers
  • [x] Floating point number without a leading zero (ie .678)
  • [x] 10_000 or 10,000 will be the same as 10000
  • [ ] * for the multiplication if one want to
  • [ ] √ for an alternative to square root
  • [ ] More builtin functions (sin, cos, tan, etc)
  • [ ] Exponent
  • [ ] Shortcuts for function's names (ie sq and sqr for sqrt)
  • [ ] Readline lib in the REPL for a better user experience
  • [ ] All units and prefix used in electronic

What's next?

Maybe Electr could infer the resulting unit:

E> 10k + 200R
10.2kΩ
E> 3V / 25mA
120Ω
E> 3V / 1mA
3kΩ

One are less prone to typing errors (less parenthesis) if one enter a complex expression on two lines:

E> 1 /
E> 2 pi 0.5uF sq(11K 22K)
20.46Hz

Beyond the calculator

Electr could be more interactive. In the following session we've got a resistor R1 and two capacitors C1 and C2. Once the formula is entered, Electr ask us for the components values, then gives us the result.

E> 1/
E> 2 pi R1 sq(C1 C2)
R1=?> 33K
C1=?> 1000pF
C2=?> 470pF
7.04kHz

Or acts like a tiny programming language.

E> R1 = 33k
E> C1 = 1000pF
E> C2 = 470pF
E> 1 / (2 pi R1 sq(C1 C2))
7.04kHz

Why not having custom functions?

E> func = { 1 / (2 pi R1 sq(C1 C2)) }
E> func(R1=33k, C1=1000pF, C2=470pF)
7.04kHz

The above syntax is just one possibility amongst a lot of others.

Contributing

  1. Fork it ( https://github.com/lkdjiin/electr/fork )
  2. PLEASE Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request

Alternatives

Some people point me to two existing softwares:

Frink is closed source, so it doesn't meet my requirements. GNU Units is awesome and close to what I want but it's so huge and not at all specialized! I want to deal with ohms, farads, volts, etc and not with kilograms nor with furlongs ;)