Schemdraw

Schemdraw provides a comprehensive library of electrical components organized by their terminal count and functional type. You can import these elements from the schemdraw.elements submodules to build circuit diagrams.

Component Categories:

• Two-Terminal Elements: Found in schemdraw.elements.twoterm and schemdraw.elements.sources. These include standard components like resistors, capacitors, and power sources.
• One-Terminal Elements: Found in schemdraw.elements.oneterm. These are components that connect to a single node (e.g., ground).
• Switches: Found in schemdraw.elements.switches.
• Lines, Cables, and Connectors: Use schemdraw.elements.lines, schemdraw.elements.cables, and schemdraw.elements.connectors to define the paths between components.
• Active Components: Includes Transistors (schemdraw.elements.transistors), Transformers (schemdraw.elements.xform), and Opamps/Integrated Circuits (schemdraw.elements.opamp and schemdraw.elements.intcircuits).
• Other/Miscellaneous: Includes specialized components in schemdraw.elements.misc, schemdraw.elements.compound, schemdraw.elements.twoports, and schemdraw.elements.tubes.

All elements have predefined anchor positions (e.g., a BJT has base, emitter, and collector; two-terminal elements have start, center, and end).

Once an element is placed in a drawing, you can access its anchor positions in two ways:

1. Attribute access: element.anchor_name (e.g., Q.base).
2. Bracket access: element['anchor_name'] (useful if the anchor name contains special characters like dots).

Note: Anchor positions are relative to the drawing origin and are only available after the element has been placed in a drawing. You can inspect all available anchors before placement using the .anchors attribute, which returns a dictionary of anchors relative to the element's origin.

with schemdraw.Drawing() as d:
    d.config(fontsize=10)
    # Assigning to a variable allows anchor access
    bjt = elm.BjtNpn()
    bjt.label('base', 'base', color='blue')
    
    # Accessing anchors after placement
    print(bjt.base) 
    print(bjt['base'])

Use schemdraw.elements.compound.ElementCompound to create a new element composed of multiple other elements. Unlike ElementDrawing, which wraps a drawing, ElementCompound acts like a Drawing itself, allowing you to add elements within a setup method.

Key Features:

• Elements added via self.add() in the setup method are part of the compound element.
• Elements assigned to an attribute of the class have absolute anchor positions accessible via index notation (e.g., instance['attr_name.anchor']).

from schemdraw import elements as elm

class RC(elm.ElementCompound):
    def setup(self):
        # Add elements using self.add()
        self.r = self.add(elm.Resistor().length(1).scale(.5))
        self.c = self.add(elm.Capacitor().length(1).scale(.5))
        # Set parameters based on other elements
        self.elmparams['drop'] = self.c.end

with schemdraw.Drawing() as d:
    r1 = RC()
    r2 = RC()
    # Accessing an internal anchor of the second instance
    print(r2['r.end'])

Schemdraw provides specialized elements for labeling electrical properties:

Voltage Labels

• Multi-point labels: Pass a list or tuple of strings to .label() to space them evenly along an element (e.g., ('--', '$V_1$', '+')).
• Gap labels: Use elm.Gap() to label voltage across a terminal or gap.
• Arc labels: Use elm.VoltageLabelArc().at(element).label('V1') to draw a voltage label as an arc over an element.

Current Labels

• Standard Current Label: Use elm.CurrentLabel().at(element).label('10 mA'). For transistors, it follows sensible bias currents by default.
• Inline Current Label: Use elm.CurrentLabelInline(direction='in'|'out').at(element).label('10 mA') to draw arrowheads directly on the leads of 2-terminal elements.
• Loop Current: Use elm.LoopCurrent([e1, e2, e3, e4], direction='cw'|'ccw').label('$I_1$') to label a loop of four elements.
• Impedance Label: Use elm.ZLabel().at(element).label('$Z_{in}$') for right-angle arrows indicating impedance at a node.

import schemdraw
from schemdraw import elements as elm

# Voltage across a gap
with schemdraw.Drawing():
    elm.Line().dot(open=True)
    elm.Gap().label(('–', '$V_o$', '+'))
    elm.Line().idot(open=True)

# Current through a resistor
with schemdraw.Drawing():
    R1 = elm.Resistor()
    elm.CurrentLabel().at(R1).label('10 mA')

# Loop current
with schemdraw.Drawing():
    R1, C1 = elm.Resistor(), elm.Capacitor().down()
    D1, L1 = elm.Diode().fill(True).left(), elm.Inductor().up()
    elm.LoopCurrent([R1, C1, D1, L1], direction='cw').label('$I_1$')

Schemdraw provides three levels of styling hierarchy:

1. Drawing level: Use Drawing.config() to apply styles to all elements within a specific drawing instance. Parameters include color, linewidth, font, fontsize, linestyle, fill, background_color, and the default 2-Terminal element length.
2. Global level: Use schemdraw.config() to apply styles to every new drawing created during the current Python session.
3. Element level: Using setter methods or keyword arguments on specific elements (highest priority).

Styling Hierarchy (Highest to Lowest Priority):

1. Setter methods (e.g., .fill()) called after instantiation.
2. Keyword arguments provided during instantiation.
3. User-defined Element.defaults.
4. Element definition defaults.
5. Drawing.config() settings.
6. schemdraw.config() settings.

import schemdraw
import schemdraw.elements as elm

# Set global defaults
schemdraw.config(lw=1, font='serif')

# Set drawing-specific defaults
with schemdraw.Drawing(color='blue', fill='lightgray') as d:
    elm.Resistor().label('100KΩ')