PrairieLearn OER Element: Analog Circuit

This element was developed as a PrairieLearn OER element. Please carefully test the element and understand its features and limitations before deploying it in a course. It is provided as-is and not officially maintained by PrairieLearn, so we can only provide limited support for any issues you encounter!

If you like this element, you can use it in your own PrairieLearn course by copying the contents of the elements folder into your own course repository. After syncing, the element can be used as illustrated by the example questions that are also contained in this repository.

pl-analog-circuit element

This element renders analog circuit schematics in PrairieLearn questions. It can render circuits from JSON circuit dictionaries or from CircuitikZ/TikZ inputs. The element itself only displays the circuit. Other elements need to be used to collect student answers for grading.

Example

<pl-question-panel>
  <p>Use the circuit below to answer the following question.</p>
</pl-question-panel>

<pl-analog-circuit answers-name="circuit"></pl-analog-circuit>
<pl-number-input answers-name="voltage" label="$V_S =$" suffix="$V$"></pl-number-input>

def generate(data):
    data["correct_answers"]["voltage"] = 9.0
    data["params"]["circuit"] = {
        "circuit": {
            "components": [
                {"from": "0,0", "to": "0,3", "type": "SourceV", "label": "$V_S$"},
                {"from": "0,3", "to": "4,3", "type": "Resistor", "label": "$R_1=7\\,k\\Omega$"},
                {"from": "4,3", "to": "4,0", "type": "Resistor", "label": "$R_2=3\\,k\\Omega$"},
                {"from": "4,0", "to": "0,0"},
                {"pos": "0,0", "type": "Ground"},
            ],
            "nodes": [
                {"pos": "0,3", "dot": "filled", "label": "a"},
            ],
            "annotations": [
                {"type": "LoopCurrent", "bounds": ("0,0", "4,3"), "label": "$I=0.9\\,mA$"},
            ],
        }
    }

Element Attributes

Attribute	Type	Description
answers-name	string (required)	Key in data["params"] containing the circuit data.
format	string (default: "json")	Circuit input format: "json" or "circuitikz".
width	integer (default: 600)	Rendered image width attribute.
height	integer (default: 400)	Rendered image height attribute.
scale	float (default: 1.0)	Coordinate scale applied while rendering.
debug	boolean (default: false)	If true, shows the parsed circuit data below the rendered image.

JSON Circuit Data

For JSON circuits, set data["params"][answers_name]["circuit"] in server.py, or place the JSON directly inside the <pl-analog-circuit> tag. The value should be a dictionary with this structure:

Key	Type	Description
components	list (required)	Wires and circuit elements to draw.
nodes	list (optional)	Named or labeled points in the circuit.
annotations	list (optional)	Top-level annotations (e.g., loop current arrows).

Circuit Components

Two-terminal components use to plus optional from, type, label, and annotations keys. If from is omitted, it defaults to (0, 0) for the first component or the previous component's to position afterward. If type is omitted, the component is drawn as a Line. One-position components, such as grounds, use pos and type.

Component type values are forwarded to schemdraw.elements, such as Resistor, Capacitor, SourceV, SourceI, Line, and Ground.

Component positions can be tuples, "x,y" strings, or node names (see below).

Component labels can be strings, label dictionaries, or lists of either form:

{"label": "$R_1$"}
{"label": [{"label": "$I$", "side": "top"}, {"label": "$+$", "side": "left"}]}

It is recommended to use side for placing labels on two-terminal components. The built-in Schemdraw placement parameter loc is also supported, but can lead to unexpected results for rotated components.

The only currently supported component annotation is CurrentLabel, with optional label, top, ofst, and reverse keys.

Circuit Nodes

Nodes require pos and can include label, name, and dot. Node labels are always plain strings. Set dot to "filled" or "open" to draw a node marker. A node name is not rendered, but can be used as a position alias in component endpoints or annotation bounds.

Circuit Annotations

The only currently supported top-level annotation is LoopCurrent, with bounds, optional pad (default: 0.3), and optional label. Bounds is a tuple or list of the top left and bottom right bounds of the annotation, which can take the same format as component endpoints.

CircuitikZ Usage

Set format="circuitikz" to render a CircuitikZ/TikZ source. This feature is rather limited and experimental. Using JSON is highly recommended!

The element accepts either a circuitikz or tikzpicture environment:

<pl-analog-circuit answers-name="circuit" format="circuitikz" scale="0.5">
  \begin{tikzpicture}
    \draw (5, 3) to[american voltage source, l={$5V$}] (5, 6);
    \draw (5, 6) to[american resistor, l={$10\Omega$}] (8, 6);
    \draw (8, 6) to[american resistor, l={$20\Omega$}] (8, 3);
    \draw (8, 3) -- (5, 3);
  \end{tikzpicture}
</pl-analog-circuit>

The parser currently reads \draw paths made of coordinates connected by --, -, or to[...]. Coordinates can be absolute, such as (2,0), or relative with ++, such as ++(2,0). Comments beginning with % are ignored.

Supported component aliases include resistors (R, resistor), variable resistors (rv, resistorvar), capacitors (C), inductors (L), voltage sources (sV, vs, voltage source), current sources (si, is, current source), batteries, diodes, and shorts/wires/lines. american in the environment options or component token selects IEEE-style resistors where available.

Labels can be supplied with l=..., label=..., a=..., or common component label forms such as R={4k} and v^>={12V}. Dot markers in path options, such as -*, o-*, and *-*, create open or filled circuit nodes. Single-position node elements are limited to node[ground], node[gnd], node[earth], node[vss], and node[vdd].