While you can draw a diagram in a lot of different applications, some are made specifically for schematic capture (drawing circuit diagrams). These will do handy things like maintaining wire connections between parts as you move them and provide libraries of the common circuit elements for you to easily include. A few good free options are:

  • Logisim (Holy Cross Edition) — Installed in the CNS labs, this is a great tool for simulating, testing, and understanding digital logic circuits in addition to its fairly good schematic capture. Use the “File > Export Image…” function to get an image you can use in your lab report. Crop the image to only include the circuit in your lab report and avoid wasting space.
    Note that Logisim does not have proper circuit diagram elements for LEDs or resistors, making it poorly suited to drawing circuits with those components. [In this course, those elements are needed in the report for Lab 1 only, and no others.]

  • Diagrams.net — A free online drawing program. It doesn’t do any sort of circuit simulation, but it does have all of the needed symbols to place and connect electrical components in a circuit diagram. Go to “+ More Shapes…” in the bottom left of the interface, then enable the “Electrical” library (under “Other” at the bottom of the list of libraries). You can search for symbols by name as well.

  • TinyCAD — Use “File > Export as image file…” to get an image for your lab report. Again, please crop the image to avoid wasting space.

  • CircuitVerse — A free online tool similar to Logisim in functionality. It has very similar capabilities and similar limitations (no LEDs, resistors as needed for Lab 1). To export an image, use Tools > Render Image, and choose the SVG format (a vector format). If you can’t import an SVG image into your word processor of choice, then use PNG with 4x resolution for the best-looking alternative. (CircuitVerse was recommended to me by a student who felt Logisim’s output was too ugly.)

  • SchemeIt — An online schematic editor provided by DigiKey, an online parts retailer. I haven’t used it myself, but a student found it useful. It may try to sell you parts (as that is DigiKey’s primary line of business).

  • CircuitLab — Another online schematic editor. It is a quality commercial product with a free demo (time limited and doesn’t allow saving) and a subscription fee: ~$80 for a year of access (the $24/yr option is too limited to be very useful).

Logisim or CircuitVerse are probably the best options in general, but students have had success with others, which you might want to try out as well.