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Breadboard Power Supply Comparison

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About This MicroSim

Four things can power a breadboard, and they fail in four completely different ways. This table puts them side by side: a 3 × AA battery pack, a USB wall charger, the MB102 module that plugs onto the power rails, and a bench supply with an adjustable current limit.

What makes this table different from most comparison charts is that every specification is clickable, and clicking it shows you where the number came from — the datasheet, the manual, or the safety bulletin — along with the exact wording in that source and how much confidence it deserves.

Ask Where the Number Came From

Volt thinking about a key concept Any table can print "1.5 A" in a box. The useful question is who measured that, and where can I read it myself? Click a cell and find out. Getting into that habit is a genuine engineering superpower — and it will save you from a lot of confidently wrong numbers on the internet.

How to Use

  1. Use the Who is building? menu to pick a situation. The table highlights the supply this book recommends and explains the reasoning.
  2. Click any specification cell — the ones with a dotted underline — to open the source panel beneath the table.
  3. Read the colored dot on each cell. It tells you how solid that number is before you rely on it.

What the Colors Mean

Dot Verdict What it means
🟢 Verified The exact number appears in a primary source, quoted in the panel.
🟩 Derived Calculated from a primary-source number; the arithmetic is shown.
🟠 Directional The effect is real but the exact figure varies by board or brand.
🟧 Qualitative only Supported in words but not reliably quantified. No number is claimed.
⚪ Project estimate This book's own classroom pricing. Check current prices.

The Comparison at a Glance

Supply On a short circuit Settable limit Replace cost
3 × AA pack Several amps briefly, then the cells sag None ~$1 + cells
USB wall charger Depends entirely on the charger None ~$1.20 each
MB102 module Limits at 0.9–1.5 A, then shuts down above 165 °C Fixed ~$2
Bench supply Clamped at whatever you dialed in Yes — you set it $50–100

A Battery Pack Is Not Automatically Safe

Volt pointing out a common mistake It is easy to assume batteries are harmless because they are small. A fresh alkaline AA has only about 0.15–0.3 Ω of internal resistance, so three of them in series can push several amps into a dead short — enough to make wires and holders hot. Batteries are a fine place to start; they are not a substitute for finding the short.

Lesson Plan

Grade Level

Grades 7–12; beginning electronics

Duration

15–20 minutes

Prerequisites

  • Ohm's law, well enough to compute current from voltage and resistance
  • Knowing what a short circuit is
  • Chapter 5 power-supply vocabulary

Learning Objective

Students will evaluate four breadboard power supplies against a situation and justify a choice using cited specifications rather than assumptions.

Activities

  1. Explore (5 min): Open every cell in the "On a Short Circuit" column. Which supply is the only one where you decide the fault current?
  2. Trace a claim (5 min): Open the MB102 short-circuit cell and follow the link to the AMS1117 datasheet. Find the current-limit row yourself.
  3. Judge the evidence (5 min): Find the one cell marked Qualitative only. Why does this book refuse to print a number there? What would it take to turn it into a verified number?
  4. Apply (5 min): Pick a scenario from the menu and argue for a different supply than the one recommended. Which cells support your case?

Assessment

Give students a situation not in the menu — a robot that must run untethered for an hour, or a class of twenty beginners sharing one supply — and ask them to choose a supply and cite two specifications from the table that justify it. Full credit requires naming the source, not just the number.

References

Every figure in this MicroSim traces to one of these sources:

  1. AMS1117 1A Low Dropout Voltage Regulator datasheet, Advanced Monolithic Systems — current limit, thermal shutdown, dropout voltage, package power rating. http://www.advanced-monolithic.com/pdf/ds1117.pdf
  2. Energizer E91 (AA alkaline) Product Datasheet, Energizer Brands LLC — nominal voltage and internal resistance. https://data.energizer.com/pdfs/e91.pdf
  3. "High Powered AA Batteries," Health & Safety Bulletin HSB18, Lincolnshire County Council, April 2013 — short-circuit hazards of alkaline cells in school circuit work.
  4. DP800 Series Programmable Linear DC Power Supply User Guide, RIGOL Technologies — constant-current crossover behavior.
  5. "USB in a NutShell — Chapter 2," Craig Peacock, beyondlogic.org, summarizing USB 2.0 bus-power limits. https://www.beyondlogic.org/usbnutshell/usb2.shtml
  6. Parts List for a $50 Kit — this book's own classroom pricing estimates.

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