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Technologies K–10 · Years 7–8

Soldering an LED indicator on stripboard

Materials and Production Processes focus area (NSW Technology 7–8, 2023); Design and Technologies: Processes and production skills, Producing and implementing (ACARA v9)

PracticalMedium risk

School laboratory, not for home

In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

The idea

A soldered joint makes a permanent electrical connection, and choosing the resistor from the LED's datasheet keeps the current safe: I = (9.0 V − 1.9 V) ÷ 680 Ω = 10.4 mA.

Safety card

Medium riskA teacher supervises

Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

Hazards

  • Burns from the soldering iron and molten solder
  • Flux fumes
  • Flying lead offcuts
  • Soldering iron left on

Controls

  • Iron always returned to its stand; hair tied back; hot tip never touched
  • Fume extractor or fan and a ventilated room; lead-free solder
  • Safety glasses; hold the lead end when cutting
  • Station switched off and cooled at the end

Note

Follow the soldering advice in the NSW Department of Education Chemical Safety in Schools package (Section 3, Curriculum support, 2021 technical update) (adequate ventilation to AS 1668, correct iron temperature, flux fume control) and NSW Department of Education TAS compliance advice (mandated controls and Equipment Safety in Schools), education.nsw.gov.au/teaching-and-learning/curriculum/tas/tas-compliance; record the activity on RiskAssess (riskassess.com.au).

What you need

  • Temperature-controlled soldering station set to the solder maker's recommended temperature, on its stand
  • Lead-free solder wire with a no-clean flux core
  • Fume extractor or a small fan wafting fumes away from the face; safety glasses
  • Stripboard 10 × 10 holes, track cutter, side cutters, damp sponge
  • 1 red 5 mm LED (1.9 V typical at 10 mA, 30 mA maximum), 1 × 680 Ω and 1 × 470 Ω 0.25 W resistor, 1 slide switch, 1 × 9 V battery and snap
  • Digital multimeter

How to do it

  1. Plan the layout on grid paper, marking track cuts, component holes and the LED's flat (negative) side.
  2. Cut the tracks where planned and check with the multimeter's continuity setting.
  3. Insert the resistor, LED and switch. Solder each joint by heating the pad and lead together for 1 to 2 seconds, feeding solder into the joint, removing the solder, then the iron.
  4. Trim the leads while holding the cut end and wearing safety glasses.
  5. Inspect every joint: a good joint is a smooth, shiny cone; a dull ball is a dry joint to redo.
  6. Connect the battery, measure its voltage and the current, and compare with the prediction; swap to the 470 Ω resistor on a test lead and measure again.

What you should see

With 9.0 V and the typical 1.9 V LED, 680 Ω gives 10.4 mA and turns 74.1 mW into heat in the resistor; 470 Ω gives 15.1 mA and 107.3 mW, both below the LED's 30 mA limit and the resistor's 250 mW rating. A fresh battery may not read exactly 9 V, so measure it and use the measured voltage in the prediction. The learner knows it worked when the LED lights at the switch, every joint is a shiny cone, and the measured current is close to the prediction from the measured battery voltage.

What changes

This activity lists no variables to change, measure and keep the same.

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

  • More solder makes a stronger joint (too much hides a dry joint and can bridge tracks).
  • The LED can go either way round (it lights in one direction only).
  • Lead-free solder has no fume hazard (flux fumes are still irritants).

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

  • Technology 7–8 Syllabus (2023), NESA. Current: taught from 2026. Code read from the outcomes page on 2026-09-22.TE4-SAF-01TE4-PPM-01
  • Technology Mandatory 7–8 Syllabus (2017), NESA. Outgoing: replaced by the Technology 7–8 Syllabus (2023) from 2026 and not available after December 2027. Code read from the official syllabus document (DOCX) on 2026-09-22.TE4-3DP
  • Australian Curriculum v9AC9TDE8P03AC9TDE8K06

Sources

The pages the author read to write this activity.

  1. curriculum.nsw.edu.au/learning-areas/tas/technology-7-8-2023/outcomes
  2. www.nsw.gov.au/education-and-training/nesa/curriculum/tas/technology-mandatory-7-8-2017
  3. education.nsw.gov.au/content/dam/main-education/asset-management/chemical-safety/3._Section_3_Curriculum_Support.pdf
  4. www.kingbrightusa.com/images/catalog/SPEC/WP7113ID.pdf
  5. education.nsw.gov.au/teaching-and-learning/curriculum/tas/planning-programming-and-assessing-tas-7-10/technology-7-8

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