LED Torch

Before assembling this torch make sure you have checked out the breadboard switch circuit so that you have an understanding of how the circuit works.

Equipment / Materials:

  • Safety Glasses
  • Solder (0.5 to 0.8mm leaded is recomended)
  • Dry scourer or wet sponge for cleaning solder tip
  • Soldering iron (adjusted to about 285 – 300 degrees)
  • Side cutters
  • Long nosed pliers
  • Component bending tool
  • Multimeter (for diagnosing problems)
  • Soldering mat (to protect bench)
  • Air fume extractor (or room with good air flow)

Safety

  • Ensure safety glasses are worn whilst cutting component leads and soldering
  • Work under fume extraction system to reduce inhalation of bad air
  • Do not touch tip of soldering iron or any component that has recently been soldered
  • Wash hands with soap after soldering to remove fluxes and lead.

Parts:

Part Qty Name
PCB 1 LED Torch PCB
R1 1 15 Ohm Resistor
LED1 1 White LED 5mm
S1 1 Push Button Switch
Bat 1 CR2450 Coin Battery
J1 1 CR2450 Battery Clip

Instructions:

1. Please check safety list before beginning above before proceeding.
Identify / collect the following tools and set up work space: component bending tool, side cutters, long nose pliers.
2LED Torch Soldering Tools2. Identify the following parts; 15 Ohm resistor, push button switch, 5mm white LED, CR2450 3V Cell battery, CR2450 battery clip and LED Torch PCB.
1LED Torch Parts3. Using the component bending tool on the second smallest step, bend both sides of the 15 Ohm (Brown, Green, Black, Gold) resistor to 90 degrees.
3LED Torch Bend Resistor4LED Torch Bent Resistor

4. Insert the resistor into the R1 location on the PCB so that the body of the Resistor covers the text “R1”.
5LED TorchInsert Resistor

5. Using long nose pliers bend both leads of the resistor out to 45 degrees. You need the bend of the resistor to be sharp and close to the PCB. This process is called semi clinching.6LED Torch Simi Clentch

6. Using the side cutters with the flat side facing the PCB and at 45 degree angle to the surface. Place the point sharp point of the blades either side of the resitor leg resting on the outside edge of the solder pad. This will automatically determine the length of the lead.

7LED Torch Cut Lead2

7. Before soldering you will need to prepare the tip of the soldering iron. Notice in the photo bellow the tip is a dull grey colour. Tinning the tip of the soldering iron cleans the surface of the tip and allows it to conduct heat into the pad faster.

Tinning Soldering Iorn 1

8. Melt some solder onto the tip of the Iron and then using either a dry scourer style or wet sponge style cleaner wipe the solder off of the tip.

Tinning Soldering Iron 2

9. Once you have tinned / cleaned the tip you will notice the tip is much more shiny and of a silver colour.Tinning Soldering Iron 3

10. Watch the video demonstration of the first resistor joint. Notice the soldering iron tip is used to heat up the solder pad for about 1-2 seconds before the solder is introduced. A small amount of solder is fed into the joint and then the solder wire is removed before removing soldering iron to allow joint to solidify.

11. Hold the LED in the long nose pliers so that the flat spots on the legs are just above the edge of the pliers jaws.

8LED Torch Bend LED

12. Carefully bend the LED to 90 degrees.9LED Torch Bent LED

13. Insert the LED into the holes labelled LED1. ENSURE YOU HAVE THE LONGER LEG ON POSITIVE SIDE. There is also a flat surface on the side of the LED that should line up with the white silk screen if the LED were standing upright.
10LED Torch Semi LED

14. Semi clench the LED legs using the same method as the resistor. Solder on leg of the LED then check it is still aligned correctly and leads are flat along the top of the PCB.

15. Insert push button switch. You do not have to bend the legs as they should spring out and hold them self.
11LED Torch Insert Push Button

16. Solder one joint of push button switch, check the switch is sitting flat on the PCB before soldering remaining three joints.

17. Sometimes the battery does not make good contact with the square solder pad that sits under the battery clip. It is recommended that you put a very thin layer of solder on the pad seen in the video below.

18. Finally insert the battery clip on the top side of the PCB.

12LED Torch Battery Holder19. It would be helpful to work in partners so that the PCB can be held upside down on the table so the battery clip is fully inserted. Solder one of the joint of the battery clip. THE WHOLE CLIP WILL GET A LITTLE BIT HOT AS IT IS CONDUCTIVE. Ensure the clip is fully inserted with no gap between PCB and sides of clip before soldering second joint.
13LED Torch Under Soldered20. Check that all joints are neat and have enough solder so that it flowed out the the edge of the pad but does not bubble up away from the PCB.

21. Insert a battery with the smaller diameter of the coin cell touching the PCB pad.
Test and or fault find.
13LED Torch Top Finished

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