Valentine Heart Project

This project flashes 18 LEDs at three different rates and you can use these to create an eye-catching Valentine Heart. The circuit is kept simple (and low cost) by using the 4060B IC which is a counter and oscillator (clock) in one package. The circuit requires a 9V supply, such as a PP3 battery. It will not work with lower voltages and a higher voltage will destroy the LEDs.

The preset variable resistor can be used to adjust the oscillator frequency and this determines the flash rate of the LEDs. The IC limits the current to and from its outputs so the LEDs can be safely connected without resistors in series to limit the current. The stripboard part of the circuit is easy to build but the wiring for the LEDs needs care so detailed instructions are provided below.

You can download our Valentine Heart template to print out and glue onto thick card, hardboard etc.

Warning!
Using a battery (or power supply) with a voltage higher than 9V will destroy the LEDs.
You can see from the circuit diagram (below) that 6 LEDs are connected in series between the +9V supply and 0V. Each LED requires about 2V across it to light, so using a voltage of about 12V (= 6 × 2V) or more will make the LEDs conduct directly, regardless of the 4060B IC. With no series resistor to limit the current this will destroy the LEDs.

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Parts Required

• resistors: 10k, 470k
• preset: 47k (this could be 100k if necessary)
• capacitor: 0.1µF
• 4060B IC
• 16-pin DIL socket for IC
• LEDs × 18, 5mm diameter, red (or any mix of red, orange, yellow and green)
• on/off switch
• battery clip for 9V PP3
• stripboard 13 rows × 18 holes

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Stripboard Layout

Building the Circuit

1. Begin by soldering the components onto the stripboard as shown in the diagram above. Do not insert the 4060B IC at this stage.

Arranging the LEDs:

2. Cut out a suitable shape from stiff card (or similar material), such as the Valentine Heart template. Paint or colour the card at this stage if necessary.
3. Plan the layout of the 18 LEDs (suggested positions are marked on the template).
4. Drill 5mm holes for the LEDs - put the card on a piece of scrap wood to do this without damaging the card or the table.
5. Push LEDs into the holes, they should be a fairly tight fit and glue should not be necessary.
6. Label the LEDs D1 - D18 at random on the back of the card.

Wiring of the LEDs:

Use stranded wire for all the connections to the LEDs and solder all wires near to the LED body so the leads can be trimmed short later on.

The wire colours are suggested to avoid confusion but you can use other colours if you wish, the electricity won't mind! For example you could use red and black as suggested but substitute yellow and white for the blue and green suggested.

7. Cut all the LED short leads to be very short to make identification easier: 
8. Connect RED wire to link up all the LONG leads of D1, D2 and D3.
   Remember to solder wires near to the LED body so the long lead can be trimmed short later on.
9. Connect BLACK wire to link up all the SHORT leads of D16, D17 and D18.
10. Use 3 pieces of BLUE wire to connect:
    • D7 short - D10 long
    • D8 short - D11 long
    • D9 short - D12 long
11. Use 12 pieces of GREEN wire to connect:
    • D1 short - D4 long
    • D4 short - D7 long
    • D2 short - D5 long
    • D5 short - D8 long
    • D3 short - D6 long
    • D6 short - D9 long
    • D10 short - D13 long
    • D13 short - D16 long
    • D11 short - D14 long
    • D14 short - D17 long
    • D12 short - D15 long
    • D15 short - D18 long
12. Connect the RED wire from the circuit board to the RED wiring on the Valentine heart (connect it to any convenient point).
13. Connect the BLACK wire from the circuit board to the BLACK wiring on the Valentine heart (connect it to any convenient point).
14. Connect the 3 BLUE wires from the circuit board to each of the 3 BLUE wires on the Valentine heart, they may be connected in any order.
15. Carefully check all wiring.
16. Trim the long LED leads.
17. Plug the 4060B into its holder.
18. Connect a 9V battery and switch on.
19. Using a small screwdriver, adjust the 47k preset variable resistor to give a suitable flash rate for the LEDs.

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Circuit diagram

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Heart-shaped Badge Project

The badge consists of eight LEDs arranged in the shape of a heart. One LED is lit at a time and this 'chases' round the shape. It would be easy to adapt this project to create other shapes with the eight LEDs. This project uses a 555 astable circuit to provide the clock pulses for the 4017 counter.

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Parts Required

• resistors: 2.2k, 47k, 270 ×8
• capacitors: 0.1µF, 1µF 16V radial
• red LEDs ×8
• 555 timer IC
• 4017 counter IC
• DIL sockets for ICs: 8-pin, 16-pin
• on/off switch
• battery clip for 9V PP3
• safety pin to attach badge
• ribbon cable 9-way about 1 metre (to connect badge to main circuit)
• stripboard: 16 rows × 19 holes for circuit, 10 rows × 9 holes for badge

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Stripboard Layouts

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Circuit diagram

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'Random' Flasher for 8 LEDs Project

This project flashes eight LEDs in an apparently random manner. It uses a 4026 combined counter and display driver IC which is designed for driving 7-segment LED displays. The sequence is not really random because seven of the LEDs would normally be the display segments, the eighth LED is driven by an output that is normally used for driving further counters. The table below shows the sequence for the LEDs. You can use less than eight LEDs if you wish and the table may help you decide which ones to use for your purpose.

This project uses a 555 astable circuit to provide the clock pulses for the 4026 counter. Resistors are not required for the LEDs because the 4026 IC limits the current to about 5mA for each LED.

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Parts Required

• resistors: 10k, 47k
• capacitor: 1µF 16V radial
• 3mm or 5mm LEDs ×8,
  they can be various colours
• 555 timer IC
• 4026 counter and display driver IC
• DIL sockets for ICs: 8-pin, 16-pin
• battery clip for 9V PP3
• stripboard: 16 rows × 14 holes

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Stripboard Layout

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Circuit diagram

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Network Lead Tester Project

This project was designed for confirming the continuity and correct wiring of computer network leads which have 8 wires, but it can be used to check any lead with up to 8 wires by using appropriate connectors. For example stereo audio leads with 5-pin DIN plugs can be checked by just using the first 5 LEDs. The tester is simple but it can save a great deal of time when making up leads and it is much cheaper than the more sophisticated alternatives!

The tester works by connecting each wire to an output at one end and an LED at the other end. The outputs are switched on one at a time in sequence so that a correctly wired lead will make each LED light in turn. The 4017 IC counts up to 10 so there is a pause (for the 9th and 10th counts) before the LED sequence repeats. If the LEDs light up in the wrong sequence one (or both) of the connectors is wired wrongly. If an LED fails to light it indicates a broken connection. Please note that the RJ45 computer network plugs cannot normally be re-wired, instead they must be cut off and replaced.

This project uses a 555 astable circuit to provide the clock pulses for the 4017 counter.

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Parts Required

• resistors: 2.2k, 22k, 180k, 560 ×8
• capacitors: 0.1µF, 1µF 16V radial ×2
• red LEDs ×8
• 555 timer IC
• 4017 counter IC
• DIL sockets for ICs: 8-pin, 16-pin
• push switch
• battery clip for 9V PP3
• RJ45 computer network sockets ×2 (a dual socket for example)
  (or suitable connectors for the leads you wish to test)
• stripboard: 16 rows × 19 holes

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Stripboard Layout

Each socket should be wired up in the same way, so that wire 1 from the stripboard connects to pin 1 on the first socket, and pin 1 on the second socket connects to LED 1. 

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Circuit diagram

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Model Railway Level Crossing Lights

A magnet under the train operates reed switches positioned on the track. The trigger reed switch starts the sequence by switching on the amber light, a few seconds later the two red lights start to flash. When the train has passed the level crossing it operates the cancel reed switch which switches off the lights until the next train arrives.

There is a PCB pattern for this project, but if you don't have facilities to make PCBs you can build this project on stripboard instead. Please see the New Railway Modellers website for a stripboard layout and advice on making model lamps and barriers.

This project uses a 555 monostable circuit to switch on the amber LED for a few seconds. When this switches off it triggers a 555 bistable circuit which switches on a 555 astable circuit to flash the red LEDs.

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Parts Required

• resistors: 680 ×3, 1k ×3, 33k, 47k, 82k, 270k
• capacitors: 0.1µF ×3, 10µF radial ×2
• red LED (3mm best) ×2
• amber* (or yellow) LED (3mm best)
  * some amber LEDs are too orange to look correct, yellow may be better
• 555 timer IC ×3
• 8-pin DIL socket for IC ×3
• on/off switch
• battery clip
• reed switch ×2
• miniature magnet - each locomotive needs one
• printed circuit board (PCB) - pattern given below

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PCB component layout

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Track connections

The reed switches can be held in place between the rails with a small piece of blu tac.
Each locomotive will need a miniature magnet glued to its underside, test first with blu tac, then use superglue.

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Circuit diagram

Circuits: 555 monostable (on left) | 555 bistable (in middle) | 555 astable (on right)

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PCB copper track pattern

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Stripboard layout

If you don't have facilities to make your own PCB you can build this project on stripboard. Please see the New Railway Modellers website for a stripboard layout as well as advice on making model lamps and barriers.

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Model Railway Signal Project

A magnet under the train operates reed switches positioned on the track. The first reed switch changes the signal to red as the train passes, then further along the track a second reed switch changes the signal back to green ready for the next train. The isolated section of track just in front of the signal is switched off by the relay when the signal is red so a train will stop automatically at the red signal.

This project uses a 555 bistable circuit.

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Parts Required

• resistors: 1k ×2, 33k ×2
• capacitors: 220µF
• 1N4001 diode
• 1N4148 diode
• red LED (3mm best)
• green LED (3mm best)
• 555 timer IC
• 8-pin DIL socket for IC
• push-switch ×2
• reed switch ×2
• relay SPCO 12V coil
• miniature magnet - each locomotive needs one
• stripboard 11 rows × 24 holes

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Stripboard layout

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Track connections

• Connect the reed switches to push-switches A and B (see the stripboard layout).
• The switches can be held in place between the rails with a small piece of blu tac.
• Connect the track wires to the COM and NC contacts of the relay.
• When soldering to the track make sure you solder to the outside of the rail.
• Each locomotive will need a miniature magnet glued to its underside - test first with blu tac, but superglue is probably best once you are sure it is in the correct position.
• Note that railway signals have red at the bottom, unlike road traffic lights where red is at the top.

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Circuit diagram

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Christmas Decoration Project

This project flashes 18 LEDs at three different rates and you can use these to create a Christmas decoration of your choice. The circuit is kept simple (and cheap!) by using the 4060B IC which is a counter and oscillator (clock) in one package. The circuit requires a 9V supply, such as a PP3 battery. It will not work with lower voltages and a higher voltage will destroy the LEDs.

The preset variable resistor can be used to adjust the oscillator frequency and this determines the flash rate of the LEDs. The IC limits the current to and from its outputs so the LEDs can be safely connected without resistors in series to limit the current. The stripboard part of the circuit is easy to build but the wiring for the LEDs needs care so detailed instructions are provided below.

You can design your own decoration or download our Christmas Tree template to print out and glue onto thick card, hardboard etc. The template has two tree outlines on one sheet of A4 paper.

Warning!
Using a battery (or power supply) with a voltage higher than 9V will destroy the LEDs.
You can see from the circuit diagram (below) that 6 LEDs are connected in series between the +9V supply and 0V. Each LED requires about 2V across it to light, so using a voltage of about 12V (= 6 × 2V) or more will make the LEDs conduct directly, regardless of the 4060B IC. With no series resistor to limit the current this will destroy the LEDs.

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Parts Required

• resistors: 10k, 470k
• preset: 47k (this could be 100k if necessary)
• capacitor: 0.1µF
• 4060B IC
• 16-pin DIL socket for IC
• LEDs × 18, 5mm diameter, any mix of colours: red, orange, amber, yellow or green
• on/off switch
• battery clip for 9V PP3
• stripboard 13 rows × 18 holes

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Stripboard Layout

Building the Circuit

1. Begin by soldering the components onto the stripboard as shown in the diagram above. Do not insert the 4060B IC at this stage.

Arranging the LEDs:

2. Cut out a suitable shape from stiff card (or similar material), such as our Christmas Tree template. Paint or colour the card at this stage if necessary.
3. Plan the layout of the 18 LEDs (suggested positions are marked on our template).
4. Drill 5mm holes for the LEDs - put the card on a piece of scrap wood to do this without damaging the card or the table.
5. Push LEDs into the holes, they should be a fairly tight fit and glue should not be necessary.
6. Label the LEDs D1 - D18 at random on the back of the card.

Wiring of the LEDs:

Use stranded wire for all the connections to the LEDs and solder all wires near to the LED body so the leads can be trimmed short later on.

The wire colours are suggested to avoid confusion but you can use other colours if you wish, the electricity won't mind! For example you could use red and black as suggested but substitute yellow and white for the blue and green suggested.

7. Cut all the LED short leads to be very short to make identification easier: 
8. Connect RED wire to link up all the LONG leads of D1, D2 and D3.
   Remember to solder wires near to the LED body so the long lead can be trimmed short later on.
9. Connect BLACK wire to link up all the SHORT leads of D16, D17 and D18.
10. Use 3 pieces of BLUE wire to connect:
    • D7 short - D10 long
    • D8 short - D11 long
    • D9 short - D12 long
11. Use 12 pieces of GREEN wire to connect:
    • D1 short - D4 long
    • D4 short - D7 long
    • D2 short - D5 long
    • D5 short - D8 long
    • D3 short - D6 long
    • D6 short - D9 long
    • D10 short - D13 long
    • D13 short - D16 long
    • D11 short - D14 long
    • D14 short - D17 long
    • D12 short - D15 long
    • D15 short - D18 long
12. Connect the RED wire from the circuit board to the RED wiring on the decoration (connect it to any convenient point).
13. Connect the BLACK wire from the circuit board to the BLACK wiring on the decoration (connect it to any convenient point).
14. Connect the 3 BLUE wires from the circuit board to each of the 3 BLUE wires on the decoration, they may be connected in any order.
15. Carefully check all wiring.
16. Trim the long LED leads.
17. Plug the 4060B into its holder.
18. Connect a 9V battery and switch on.
19. Using a small screwdriver, adjust the 47k preset variable resistor to give a suitable flash rate for the LEDs.

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Circuit diagram

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Light-sensitive Alarm Project

The circuit detects a sudden shadow falling on the light-sensor and sounds the bleeper when this happens. The circuit will not respond to gradual changes in brightness to avoid false alarms. The bleeper sounds for only a short time to prevent the battery running flat. Normal lighting can be used, but the circuit will work best if a beam of light is arranged to fall on the light-sensor. Breaking this beam will then cause the bleeper to sound. The light sensor is an LDR (light-dependant resistor), this has a low resistance in bright light and a high resistance in dim light.

• The light-sensitivity of the circuit can be adjusted by varying the 100k preset.
• The length of bleep can be varied from 0.5 to 10 seconds using the 1M preset.

Using the 7555 low-power timer ensures that the circuit draws very little current (about 0.5mA) except for the short times when the bleeper is sounding (this uses about 7mA). If the circuit is switched on continuously an alkaline PP3 9V battery should last about a month, but for longer life (about 6 months) you can use a pack of 6 AA alkaline batteries.

This project uses an edge-triggered 555 monostable circuit.

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Parts Required

• resistors: 10k, 47k, 1M ×3
• presets: 100k, 1M
• capacitors: 0.01µF, 0.1µF, 10µF 25V radial
• transistor: BC108 (or equivalent)
• 7555 low-power timer IC
• 8-pin DIL socket for IC
• LDR (light-dependant resistor) type ORP12
• bleeper 9-12V
• on/off switch
• battery clip for 9V PP3
• stripboard 12 rows × 25 holes

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Stripboard Layout

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Circuit diagram

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Adjustable 1-10 Minute Timer Project

The circuit starts timing when switched on. The green LED lights to show that timing is in progress. When the time period is over the green LED turns off, the red LED turns on and the bleeper sounds.

The time period is set by adjusting the variable resistor. It can be adjusted from 1 to 10 minutes (approximately) with the parts shown in the diagram. You can mark the times on a scale drawn on the box.

Please note that the range of time periods is only approximate. With perfect components the maximum time period should be 4½ minutes, but this is typically extended to about 10 minutes because the 220µF timing capacitor slowly leaks charge. This is a problem with all electrolytic capacitors, but some leak more than others. In addition the actual value of electrolytic capacitors can vary by as much as ±30% of their rated value.

This project uses a power-on triggered 555 monostable circuit.

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Parts Required

• resistors: 470, 33k, 100k
• variable resistor: 1M
• capacitors: 0.1µF, 220µF 16V radial
• LEDs: red, green
• bleeper 9-12V
• 555 timer IC
• 8-pin DIL socket for IC
• on/off switch
• battery clip for 9V PP3
• stripboard 10 rows × 22 holes

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Stripboard Layout

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Circuit diagram

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Simple Electronic Lock Project

There are six (or more) push switches. To 'unlock' you must press all the correct ones at the same time, but not press any of the cancel switches. Pressing just one cancel switch will prevent the circuit unlocking. When the circuit unlocks it actually just turns on an LED for about one second, but it is intended to be adapted to turn on a relay which could be used to switch on another circuit.

Please Note: This circuit just turns on an LED for about one second when the correct switches are pressed. It does not actually lock or unlock anything!

This project uses a 555 monostable circuit.

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Parts Required

• resistors: 470, 100k ×2, 1M
• capacitors: 0.1µF, 1µF 16V radial
• red LED
• 555 timer IC
• 8-pin DIL socket for IC
• on/off switch
• push-switch ×6 (or more)
• battery clip for 9V PP3
• stripboard 12 rows × 25 holes

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Stripboard Layout

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Circuit diagram

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Flashing LED Project

LED stands for Light Emitting Diode

This project is designed as an introduction to soldering, identifying common components, using the resistor colour code and placing components correctly on stripboard. The LED flashes at about 3Hz (3 flashes per second). This project uses a 555 astable circuit.

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Parts Required

• resistors: 470, 1k, 220k
• capacitor: 1µF 16V radial
• red LED (or orange, yellow or green if you prefer!)
• 555 timer IC
• 8-pin IC holder (a 'DIL socket') for the 555 IC
• battery clip for 9V PP3
• stripboard: 6 rows × 21 holes

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Instructions

1. Solder the 8-pin IC holder in the correct place on the stripboard.
2. Break the 4 tracks under the IC holder with a track cutter tool. You can allow extra holes if your piece of stripboard is large enough.

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3. Use the resistor colour code to identify the resistors which are marked with coloured bands to show their value.
4. Insert and solder the resistors in the correct position, they can be put in either way round, but you must line them up correctly with the IC holder.
5. Identify the other parts, then solder them in the correct position and the right way round. To help you identify the parts please see our page on soldering.

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6. Solder the 2 wire links in place around the IC holder, it is easier to use plastic-coated single-core wire. (The flexibility of stranded wire is not needed for connections like this and the strands can be difficult to push through the small hole).
7. Finally insert the 555 timer IC and connect a battery!

For a circuit diagram of the 555 astable circuit used in this project please see the Stripboard page.

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Simple Component and Continuity Tester

This simple project may be used for testing components, as well as checking circuit board tracks, wires and connections for continuity (conduction). It tries to pass a small current through the item being tested and the LED will light brightly, dimly or not at all according to the resistance of the item:

• LED bright means the resistance is low, less than about 1k
• LED dim means the resistance is medium, a few k
• LED off means the resistance is high, more than about 10k

When not in use the 9V PP3 battery should be unclipped or the crocodile clips attached to a piece of card or plastic to prevent them touching. You could add an on-off switch in the red wire from the battery clip and this may be the best option if you mount the simple tester in a box.

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Parts Required

If you think this project is too simple to be useful, please see the table of components which it can be used totest and think again!

• resistor: 390
• red LED 5mm diameter, standard type
• battery clip for 9V PP3
• crocodile clips: miniature red and black
• stripboard: 5 rows × 7 holes

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Stripboard Layout

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Testing stripboard, PCB tracks, wires and connections

Circuit diagram

Connect a crocodile clip on each side of the suspected fault:

• LED bright means there is a connection.
• LED off means there is no connection.

If you are testing a stripboard or PCB which has components soldered in place, beware of possible connections via the components and allow for this when interpreting the results.

Stripboard circuits can suffer from two common problems: solder bridging between adjacent tracks making a connection where there should be none, and tracks broken with a track cutter which have an almost invisible thread of copper conducting across the break.

If a PCB has etched poorly the tracks may be very thin in places or there may be traces of copper bridging between adjacent tracks.

Wires and connections may be checked for continuity (conduction). 

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Testing components

Connect a crocodile clip on each side of the component. They can be connected either way round unless stated otherwise in the table below. 

Component	Test results for a component in good condition
Resistor	LED bright for low resistance, less than about 1k. LED dim for medium resistance, a few k. LED off for high resistance, more than about 10k.
Variable Resistor	Across the two ends of the track the LED brightness will depend on the resistance value (see above). Between one end of the track and the wiper you should see the LED brightness vary as you adjust the variable resistor. However, for high resistances (>10k) the LED will only light near one end of the track.
Diode	LED bright with red lead to anode and black lead to cathode (stripe). LED off with black lead to anode and red lead to cathode (stripe).a = anode, k = cathode (the end with a stripe)
Zener Diode	LED bright with red lead to anode and black lead to cathode (stripe). LED dim with black lead to anode and red lead to cathode (stripe) if the zener diode voltage is less than about 7V. LED off with black lead to anode and red lead to cathode (stripe) if the zener diode voltage is greater than about 7V.a = anode, k = cathode (the end with a stripe)
LED Light Emitting Diode	LED bright with red lead to anode and black lead to cathode (short lead) - the LED being tested will also light. LED off with black lead to anode and red lead to cathode (short lead).a = anode (long lead), k = cathode (short lead, flat on body)
Transistor B = base, C = collector, E = emitter Please refer to a supplier's catalogue to identify the leads.	For each pair of transistor leads connect the tester leads first one way, then the other way.These are the results for an NPN transistor in good condition: CE pair: LED off both ways. BC pair: LED bright with red lead on B, LED off the other way. BE pair: LED bright with red lead on B, LED off the other way. These are the results for a PNP transistor in good condition: CE pair: LED off both ways. BC pair: LED bright with black lead on B, LED off the other way. BE pair: LED bright with black lead on B, LED off the other way. Note that you can use the tester to identify the B lead (the one which always conducts one way) and to distinguish NPN and PNP transistors (by the tester lead colour when B conducts). However, the tester cannot distinguish the C and E leads.
Capacitor less than 1µF	LED off. Please bear in mind that a broken connection will give the same result.
Capacitor 1µF and greater	If the capacitor is polarised (most will be) connect the red lead to positive (+) and the black lead to negative (-). The LED will flash briefly when first connected. Reverse the connections: the LED will give another brief flash. With low values like 1µF the flash will be almost too brief to see, but larger values such as 100µF will give longer flashes. Electrolytic capacitors may leak a little when connected the wrong way round, making the LED light dimly continuously.
LDR Light Dependent Resistor	LED bright when the LDR is in bright light. LED dim when the LDR is in normal room light. LED off when the LDR is in darkness.
Thermistor	LED dim when the thermistor is warm. LED off when the thermistor is cold. These are typical results, the exact results depend on the thermistor's resistance.
Lamp	LED bright. Note that the lamp itself will NOT light because the test current is too small.
Switch	LED bright when switch contacts are closed (on). LED off when switch contacts are open (off). Note that you can use the tester to identify the switch contacts if necessary.
Fuse, Motor, Loudspeaker, Inductor,Relay coil, Wire	LED bright.

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Model Lighthouse Project

This project was designed for a model lighthouse to flash a lamp in a simple sequence: two flashes of 2s with a short gap of 1s, followed by a longer gap of 5s before repeating the sequence. 

The 555 timer is connected as an astable to provide clock pulses for the 4017 counter. The 4017 has ten outputs (Q0 to Q9) and each one becomes high ('on') in turn as the clock pulses are received. Outputs Q0, Q1, Q3 and Q4 are combined with diodes to produce the flash sequence. A transistor amplifies the current to power the lamp, or LED if you prefer (a 470 LED resistor is included on the stripboard layout). The 1M preset controls the time period (T) of the 555 astable from about 0.1s to 1.5s, for example set T = 1s.

For a different flash sequence connect the diodes to combine different 4017 outputs (Q0-Q9). If the full count from 0 to 9 is not required one of outputs can be connected to the reset input (pin 15). For example connecting Q8 (pin 9) to reset (pin 15) reduces the long gap at the end of the sequence to 3s (with T=1s).

This project uses a 555 astable circuit to provide the clock pulses for the 4017 counter.

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Parts Required

• resistors: 470, 2k2, 22k, 100k
• capacitors: 0.1µF, 1µF 16V radial
• diodes: 1N4148 ×4
• transistor: BC108 (or equivalent)
• 1M preset, horizontal
• 6V 60mA MES lamp
• MES lampholder
• 555 timer IC, such as NE555
• 4017 counter IC
• DIL sockets for ICs: 8-pin, 16-pin
• on/off switch
• battery clip
• 9V battery box for 6 AA cells
• stripboard: 19 rows × 21 holes

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Stripboard Layout

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Circuit diagram

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