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| INTRODUCTION:
A versatile timer that can be used in a wide range of projects.
It's compact and runs from an on board 3v button cell and with a micro-controller it can go to "sleep" when not in use conusming a few micro-amps meaning battery life up to 12 months. So no wires and no power switch!
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Set in 30 second intervals, by repeatedly presseing the button up to a maximum of 5 miunutes. There are 4 LEDs which indicate the last 120 seconds. To cancel just pause and press the button again
This project is available in our shop now!.
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With such a wide range of applications, this can be easily tailored to cover a topic chosen by a student, or to explore ideas in one particular topic selected by the teacher.
Some suggested applications are:
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- Fitness program, reps, HIT
- Turn time when playing games
- Shower timer using water wisely
- Cleaning teeth
- Cooking eggs, meats, steak
- Developer timer.
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| CIRCUIT DESCRIPTION |
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The timer has a range of extra functional features listed below.
- Every press of the button the timer flashes an LED up to 2 minutes to show it has been set
- Every 30 seconds of count down the timer beeps twice with the pitch getting progressively lower.
- When timing finishes, it plays a brief tune.
- If the timing is cancelled it plays a sequence of notes with a falling pitch and the LEDs seqence down
Amazing what you can program a PIC chip to do!
This is the new version (v3.14) which is shown below and makes the buzzer a little louder.
If you need to look at the circuit of the old version 2 then click here.
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An example of the PCB from our shop
The PCB measures approximately 60mm x 29mm with an extra 6mm needed for the button cell.
The component layout is identical for versions 2 and 3 but the components are not. Assembly details are available at the bottom of the page.
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| Circuit Diagram - v3.14
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The heart of the circuit is a PIC micro-controller that has runs a programme pre-loaded into it. It generates the timing, control of the LEDs and sound effects.
When functioning the circuit draws around 5mA which is mainly due to the LEDs. When not in use, the controller goes into "sleep" mode where it almost shuts down, saving power. When the button is pressed, it immediately wakes up. This means that the button cell lasts for months and there is no need for a switch and with everything on the PCB, it means no wires either!
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| CONSTRUCTION |
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The projects shown are made using "layering" where a drawn or cartoon image is taken and split into layers and sections. A particular area can be chosen for the LEDs and button depending on the image or theme chosen. The position of the PCB, LEDs and button can be found using a template.
For example, a cooking timer could use a Chef as the design:
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Select a cartoon of a character you want to use for the timer. It needs to be fairly simple in order to split it into seperate parts.
Use a template of the PCB showing the position of the LEDs and the button, to find a suitable position for them to go. The thickness of the material can be up to 5mm.
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PCB Dimensions
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There are templates below available for download - print out on to card. |
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Break the image into simple shapes allowing some overlap where pieces join together. Also layer some features.
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Draw these pieces onto 4mm birch plywood or MDF. Fit them neatly so to save materials. Cut out using a fine blade coping saw or powered fret saw
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Paint the front, sides and back using poster paint or PVA paints. Try to leave areas clear where gluing together.
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When gluing together, ensure that the buzzer and IC is not obstructed so that the PCB sits flat.
The PCB can be held in place with a 12.5mm x 4 self-tapping screw with a pilot hole of 2.5mm drilled into the plywood or MDF. Be sure not to drill too far. In most cases only one screw is needed. The PCB fits 6.5mm from the back of the model. A guide can be used to help solder the LEDs at the correct height.
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| The finished model can be placed on an oval plinth with triangle supports behind the feet to strengthen the join. |
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