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/ headclock.htmlKeeping track of time while in suit is often found to be surprisingly difficult. Several hours can seem to pass very quickly, and this can be problematic when pacing the silliness to sustain it for a prolonged appearance.
The circuit described below uses an audio and vibrational cue to indicate the passage of time, in the same was as a traditional chiming clock. It is also a "repeater" as there is a button which causes the elapsed time to be chimed.
| Quantity | Description | Circuit Ref. |
|---|---|---|
| 1 |
Programmed
PIC 12F683 Microcontroller |
U1 |
| 1 | 78L05 | U2 |
| 1 | BC547 | Q1 |
| 1 | 4MHz crystal oscillator | XTL1 |
| 2 | 15pF (typically trace capacitance) | C1, C2 |
| 1 | 10µF 12v electrolytic | C3 |
| 1 | 100nF ceramic | C4 |
| 1 | 2K2 1/4w | R1 |
| 1 | 10K 1/4w | R2 |
| 1 | Push button switch | SW1 |
| 1 | Piezo sounder | PZ1 |
| 1 | 5v Pager motor | M1 |
| 1 | PP3 9V battery and clip | BT1 |
| 1 | 100mA Fuse and holder | F1 |
The pager motor is a small motor with a weight eccentrically mounted on it, and is used for the vibrate function in pagers, mobile phones, and disposable electric toothbrushes. Often available from surplus suppliers and places specialising in BEAM parts.
Piezo sounders can be found in many devices, but it is perhaps most satisfying to salvage one from an annoying musical greetings card.
The push button is really anything that fits with the design of the suit. Flat buttons mounted just under the fur can provide concealed operation. Choose a part that is washable to avoid problems with moisture in the head.
The prototype was built on strip board. Some care should be taken not to allow the traces to the crystal to become overly long. The trace capacitance between the tracks should be sufficient to ensure the oscillator works correctly without adding the 15pF capacitors.
The degree to which the sound and the vibration can be heard and felt depend largely on the construction of the head and how the devices are mounted. Some adjustment may be needed to ensure they cannot be detected by the audience.
The detailed operation is all contained within the the source code for the microcontroller. The crystal is used to generate a stable 4MHz clock that is divided down to a more manageable 125Hz interrupt. An interrupt service routine counts these, and increments the secounds, minutes, quarters, and hours accordingly. It also handles polling and debouncing the button state.
The main program responds to the state updated by the interrupt and toggles the motor and sound outputs to generate the required signal.
The main code also includes a sleep mode that disables the crystal oscillator and interrupts and uses a slow 31kHz clock to poll for a button press that signals a wake-up. In this state the circuit draws less power.
This circuit is provided as an application idea. I cannot accept any responsibility for use of this idea whether it is constructed correctly or not. I'd recommend thoroughly testing any constructed circuit before including it in a fursuit, and taking care to ensure the performer and the circuit cannot come to any harm in the event of an accident.
This work is licenced under a
Creative Commons Licence.
I'd appreciate a quick
e-mail
or feedback if you have used or improved on the design.