Idea 3

For our final idea, we have decided to use a 555 timer to produce our frequency with a variable resistor to alter the frequency. The gas will be controlled by a simple regulator.

Input:

 The input to our circuit will either be a variable resistor for varying the frequency of the 555 timer. Another option would be to use a rotary switch switch as a single pole 5 throw with a predetermined resistor. The advantage of this would mean that a set frequency could be achieved. Decals or labels could be used on the device to tell the user the frequency.

Rotary Switch

Control:

For the control, we have used a 555 timer in astable configuration to provide our frequency.
The frequency, of the output pulses is determined by the values of two resistors, R1 and R2 and by the timing capacitor, C.
The design formula for the frequency of the pulses is:

 




The period, t, of the pulses is given by:



The HIGH and LOW times of each pulse can be calculated from:

The duty cycle of the waveform, usually expressed as a percentage, is given by:




Fro, this we calculated the values of our resistor and capacitor so that the frquency can vary between 2 and 8KHz. Below shows a simple schematic of our circuit

555 in Astable mode

Output:

The gas output of this idea takes a more mechanical approach. The gas will be controlled by a built in regulator such as this one below

Mini CO2 regulator

This regulator will be used in conjuction with a helium canister or 'charger' like this. The problem with this concept is that the chargers fro helium are rather expensive, however it is the easiest route to go.