[DESIGN] - Mesh Nebulizer Driver Circuit

[JLefebvre55]

Completion is tracked in the linked PR.

Design Scope

Design a driver circuit for a mesh nebulizer.

Purpose

The purpose of the driver circuit is to cause the piezoelectric mesh disc to oscillate.

Function

Inputs:

• VDD (IC/MOSFET gate/logic voltage)
• VCC (disc voltage is +/- VCC)
• Enable/disable signal (0V or VDD)

Outputs:

• AC sinusoid (+VCC to -VCC, constant frequency)

It interfaces with/depends on the following systems:

• Automation

System operation assumes:

• Water supply
• Power

Method

1. Square Wave Generator: Astable 555 IC (input: on/off signal, VDD; output: 0V/5V square wave, fixed frequency, ~50% duty cycle)
2. Inverter Stage: MOSFET H-bridge (input: square wave, VCC; output: -VCC/+VCC square wave, same properties)
3. Filter Stage: 3-stage RC filter (input: square wave; output: sine wave)
4. Power Stage

Requirements and Validation

What does this design need to accomplish? How do we know it has accomplished this?

List any applicable metrics with criteria/constraints, applicable to purpose, function, method, and each feature, as well as how to test them.

1. Power consumption when off
2. Efficiency when on

Verification

Each test should be performed and documented, and the testing documentation attached to the PR. The testing suite should address the full scope of the function (i.e. ensure inputs are met and outputs work), method (all steps execute correctly), and features (each feature performs as expected) with respect to the purpose and requirements.

How does this design achieve its method effectively, safely, and reliably? How do we test this?

Specific testing procedure:

1. Generates ideal sinusoid

Additional context

Add any other context about the design scope or additional deliverables here.

[JLefebvre55]

WIP Simulation: Here

Background

Reference design:
https://www.youtube.com/watch?v=aKhPj7uFD0Y
https://www.youtube.com/watch?v=OOZi3QnnDCo

ToDo

• Design astable timer stage (select passive component values)
• Design inverter stage (push-pull)
• Design filter stage (select passive component values)
• Design power stage
• Simulate circuit
• Select/order breadboard components, test w/o load (oscilloscope verification)
• Design PCB, reselect components
• Determine piezoelectric disc requirements (VCC, frequency) and characteristics (R, C, L)
• Order PCB, components