Lab 3 Writing Assignment

Electrical Schematics and Mechanical Drawings

Writing Assignment

In this writing assignment you will learn to make high quality electrical schematics and mechanical drawings. You’ll then write text to describe the operation of the electrical system and the key aspects of the mechanical design presented.

Statement of Work

Prepare high-quality electrical schematics and a mechanical drawing to include in a methods section of a technical memo describing the operation of the turbidity meter you built in Lab 3. You should include a schematic for your 555 timer circuit and your transimpedance amplifier. The accompanying text should describe how the circuit and cuvette holder are used to build the turbidity meter.

An electrical schematic describes the functional connection of the components in an electrical circuit. It does not directly represent the physical layout of the circuit in 3d-space on a breadboard or printed circuit board. However, there are certain conventions you should follow when drawing your schematic to allow it to be easily read and understood. These are detailed in the lab submission sheet and the specs below.

For this assignment, draw schematics for the 555 timer circuit and the transimpedance amplifier you developed for your turbidity meter. Ensure your schematics follow all the proper conventions as detailed in the specs below and in the lab manual. After each schematic, include a 100-150 word section of text to describe its design and operation.

The mechanical drawing for this lab is a three-dimensional view of the 3d-printed cuvette holder for the turbidity meter. Your drawing should convey to the reader the key features of the design along with the most important dimensions needed to understand the scale of the design. It does not need to include all the relevant dimensions in order to manufacture the part. The function of the diagram for the written assignment is to communicate how it is used in the experiment. Include a 100-150 word section of text to describe how the cuvette holder is used in the turbidity meter.

Learning Objectives

By the end of this writing assignment you will…

• Draw a neat and complete electrical schematic.
• Create a clear mechanical drawing with relevant details included.
• Write text to reference the schematic and drawing to explain the operation of the turbidity meter.

Required Resources

• Source code for a schematic of the 555 timer circuit used in lab.
• Source code for a schematic of the transimpedance amplifier used in lab.
• Source code for Solidworks drawing of the cuvette holder used in the turbidity meter.

Specifications

Effort

• Electrical schematic present.
• Text is present explaining the function of the circuit in the turbidity meter.
• Mechanical drawing is present.
• Text is present explaining the cuvette holder and how it is used in the turbidity meter.

Completion

Electrical Schematics

• Standard electrical schematic symbols are used whenever possible (i.e., don’t make up new symbols for resistors, amplifiers, etc.)
• All lines connecting elements are straight lines wherever possible (i.e., no curved lines)
• All junctions indicated with a solid circle at the intersection point
• No 4-way wire junctions
• Use line weights and fonts that are clearly visible.
• Reference designators and the values for parts are placed nearby the parts.
• Draw pins according to function (i.e., not just according to the physical layout of the pins on the chip.)
• All pins labeled with number
• All pins labeled with name/description of function
• Decoupling capacitors are placed nearby the part that they accompany.
• If needed, notes are legible and well-placed

Mechanical Drawings

• Clear depiction of components and how they fit into assembly
• Drawings only include enough detail to make your point (i.e., you need only show the relevant dimensions in the drawing)
• Follow mechanical schematic drawing conventions, such as the layout, flow and symbols
• Use heavy line weights and large fonts
• Part geometry is clear and well illustrated
• Drawing is clear and fully labeled
• If needed, notes are legible and well-placed
• Clearly makes the point that is suggested in the text

Supporting Text

• Refers to each schematic/drawing.
• Correct sentence mechanics like cohesion and coherence between sentences and no run-ons.
• Correct paragraph mechanics like topic sentences and placement at breaks between ideas.
• Language is not stilted and jargon is kept to a reasonable minimum.

Tools for Mechanical Drawings

You may use whatever tool you are most comfortable with for preparing your mechanical drawings. Solidworks is a good choice since you learn it in E4, but sometimes can be difficult to run on your personal computer. Onshape is a popular alternative which runs in your browser and has free education accounts.

If you’d like to use Onshape, first create an account. Then, you can create a new workspace and import the .sldprt files for the cuvette holder. Alternatively, you may directly make a copy of this Onshape document which has the parts already imported and a drawing made to which you can directly add relevant dimensions for your figure.

The screenshots below in Figure 1 and Figure 2 show how to copy the workspace and add dimensions.

Figure 1: Use the dropdown menu to create a copy of the Onshape workspace.

Figure 2: Use the Dimension tool in the Drawing tab to add dimensions to your drawing as you see fit.