Lab 3 Prelab Help Sheet

This help sheet is not going to be as comprehensive as the prelab help sheet for lab 1, and next week will be even less thorough. Part of the goal of this class is for you to be able to devise prelab activities on your own. So if you’re running out of ideas for things to do, please review last week’s help sheet.

Think carefully about which group members you want to complete each section. Many of the topics here are interconnected, so it often helps to make sure everyone does them (or, at minimum, that you meet and share out what you learned during prelab.) We especially encourage everyone to do the reading and watch the videos.

Reading and Reference

• Watch lecture videos.
• Watch op-amp videos 1 & 2.
• Read the lab.
• Flag parts of the lab that didn’t make sense for discussion with your team or a prof.
• Read the submission sheet and notice:
  1. What are the deliverables?
  2. What are the specifications on those deliverables?
• Read the reference document about diodes
• Read the reference document about turbidity, and make note of the visual reference of what different turbidities look like.
• Read the turbidity meter instruction manual
• Read all linked datasheets

Circuit Design

• Design all the circuits in advance and analyze them on paper. Analysis should include predicted output Voltages and component selection calculations.
• Test out your designs using a simulator program like Falstad or ltSpice
• Plan how your circuits will fit on your breadboard ahead of time using a breadboard simulator like fritzing or Tinkercad
• What formula describes a non-inverting amplifier’s output?
• What formula describes an offset amplifier’s output?
• What formula describes a transimpedance amplifier’s output?
• What formula describes a 555 timer’s frequency when it is configured as an oscillator?
• What formula describes a 555 timer’s duty cycle when it is configured as an oscillator?
• What formula describes current through a series resistor-diode?
• What is the maximum current allowed in our IR LEDs?
• What’s a rough guess at the resistances you’ll need in your photodiode test circuit and your transimpedance amplifiers.

Schematics

• Try drawing a schematic using schematic drawing software like draw.io, ltSpice, or Powerpoint.
• Draw all the schematics for the circuits you have designed, paste copies in appropriate places in the submission sheet, and distribute schematic source files to both subteams.
• Have a professor review your schematics for style considerations in office hours.
• Can you quickly modify your schematic if you find that you need to change a component value in the lab?
• What does connect-by-name mean in the context of electrical schematics?

Mechanical

• What’s a cuvette?
• View the Solidworks designs for the turbidity meter fixture
• Make a sketch of how your breadboard, circuits and turbidity meter fixture will fit together

Statistics

• How do you calculate a line of best fit and appropriate uncertainty measures? How do you report the uncertainty?
• Write code or make a spreadsheet that can calculate a line of best fit and appropriate statistics from a set of x,y points.
• Write code or make a spreadsheet that can plot a set of x,y points, a line of best fit, and appropriate uncertainty indicators.

Results

• Make a plan for how your team will split its time in lab.
• Write up parts of your submission sheet that you are able to, including pasting in appropriate schematics, so that you can just paste in results in lab.