#due20140410

Due dates

An initial prototype of the lab is due on Tuesday, April 8th. Bring the prototype to class so it can be properly soldered and tested. The report is due on Thursday, April 10th.

How to turn this lab in

Please post the requirements above to this tumblr tagged with #lab03 and #due20140410. Confirm that the post is correctly tagged by visiting http://pcceltn130.tumblr.com/tagged/lab03 and http://pcceltn130.tumblr.com/tagged/due20140410

The link for posting is http://www.tumblr.com/blog/pcceltn130

If you have a blog elsewhere and want to use that site to host a longer post, update this tumblr with a link to what you have written.

If you feel strongly about not posting your lab in public or tumblr still confuses you, email your write up to the professor at the email listed on the about page. However, posting a lab publicly by the end of the semester is a requirement for this class.

What this lab is about

A build your own switch lab with a single switch and a predefined problem to solve.

An introduction to building your own test equipment.

Covered Building Standards: schematics, possible soldering

Covered Concept Standards: simple series circuits, SPST switches, continuity

Covered Test Equipment Standards: Ohmmeter, Ammeter, Voltmeter all used to to test the specifications of your DIY equipment.

Overview

In this lab design an interface that solves a problem using one switch. The problem? The student doesn't have a multimeter or has one with out a continuity buzzer. The student has a professor that keeps assigning work to do at home that requires requires continuity testing. The student, realizing that they are going to be stuck testing continuity for a long long time decides to build a continuity tester. *

* because said professor is making them.

Product Specification

Product must have test leads. Test leads should either have a narrow tip for precise placement or the ability to clip on to the circuit being tested.

The user needs to be able to detect a successful continuity test from a distance of one foot or greater from the tester. Sound and light are very good options for this.

To protect the circuits being tested, the voltage of the circuit should be low. Rule of thumb: don't use a circuit that requires more than 4 1.5 V batteries in series, ideally 2 or less.

To protect the circuits being tested, the current of the circuit should be low. Rule of thumb: batteries should be AA or smaller.

The tester should be portable.

Basic Steps

Collect the materials. (see below).

If you've chosen to do a hack, do an initial take-apart of the device and plan where the probes will attach.

Draw a schematic. It does not matter if your schematic is exactly like the one shown in class. Draw it yourself. Take a picture, include it in the lab write up. If you have questions about this, ask the instructor on Tuesday.

Build a continuity tester. (see below).

Check it that it works, and bring it to class on Tuesday to finish testing it with a Multimeter.

Write up the lab with ALL of the questions answered.

Lab Report Questions

For all of the questions, include HOW you determined the answer to the question as well.

What is the basic schematic of your circuit?

How much total voltage is in the continuity testing circuit?

How much voltage is applied to the circuit being tested? What does that depend on?

At what resistance value does your continuity tester fail?

How much current will your tester be sending through the circuit, at a minimum?

What is your favorite feature of your new continuity tester?

What would you do differently next time?

Materials & Methods

Option 1: Radio Shack or other local electronics store

Requires soldering. Soldering irons are available in room 227 8 am to 2pm M thru F, when there is no class in that room. The engineering club also has them and will lend them to student in the class. I found a brief tutorial online using similar parts (it is about halfway down the page.)

a battery holder

mini buzzer

alligator clips

A switch (SPST Toggle. Optional if you want a way to turn the device off other than removing a battery or isolating the leads from each other.)

stranded wire (why stranded?) (Buy a spool at radio shack or something with an inexpensive cable at the dollar store/thrift store)

Option 2: Dollar store

Student is welcome to copy one of the two examples shown in class.

The first one, the door/window alarm hack, is destructive. It requires cutting a wire. But once that connection is soldered, the tester will be a stable device.

The second one, the bicycle light, is reversible. The lead wires are hijacking the battery connection, insulated by a piece of cardboard. It works, but is temporary.

The door/window alarm hack uses a toggle button and the bicycle light has a momentary button. Do you remember which was easier to use with just two hands? Select accordingly.

If hacking an existing item, buy two in case the first one gets broken.

Option 3: Surprise Me.

There are many people who have solved this problem before you, so you'll be in good company. I have found several tutorials that do not require more knowledge than we have covered in class.

http://www.instructables.com/id/Continuity-Tester/

http://www.instructables.com/id/Easy-Electrical-Continuity-Tester/

http://www.instructables.com/id/Continuity-Tester-PEN/

http://electronicsclub.info/p_simpletester.htm (higher voltage than recommended, but works)

http://www.instructables.com/id/How-to-turn-a-ThinkGeek-Screaming-Monkey-Slingshot-1/