To the person with circuit assembly experience, this project will be easy but for others with limited or no experience, it may be challenging so I am going to describe the process in detail.

1) Preparing the battery holder.

1a) Drill new mounting holes. The existing mounting holes on the Radio Shack battery holder are too close to the side of the holder and there is no room for the heads. The way to deal with this is to drill new holes away from the the side as shown in this picture.

The white holes represent the existing holes and the blue holes are the new ones. Notice that the new holes are opposite the existing holes and slightly larger. I suggest that you use a 3/32″ drill for these hole. Check to make sure the screws fit with the head flat to the bottom.

1b) Cut off the wings that hold the battery in place. These tabs or wings hold the battery securely in place during normal use but they are a nuisance if we want to easily inserting and remove batteries as we test them. Use your diagonal cutting pliers to snip them off. See the blue dashed line in the image below.

2) Mounting Parts

Layout each of the components then drill and mount each of the three parts. Refer to this image of the completed battery tester.

 Use something with a sharp point such as a ”scratch awl”, ice pick or nail to mark the location of each hole and serve as a guide to the drill. Then drill the holes using the 5/64″ drill. (The 3/32″ will also probably be OK but its diameter is just a little bit smaller than the threads of the screw itself. It’s always good to use a drill that is sized so the threads of the screw have plenty of wood to grab.) It’s best to “mark” one hole, drill it, place the part and fasten it down with a screw in the hole you have just drilled before marking and drilling the second hole. This method should insure that the second hole will be in the right place the first time that you drill it. If you mess up, start over by moving the part a little ways in any direction and following the same procedure.

3) Wiring

3a) The end of each wire should have about 3/8″ of insulation removed by whatever method you have available. A wire stripper is the perfect tool for this job but a pocket knife will also work if you don’t mind the possibility that you will cut something other than the insulation in the process. If you are unfamiliar with this process, find some other wires to practice on. Use your long nose pliers to hold the wire in the middle while you strip the end.

I recommend that you use a soldering iron to “tin” the ends of each wire that you strip. This makes them easier to connect securely. Tinning is the process of heating the twisted stands of the wire with the iron and adding a small amount of solder so it flows into the strands and bonds them together. Be careful with the soldering iron. Using it is not a job for children. The tip is hot enough to burn skin instantly. Be very careful and keep it away from whoever is helping you.

3b) Stretch out the red battery holder wire so it reaches to the nearest switch contact. Add an inch or so and cut it off. The piece you just cut off will used to connect the switch to the lamp socket.

3c) You should understand the process well enough at this point to stip, tin and connect the wires. Note that the lamp socket has a nut on the bottom of each connector. You will probably have to remove the socket so you can get to the nut.

4) Testing

Insert battery and screw in bulb. Close switch. The lamp should light and you and your kid(s) should be beaming with pride at your finished project.

Grandfather

PS: I’m sorry that this lesson was so slow in coming. Grandmother and I have left the Workshop while we are on vacation. You can travel along with us here. It will be updated with an image or two for each day of our vacation so if you like what you see, be sure to come back later for more.

Well, I didn’t even realize, until I started this post, how many tools it takes to build the battery tester. I am so used to just getting the tools I need from my workshop that I never even think about them. Here are the tools that we actually used to assemble the battery tester. You can probably make do with a lot less. Maybe you can borrow what you don’t have until this job is done. 

1) Drill (hand or electric)

2) Drill bit (3/32″ or 5/64″ or both) for drilling pilot holes for the screws

3) Scratch awl (Craftsman 42017) a pointy thing for making a pilot hole in the wooden base to guide the drill bit. Alternates: an ice pick or, better yet, a small nail.

4) Hammer of any kind to give encouragement to the pointy thing so that it makes a small dent to guide the drill bit

5) Diagonal pliers for cutting wires

6) Stipping pliers for removing the insulation from the wires

7) Long nose pliers for holding the wire while you’re stripping insulation and any job when your fingers are not long enough and pointy enough

8 Soldering iron for tinning the ends of the wires before connecting them

9) Solder

10) Sponge for cleaning the tip of the soldering iron

11) Small Phillips Head screwdriver for screwing in those tiny screws. Mine came from Ace Hardware and it is marked as a #0×2-1/2″ (P/N 24348). It is just the right size for the screws.

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Some other things that might come in handy for our future projects.

1) Rechargeable drill (We actually used this drill because Blue Yonder had our hand drill.)

2) Set of drill bits

3) Roll of electrical tape

4) Rolls of insulated hookup wire

5) Irwin Quick Grip (1 1/2″ - 38mm size) for holding stuff - when two hands are not enough

Grandfather

Two of my nine grandkids are crazy about making “computers” from discarded keyboards, wires, cables, and whatever other electronic odds and ends they can find. Here’s an example:

Even though they are just turning six, one of them is certain that he wants to be an Electrical Engineer. They were particularly impressed by a little battery tester I had made to check AA, C and D cells so making one like it became the subject of the first meeting of our “Engineering Club”. My daughter in law, who goes by the pseudonym “Blue Yonder“, thought it would be helpful to share projects like this with others so here we are in “Grandfather’s Workshop”!

The easy part is putting the battery tester together. Finding the parts is a little harder. Here’s the parts list:
1) mounting board – minimum size of 4.5″ x 4.5″ x 1/2″
2) mounting screws – #4 x 1/2″ metal pan head (Home Depot 24741)
3) battery holder – AAA, AA, C or D (AA – Radio Shack 270-401A or see below)
4) knife switch – SPST (single pole, single throw)
5) bulb holder – miniature, screw type
6) bulb – screw type, 1.5 volts
7) wire – no extra wire is required

There are a number of places that have one or more of the electrical items but I found only one place that has them all, Christian Book Distributors. If you find any other sources please let me know.

At these prices, get an extra bulb holder, battery holder and maybe a SPDT switch. We will need them for future experiments. Other sources to check are Arbor Scientific, Science Lab and Hobby Engineering.

It’s not much but they seemed very pleased with the results and we had a lot of fun building it.

Grandfather.