Biological and Agricultural Engineering

Battery Tester

OBJECTIVE:
4-Hers and youth will construct a device to use for the testing of electrical charge and learn the continuity of circuits on 1.5 volt to 9 volt batteries.

SKILLS LEARNED:
Sanding and Wood Burning Measuring, cutting and stripping wire. Soldering electrical connections. Safe use of electric screwdriver. Understanding of basic electric circuits

TIME: One to 11/2 hours for a group of 20 4-H'ers.

INSTRUCTOR NEEDS: One adult project leader and 2 to 3 adult or teen leaders.

PARTS LIST:

• Wood Base 3" x 5" x 5/16"
  
• 2 Screw-bulb socket bases
  
• One 2.5-volt screw-base bulb
  
• One 7.5-volt screw-base bulb
  
• 4 sheet-metal screws #10 (1/2")
  
• 1 1/2 foot (18 inches) of 2-conductor or 36 inches of single conductor
• # 22 gauge wire

TOOLS & SUPPLIES:

• 4 to 6 soldering irons
  
• 4 wood burners
  
• 2 electric power strips
  
• 2 extension cords
  
• 1 roll rosin-core solder
  
• 4 to 6 pairs of wire strippers
  
• 2 cordless electric screwdrivers
  
• 6 each 12"-long rulers
  
• 3 heavy poster strips 12"x24"
  
• 1 roll duct tape
  
• Fine-grained sandpaper
  
• Burn spray

ASSEMBLY PROCEDURE: Divide 4-H'ers and youth into four groups and start assembly as shown below:

A. SANDING STATION
1. Give each 4-Her and youth a wood block. 4-Her and youth should determine which side of block will be top.
2. Sand top and edges till smooth.
3. Draw labels for 15 V and 6 - 9 V bulbs with pencil on top of wood block for woodburning.

B. WOODBURNING STATION
1. Slowly trace over labels with wood burner allowing tip to burn into wood to desired depth. Decorations may be added if time allows. HOT! - BE CAREFUL!
2. Do not allow tip of woodburner to touch anything other than wood block; at 950 degrees Fahrenheit, it will burn most anything. Have burn spray handy in case of an accident.

C. CUTTING AND WIRE STRIPPING STATION
1. Measure and cut 2 wires 9" long if using the 2-conductor. Cut 4 wires if using the single conductor wire.
2. Strip lt2" of insulation from the ends of each wire (figure C).
3. Twist ends of each wire so that no strands are sticking out. BE CAREFUL! when using wire strippers; cutting edges are sharp.

D. SOLDERING STATION

To set up this station, tape 2 soldering irons on each piece of cardboard strips and tape cardboard strips to table top. This will hold the soldering irons firmly in place and protect the table top from dripping solder.


1. Solder one gray wire to one terminal of each bulb base and one white wire to the other terminal of each bulb base (figure D).
2. Tin the free ends of each wire with solder to prevent them from becoming frayed.

E. FINISHING YOUR BATTERY TESTER

1. Attach bulb holder on to the board with sheet metal screws
2. Screw bulb into bulb holder

Click on small picture to see full size.

TEST BATTERIES: Instruct 4-H'ers and youth on proper way to test batteries (if battery is good, bulb will burn brightly). You will need several batteries in varying states of discharge. Instruct 4-H'ers and youth on how to use the tester as a continuity tester.

BASIC ELECTRICAL CONCEPTS: How a light bulb works and what are its parts. AC/DC current. Circuits and electron flow (open circuit, closed circuit & short circuit).