Nuts & Bol

Craft &

WHEN IT COMES TO building, restoring,

The a d v a n t a g e of this tester over a VOM and fixing airplanes, w i t h a buzzer is t h a t electricity is usually the tester sounds off A blind person's voltage and continuity checker the most challenging for both tests. It's also (frustrating?) because •-•!.less expensive, and WILLIAM RYNONE, PH.D., RE. you can't see what's •• •• it's more t o l e r a n t of not working correctly. abuse ( d u e to drop Have you ever been lying on your ever, an inexpensive tester that lets damage) than a VOM. back with your noggin jammed up you listen for a tone that indicates under the instrument panel trying circuit continuity and voltage, which Construction to manipulate two test probes for a lets you keep your noggin buried Building the audible tester takes a volt-ohm-milliampmeter (VOM) while troubleshooting. few hours and will cost around $20 and still see the mein parts (or less, if you Voltage Continuity Tester with Audio Output ter's dial? If you have, already have some of I'll bet you've wished the items). You can get Red Banana for a helper to tell you most (if not all) of the Jack 9-volt what the meter was parts from your local Battery Radio Shack. The acindicating. companying parts list Some VOMs have a b u i l t - i n "helper," a gives the part numbers for Radio Shack and anbuzzer that denotes a circuit's continuity. other supplier, All Electronics, and the But even with the schematic diagram gives buzzer, you still need the circuit's layout. to wiggle out from unThe tester consists of der the panel to read a small enclosure or the meter's indication. Black Banana box, a buzzer, a switch There is a solution to Jack that lets you choose bethis challenge, how-

Audible Electricity

Parts List Part Buzzer: 6-27 Volt DC Project Box: 2 x 2.5 x 5 inches Switch: SPOT (single pole, double throw) 9-Volt Battery Battery Connector Battery Holder Banana Jacks: Red & Black Test Leads (with plugs & probes) Fuse Holder Fuse: 1/2 Amp, 3 AG 106

DECEMBER 2000

Radio Shack #273-0758 ($6.99) #270-1803 (3.29)

All Electronics (800/826-5432) #SBZ-328 ($3.75)

#275-564 ($2.59) #23-875 ($2.39) #23-270-325 ($1.39/5)

#MTS-4 ($1)

#274-662A ($0.40) #278-704 ($3.99) #270-364 ($1.59) #270-1003 ($1.79/4)

#PRC-1604 ($2.25) Not needed if you use battery holder. #BH-9 ($0.85) #BJC-B & #BJC-B ($0.40)

#TL-100 ($2) #FHPM-31 ($0.75)

#FS-l/2 ($1/5)

tween the voltage or continuity test,

DUAL ST

a 9-volt battery and its holder, a fuse, two banana jacks for the test leads, and the leads. If you want to save some assembly time and money, you can omit the banana jacks and wire the leads directly into To reduce the cost further, you can also omit the battery holder and fuse, but if you omit the fuse, you

Passenger

should follow exactly the steps given below for using the tester to keep from damaging it. If you use a buzzer

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other than the Radio Shack unit specified, it must operate over a

voltage range of 9 to 24 volts, 9 volts for the continuity tester and 24 volts

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for checking the voltage. Of course, the 9- to 24-volt range enables you

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to test 12-volt systems.

1

Using the Tester When using the instrument to ver-

ify a circuit's continuity, make sure that the system you're testing is completely de-energized. In other words, make sure the airplane's master switch is OFF. If you're using the instrument under the dash of your car, you should (must, if you've not

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included the fuse) disconnect the cable attached to the battery's negative pole. Even t h o u g h the i g n i t i o n switch is off, power is still flowing

under the car or truck's dash to power such things as the clock. With the system de-energized,

place the test probes on either side

of the suspected problem. The 9-volt battery provides the power to test

the circuit's continuity, and if the buzzer sounds, the circuit is good.

(The tester, unfortunately, doesn't remove all the challenges from dealing with electrical problems.) To test the voltage of a circuit, flip the unit's switch to that test, turn on the aircraft's master switch, and apply the leads to the test area. If whatever you're t e s t i n g is receiving power, the buzzer will sound. It couldn't be any simpler. ££*> Acknowledgments: Oscar Ramsey built the unit, and Dick Wilkinson photographed it.

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