12 



Apply PVC cement to the test cap and lip inside the elbow 

 before seating. Make sure the hooked wire can move freely in 

 the hole. 

 4. Saw a slit in the rim of the adapter, extending perpendicu- 

 larly from the edge to the flange. This slit allows the adapter 

 and cap to be removed without disturbing the wire hook (b). 

 Add silicone grease to the rim of the elbow and adapter, then 

 screw the PVC plug firmly into the adapter. Align the slit 

 with the hooked wire, and seat the adapter into the elbow. 



Preparing the Sensing Element Tension-adjustor Assembly 



Materials 



(1) PVC adapter with plug 



(1) PVC elbow (90 degrees) 



(1) 10 cm length of polyester string 



(1) 6.0 mm diameter by 10 cm length screw-eye bolt 



(1) dial knob (with set screw) that will accept a 6 mm shaft 



(1) wing nut (for screw-eye bolt) 



Instructions (refer to Fig. 15) 



1 . Drill a 6.0 mm hole through the PVC elbow (a). The hole must 

 align with the 6.0 mm hole drilled into the sensor relay elbow. 



2. Drill a 1.0 mm hole through the mid-point of the screw-eye 

 bolt. 



3. Drill 6.0 mm holes through both sides of the PVC elbow (c). 

 The eye-bolt will be threaded through these two holes, so 

 they should be drilled in a direct line through the center of 

 the elbow. When the eye-bolt is threaded, its center should be 

 perpendicular to the 6.0 mm hole drilled in step 1 (see c. Fig. 4). 



4. Thread the screw-eye bolt into the PVC elbow. 



5. Remove the eye of the bolt by sawing, and replace with a dial 

 knob. 



6. Screw the wing nut onto the threaded end of the eye-bolt. 



7. Attach a short length of polyester string to the 1.0 mm hole 

 in the eye-bolt, and pass the string through the 6.0 mm hole 

 in the front of the elbow. This string will be used later for 

 attaching the tension-adjustor assembly to the sensor ele- 

 ment. 



Installing the Sensor-indicator Light-Emitting Diode (LED) 

 and Switch 



Materials 



(!) LED lamp Tl % (Radio Shack, Model 276-041) 



(1) momentary-on pushbutton switch, SPST (Radio Shack, 



