List of Miscellaneous

Here is the list of miscellaneous: 

• RLA .................................... 5v p.c.b mounting miniature relay 200mW nom operating power (2 pole changeover)
• S1 .......................................  3-pole 4-way rotary switch, break-before-make 
• SK1 ....................................  2.5mm power socket, single hole fixing with break contact
• SK2 ....................................  3.5mm open mono jack socket
• WD1 ..................................  low profile wire-ended piezo electric sounder 

List of Semiconductors

Both figure above showed the list of semiconductors: 

• D1 .......................... 5mm l.e.d 
• D2, D3 .................. 1N4001 50v 1A rect diode (2 off)
• TR1 ....................... 2N3904 npn low power transistor
• TR2 ....................... BC337 npn medium power transistor
• IC1, IC2 ................ ICM7556IPA low power dual timer (2 off)
• IC4 ........................ LM2940HCT 1A low dropout regulator
• IC3 ........................ HCF4520BEY dual binary counter 

List of Capacitors

This is the list of capacitors that needed for the Body Detector circuit: 

• C1, C4 .............100p metallised ceramic plate, zero temperature coefficient (2 off)
• C2, C5, C9, C13 ...... 100n metallised polyester film (4 off)
• C3, C6.............. 100micro sub-miniature radial electrolyte 10v (5 off)
• C8 .................... 4n7 multilayer metallised polyester film
• C10 .................  150p metallised ceramic plate, zero temperature coefficient 
• C14 .................  100n metallised polyester film 
• C15 .................  1000micro miniature radial electrolytic 10v
• C16 .................  10micro sub-miniature radial electrolytic 35v 
• Cx ...................  a variety of metallised ceramic plate from 1p to 100p. 

All metallised ceramic plate capacitors have zero temperature coefficient

List of Resistors and Potentiometers

Here is the list of the resistors that need and involved in the Body Detector circuit: 

• R1, R2, R4, R5, R7, R10 ................................................................  10k (6off)
• R3 ..................................................................................................   470kOhm
• R6 ..................................................................................................   3M3
• R8 ..................................................................................................   270k
• R9 ..................................................................................................   150k
• R11 ................................................................................................   100k
• R12 ................................................................................................   2k2
• R13 ................................................................................................   220k
• R14 ...............................................................................................   15k
• R15 ...............................................................................................   68ohm 

All metal film 0.6W 1% (50ppm/ ohm C temperature coefficient)


List of Potentiometers:

• VR1 ........................ 200ohm to 500ohm 10 or multi turn wirewound potentiometer 
• VR2, VR3 .............. 50k 18 or multi turn horizontal cermet preset (2 off) 
• VR4 .......................  470k vertical sub-miniature carbon preset, linear cermet preset 100ppm/ degree circus temperature coefficient

Body Detector Components

This is the list of the Body Detector component:

 

Calibration

To undertake initial setting-up, use a test lead terminated at each end with a crocodile clip. Attach one end to the sensor bolt and the other to a piece of tin-foil about 300mm square. Due to the sensitivity of the circuti, it is important that both ends of the test lead should have a sure connection. Turn carbon preset VR4 back completely. Turn multiturn preset VR3 to 40 kilohms (40k) and multiturn preset VR2 to its maximum setting 50k. Turn the multiturn potentiometer VR1 to its mid-point. If at any time the circuit does not behave as described, switch off immediately and check the wiring carefully. 

Be aware that the presence of your body may affect the turning. Use a plastic or insulated screwdriver to turn VR2 and stand back from the circuit to see weather the crackling stops. If not, continue to back-off VR2 very carefully until the crackle just stops when stand back. Now set switch S1 to activate. The unit should now react when your hand approaches the sensor plate from a distance of few centimeters. Experiment a little to discover the best setting for preset VR2 and potentiometer VR1. A single "crackle" triggers monostable IC2b. 

Note that that the Activate position of S1 is optimised both for small sensors such as the 300mm square tin-foil sensors used in testing and a moderate temperature range (10 degree circus or 15 degree circus variation). Other application may require calibration in the Activate setting, monitoring the voltage across capacitor C10 by means of the test bolts provided. 

Casing Up without Circuit

The Body Detector is built into a plastic case with slotted walls, size 158mm x 95mm x 54mm approx. Holes are prepared on top of the case for VR1, S1, L.E.D D1, and the sensor bolt. Two small holes are also carefully positioned on top of the case to expose multi-turn presets VR2 and VR3, so that these may easily be adjusted from outside the case.

 

It is suggested that the holes for the presets be clearly labelled, so that their purpose is not forgotten with the passing of time. The author has more than once returned to a past project, only to puzzle over what the various adjustments might once have been for. Power socket SK1 and jack socket SK2 are mounted on the back of the case. Drill a hole for the insertion of a thermometer. 

 

The test bolts and piezo disc WD1 are mounted on the case. The piezo disc may be mounted behind a small hole on the front wall of the case. Board B is slotted into the case with the multiturn cermet presets VR2 and VR3 face downwards. Cable ties may be used to tidy up the connecting wires. Make sure that the battery is secure since a change in its position inside the case could slightly affect the unit's calibration.