Preliminary Tests

Meaningful testing can only be carried out once the oscillator board has also been completed and connected up. For the time being, it may establish that regulator IC4 is supplying the correct voltage. Attach a 9v PP3 battery to the battery clip, switch S1 to any position other than Off and measure the voltage across capacitor C15. This should be close to 5v. The regulator i.c should remain fairly cool and supply current should not rise above 15mA.

If any specified components for the Body Detector cannot be sourced at this stage, it is important that equivalents should have low temperature coefficients particularly capacitors C1 and C4 which should if possible have a zero temperature coefficient. The multiturn  potentionmeter VR1 may be pricy. however, these devices may sometimes be obtained cheaply as surplus goods. Alternatively, use a cheap 470ohms or 1 kilohms potentiometer, although this will not offer the same high degree of precision when it comes to calibration. 

OSCILLATOR BOARD

Having completed the preliminary checks, we can now tackle the construction of board B, which includes the h.f.o.s, the l.f.o and monostable. We shall also be casing the unit and calibrating it. Taking the second piece of strip-board, again having 18 holes by 34 cooper strips, create the breaks in the underside copper tracks with with a drill bit or other appropriate tool. Details of the topside component layout together with the underside details. 

Solder in position the wire links and solder pins, then the dual-in-line sockets then the resistors and multiturn presets continuing with the capacitors. Be careful to observe the correct polarity of the electrolytic capacitors and the correct orientation of IC1 and IC2, when inserting them into their holders. Pin 1 of IC1 and IC2 lies close to the small indentation on one of their encapsulation. 

Next, prepare seven sheathed wires 15cm long and solder them to potentiometer VR1, the sensor solder tag and sections S1b and S1c of the mode switch. Finally attach the leads from VR1 to the solder pins on the topside of the strip-board, the wire from the sensor solder tag and then the eight colour-coded wires from board A. Jack socket SK2 is included for switching small external loads- a second jack socket may easily be added. solder pins have been provided for this purpose at the opposite side of relay RLA at board position R9 and R13 on board A. the specified relay is rated at 60W 250V a.c and would therefore also be capable of switching small a.c resistive loads.