This zener tester based on famous 741 operational amplifier. RV1 can be calibrated in volts, so that when LED 1 just lights, the voltage on pins 2 and 3 are nearly equal. Hence, the zener voltage can be read directly from the setting of RV1. The supply need only be as high a value as the zener itself For a more accurate measurement, a precision pot could be added and calibrated.

Zener tester parts  list :
R1 : 4K7
RV1 : 10 K linier variable resistor
Led
IC1 :  LS741

Diode tester parts list :
D1, D2 : HEP R0052
LP1, LP2 : GE 4B lamp
X1 : 120V tp 6.3V, transformer, Lafayette 33P80508

The Rain Alarm circuit applies 4 NAND gates of the 4011 IC. In each individual oscillator, while a single gate is configured a straightforward inverter, some other has one input that will act as a control input. Oscillator action is inhibited if this enter is held low. The first oscillator (IC1a and also IC2b) has this kind of input tied low through a high value resistor (R1) which acts as a sensitivity control. Thus this oscillator will be disabled until the control input is taken high. Any moisture bridging the sensor track will so enable the output which is a square wave at about 10 Hz. This in turn will gate on and off the 500 Hz oscillator formed by IC1c and IC1d. This latter oscillator drives the loudspeaker via R6, the Darlington pair formed by Q1 and Q2, and resistor R7.

Solid-state AC switch schematic diagram

Main technical characteristics:
Maximum switching voltage, V 250 maximum average switch current (no radiator), and 1.8 current, mA 10 overall dimensions 60/20/25mm

The device is based on a particular form of consumption cooler current ( ric. 2 ). With the resistor R1 is removed voltage proportional to current through the cooler, with an amplitude of pulses of about 2V. C1R2 filter suppresses the DC component signal to the pulse in the absence of transistor VT1 was completely closed. Each pulse of current (one turn cooler) for a short time opens the transistor VT1, discharging the capacitor C2. After the pulse the transistor is closed, the capacitor C2 is gradually charged through R4, but during normal operation to a cooler time of arrival of the next pulse he can be charged by little, at the inlet 9 DD1 ever-present low level. At breakage, jamming or closure of the cooler current pulses cease to act on the input of the indicator, the transistor VT1 permanently closed, and capacitor C2 is charged ( resistance resistor R4 is chosen so that the steady-state voltage on C2 surely be recognized as a high level of chip). High level input 9 DD1 allows the generator assembled on valves DD1.1-DD1.4 and forming an intermittent beep. The frequency of the sound depends on the C4 and R6 (shown in the diagram correspond to the nominal values ​​of approximately 2 kHz), frequency of interruption of the sound – with the help of C3 and R5 (scheme 9.10 Hz). As the sound radiator cap can be used piezoelectric (like used in the electronic alarm clocks and telephones). Option PCB and alarm wiring diagram shown in Fig. 3 .

Setting the indicator is performed in two stages. First choice of R1 and C1 require sustained opening of transistor VT1 positive current pulses of the cooler. Then the selection of R4 and C2 set the permissible range between pulse, after which the alarm system. (It is desirable to control the shape of the voltage on the capacitor C2 with a scope.)

Figure 1

The scheme works very simply. When you turn on the device after assembly of all components, including a fluorescent lamp, the lamp will be lit for 10 seconds, stops for 30 seconds, turn on again for 10 seconds, and finally shut down. Now the scheme is ready to work.

When motion is detected at the base of transistor T1, which is included in the collector coil relay RL1, will be voltage of 3.3 V, and the relay turns on. As a result, triac Triac1 (BT136) opens, Fluorescent receive full board and 230 lights. The other, normally open relay contact (N/O2) is used to hold out until reset. If switch S1 is not in the “HOLD” light stays on for about 10 seconds (according to how the motion sensor is programmed). In short, when a motion detector near the fluorescent lamp is turned on and off about 10 seconds, if the switch is set to “Reset” or constantly lit when the switch S1 in position “HOLD”.

Scheme can be collected at the breadboard and hide the body in appropriate sizes. To connect the sensor using three-pin plug, and do not reverse the polarity of conclusions sensor. A motion sensor is covered with a transparent semi-circular cover (Fig. 2).

Figure 2

Figure 3 shows the design of the prototype, assembled by the author, and in Figure 4 shows the method of installation design in luminaire. In the luminaire installed capacity of 23 fluorescent Tues Protect your body from moisture sealant. Isolate the circuit board of the tracks with insulating foam and glue to the bottom.

Figure 3

Figure 4

This is how simple lie detector work : The circuit uses an oscillator that has a frequency based on C1, R2, and skin resistance at the touch pad. Because C1 and R2 value is fixed, only the skin resistance at the touch pad that can change the tone oscillator. To maintain oscillation, the C1 provides some output from Q2 back to the input of Q1 through R1.

Q1 is NPN type transistor and Q2 is PNP type transistor. Output Q2 is given to a small speaker.
Part List :

• C1 = 10 nF
• R1 = 4K7 ohm
• R2 = 82 kohm
• Q1 = 2N3904
• Q2 = 2N3906

Component Parts:
R1 = 100K
R2,R5 = 1K
R3,R6 = 470R
R4 = 12K
C1 = 1000µF 25V
D1-D4 = 1N4007
D5 = SCR P0102D
Q1 = BC327
Q2 = BC337
SK1 = Female Mains socket

How it works:
The device formed by Q1, Q2 and related resistors triggers the SCR. The frequency of flashing is provided by R1, R2 and C1. If you want to change the flashing frequency value, you need to  set C1 value. The range is from 100uF to 2200µF, please don’t modify R1 and R2.

The Best performances of this circuit are obtained with C1=470uF or 1000µF and R4=12K or 10K. Due to low consumption of normal 10 or 20 lamp series-loops, very small and cheap SCR devices can be used, for example C106D1 or TICP106D.

Source of circuit: redcircuits.com