Latching Relay On/Off Switch Circuit Latching Relay On/Off Switch Circuit

The ambit beneath switches AC or DC ability to a amount application an ultra low ability 3v latching broadcast with two coils. The broadcast can handle about 10 amps of current, up to 250vac. Anniversary time the baby pushbutton is pressed, the ambit either latches the broadcast contacts bankrupt or alleviate them open. The 3v powered ambit uses a distinct 74HC14. This accessory contains six Schmitt activate inverters in the one
14 pin package. Two inverters anatomy a flip/flop circuit. Anniversary time the pushbutton is pressed, the ambit changes accompaniment and stays in that accompaniment until the button is apprenticed again. With anniversary accompaniment change, a 25ms latching or unlatching beating is produced and is baffled to the actual broadcast coil. The braid attrition is about 45 ohms so about 70ma of accepted is fatigued from the 3v array for anniversary broadcast pulse. The boilerplate ability is so low that the ambit can accomplish for abounding years on one set of batteries. I would advance application two AA or AAA acrid cells.

Read More --►

Rangkaian Saklar Tepuk (Clap Switch Circuit) Rangkaian Saklar Tepuk (Clap Switch Circuit)

A clap switch circuit is a classic beginner’s project. Equipment can be switched on and off by just clapping your hands. Add a tiny microcontroller and you can easily build-in some more useful features.
The microcontroller in this circuit makes it a simple job to add some useful features that are not seen on other clap switch designs:
 


– Changeover relay contacts enable the unit to be wired in conjunction with a manual changeover switch so
that manual override of the switched equipment is always possible.
– The unit is only responsive to a specific sequence of sounds i.e., two claps within a defined time window.
– A safety feature masks the input for a given time window if misuse (repeated commands) is detected (useful if children have discovered how it works).
The safety feature and two-clap sequence detector can be built using TTL or CMOS flip-flops but by using a single microcontroller the circuit can be greatly simplified. A mains power supply is included so no additional power source is required.
The Microchip flash PIC12F629 microcontroller is a neat device; the small 8-pin package contains a complete microcontroller including clock generator, reset circuitry, Flash ROM, RAM and EEPROM. Two of the eight pins are used for the supply connections while the remaining six are general-purpose I/O pins. A few of these pins have special function like the comparator inputs. The sound sensitivity of the circuit can be adjusted by programming the comparator threshold level in software.

Clap switch COMPONENTS LIST:
Resistors:
R1,R6,R7 = 4kΩ7
R2 = 150kΩ
R3 = 22kΩ
R4 = 10kΩ
R5 = 150Ω
P1 = 100kΩ preset H
Capacitors:
C1 = 220μF 25V radial
C2 = 100nF
C3 = 1μF 16V
Semiconductors:
B1 = B80C1500 (round case, 80V piv, 1.5A)
D1,D2 = 1N4148
D3 = bicolour LED (red/green)
IC1 = 78L05
IC2 = PIC12F629CP, programmed
T1,T2,T3 = BC238 or BC547
Miscellaneous:
JP1 = 2-way pinheader with jumper
K1 = 2-way PCB terminal block, lead pitch 7.5mm
K2 = 3- way PCB terminal block, lead pitch 7.5mm
MIC1 = 2-terminal electret microphone capsule
Re1 = bistable relay, 2 x changeover (e.g., Schrack RT314F12)
Tr1 = mains transformer 1 x 6V, min. 2VA, short-circuit proof (e.g., Marschner VN30.15/10522 or Era 030-7340.0T; Conrad Electronics # 506141)

Read More --►

Auto Switch-Off Torch Auto Switch-Off Torch

An elderly acquaintance who couldn't cope with battery recharging was getting through dry cells rapidly by leaving their torch switched on, so I built the following LED torch circuit which switches off automatically after about five minutes. Switching the torch off manually then resets the circuit.

Operation

On closing the switch G1 output goes high and the capacitor charges slowly through R2. The high output of G3 provides base current for Tr1 via R3. If the voltage dropped across R4 exceeds 0.6V Tr1 begins to conduct and robs Tr2 of base current, thus lowering the collector current of Tr2 and the R4 voltage. Tr1 and Tr2 hence provide an approximately 20mA constant current source for the LED. After about 5 minutes the capacitor voltage reaches the Schmitt threshold voltage and gates G2, G3 and G4 change state. The now low output from G3 switches off Tr2 and hence the LED. If the switch is then opened G1 discharges the capacitor rapidly through the diode across R2, resetting the circuit.

Notes and Modifications

The value of R1 is not critical (anything ~1 meg or more will do, and higher values will give greater protection against static damage to G1 if the battery terminals are touched).
Tr1 and Tr2 are any general-purpose npn transistors, e.g. 2N2222, 2N3904.
By removing Tr1, R4 and the LED and connecting Tr2 emitter directly to ground the circuit could be used to switch other loads. R3 might then need to be reduced in value.

Read More --►