Various diagram: controlled

Tuesday, November 4, 2014

Light Controlled Pond Pump

This circuit was constructed to control the pump in a garden pond, so that it automatically turns on at dawn and off again at dusk. Not only does this mean that we don’t have to get cold and wet when turning the pump on or off manually but it’s also one less job for our kind neighbours when we go away on holidays! The controller is powered from the pump’s existing 25VAC mains transformer. A bridge rectifier (BR1) and 1000μ F capacitor provide DC power to the circuit. For dependable operation, this is regulated to +12V by a 7812 regulator (REG1), while a red LED (LED1) provides power-on indication. The light sensor (LDR1) is a Cadmium-Sulphide photocell obtained from Tandy Electronics. The photocell forms a voltage divider with trimpot VR1.

Light-Controlled Pond Pump Circuit diagram:

With no light on the photocell, the voltage on the base of Q1 is greater than 0.6V and therefore it is switched on. When light falls on the photocell, its resistance decreases, lowering the bias voltage on Q1 and switching it off. This in turn allows Q2 to switch on, energised the relay and turning on the pond pump. In use, the 2.2MΩ trimpot is adjusted so that the pump cuts out at the desired light level. A 47μ F capacitor across LDR1 prevents transient light changes from affecting circuit operation. S1 is a miniature SPDT centre-off toggle switch, allowing the pump to be turned on or off manually, or switched to automatic mode.

The circuit was constructed on a small protoboard from Dick Smith Electronics (Cat. H 5604) and housed in a bulkhead box, which was then attached to the transformer housing. The photocell was soldered to a length of figure-8 cable and sheathed in a short length of heatshrink tubing to form a light probe. This was attached to a nearby fence post to provide suitable exposure to sunlight.

Author: Ian Hogan - Copyright: Silicon Chip Electronics

Using 555 Timer Voltage Controlled Switch

In this schema the 555 timer is used in a novel way, as a voltage controlled switch.The old and omnipresent NE555 can be very good at something it was not meant for: driving relays or other loads up to 200 mA. The picture shows an example schema: if the input level rises over 2/3 of the supply voltage - it will turn on the relay, and the relay will stay on until the level at the input drops below one third of the supply voltage.

If the relay and D1 were connected between pin 3 and ground, the relay would be activated when the input voltage drops below one third, and deactivated when the input voltage goes over two thirds of the supply voltage. It is also a nice advantage that the input requires only about 1 uA, which is something bipolar transistors cant compete with. (This high impedance input must not be left open.) A large hysteresis makes the schema immune to noise. The output (pin 3) can only be either high or low (voltage-wise), and it changes its state almost instantenously, regardless of the input signal shape.

Voltage Controlled Switch Circuit Diagram

The voltage drop across the NE555s output stage (at 35-100 mA) is 0.3-2.0 V, depending on the way the relay is connected and the exact current it draws. D1 is absolutely vital to the safety of the integrated schema.

Remote Controlled Fan Regulator Wiring diagram Schematic

Remote-Controlled Fan Regulator Circuit Diagram. Using this schema, you can change the speed of the fan from your couch or bed. Infrared receiver module TSOP1738 is used to receive the infrared signal transmitted by remote control. The schema is powered by regulated 9V. The AC mains is stepped down by transformer X1 to deliver a secondary output of 12V-0-12V. The transformer output is rectified by full-wave rectifier comprising diodes D1 and D2, filtered by capacitor C9 and regulated by 7809 regulator to provide 9V regulated output. Any button on the remote can be used for controlling the speed of the fan. Pulses from the IR receiver module are applied as a trigger signal to timer NE555 (IC1) via LED1 and resistor R4.

Remote-Controlled Fan Regulator Circuit Diagram

IC1 is wired as a monostable multivibrator to delay the clock given to decade counter-cum-driver IC CD4017 (IC2).Out of the ten outputs of decade counter IC2 (Q0 through Q9), only five (Q0 through Q4) are used to control the fan. Q5 output is not used, while Q6 output is used to reset the counter. Another NE555 timer (IC3) is also wired as a monostable multivibrator. Combination of one of the resistors R5 through R9 and capacitor C5 controls the pulse width. The output from IC CD4017 (IC2) is applied to resistors R5 through R9. If Q0 is high capacitor C5 is charged through resistor R5, if Q1 is high capacitor C5 is charged through resistor R6, and so on.

Optocoupler MCT2E (IC5) is wired as a zero-crossing detector that supplies trigger pulses to monostable multivibrator IC3 during zero crossing. Opto-isolator MOC3021 (IC4) drives triac BT136. Resistor R13 (47-ohm) and capacitor C7 (0.01µF) combination is used as snubber network for triac1 (BT136). As the width of the pulse decreases, firing angle of the triac increases and speed of the fan also increases. Thus the speed of the fan increases when we press any button on the remote control. Assemble the schema on a general-purpose PCB and house it in a small case such that the infrared sensor can easily receive the signal from the remote transmitter.

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Various diagram

Tuesday, November 4, 2014

Light Controlled Pond Pump

Monday, September 1, 2014

Using 555 Timer Voltage Controlled Switch

Voltage Controlled Switch Circuit Diagram

Friday, August 22, 2014

Remote Controlled Fan Regulator Wiring diagram Schematic