Posts Tagged ‘relay driver circuit’

Smartcard controlled Lock with Relay

This design uses a smart card to enable a relay. A Nutchip recognizes its mating smart card among thousand similar ones, because you choose the code to be programmed in the card’s memory. No speacilized knowledge is necessary, as we supply the card program and codes. Nutchip truth table is simple as well, so you should be able to adapt it to your needs (e.g., adding more than one card, or timing the relay). Even in its actual form, the board is ready to work in many useful applications: open gates e.g. for park lots. access control to gyms, swimming pools, tennis play fields. switch on central heating or showers, or the football field lights. enable TV viewing, photocopyng, faxing, coffe machine use, telephones etc. ..

Read more source:http://www.nutchip.com/progetti/card/card_en.htm

Water Pump Relay Controller Circuit Schematic

Water reservoir automatic level control
Simple circuitry – 12V supply

Device purpose:
By means of a Relay, employed to drive a water pump, this circuit provides automatic level control of a water reservoir or well.
Circuit operation:

The shorter steel rod is the “water high” sensor, whereas the longer is the “water low” sensor. When the water level is below both sensors, IC1C output (pin #10) is low; if the water becomes in contact with the longer sensor the output remains low until the shorter sensor is reached. At this point IC1C output goes high, Q1 conducts, the Relay is energized and the pump starts operating.
Now, the water level begins to decrease and the shorter sensor will be no longer in contact with the water, but IC1C output will be hold high by the signal return to pin #5 of IC1B, so the pump will continue its operation. But when the water level falls below the longer sensor, IC1C output goes low and the pump will stop.

SW1 is optional and was added to provide reverse operation. Switching SW1 in order to connect R3 to pin #11 of IC1D, the pump will operate when the reservoir is nearly empty and will stop when the reservoir is full. In this case, the pump will be used to fill the reservoir and not to empty it as in the default operating mode.

Parts:
R1,R2___________15K 1/4W Resistors
R3______________10K 1/4W Resistor
R4_______________1K 1/4W Resistor
D1______________LED any type and color
D2___________1N4148 75V 150mA Diode
IC1____________4001 Quad 2 Input NOR Gate CMos IC
Q1____________BC337 45V 800mA NPN Transistor
SW1____________SPDT Toggle or Slide Switch (Optional)
RL1___________Relay with SPDT 2A @ 230V switch
Coil Voltage 12V – Coil resistance 200-300 Ohm
Two steel rods of appropriate length

Read more source: http://www.redcircuits.com/Page129.htm

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Relay Coil Energy Saver

Some relays will become warm if they remain energized for some time. The circuit shown here will actuate the relay as before but then reduce the ‘hold’ current through the relay coil current by about 50%, thus considerably reducing the amount of heat dissipation and wasted power. The circuit is only suitable for relays that remain on for long periods. The following equations will enable the circuit to be dimensioned for the relay on hand: R3 = 0.7 / I Charge time = 0.5 × R2 × C1 Where I is the relay coil current. After the relay has been switched off, a short delay should be allowed for the relay current to return to maximum so the relay can be energized again at full power. To make the delay as short as possible, keep C1 as small as possible. In practice, a minimum delay of about 5 seconds should be allowed but this is open to experimentation.
The action of C2 causes the full supply voltage to appear briefly across the relay coil, which helps to activate the relay as fast as possible. Via T2, a delay network consisting of C1 and R2 controls the relay coil current flowing through T1 and R3, effectively reducing it to half the ‘pull in’ current. Diode D2 discharges C1 when the control voltage is Low. Around one second will be needed to completely discharge C1. T2 shunts the bias current of T1 when the delay has elapsed. Diode D1 helps to discharge C1 as quickly as possible. The relay shown in the circuit was specified at 12 V / 400 ohms. All component values for guidance only.
Author: Myo Min – Copyright: Elektor July-August 2004