Dual High Side Switch Controller

Circuit diagram :

Dual High Side Switch Controller Circuit Diagram

One of the most frequent uses of n-channel MOSFET’s is as a voltage controlled switch. To ensure that the MOSFET delivers the full supply voltage to the load it is necessary for the gate voltage to be a few volts above the supply voltage level. This can be a problem if no other suitable higher volt-age sources are available for use elsewhere in the circuit. The LTC 1982 dual high-side switch controller from Lin-ear Technology (www.linear-tech.com) solves this problem by incorporating a voltage tripler circuit in the gate driver stage. The gate voltage is limited to +7.5 V which is 2.0 V above the IC’s maximum operating voltage. It can directly drive the gate of logic-level MOSFET with a VGS(th) from 1.0 V to 2.0 V. A suitable n-channel logic level MOSFET would be the BSP 295. This device can switch up to 1.5 A and is available in an SOT 233 SMD package.

http://streampowers.blogspot.com/2012/06/dual-high-side-switch-controller.html 

Continue Reading..

Cellphone Based Remote Controller for Water Pump

Cellphone-Based Remote Controller for Water Pump

Design By Sunil

---

Inconvenience in switching on a water pump installed in a remote farm is a common problem faced by farmers. Many circuits have been developed to solve this problem. Most of them are expensive and microcontroller-based. Here we present a cellphone-based remote controller for water pump. By calling the cellphone attached to the controller, the water pump can be directly activated.

Circuit and working
Fig. 1 shows the block diagram of cellphone-based remote controller for water pump. Fig. 2 shows the circuit. The circuit is built around DTMF decoder IC MT8870 (IC1), timer NE555 (IC2) wired as monostable multivibrator and a few discrete components. The main component of the circuit is IC MT8870. This DTMF decoder has band-split filter and digital decoder functions. It offers the advantages of small size, low power consumption and high performance.

Fig. 1: Block diagram of cellphone-based remote controller for water pump

Fig. 2: Circuit of cellphone-based remote controller for water pump

Once monostable timer IC2 is triggered, its output goes high for the preset time period. The time period depends on the values of resistor R7 and capacitor C4. It can be adjusted between 8 and 50 minutes using pot-meter VR1. The high output at pin 3 of IC2 energises relay RL1 to switch on the water pump.

The triggering pulse for IC2 is generated by DTMF decoder IC1 and the arrangement of diodes D1 through D5. Std pin of IC1 provides a high pulse when a valid tone-pair is received. Transistor T1 conducts only when outputs Q0 through Q2 and Std are high simultaneously. This can be achieved by sending digit ‘7’ through DTMF.
The water pump controller is connected to a dedicated cellphone through connector J1 with auto-answering mode enabled. The DTMF signal sent from the user end is decoded by the DTMF decoder and the corresponding binary-coded decimal (BCD) value appears on outputs Q0 through Q3. In this circuit only three of them are used.

Working of the circuit is simple. To switch ‘on’ the water pump, call the cellphone connected to the controller circuit and press ‘7’ once the ring stops. LED1 will glow to indicate that the water pump is switched on. The water pump turns off automatically after the preset time. LED1 turns off simultaneously.

Construction and testing
An actual-size, single-side PCB for cell-phone-based remote controller is shown in Fig. 3 and its component layout in Fig. 4. Suitable connector is provided on the PCB to connect the cellphone. Assemble the circuit on a PCB to minimise time and assembly errors. Carefully assemble the components and double-check for any overlooked error. Use suitable IC socket for MT887 and NE555 ICs.

Fig. 3: An actual-size, single-side PCB for cellphone-based remote controller

Fig. 4: Component layout for the PCB

Use relay RL1 with contact current rating capable of carrying the water pump’s current.

To test the circuit for proper functioning, press switch S1 and verify 5V at TP1 with respect to TP0. Connect the cellphone to the controller using connector J1. Call this cellphone and press ‘7’ once the ring stops. At the same time, verify high-to-low triggering pulse at TP2. TP3 now should be high for the preset time period.

---

The author is a final year B.Tech (electrical and electronics engineering) student at MG University. His areas of interest include embedded systems and power electronics

Continue Reading..

Self Writing LED Display Sign Controller

This is a design for a circuit of self-writing LED display sign controller. This circuit consist of eight power shift register which are installed in cascade. The shift registers are used to turn on a string of 64 lamps or LEDs sequentially. This is the figure of the circuit;

When the shift register clock (SRCK) is clocked, the register is clocked, so that the display is update after each bit of data is shifted in. The LEDs strobe on from left to right and until the LEDs strobe off in the same manner because of the serial input data (SER IN) is held alternately high and low for any period greater than 64 clocks. The display sign is dynamic and attractive because the LEDs arranged sequentially as in written message.

This circuit uses LM556 timer to generate the clocks and requires only one IC in addition to the shift register. To blanking or blinking the LEDs, this circuit uses the output enable. [Circuit diagram source: Texas Instruments Application Report]

Continue Reading..

Stepper Motor Controller

This is one kind of design control circuit. This a motor stepper controller circuit that is a simple, low cost, and accurate position controls. Stepper motor can be driven by circuit mounted close to the motor, and controlled by a remote control circuit through long cable. The interesting thing of this circuit is that the power for both motor and the driver circuit is carried over two wires, the same wires that carry the control signal. This is the figure of the circuit.


LMC555 CMOS timer integrated circuit (IC1) generates 200 microsecond pulses to step the motor and control its speed. The speed of the motor can be changed by changing the frequency of this pulse, R1 variable resistor is provided for this purpose. At the output of IC1 (pin 3), a negative going clock pulse drive the gate of IRL530N (Q1) power FET that momentarily turns OFF and disconnects the driver board from ground. This power interruption sends a signal to the motor driver to step the motor. The rotation direction is controlled by the polarity of the voltage applied to the driver circuit through interconnect lines L1 and L2. MPSA05 Bipolar NPN transistor Q2 and MPSA55 PNP transistors Q3 and Q4 invert the pulse from pin 3, pull the drain of Q1 UP when it is OFF. Toggle switch S1 sets its direction by switching polarity. Pushbutton S2 starts and stops the motor by turning the clock on and off.

Parts
C1 – .47 MFD 35 volt tantalum
C2 – 1000 MFD 35 volt electrolytic
C3 – .1 MFD 50 volt metalized film
C4 – .001 MFD 50 volt metalized film
C5 – 100 MFD 16 volt electrolytic
R1 – 5MEG potentiometer
R2, R8, R10 – 100K 1/8 watt 5%
R3 – .56K 1/8 watt 5%
R4, R5, R7 – 10K 1/8 watt 5%
R6 – 2K 1/8 watt 5%
R9 – 4.7K 1/8 watt 5%
Q1 – MPSA05 NPN transistor
Q2, Q3 – MPSA55 PNP transistor
Q4, Q5, Q6, Q7, Q8 – IRL530N Hexfet
D1, D2, D3 – 1N914 silicon diode
D4, D5 – 1N4752 zener diode
D6 – 1N4004 rectifier
BR1 - 2 AMP 400 volt bridge rectifier
IC1 – LMC555 CMOS timer
IC2, IC5 – 78L05 5 volt regulator
IC3 – CD4013 dual D flip flop
IC4 – CD4070 quad exclusive or
S1 – momentary N/O push button switch
S2 – double pole double throw toggle switch
T1 – DC or AC adapter transformer to match motor
IC socket – 1 eight pin
IC sockets – 2 fourteen pin
Terminal blocks – 2 two position
M1, M2 – two phase unipolar 24 volts

Continue Reading..