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This is a universal version of the Four-Digit Alarm Keypad . I have modified the design to free up the relay contacts. This allows the circuit to operate as a general-purpose switch. It also means that it can be used to control all of my Alarm Circuits. Ive used a SPCO/SPDT relay - but you can use a multi-pole relay if you wish.

The relay is energized by pressing a single key. Choose the key you want to use - and connect it to terminal "E". Choose the four keys you want to use to de-energize the relay - and connect them to "A B C & D". Wire the common to R1 and all the remaining keys to "F".

The Circuit is easy to use. When you press "E" - current through D2 & R9 turns Q6 on - and energizes the relay. The two transistors - Q5 & Q6 - form a "Complementary Latch". So - when you release the key - the relay will remain energized.

To de-energize the relay - you need to press keys "A B C & D" in the right order. When you do so - pin 10 of the IC goes high - and it turns Q4 on through R8. Q4 connects the base of Q6 to ground. This unlatches the complementary pair - and the relay drops out.

Any keys not wired to "A B C D & E" are connected to the base of Q3 by R7. Whenever one of these "Wrong" keys is pressed - Q3 takes pin 1 low and the code entry sequence fails. If "C" or "D" is pressed out of sequence - Q1 or Q2 will also take pin 1 low - with the same result. If you make a mistake while entering the code - simply start again.

The Keypad must be the kind with a common terminal and a separate connection for each key. On a 12-key pad, look for 13 terminals. The matrix type with 7 or 8 terminals will NOT do. With a 12-key pad - over 10 000 different codes are available. If you need a more secure code - use a bigger keypad with more "Wrong" keys wired to "F". A 16-key pad gives over 40 000 different codes.

One technique relay drivers from the microcontroller or computer can be made with the driver PNP transistors like the article "Interface Relays With PNP Transistor" ini.This circuit interface is simple and easily applied to a microcontroller or computer parallel port. Interface Relays With PNP Transistor uses 2 transistors 2N3904 and 2n2905/2N2907 UAH as a power relay drivers. The advantages of this circuit can menggeran relay with considerable power with TTL logic input from the computer and microcontroller. Source voltage required to follow the relay circuit is used, for example using a 12V relay, the source voltage to 12V or 24V relays the 24V voltage source. Detailed relay interface circuit and microcontroller or computer can be seen in the following figure.

Function diodes mounted parallel with the relay to prevent backflow into the transistor due to magnetic induction of the relay coil, therefore these diodes must be installed. For installation with a microcontroller or computer which need to be noticed is the Grund computer or microcontroller circuit must be connected to ground in series Interface Relays With this PNP transistors.

The new archetypal of RS485 advocate overcomes the RTS controlled botheration accomplished by our chargeless design. However, to do that requires a microprocessor, so there is a greater complication to the design. We advertise this unit, although currently we are attached our sales to barter who can pay by coffer alteration – which in absoluteness is bounded Australian companies. 

This architecture has been almost agitation free, and if you crave quantities we can acclimate the adapter pinout to clothing your appliance – about again the accessory will no best fit the simple little D25 case in which you see it pictured.

* Data (vs RTS) controlled – does not rely on PC handshake timing

* DB25 RS232 connector compatible with PC

* TxD and RxD translated from RS232 to RS485

* Direction of transmission controlled by Data

* Handshake loop the PC connection so it works with all software

* RS485 signals output on D9 male with lots of Ground pins

* Indicator LED(s) to show communications traffic

* Line powered – powered by RS232 handshake lines

* RS485 Termination resistor not included

* Pullup/Pulldown resistors on RS485 to establish line-idle condition

* Baud rate is dipswitch selectable 1200 – 115.2k

Series NIMH Battery Charger with IC LT4060 is a NIMH battery charger is powerful, effective and efficient. Featur owned by IC LT4060 is a specialization of a NIMH battery charger. NIMH Battery Charger with IC LT4060 can perform safely charging NIMH batteries because it comes with a battery temperature protection is in charge and the peak level detection system of the battery voltage is in charge. Battery temperature protection system from the excessive use of NTC temperature sensor. Series NIMH Battery Charger with IC LT4060 also features a charging indicator that will light up when charging and will die when the battery is full. IC 4060 used in this NIMH battery charger from Linear Technology is a production that is designed special for NIMH battery charger.

Power Supply in this post is using a regulator which is composed of 2 pieces of NPN transistor. A transistor acts as a power regulator and a transistor again serves as a controller output voltage. Power Supply has an adjustable output with a range of 6-12 VDC. The part that serves as a power regulator is Q1 TIP31. Then the controller output voltage is a voltage divider composed of R3, R4, VR1 and R2 provide bias to the base of Q2 to control the power regulator Q1. In a series of power supply is mounted 5.1 V zener diode which serves to make the minimum limit the output voltage with Q2.

Power Supply With transistor circuit is quite simple and can be made with the PCB holes, so for those who want to try to directly mempraktikannya. May the power supply circuit can be useful for readers, especially for friends who need a power supply circuit with the regulator transistor.

Running LED with 4017 complete with PCB layout. The series of 8 LED current is the basis for creating an 8-point LED. Slightly different from the running LED with IC 4017 (decade counter), 8 running this led is lit in sequence, but that has been previously flame does not die when the led is lit afterwards. 8 led to death after led to the fire-8. Meanwhile in the running LED (decade counter), the system LED lights like "point", there is only one LED that flashes between the tenth led.

The main component is the IC 74LS164 (SHIFT REGISTER), with its timer is astable multivibrator circuit (using IC NE555).

The series will be more efficient when using a stable power supply (regulator) using IC Regulator 7805. Under this scheme a series of stable power supply 5 volts dc.

Learning Programming MCS51 becomes mandatory we learn if we want to use the MCS51. In the first part of this Learning Programming MCS51 we will learn together about the basic programming language MCS51 microcontroller. Where to program MCS51 outline there are 2 core parts of pemrogramanya language is "Words Work" and "Object". In the article Programming MCS51 this first part we will study first the "verb" is a command group Peng-copies of data, the command group arithmetic and logic command group.

Reference to DATA IN PROGRAMMING MCS51

Data can be in many different places, thus known a few ways to describe the data (in English often referred to as Addressing Mode), among others, as follows:

The mention of constant data (immediate addressing mode): MOV A, # $ 20. Constant data is data that was in the instructions. Examples of this instruction has the data meaning a constant $ 20 (as a constant data marked with #) on-copy it into the accumulator A. What needs to be properly addressed in this order is the number $ 20 is part of the instruction.

Reference to data directly (direct addressing mode), this method is used to refer to data residing in memory by calling the memory number where the data are: MOV A, $ 30. Examples of these instructions have the meaning of data in the memory number $ 30 in-copy it to the accumulators.

At first glance these same instructions to the instruction constant data above, the difference above instructions using the # which marks the $ 20 is a data constant, whereas in this instruction because there was no sign # then $ 30 is a number from memory.

The mention of indirect data (indirect addressing mode), this method is used to refer to data residing in memory, if memory data storage is changing its location so that the memory number is not called directly but in-titip her into another register : MOV A, @ R0.

In this instruction versatile R0 register is used to record the number of memory, so that this instruction has a memory meaning that the number recorded in the contents of R0-copy it into the accumulator A.

Sign @ is used to mark the memory number stored in R0.

Compare this with the instruction memory number directly mention above, in this instruction first memory numbers are stored in R0 and R0 appoint a role which memory is used, so that if the value of R0 change the designated memory will also be changed as well.

In this instruction registers R0 functioning multipurpose container for the address register (indirect address register), other than all-purpose registers R0 R1 can also be used as a container for the address register.

Reference to data in the register (register addressing mode): MOV A, R5. This instruction has the meaning of data in all-purpose register R5 is copy it into the accumulator A. This instruction makes all-purpose registers R0 to R7 as a place to store data that is very practical that it works very fast.

The data referred to in the discussion above all in the data memory (including all-purpose registers are also located in data memory). In writing the program, often required standard table that is stored along with the program. Tables of this kind is really a data residing in program memory!

For this purpose, MCS51 have any mention of data in memory means programs conducted by indirect (indirect addressing code mode): MOVC A, @ A + DPTR.

Notice in this MOV instruction is replaced with MOVC, the additional letter C is meant to distinguish that this instruction is used in the program memory. (MOV without the letter C means that the instruction used in the data memory).

Sign @ is used to mark A + DPTR is used to indicate the number of contents in-memory copy it to the accumulator A, in this case the value stored in the DPTR (Data Pointer Register - 2 bytes) plus the value stored in accumulators A (1 byte) is used to refer to the program memory numbers.

Verb in AT89Cx051

Overall AT89Cx051 have as many as 255 kinds of instruction, which was formed by combining the verb and objects. "The verb is the group discussed the following:

PENG GROUP-COPY-DATA AN MCS51

Basic code for this group are MOV, abbreviation of MOVE, which means to move, though more correct to say this command have meaning copying the data. This can be explained the following: after the instruction MOV A, R7 done, accumulators A and all-purpose register R7 contains the same data, originally stored in R7.

MOV command is distinguished according to the type of memory AT89Cx051. This command is on the memory data is written into MOV, for example:

MOV A, $ 20

MOV A, @ R1

MOV A, P1

MOV P3, A

To use the program memory, this command is written into MOVC, there are only 2 types of wear MOVC instructions, namely:

MOVC A, @ A + DPTR; DPTR as register indirect

MOVC A, @ A + PC, PC as the register indirect

In addition, there is also known MOVX command, the command that is used for external data memory (X singkatakan from External). This command is only available to the MCS51 family members who have an external data memory, for example AT89C51 and so forth, and certainly not known by the group that tidam AT89Cx051 have external data memory. There are only 6 kinds of wear MOVX instruction, these instructions are:

MOVX A, @ DPTR

MOVX A, @ R0

MOVX A, @ R1

MOVX @ DPTR, A

MOVX @ R0, A

MOVX @ R1, A

GROUP ARIMATIK (ADD, ADDC, SubB, DA, MUL and DIV)

ADD and ADDC command

The contents of accumulators A plus the number 1 byte, the sum will be collected back in the accumulator. In this operation Carry bit (C flag in the PSW - Program Status Word) serves as a reservoir overflow of the sum. If the sum of the abundance (a value greater than 255) will carry bit value 1 , if not Carry bit value 0. ADDC same with ADD, only in bits Carry ADDC value in the previous process involved summed together.

Numbers 1 byte is added to the accumulator, can be derived from a constant, from the all-purpose register, memory data from memory number is called directly or indirectly, as shown in the following example:

ADD A, R0; register versatile

ADD A, # $ 23; a constant

ADD A, @ R0; no memory indirect

ADD A, P1; no direct memory (port 1)

ORDERS IN PROGRAMMING SubB MCS51

The contents of Accumulator A less the number 1 byte follows with Carry bit value, the reduction will be accommodated again in the accumulators. Carry bits in this operation also serves as a reservoir overflow of the reduction. If the reduction is abundant (score less than 0) bits Carry would be worth 1 , if not Carry bit value 0.

SubB A, R0; A = A - R0 - C

SubB A, # $ 23; A = A - $ 23

SubB A, @ R1

SubB A, P0

DA command

DA command (Decimal Adjust) is used after the command ADD, ADDC, or SubB, used to convert 8-bit binary value stored in the accumulator into 2 pieces decimal number, each consisting of 4-bit binary value.

MUL AB ORDERS IN PROGRAMMING MCS51

8-bit binary number in accumulator A is multiplied by an 8-bit binary number in register B. The result of multiplication of binary 16-bit, 8 bit binary number that greater weight be accommodated in the register B, while the other 8 bits are accommodated in the smaller weight accumulator A.

OV bit in the PSW (Program Status Word) is used to mark the result of multiplying the existing value in register B. OV bit will be worth 0 if register B is worth $ 00, if not worth OV bit 1.

MOV A, # 10

MOV B, # 20

MUL AB

DIV AB ORDERS IN PROGRAMMING MCS51

8-bit binary number in accumulator A is divided by an 8-bit binary number in register B. The result of the division of 8-bit binary numbers stored in the accumulator, while the rest of the division of 8-bit binary number stored in register B.

OV bit in the PSW (Program Status Word) is used to mark the value before the division that exists in the register B. OV bit will be worth 1 if register B originally worth $ 00.

GROUP LOGIC (ANL, ORL and XRL) IN PROGRAMMING MCS51

This command group used to perform logic operations MCS51 microcontroller, logic operations can be done is the AND operation (operation code ANL), OR operation (operation code ORL) and the Exclusive-OR operation (XRL operation code).

The data used in this operation can be data that is in the accumulator or data that are in-memory data, this is a little different with arithmetic operations that must be actively melihatkan accumulators.

Operating results are accommodated in the first data source.

AND logic operation is widely used to me 0 a few specific bits of an 8-bit binary number, the way to forming an 8-bit binary numbers as a data-ANL constant in a number of origin. Bit-0 want in a represented by 0 in constant data, while other bits given the value 1, eg

Instructions ANL P1, #% 01111110 will result in bit 0 and bit 7 of Port 1 (P1) value 0 while the other bits remain unchanged in value.

OR logic operation is widely used to me 1 a few specific bits of an 8-bit binary number, the way to forming an 8-bit binary numbers as constant data in a number-ORL origin. Bit-1 want in a represented by 1 in constant data, while other bits given the value 0, eg

Instructions ORL A, #% 01111110 will result in bit 1 to bit 6 of the accumulator value 1 while other bits remain unchanged in value.

Exclusive-OR logic operation is widely used to reverse the value (complement) some particular bits of an 8-bit binary number, the way to forming an 8-bit binary numbers as constant data in a number-XRL origin. Bit you want behind-the value represented by 1 in constant data, while other bits are the value 0, eg

Instructions XRL A, #% 01111110 will result in bit 1 to bit 6 of the accumulator turned value, while other bits remain unchanged in value.

Digital Thermometer 0-100.0 ° C is a digital thermometer that operates in mode temperature measurement in Celsius (° C). Digital Thermometer 0-100.0 ° C in this article using the form data processing microcontroller AT89C4051. Temperature sensors used in Digital Thermometer 0-100.0 ° C. This temperature sensor LM35D. Digital Thermometer 0-100.0 ° C. It uses the temperature measurement data viewer in the form of 1 line LCD viewer. Digital Thermometer 0-100.0 ° C. It can display the temperature measurement data with a resolution of 0.1 ° C.

Digital Thermometer 0-100.0 ° C. These temperature sensors make use of LM35D as temperature sensing. In Digital Thermometer 0-100.0 ° C. This temperature sensor measurement data this LM35D (Level Voltage) is then converted into 4-bit binary data using the ADC CA3162. Then the 4-bit data from ADC CA3162 which is a measurement of data if the temperature is in the AT89C4951 microcontroller so that it becomes an operating principle of temperature measurement based on digital thermometers. In the final stage of the Digital Thermometer 0-100.0 ° C. These data digitla adlah appearance temperature measurement, using digital data viewer of the LCD 1 line.

Digital visitor counter is a reliable circuit that takes over the task of counting Number of Persons/ Visitors in the Room very Accurately. When somebody enters into the Room then the Counter is Incremented by one and when any one leaves the room then the Counter is Decremented by One. The total number of Persons inside the Room is displayed on the seven segment displays.The microcontroller do the above job it receives the signals from the sensors, and this signals operated under the control of software which is stored in ROM.

DCF77 Preamplifier Circuit Diagram A popular project among microcontroller aficionados is to build a radio-controlled clock. Tiny receiver boards are available, with a pre-adjusted ferrite antenna, that receive and demodulate the DCF77 time signal broadcast from Mainf lingen in Germany.

DCF77 has a range of about 1,000 miles. All the microcontroller need do is decode the signal and output the results on a display. The reception quality achieved by these ready-made boards tends to be proportional to their price. In areas of marginal reception a higher quality receiver is needed, and a small selective preamplifier stage will usually improve the situation further. 

The original ferrite antenna is desoldered from the receiver module and connected to the input of the preamplifier. This input consists of a source follower (T1) which has very little damping effect on the resonant circuit. A bipolar transistor (T2) provides a gain of around 5 dB. The output signal is coupled to the antenna input of the DCF77 module via a transformer. 

DCF77 Preamplifier Circuit Diagram The secondary of the transformer, in conjunction with capacitors C4 and C5, forms a resonant circuit which must be adjusted so that it is centered on the carrier frequency. An oscilloscope is needed for this adjustment, and a signal generator, set to generate a 77.5 kHz sine wave, is also very useful. This signal is fed, at an amplitude of a few milli-volts, into the antenna input. With the oscilloscope connected across C4 and C5 to monitor the signal on the output resonant circuit, trimmer C5 is adjusted until maximum amplitude is observed.

It is essential that the transformer used is suitable for constructing a resonant circuit at the carrier frequency. Our proto-type used a FT50-77 core from Amidon on which we made two 57-turn windings. It is also possible to trim the resonant frequency of the circuit by using a transformer whose core can be adjusted in and out. In this case, of course, the trimmer capacitor can be dispensed with. Rainer Reusch Elektor Electronics 2008

Easy Downloader Circuit

Atmel microcontroller series AT89Cxx51 Easy Downloader is one of the downloader that is often used to write data to program the Atmel microcontroller AT89CXX51. Easy Downloader AT89Cxx51 ATMEL microcontroller is using the serial port as a channel of communication with the computer. 

This circuit employs the popular and easy to find LM3914 IC. This kind of IC is quite very simple to drive, requires no voltage regulators (it features a built in voltage regulator) and can be powered from almost every resource.

This LM3914 IC based on Simple Battery Tester is very simple to explain:
Once the test switch is pushed, the Car battery voltage is supply into a high impedance voltage divider. His function is to divide 12V to 1, 25V (or lower values to reduced values). This solution is much better than enabling the internal voltage regulator set the 12V sample voltage to be feed into the internal voltage divider simply because it cannot regulate 12V if the voltage falls lower (linear regulators only step down). Simply wiring with no change, the regulator provides secure 1, 25V which can be fed into the precision internal resistor cascade to create sample voltages to the internal comparators.

In any case the default establishing let you to determine voltages between 8 and 12V however you can measure even from 0V to 12V setting the offset trimmer to 0 (but i believe that below 9 volt your vehicle would not start). There is a smoothing capacitor (4700uF 16V) it is used to adsorb EMF noises produced from the ignition coil if youre testing the battery during the engine working. Diesel engines would not need it, but i am not sure. If you want more a level graph rather than a bar graph simply disconnect pin 9 on the IC (MODE) from power. The calculations are usually simple (default).

This circuit uses a sensor made of a small piece of circuit board and recorded a simple SCR circuit to detect rain and sound of a bell. The SCR could also be used to activate a relay, light a lamp, or send a signal to a security system.

2. Make sure to use a loud buzzer.

Tone control or pre-amplifier is an amplifier circuit supporters. Sometimes some of us do not know where a good amplifier, a raft alone and the results are not much different or even the same. Therefore we must know the character of the advantages and disadvantages of each amplifier equipment.

Tone control low noise here does not mean without noise, but noise compared with the lowest tone control on the market, for example Ronica transistor 4, TL-084, TC-2 LM833 etc.

Jump toexplanation of each component ...

Potensio 1 serves to regulate the intensity / level of the incoming signal is assisted potensio 2 as balance / counterbalance. Potensio 2 is still installed and is usually an optional component. 1-2uF/250V capacitor R1 is actually a brand name,but I prefer to replace it with a 1K resistor / 5% normal for reasons to avoid hum and interference sensitive. R2 R3 while minimizing interruption to adjust the impedance OP-amp 1. R4 and R5 serves to increase the gain of 1.3 times. Pre amplifiers typically use a strengthening standards by 2 times, but by most of us think it has a noise. So I chose the value of 1.3 times, but the most minimal noise signal from the volume is enough to make the lamp light peak.

For low noise ...Cause of noise in op amp 1, apex audio even eliminate this stage. CanThis step is also used as a buffer (jumper R5), the strengthening of a time. Lower values ​​increase the value of R5 or R4 with consequent gains to be less, but remains at a value above 1 times due to input non-inverting path to take, so that the signal and noise can be reduced. R4 can also be replaced with a 10K trimpot and middle leg into the bass range adjuster (bass resonance).

C1 and C6 as a filter to reduce the treble / high frequency of excessive or often called oscillation prevention. R6 is actually an optional component of the impedance a little help customize the system. Ideally the same as the R8 R7 to facilitategive the sign of the gain on potensio panel tone control. C2 and C3 form a series circuit treble filter (high pass filter), its value is greater then the sound that passed the mid. C4 and C5 assisted by R9 and R10 form the low pass filter (filter bass), the greater the value of C is a bass sound that will be missedthe soft / low (maximum of 47nF), the smaller the value of c is the bass signal that is passed will further dip (dig-dig, c4 = c5 = 22nF). This value is suitable for 27-33nF, 47nF instead (depending on taste). Pot 3 & 4 pot set treble and bass levels, the greater the greater the value of this potensio gains (bass & treble including potensio volume). R11 adjusts the output impedance, while the R12 and the red LED indicator that shows if the amplifier Peak has been given a full signal.

15V maximum supply. TL074 IC can, but in designing the PCB, IC can bereplaced with 2x TL072/NE5532/4558.

Easy low power car audio amplifier circuit on TDA 2003. The circuit is Easy to construct. TDA2003 is an integrated radio amplifier from ST Micro electronics that like short circuit protection for all pins, thermal over low harmonic distortion, low cross over distortion etc. In the circuit given here TDA2003 is wired as a mono amplifier operating from a 12V .

Resistors R2 and R3 forms a feedback network that sets the amplifiers gain. C7 input DC de-coupling capacitor and C5 couples the speaker to the amplifiers output. C4 } for improving the ripple rejection C1 and C2 are employed for power filtering. C3 and R1 are used for setting the frequency cut-off. Network comprising of C6 and R4 for frequency stabilization and oscillation.