Keypad Circuit

Keypad Combination Lock circuit

This simple circuit is the electronic version of the combination lock. Using the special purpose LS7220 digital lock IC, the circuit allows a 4 digit combination of your choice to activate a relay for a set period of time. This relay can then be used to trigger a lock solenoid, enable a starter button, open a motorized door, or many other tasks that require a momentary signal...

Keypad Combination Lock Relay

Only one out of 9,999 possible codes has the power to unlock this simple, yet effective, electronic lock. A combination lock is not just a perfect system to protect your belongings, it is also a valid system to let everyone to know that you are vigilant: an electronic system with a silicon heart is controlling the area, day and night without interruption, so everyone is warned! You can use this combination lock circuit as a replacement or in addition to normal locks. It is very handy when a group is entitled to enter a common area, as parking lots or sport resort facilities for example. It is often the case where traditional keys are expensive, not appropriate or just not convenient: not to mention when the keys need to be replaced very often (e.g. in the case of parking lots the cars can change). ..

Door electronic lock with Keypad

It is a relatively simple circuit of electronic lock of safety with code of 7 digits. It should is given attention in the time that will be stepped the keys, that shape code and it does not exist it delays. With the right step of keys and if code is right then is activated exit Q7 for roughly 4 seconds, driving the transistor Q2, which with the line can drive one relay, for the opening of door, or any other circuit. With LED D we can have optical clue of activation. The code of circuit, as it has been given have been:1704570 but can change, if we change the connections between in the exits of IC1 and the switches...

CMOS Combination lock

his Electronic Lock circuit is not only simple but it is also very good. It can easily be configured to provide either momentary or continuous output. Key sequences of up to 9 digits are possible. You can pre-enter part of the combination and then have someone else enter the last few digits at a later time allowing for one-time access. This circuit has good debounce but there are some REALLY crappy switches out there so please look for types with spring or snap contacts. For better security or for a mad-scientist look you might use unlabelled pushbuttons arranged in some unusual shape...

Remote IR controller

This unit provide 2 way IR communications using a numeric keypad and an LCD display. Data is sent and recieved in ASCII with no regard to what the data means to any particular device. The ASCII data still needs some form of encoding. For this I chose 10-pulse coding of 38Khz IR using a nifty 99 cent receiver chip , TSOP4838 The transmitting is done with a straight IR LED with both carrier and coding done in software...

Security Lock with keypad and LCD (PIC16F84A)

Finally I was able to control an LCD Hitachi display and a 12-key matrix keypad with only one 16F84 or 16F628. In a near future, I will be able to control a full QUERTY-type keyboard and a LCD display. The biggest improvement on this projects was the compatibility with the Microchip PIC 16F84 and the 16F628, also the 16x1 or the 8x1 LCD Hitachi can be used. To reduce the cost of this proyect, is possible to remove the LCD and the circuit will work with the beep codes. Basically, the hardware is a mini-terminal controlled by a 16-pin PIC...

This circuit is very basic to build. To open a lock which is connected to the K1 Load, you must press each momentary switch in the correct sequence. The sequence used in this circuit is S1, S2, S3 and finally S4. If any of the other switches are pressed the circuit will be reset and you will need to start over. ..

The MM74C922N combines all elements needed to scan detect, debounce, encode, store, and transmit contact closures in an X/Y switch matrix. The IC combines these functions in a way that makes it useful in stand-alone applications and as a bus-oriented system device. An internal RC oscillator (or an external frequency source) and scanning circuit poll the X/Y switch matrix for switch closures...

First, using interrupts frees the microcontroller to perform other tasks or to switch into an idling or power-down mode while awaiting the next key closure. Second, using interrupts helps reduce electromagnetic interference produced by continuously scanning the keypad`s lines. Figure 1 shows an interrupt-driven keypad implementation that`s based on Atmel`s AT89C52 version of the popular MCS-51 family of microcontrollers...

The alarm will switch off when the 4 keys connected to "A,B,C,D" are pushed in the right order.The circuit works because each gate `Stands` upon its predecessor.If any key other than the correct key is pushed, then gate 1 is knocked out of the stack, and the code entry fails. Pin 1 is held high by R4. This `Enables` gate 1; and when button `A` is pressed, the output at pin 3 will go high. This output does two jobs.It locks itself `ON` through R2 and it `Enables` gate 2, by taking pin 5, high. Now, if `B` is pressed, the output of gate 2, at pin 4 will go high. This output does two jobs. It locks itself `ON` through R3 and it `Enables` gate 3 by taking pin 12 high...

You can divide a large keypad or keyboard into sections of 12 keys each (Figure 1). Each section connects to a separate comparator circuit, which detects a keystroke and generates a trigger pulse using the monostable circuit of IC4, and you can add more sections in the same manner. Diodes D1, D2, and D3 couple and isolate the comparators` outputs to Pin 2 of IC4. Each keypad section connects the same selection of timing-resistor values to the monostable. Therefore, each keypad section`s output pulse widths occupy the same range: 110 to 1320 µsec...

First, consider some ways to effect key reading. Table 1 presents a comparison of four methods with references to circuit configurations (Figure 1, Figure 2, Figure 3 and Figure 4). As you can see, the best choice for reading many keys is to use the A/D converter that is inherent in many microcontrollers...

Typically applications having LEDs and keypads also keep track of real-time, in order to synchronize certain related events. An Industrial Clock/Timer example has been used in this application note as a demonstration of these functions. The software overhead to keep track of real time is minimal and the user can modify the code to significantly expand the functionality of this circuit...

The circuit, shown Figure 1, depicts an application with two keys. The PIC16C54 is normally in SLEEP mode consuming very little operating current. If either of the two keys is pressed, the PIC16C5X wakes up, scans the keys and turns on one or both of the LEDs...

This application note describes the implementation of an IBM MF2 compatible keyboard with National Semiconductor`s COP888CL or COP943C/COP880CL microcontrollers. Two different solutions have been developed. One solution, suitable for laptop/notebook keyboards is based on the COP888CL with special power saving techniques...