22-03-2015, 07:23 PM
content and working of electronic card system
|
electronic card lock system circuit diagram
|
content and working of electronic card system
09-03-2017, 12:37 PM
When the card is inserted into its mechanism, depending on the position of the hole drilled in the card, a particular device would turn on.
![[Image: 48Z_electronic-card-system-_-efy-1-1.jpg]](http://electronicsforu.com/wp-contents/uploads/2016/04/48Z_electronic-card-system-_-efy-1-1.jpg)
The card is inserted as a diskette into the disk drive. This card should be rectangular with only one hole drilled into it.
The circuit uses eight photo-transistors (T1 to T8). When there is no card in the lock, the L1 incandescent lamp light (40 watts, 230 V) falls on all phototransistor detectors. Transistor T8 is used as an enable detector for IC1 (74LS244). When the light is incident on it, it conducts and its collector voltage goes down. This causes the T16 transistor to be cut off, and its collector voltage rises. This high logic at its collector terminal will inhibit IC1 while the light is present in phototransistor T8.
IC1 will only activate when the card is fully inserted into the locking mechanism. This arrangement ensures that only the selected appliance is turned on and prevents malfunction of the system.
Making :
A small rectangular notch is made on this card to indicate the proper direction for insertion of the card. If you try to insert the card incorrectly, it will not fully enter the mechanism and the system will not be enabled.
When the card of any apparatus (say apparatus 1) is completely inserted into the mechanism, the light will only fall on the phototransistor T1. Only T1 will be on and other photo-transistors will be off. When the transistor T1 is turned on, its collector voltage drops, causing the transistor T9 to be cut off. As a result, the collector voltage of transistor T9 as well as pin 2 of IC1 go high logically. This causes pin 18 (output Q1) to also rise, turning on LED1. Simultaneously, the output Q1 is connected to the pin 1 of IC2 (ULN2003) to actuate the relay corresponding to the apparatus 1. Similarly, if a card for the device 2 is inserted, only the output pin 16 (Q2) of IC1 Will Activate Relay of the same time for device 2 using ULN2003. The same is true for other cases / appliances as well. The time during which the card is present inside the mechanism, the system generates the musical tone. This is achieved with the aid of diodes D1 to D7 which provide a wired OR connection at their common cathode junction. When any of the outputs of IC1 is logic high, the common channel junction of diodes D1 to D7 also goes to logical high, allowing IC3 (UM66) to generate a musical tone.
In this circuit IC1 (74LS244) is used as buffer with Schmitt trigger. All outputs (Q1 to Q7) of this IC are connected to IC2 (ULN2003) which is used as a relay controller. IC2 consists of seven high current relay conductors. IC2 consists of seven high current relay conductors having intergal diodes. Therefore, external free wheel diodes are not required.
When an input of this CI becomes high logic, the corresponding output will be placed under logic and the relay connected to that pin will be energized. This activates a specific device and the corresponding LED.
Once a specific card is inserted to switch on a specific relay, that relay is locked through its second pair of contacts. Thus, even when the card is removed, the specific device remains on. The same goes for all other relays / appliances as well. The only way to deactivate a relay when the corresponding relay is removed is to disconnect the corresponding switch (S1 to S7) which would cut off the power to the desired relay.
Supplies of + 5V and + 12V can be obtained in a conventional arrangement using a reducing transformer followed by rectifier, filter and regulator (using 7805 and 7812, etc.).
![[Image: B18_Electronic-code-2_-efy-1.png]](http://electronicsforu.com/wp-contents/uploads/2016/04/B18_Electronic-code-2_-efy-1.png)
The card is inserted as a diskette into the disk drive. This card should be rectangular with only one hole drilled into it.
The circuit uses eight photo-transistors (T1 to T8). When there is no card in the lock, the L1 incandescent lamp light (40 watts, 230 V) falls on all phototransistor detectors. Transistor T8 is used as an enable detector for IC1 (74LS244). When the light is incident on it, it conducts and its collector voltage goes down. This causes the T16 transistor to be cut off, and its collector voltage rises. This high logic at its collector terminal will inhibit IC1 while the light is present in phototransistor T8.
IC1 will only activate when the card is fully inserted into the locking mechanism. This arrangement ensures that only the selected appliance is turned on and prevents malfunction of the system.
Making :
A small rectangular notch is made on this card to indicate the proper direction for insertion of the card. If you try to insert the card incorrectly, it will not fully enter the mechanism and the system will not be enabled.
When the card of any apparatus (say apparatus 1) is completely inserted into the mechanism, the light will only fall on the phototransistor T1. Only T1 will be on and other photo-transistors will be off. When the transistor T1 is turned on, its collector voltage drops, causing the transistor T9 to be cut off. As a result, the collector voltage of transistor T9 as well as pin 2 of IC1 go high logically. This causes pin 18 (output Q1) to also rise, turning on LED1. Simultaneously, the output Q1 is connected to the pin 1 of IC2 (ULN2003) to actuate the relay corresponding to the apparatus 1. Similarly, if a card for the device 2 is inserted, only the output pin 16 (Q2) of IC1 Will Activate Relay of the same time for device 2 using ULN2003. The same is true for other cases / appliances as well. The time during which the card is present inside the mechanism, the system generates the musical tone. This is achieved with the aid of diodes D1 to D7 which provide a wired OR connection at their common cathode junction. When any of the outputs of IC1 is logic high, the common channel junction of diodes D1 to D7 also goes to logical high, allowing IC3 (UM66) to generate a musical tone.
In this circuit IC1 (74LS244) is used as buffer with Schmitt trigger. All outputs (Q1 to Q7) of this IC are connected to IC2 (ULN2003) which is used as a relay controller. IC2 consists of seven high current relay conductors. IC2 consists of seven high current relay conductors having intergal diodes. Therefore, external free wheel diodes are not required.
When an input of this CI becomes high logic, the corresponding output will be placed under logic and the relay connected to that pin will be energized. This activates a specific device and the corresponding LED.
Once a specific card is inserted to switch on a specific relay, that relay is locked through its second pair of contacts. Thus, even when the card is removed, the specific device remains on. The same goes for all other relays / appliances as well. The only way to deactivate a relay when the corresponding relay is removed is to disconnect the corresponding switch (S1 to S7) which would cut off the power to the desired relay.
Supplies of + 5V and + 12V can be obtained in a conventional arrangement using a reducing transformer followed by rectifier, filter and regulator (using 7805 and 7812, etc.).
|
« Next Oldest | Next Newest »
|
