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Shocking Security System By Cato Yang Neal Craig ECE 345, SENIOR DESIGN PROJECT Spring 2003 TA: Chirantan Mukhopadhyay May 5, 2003 Project No. 6 i ABSTRACT The purpose of our Shocking Security System is to provide a deterrent for those attempting unauthorized entry to a secure door. A non-lethal electric shock will be delivered through the door handle to anyone attempting to open the door while it is in the locked and armed state. A keypad will serve as the user interface to the system, allowing the user to lock/unlock, arm/disarm, and change the password to the door. We sought to design our own variable voltage shocking circuit, and use the HC12 microcontroller to control the entire project. This paper will outline our efforts in design, implementation, and testing throughout the engineering process. ii TABLE OF CONTENTS 1. INTRODUCTION ..................................................................................... 1 1.1 Design Goals and Features.....................................................................1 1.2 Block Diagram .......................................................................................1 1.2.1 Line Input 120VAC ......................................................................2 1.2.2 Power Supply 5VDC.....................................................................2 1.2.3 High Voltage Power Supply .........................................................2 1.2.4 Solenoid ........................................................................................2 1.2.5 DC Amplifier Circuit ....................................................................2 1.2.6 Triacs.............................................................................................2 1.2.7 Door Latch Switch ........................................................................2 1.2.8 Door Handle ..................................................................................2 1.2.9 HC12 Microcontroller ...................................................................2 1.2.10 Keypad ........................................................................................2 1.3 Performance Specifications ...................................................................3 2. DESIGN PROCEDURE ..............................................................................4 2.1 Amplifier Circuit ....................................................................................4 2.2 High Voltage Power Supply ..................................................................4 2.3 Locking Mechanism...............................................................................4 2.4 Switching ...............................................................................................4 2.5 Keypad ...................................................................................................5 2.6 HC12 Microcontroller ............................................................................5 3. DESIGN DETAILS ................................................................................... 6 3.1 Amplifying Circuit .................................................................................6 3.2 High Voltage Power Supply ..................................................................7 3.3 Switching ...............................................................................................7 3.4 Keypad ...................................................................................................8 3.5 HC12 Microcontroller ............................................................................9 4. DESIGN VERIFICATION ...................................................................... 10 4.1 Testing Hardware .................................................................................10 4.2 Testing Software ..................................................................................10 5. COST ....................................................................................................... 11 5.1 Labor ....................................................................................................11 5.2 Parts......................................................................................................11 6. CONCLUSIONS........................................................................................12 References ..................................................................................................13 iii 1. INTRODUCTION 1.1 Design Goals and Features This device will act as an alternative to a security alarm by delivering a shock. It will act like an electric fence and a non-lethal dose of electricity will be sent through a doorknob or other point of entry to deter any intruder. Our project will focus on protecting standard doors. The shocking device can be activated or deactivated using a keypad. Once armed, the door will deliver a shock if the door handle is turned. A shocking circuit and power supply will be developed that will vary the voltage up to 1000VDC for easy measurement in the lab. The locking mechanism for the door will be accomplished through the use of a pull type solenoid. The HC12 microcontroller will be used to control the project by taking the keypad inputs, and outputting the correct control signals. Proper amounts of electricity will be researched as to not cause serious harm to an intruder. Programmable password for increased security Deter unauthorized entry into building or room Warning LED’s for door states: Armed/Disarmed, Locked/Unlocked, and Shocking Variable shock voltage Will not shock intruder until doorknob is turned 1.2 Block Diagram 1 1.2.1 120VAC Line Input The 120VAC line input is a 60Hz standard input from the wall outlet to supply power to the entire circuit. 1.2.2 5VDC Power Supply This power supply powers the HC12 and the keypad circuit. 1.2.3 High Voltage Power Supply The high voltage power supply offered 12VDC for the DC amplifying circuit as well as a variable voltage. The variable voltage ranged from 0V to 19V. 1.2.4 Solenoid The solenoid acted as the electrical to mechanical coupling to convert the signal to lock the door into a deadbolt device. 1.2.5 DC Amplifier Circuit The DC amplifier consisted of a flyback transformer with some circuitry. It was powered by the constant 12VDC supply and then amplified the input voltage that ranged from 0V to 19V, outputting between 0VDC and 1000VDC. 1.2.6 Triacs The triac is essentially an electronic controlled switch. An AC version was used to operate the solenoid while a DC triac was used to turn on the DC amplifier circuit. 1.2.7 Door Latch Switch A mechanical pushbutton switch was mounted inside the door frame. When the door was closed the door latch depressed the switch and the DC amplifier circuit was open. If the door knob was turned the switch would cause the circuit to be closed and functional, if the triac were armed. 1.2.8 Door Handle Ultimately the door handle was electrified with the amplified voltage if the triac was switched on and the door handle was turned, closing the circuit. This is equivalent to grabbing onto the wire of an electric fence. 1.2.9 HC12 Microcontroller Takes inputs from the keypad, and sends shock and lock signals to the rest of the circuit and the indicator LED’s. It controls the states of the project. 1.2.10 Keypad 16-Key keypad serves as the user interface to the system. Takes the pass code, and allows the user to lock/unlock, arm/disarm, and change the password. 2 1.3 Performance Specifications For our design, the key performance specification was the shocking circuit. We required a variable DC voltage source to power the shocking circuit. Our power supply, converted the 120VAC wall source to DC voltages that were amplified. We desired a DC voltage of around 1000VDC to provide an adequate deterrent shock, and also be easily measurable in the lab. Also, it was necessary for the microcontroller to behave as designed, and send out the proper control signals to the rest of the system. The microcontroller must read the correct keypad press, take the correct pass code, and reject incorrect pass code entries. Once the correct code was entered, the microcontroller must update the states, or change the password as instructed by the user via the keypad. 3 2. DESIGN PROCEDURE 2.1 Amplifier Circuit The backbone of the DC amplifier was the flyback transformer. Flyback transformers are used in computer monitors and televisions, so instead of buying a new one I parted an old monitor. There were three inputs among 8 that had to be determined before the transformer could be used; the output was obvious, it had a large suction cup attached to it. The flyback transformer would not amplify DC voltage directly, so I had to create an alternating current from my set 12VDC. This was accomplished with a timer and other suggested circuitry for flyback transformer set-ups. 2.2 High Voltage Power Supply It was necessary per the requirements of the flyback transformer to design a power supply with multiple outputs. We started the power supply with a 25.2V CT 3A step down transformer. This transformer accepted the 120VAC 60Hz from the wall. After being rectified with a full-wave rectifier we separated the design into two sections. The circuitry that powered one end of the transformer needed 12VDC. This was easy to construct because these power supplies were actually constructed in ECE 343, a previous course at the university. Additionally, I needed a variable voltage power source. For this I simply used a resistor to get the maximum voltage I needed, 19VDC, and then added a potentiometer in series to drop the voltage down to achieve 0VDC. We felt ambitious at one juncture and tried to combine all three power supplies into one. Namely, both for the shocking circuit and also the 5V supply for the microcontroller and its circuit. Unfortunately, the second to last day showed us that one power supply could support the load of both the amplifying circuit and the control circuit, so we were forced to abandon this extra goal. 2.3 Locking Mechanism The physical locking of the door is necessary for any security system. We decided that a solenoid mounted on the stud inside the wall would be a good way to electronically control the locking of the door. We were given the task of converting a pull-type solenoid into a deadbolt. We accomplished this task by developing a steel L- bracket that attached to the solenoid. The solenoid was then mounted backwards facing away from the door with the long end of the L- bracket pointing towards the door. Thus, when the solenoid (accepting 120VAC straight from the wall) was turned on, the L-bracket, now the deadbolt, would go through the door frame and into the door, locking it. 2.4 Switching An interface between the electronic microcontroller and shocking circuit and the mechanical solenoid and door knob movement had to be developed. Firstly, we mounted a switch inside the door frame. The pushbutton of this switch was depressed when the door was closed by the door latch. The switch, in this state, caused and open circuit and the Amplifying Circuit was off. When the door knob was turned the latch would be moved and the switch would close the circuit. Now, the state of the amplifying circuit rested on the microcontrollers command. If the user had armed the security system, the microcontroller would send a voltage of 5V to the triac that was in series with the mechanical switch previously mentioned. As a result, the triac, an electrical switch, would cause a closed circuit. Hence, if the circuit is armed and the knob is turned, the amplifying circuit is on and the doorknob is supplied with the set voltage. 4 The user could also only lock the door. When the lock command was entered into the microcontroller, a 5V signal would be sent to the triac of the locking circuit. This triac, however, allowed AC current to flow through it, so we simply had to cut the power cord for the solenoid and add it in directly. 2.5 Keypad We used a 16-key keypad for our design along with the 16-key encoder. This was adequate for our design to enter a four digit pass code, and give the user 3 options: lock/unlock, arm/disarm, and change the password. 2.6 HC12 Microcontroller We decided to use the HC12 microcontroller because of its versatility, portability, and abundance of support material that was easily found on the course webpage. We did not have much experience programming the HC12 or coding in Assembly language, but were confident that the microcontroller would suit our needs, and given time, we would be able to have a reliable program to control our project. The program for our project seemed fairly simple at first glance, basically, the microcontroller was to take the keypad inputs, compare them to the pass code stored in memory, and then perform the appropriate task. When the correct pass code was inputted, the program would wait for the user to press a button corresponding to either lock/unlock, arm/disarm, or pass code change. 5 3. DESIGN DETAILS 3.1 Amplifying Circuit The pin layout on the transformer we recovered from the computer monitor had to be found. Since there was no part number on the case of the transformer, we had to do some tests. The ground terminal was easily found by attaching a 24 V DC power supply and a digital voltmeter set in 20 V range. We connected the positive input of our voltmeter to the output wire and the ground to the 0V of our power supply. Then, with the +24V output from our power supply, we tested each input pin of the flyback transformer. When we measured a voltage of 8V, we knew we had found the ground pin of the flyback. To find the inputs to the coils we simply had to test the resistance of all combinations between two of the remaining input pins. The ohmmeter read infinite resistance for all combinations except that of the coil inputs, which read approximately .8 ohms. Layout to find ground terminal Layout to find coil inputs The flyback transformer needed a pulsed current into one of its coil inputs. We found information describing the behavior of flyback transformers and suggested circuit layouts. Combining these suggestions with out own knowledge of circuit we found an optimal circuit for our project. 6 3.2 High Voltage Power Supply The power supply incorporated the design of three into one. The 12V supply used the zener diode design that we learned in previous classes. This had a very low ripple that was necessary for the control circuit of the flyback transformer. The 5V supply attempt used a voltage regulator with capacitors. This circuit was not completely tested and was only a bonus at the end had it worked out as planned. Lastly, the variable voltage section was quite basic and only used a resistor to control the voltage level. This voltage was not required to have a low voltage ripple because it was only powering the flyback transformer, which accepted a varying voltage just as openly as a steady voltage. Thus spending time on the ripple was not a concern. Although in the end we did not use the 5V supply, it was already hardwired together with the 12V and variable voltage supplies. 3.3 Switching The triacs we used were both of AC and DC type. The triac to control the arm/disarm command was of DC type. Its input was the variable voltage and it outputted to the switch that was mounted in the door frame. After the switch, the voltage was allowed to continue into the DC amplifying circuit. The lock/unlock function was controlled by an AC type triac. This triac had an input directly from the wall outlet and an output that went to the solenoid. Both triacs took 5V for on and 0V for off inputs from the microcontroller for control. Arming Circuit 7 Locking Mechanism 3.4 Keypad The keypad circuit is as follows, and was found in the data sheet for the asynchronous data entry onto bus mode. A is the low bit and D is the high bit, and they correspondingly input into PORTA of the microcontroller. Starting in the top left corner, a 1 key-press corresponds to a 0000 output value, a 2 key-press outputs as 0001. The remaining truth table is simple to determine. The data available bit is important to tell the microcontroller when a key has been pressed, and is bit four of PORTA 8 3.5 HC12 The actual code used in our project can be referenced through Appendix A. The microcontroller program was needed to check the keypad inputs against the pass code stored in memory. To do so, the keypad data was read from PORTA, and the data available bit was checked to make sure a button was pressed. To avoid reading the value repeatedly while the key was being held down, the program waits for the key to be released before continuing with the rest of the code. The input is stored and compared to the values stored in memory. When the correct pass code is entered the program allows the user to change the state. There are three options for the user at this point: Arm/Disarm, Lock/Unlock, or change pass code. Pressing either the A or B button on the keypad will Arm/Disarm, or Lock/Unlock the system respectively. To do so, the code simply inverts the signals by XORing the signal and sending it to the output at PORTB. Pressing the C button will allow the user to change the pass code to any 4 key value. Changing the pass code is simple and accomplished by repeatedly getting an input, and storing the pass code key. 9 4. DESIGN VERIFICATION 4.1 Testing Hardware The High Voltage Power Supply was tested using the Voltmeters and Ammeters in the lab. The design for the 12V supply was originally made using PSPICE in the past, so the specifications were already known. Additionally, with specific meters with 1000VDC peak we were able to measure the voltage output of the Amplifying Circuit. The 5V supply was made with little testing involved, but we found that its current was too low to power to the entire microcontroller circuit while the amplifying circuit was active. The correct operation of the shocking triac was observed using LED’s to check if either, or both, the input or the output were high. The operation of the solenoid was easily checked by whether or not the door locked. 4.2 Testing Software The testing for the microcontroller and keypad was mostly trial and error; however, a few well placed LED’s allowed us to recognize some of the problems more easily. LED’s attached to the output allowed us to track the controller states, and whether the controller was behaving properly when we inputted the initial code and tried to change the states. LED’s attached to the 16-key encoder allowed us to notice that we needed to follow the asynchronous data entry circuit to get the correct inputs. Near the end of the project we used LED’s and PORTP to track the key press that the microcontroller was storing as the input. This was particularly helpful, because if the key press was not firm, the microcontroller sometimes did not take the correct input. This allowed us to focus on the program itself, and not input error at the keypad. 10 5. COST 5.1 Labor Cost: hourly salary actual hours spent 2.5 ($32 / hr ) 100 2.5 $8,000 $8,000 2 Engineers $16,000 5.2 Parts: Flyback Transformer $18.00 Keypad $1.00 HC12 Microcontroller and board $125.00 HV Power Supply Components $5.15 Triac Driver (x2) $4.34 Solenoid $7.79 Lumber for Door frame/Door knob $45.00 Miscellaneous components (wires, LED’s, logic chips) $5.50 Surge Protector (x2) $8.55 TOTAL PARTS $ 220.33 Table 1 - Price List Total Parts and Labor = $16,000 + $220.33 = $16,220.33 11 (6) 6. Conclusion The High Voltage Power Supply and Amplifying Circuit worked as we originally planned. The voltage was easily adjustable from 0VDC to 1000VDC. When the user entered the correct password and pressed the necessary enter key- lock/unlock, arm/disarm, or change code- the microcontroller acted correctly. The triac and switch that controlled the shocking circuit as well as the triac for the locking device correctly accepted the control of the microcontroller and allowed the voltage to flow only when expected. 12 References 16-Key Encoder Datasheet www.fairchildsemi.com/ds/MM/MM74C922.pdf EE 308, Microcontrollers, New Mexico Institute of Mining and Technology, “Lecture Notes,” www.ee.nmt.edu/~rison/ee308_spr03/homepage.html Amplifying Circuit/Flyback Diagrams www.jlnlabs.org 13 14