Electronic Resistive Key

The code comes established from the value of 3 resistances present in the key.

Schematic

reskey_sch.pdf

The schematic introduces a classic configuration of dial gauge inputs in order to find the value of the 3 Resistances. In fact all it is based on the loading time of the C7 condenser (that in fact it is a NPO) that it is directly proportional to the value of the Resistances present on the Key. This Resistive Code will be saved in the memory EEPROM 24C01.

COMPONENT LIST

Item	Quantity	Reference	Part
1	7	C1,C3,C4,C5,C7,C9,C10	10nF
2	1	C2	15pF
3	1	C6	1uF
4	1	C8	10uF
5	1	DL1	LED RED
6	4	D1,D2,D3,D4	1N4148
7	1	D5	1N4001
8	1	EF1	EMI
9	1	IC1	LM78L05
10	1	JP1	HEADER 6
11	1	JP2	HEADER 3
12	1	JP3	HEADER 2
13	1	J1	JUMP
14	1	K1	RELAY SPDT
15	2	Q2,Q1	BC547
16	12	R1,R2,R3,R4,R5,R7,R10,R11,R15,R16,R18,R19	10K
17	3	R6,R13,R21	100K
18	4	R8,R12,R20,R25	22K
19	1	R9	8K2
20	3	R14,R22,R23	470
21	1	R17	100
22	1	R24	150K
23	1	S1	SW
24	4	TP2,TP3,TP4,TP5	HOLE
25	1	U1	LM339
26	1	U2	PIC16C54
27	1	U3	24C01

PCB

This is the TOP side component (can be noticed the tracks of the delay - minimal - on the inputs) and the plan of mass

This is the BOT side weldings (can be noticed the Points of discharge on the inputs and the plan of mass)

This is the serigraphy (to notice the compactness of the given circuit its realization in smd)

FIRMWARE

;*************************************
;* RESKEY
;* Chiave elettronica resistiva ad autoapprendimento
;*
;* Revisione 2
;*
;* PIC 16C54 RC
;* f= 4MHz
;* 2 livelli stack
;* 512x12 EPROM 32x8 RAM (24 general purpose register)
;* 13 I/O 18 PIN
;*
;******************************************
w equ 00h ;Accumulatore
rtcc equ 01h ;fosc/4 x prescaler
pc equ 02h ;Program counter 9bit
status equ 03h ;Status word register
fsr equ 04h ;Registro indiretto
porta equ 05h ;RA0-RA3
portb equ 06h ;RB0-RB7
RXRIP equ 07h ;NON USATO
TIMER EQU 08H ;Contatore convertitore A/D
ERRO1 EQU 09H ;Key false x inibizione
VOLTE EQU 0AH ;Letture x 16
MIS0 EQU 0BH ;RA0x16/MIS3
REG0 EQU 0CH ;Registro var. program
MIS1 EQU 0DH ;RA1x16/MIS3
REG1 EQU 0EH ;Reg. vario + timer
MIS2 EQU 0FH ;RA2x16/MIS3
REG2 EQU 010H ;Reg. vario + timer
COD0 EQU 011H ;Codice RA0
LO EQU 012H ;Byte basso misura
MIS3 EQU 013H ;Variabile carica condensatore x16/16/2
COD1 EQU 014H ;Codice RA1
TXBUF EQU 015H ;Eeprom
HI EQU 016H ;byte alto misura
COD2 EQU 017H ;Codice RA2
EMA EQU 018H ;Ripetizioni misura nel main
REG EQU 019H ;Reg. vario + timer + divis
MIS3H EQU 01AH ;Byte alto di MIS3
ADDR EQU 01BH ;Indirizzo eeprom
DAT EQU 01CH ;Dato eeprom
COUNT EQU 01DH ;Eeprom
RXBUF EQU 01EH ;Eeprom
EEP EQU 01FH ;Eeprom
;
TOLL EQU .7 ;tolleranza +- della lettura
;
LIST P=16C54
ORG 1FFH
RESET
GOTO main
ORG 00H
;
confronto goto conf
;***************************************************************
; READ/WRITE 24C02
;***************************************************************
;***************************************************************
;* TIMER
;* tim200 = 200ms
;* tim4s = 4s
;* Usati REG REG1 REG2
;* f=4MHz
;**************************************************************
t
;**************************************************************
;Div16 divides for 16 and then for 2
;
;Divis enters with hi and the /mis3 and exits with reg=result
;
;***********************************************
;Controls if the key is inserted
;
;***********************************************
;Charge and discharge cap. with delay
;
;****************************************************
; Misura
;Exit with MIS0, MIS1, MIS2 gi... divided for the relative MIS3
;Therefore the discharge comes multiplied x 16 and divided for MIS3
;MIS3 comes multiplied for 16 and div for 16 and 2
;TIMERx16/MIS3x16/16/2=MIS0
;****************************************************
;***************************************************************
; ACTIVATION RELE and LED if j=0 then step-step for the time key
;***************************************************************
;***************************************************************
; ERRORE antisabotaggio ERRO1=240 to the reset
; if error for 16 times then inhibition for 16s
;***************************************************************
;**************************************************************
; EXTERNAL COMPARISON EEPROM CODE WITH EXTERNAL CODE
; MIS0-MIS1-MIS1 with COD0-COD1-COD2***exit with error or assets
;**************************************************************
;********************************************codice riconosciuto
;***************************************************************
; PROGRAMMING KEY
;***************************************************************
;***************************************************************
; MAIN PROGRAM
;
;***************************************************************
;*****************************reset memoria eeprom
;
END

DOWNLOAD THE FIRMWARE IN PDF -->reskey_asm.pdf

INSTRUCTIONS

The reskey finds its natural application in the security systems, therefore in order to activate and to deactivate the antitheft systems, in the automatic doors and in the access control. The reskey in an analogic electronic key with one innovative characteristic: The codes are to autolearning. The reskey has been planned following norms the CEI 79/2 and the directives on the electromagnetic compatibility (marcatura CE). Also the STATUS of the system comes constantly saved on the not volatile memory EEPROM.

Download the instructions in PDF -->reskey_instr.pdf

PERFORMANCES

1. RELE' 1A 1FORM C (DOUBLE EXCHANGE).
2. RELE' PASSO-PASSO OR IMPULSIVE PROGRAMMABILE.
3. THE IMPULSIVE TAKES THE TIME OF THE KEY INSERTION.
4. INSERTOR TO 4 LED. FALSE KEY OUTPUT .
5. SYSTEM INHIBITION IN CASE OF FALSE KEY.
6. AUTOLEARNING CODE.
7. ELECTRONIC CARD OF REDUCED DIMENSIONS.
8. DESIGN OF THE WINNING KEY.
9. SELF-CLEANING AND PROTECTED CONTACTS
10. PUSH-BUTTON FOR PROGRAMMING KEYS AND INITIALIZATION.
11. LED ACTIVATION \ PROGRAMMING \ ERROR \ INITIALIZATION.
12. MIROCOMPUTER RISC FOR THE MANAGEMENT OF THE SYSTEM.
13. MEMORY NOT VOLATILE EEPROM FOR THE SYSTEM STATUS.
14. PREDISPOSITION TO THE OPERATION IN POSITIVE EMERGENCY.
15. PASSIVE EMI FILTER AND PROTECTIONS ON THE INPUTS.
16. MANAGEMENT OF 1.000 CODES.
17. IN COMPLIANCE WITH DIRECTIVE 89/336 THE EEC (MARCATURA CE).
18. IN COMPLIANCE WITH 79/2 NORM CEI I° LEVEL.

APPLICATIONS

>Burglar alarm systems, Access Control