Program for measuring relay contact bounce time. Scheme, description

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A program for the Z80 microprocessor that measures the bounce time of the relay contacts. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Note to the student

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The program for the Z80 microprocessor described here, which is oriented to execution in automatic test microprocessor systems, measures the time of retracting the core of the relay and the bounce of the relay contacts, which eliminates the need for complex equipment if this standard program is used as part of test programs. The proposed program also provides sufficient measurement accuracy. The total contact closure time can be found by adding the core retraction times and relay contact bounce times.

The two-part program is executed when the relay under test is connected to a DI digital data input port that implements logic level conversion. The first part of the program, forming cycle 1, determines the time for the relay core to retract. The second part counts the bounce time of the relay contacts.

Block diagram of the program for measuring the time of rattling relay contacts (click to enlarge)

SOFTWARE FOR Z80 MICROPROCESSOR,
MEASURING RELAY CONTACT Bounce Time

Line Address B1 B2 B3 B4
1
2 ;Bounce time meter
3
4 ;This program will measure the contact bounce time and retract time
5; bending of the core. The bounce time value will be in the HL register,
6 ; and the pull-in time in the DE register.
7
8
9
10 ;TITLE "BOUNCE TIMER"
11 LIST B, X
12 NAME BOUNCE
13 ASEG
14ORG-3000H
15
16 3000 BOUNCE:
17 3000 F3 DI ; Disable interrupts
18
19 3001 21 18 FC LD HL,-TIMEOUT ;Subtract contact time from
;bounce time counter
20 3004 01 E8 03 LD SU, TIMEOUT ;Set contact time counter
21 3007 11 FF FF LD DE, -1 ;Set retract time counter
22
23 3000A ZE 07 LD A, CLOSE ;Close relay
24 3000C D3 C OUT (PORTST), A
25
26 ;Core retraction time
27
28 3000E LOOP1:
29 3000E 13 INC DE ;Increment counter
30
31 300F DB 92 IN A, (PORTIM) ;Get relay status
32 3011 FE FF CP TRUE ;Wait for first unstable
;contact closure
33 3013 20 F9 JR NZ, LOOP1 - $
34
35 ;Bounce time
36
37 3015 LOOP2:
38 3015 23 INC HL ;Increase bounce time counter
39
40 3016 DB 92 IN A, (PORTIM) ;Get relay status
41 3018 FE FF CP TRUE ;Relay status true?
42 301A C2 23 30 JP NZ, RESEIC ;If not, restore contact time counter
43
44 301D 0B DEC BC ;Decrease contact time counter
45 301E 78 LD A, B ;Set flags
46 301F Bl OR C
47 ;Run a cycle while the time counter
48 3020 20 F3 JR NZ, LOOP2- $ ; no contact = zero
49
50 3022 C9 RET ;Return, bounce time value
; in the HL register, and the pull-in time
51 ;in register DE
52
53 ;Restore contact time counter
54
55 3023 RESETC:
56 3023 01 E8 03 LD BC, TIMEOUT ;Restore contact time counter
57 3026 00 NOP ;Keep cycle time constant
58 3027 18 EU JR LOOP2-$
60
61
62 ;DATA
63
64 03EB TIMEOUT EQU 1000
65 00FF TRUE EQU 0FFH
66 0007 CLOSE EQU 07H
67 00C2 PORTST EQU 0C2H
68 0092 PORTIM EQU 92H
69 3029 END

Assembly errors pa = 0

Interrupts are disabled in order to maintain measurement accuracy in each cycle. Loop 1 (pull-in time counter) consists of counter increment and check routines. Each time through the loop, the state of the DI port is checked for the first intermittent relay contact closure. When such an effect is detected, the program measures the retraction time of the core and stores this value in the DE register. However, the true pull-in time is calculated by multiplying the contents of the DE register by 36 and dividing the result by the clock speed of the Z80 microprocessor.

Cycle 2 (relay bounce time counter) is the increment and test subroutine, and contains an additional routine to run the contact and recovery time counter. Each time through the loop, the contents of the HL register are incremented and the state of the DI port is checked. If the relay contacts are open, then a predetermined value of this time is loaded into the contact time counter. In the event of a relay contact closing, the contact time counter value is decremented until it reaches zero. When the contents of the contact time counter register is zero, the program measures the contact bounce time, and this value is stored in the HL register. However, in order to get the true bounce time, the HL register is first written with the additional binary code of the contact time value, then its contents are multiplied by 60, and the result is divided by the clock frequency of the Z80 microprocessor.

Author: Van Harris; Publication: N. Bolshakov, rf.atnn.ru

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