GROAN DETECTOR SYSTEM

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Diane Atkinson
6 years ago
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1 GROAN DETECTOR SYSTEM This project is what I call a groan detector. A friend referred a woman (Marie) to me whose husband (John) had been stricken with a stroke and became paralyzed. His mind is good, but he cannot move anything below his neck and can only make a sound that Marie calls an aaaahhhh sound when he needs assistance. For reference, I call this sound a groan. The couple has a live-in caregiver, who sits with the man all day, but sometimes needs to sleep. When sleeping or otherwise away from the man s bed, the caregiver uses a baby monitor to listen to the patient. The baby monitor does not work well for transmitting John s low-pitched sounds. The caregiver has to sleep with one ear open and cannot get a good night s rest. Marie asked for a device that would sound a remote alarm that can wake up the sleeping caregiver if John groans for assistance. The device must not annoy the caregiver with false triggers from nearby speech, John s favorite radio program, or other background noise. After unsuccessfully trying to detect the unique characteristics of John s voice, I remembered an answering machine I had 30 years ago that detected gaps or brief interruptions in the audio in order to record speech instead of a dial tone. I designed a circuit to do that and realized it was just what I needed. Also, the circuit doesn t have to be tuned to a particular patient s voice, so it can be passed on to someone else when John no longer needs it. The circuit consists of a variable gain microphone amplifier (Q1 and U1) and a threshold detector (U2). I used a PIC microcontroller for the gap detector, because it is simple and very precise. I set the detectable gap length at 15mS. This would make any audio, passing through the threshold detector with frequency content above 66.7Hz appear as a continuous signal, while immediately detecting any signal loss. The microphone gain is adjusted by R6 so that signals of varying amplitude, like music, will intermittently pass through the threshold detector. An LED (D2) tells the user when a signal has passed through the threshold detector in order to assist in setting the gain control. A continuous sound, like a groan, close to the microphone and of relatively constant amplitude will pass uninterrupted through the threshold detector. If the sound is uninterrupted for 1.5 seconds, the device is triggered and the remote alarm is sounded. The receiver has a MUTE button to mute the alarm for 10 minutes or unmute it. If not muted, the alarm will sound for one minute. I have sinus trouble and sometimes mucus builds up on my vocal cords, causing my voice to break up. This produces gaps in my speech that make it difficult for me trigger the device. Believing that a patient could have the same problem, I added a switch labeled HOARSE which changes the minimum detectable gap length to 50mS, making it easier for someone with a hoarse throat to trigger the device. Note that this may reduce the circuit s resistance to music and background noise. Before getting a noise-cancelling (i.e. cardioid) microphone, I observed that the device would sometimes trigger on low frequencies, like a large vehicle driving by my house, motorcycles, or a low flying small airplane. To reduce this problem, I added a FILTER switch that changes the low-pass filter s 3db response from 500Hz to 1000Hz. This allows the gain control to be turned down a bit, decreasing the sensitivity to low frequencies. Also, the device might one day be used on a female patient who may not have a lot of frequency content in her voice below 500Hz, requiring the FILTER switch to be set to the upper (1KHz) position. The FILTER

2 switch may not be needed at all to stop low frequency interference while using a noisecancelling microphone. Due to the physics of sound, a noise-cancelling microphone will be much more effective at the lower frequencies. Since installing the noise-cancelling microphone, the device has only responded to a loud commercial lawn mower right outside my door and to my vacuum cleaner. Also, the system s resistance to false triggering by music has greatly increased. The noise-cancelling mike, the low-pass filter and the gap detector, all together, make an effective system for blocking interference. Figure 1. Signal processing circuit. I tested several electret microphones and they all kept a voltage of around 2.5 volts when fed with a 10K resistor to 5 volts. I took advantage of that when I designed the microphone preamp circuit (Q1) to minimize noise pickup. When the gain control (R6) is turned up too high, 60Hz electrical noise and sub-audible noise from the microphone can trigger the device. Transistor and power supply switching noise is mostly removed by the low-pass filter.

Figure 2. The rest of the Groan Detector transmitter. Note that the RF transmitter is on a separate circuit board from the rest of the electronics. Be sure to include the bypass capacitor C10.

3 Figure 2. The rest of the Groan Detector transmitter. Note that the RF transmitter is on a separate circuit board from the rest of the electronics. Be sure to include the bypass capacitor C10. The RF link has a range of at least 70 ft. (the length of my house) with the telescopic antenna in the receiver all the way down. Who knows what the range would be with the antenna fully extended. The antenna is 20 cm long fully extended and was salvaged from some piece of thrown-away wireless electronics. The beeper signals the user when the device has been triggered. Figure 3. Front panel of the transmitter. Some labels have been left off to avoid cluttering the panel. The TEST button repeatedly sends a coded signal to the receiver so that the user can test the RF link. The TRANSMIT switch turns the transmitter on and off so that the user can find the optimum sensitivity setting without triggering the receiver. The functions of the other two switches and the LED are described elsewhere in this article. The mike jack is mounted in a way to accommodate the locking nut on the noise-cancelling microphone. Most cardioid microphones with a 3.5mm stereo or mono plug will work fine. The tip is positive, the sleeve is negative and the ring is not connected. The enclosure is Radio Shack SKU#

The hot glue might not look professional, but I don t want switches and screws to come loose over time.

4 Figure 4. Interior of the transmitter. Note the 433 MHz RF transmitter with its coiled antenna on a separate circuit board. The hot glue might not look professional, but I don t want switches and screws to come loose over time. No one s going to see inside the box. A small blue LED is mounted above the power jack on the back of the enclosure as a power indicator. Figure 5. Transmitter circuit board. Some resistors have one of their leads coiled in a loop for a test point.

5 Figure 6. Transmitter circuit board layout. Figure 7. The receiver circuit.

The receiver produces a pulsating 1 KHz tone when triggered. The green LED in the middle (normally on as a power indicator) flashes on and off once per second when the receiver is muted.

6 Figure 8. The receiver unit. Note the amplified speaker box attached with Scotch Velcro-like Command Strips to the top of the box. The end user needs enough audio volume to wake up a sleeping caregiver. This speaker s 2 watt output does the job. The speaker is Auvio, model number , available at Radio Shack. The receiver produces a pulsating 1 KHz tone when triggered. The green LED in the middle (normally on as a power indicator) flashes on and off once per second when the receiver is muted. It times out after 10 minutes to prevent leaving it muted indefinitely. Both the transmitter and the receiver are powered by discarded 5 volt cellphone chargers which have been fitted with 5.5/2.1 mm (size M) power plugs. The speaker requires 5 volts at 1 amp. The transmitter uses less than 100mA at 5 volts. Both chargers must be regulated. The enclosure is Radio Shack SKU# The microphone came from Amazon.com. Pro Lavalier Lapel Microphone MIC-J 016 Figure 9. Receiver interior

Figure 10. Receiver board layout. Figure 11. The RF transmitter and receiver set used in the project. Here is the link to the website. Delivery from China took about 2 weeks. http://www.ebay.

7 Figure 10. Receiver board layout. Figure 11. The RF transmitter and receiver set used in the project. Here is the link to the website. Delivery from China took about 2 weeks. They also sell a 315 MHz version of the set. They sell coiled antennas for the T/R sets, as well. ; Groan transmitter.asm source code ; Created ; Last modified ; Written by: ; Andrew R. Morris ; morr3763@bellsouth.net ; The purpose if this program is to beep and activate a remote ; alarm monitor when a paralyzed patient groans to call for ; help. The program minimizes false triggering from ambient ; noise or speech. The hardware contains a 500Hz low-pass-filter. ; This device responds to a low-frequency sound with no gaps ; longer than 15mS and sustained for one and a half seconds. A

8 ; wider gap can be selected in case the patient has a hoarse throat. ; The code is written to detect 1.5 seconds of uninterrupted audio. ; This will block out brief bursts like slamming doors, barking dogs ; and most conversation. Music or other continuous sounds may ; trigger it. The hardware has a manually operated sensitivity ; adjustment. The software controls an LED to facilitate making ; the sensitivity adjustment. ; The radio receiver used in this project cannot tolerate a ; DC component in the data stream. Manchester encoding is too ; complex for this project, since only one code will ever be ; transmitted. A bipolar sync pulse, followed by a series ; of alternating ones and zeros, forms the data stream. ; This code was written for a PIC10F508 LIST P=12F508 #include P12F508.INC errorlevel -302 ;suppress message 302 from list file CONFIG _CP_OFF & _MCLRE_OFF & _WDT_OFF & _IntRC_OSC ;Register equates LCVR1 EQU 10 ;Loop count variable register 1 LCVR2 EQU 11 ;Loop count variable register 2 LCVR3 EQU 12 ;Loop count variable register 3 LCVR4 EQU 13 ;Loop count variable register 4 ;Initialization equates INIT_GP EQU B' ' ;Initialize GPIO CFG_GP EQU B' ' ;Configure GPIO OPTINI EQU B' ' ;Initialize option register ;Parameter equates BEEP_PITCH EQU D'69' ;2400Hz BEEP_DURATION EQU D'19' ;Approx. 200mS with 2400Hz pitch NARROW_GAP EQU D'15' ;Audio gap time in 1mS increments WIDE_GAP EQU D'50' ;Wider gap time for hoarse throat. GROAN_TIME EQU D'46' ;Time required to trigger device. ;31 is one second. ;I/O pin equates ;GPIO TST_IN EQU 0 ;Test button, pin 7 GAP_SEL EQU 1 ;Selects minimum detectable audio gap, pin 6

9 LED EQU 2 ;Output to LED, pin 5 SIGNAL_IN EQU 3 ;Input from signal conditioner, pin 4 XMTR_OUT EQU 4 ;Output to transmitter, pin 3 BEEPER_OUT EQU 5 ;Output to beeper, pin 2 ; ORG 0 ;Reset vector rolls over to here GOTO Boot ;Go to beginning of program ;Subroutines BEEP MOVLW BEEP_DURATION MOVWF LCVR1 BLP1 MOVLW D'25' MOVWF LCVR2 BLP2 BSF GPIO,BEEPER_OUT ;This counts the time that the beeper MOVLW BEEP_PITCH ;output is high for the tone. MOVWF LCVR3 LCVR3,F GOTO $-1 NOP ;NOPs to compensate for looping delay NOP ;to maintain a square wave. BCF GPIO,BEEPER_OUT ;This counts the time that the beeper MOVLW BEEP_PITCH ;output is low for the tone. MOVWF LCVR3 LCVR3,F GOTO $-1 LCVR2,F ;This block counts off the duration of GOTO BLP2 ;the beep LCVR1,F GOTO BLP1 RETLW 0 SDLY ;Short delay routine. MOVWF LCVR1 ;0.1 ms increments. MOVLW D'32' MOVWF LCVR2 LCVR2,F GOTO $-1 LCVR1,F GOTO $-5 RETLW 0 BIT0

10 BSF GPIO,XMTR_OUT MOVLW D'3' ;High for 0.3mS CALL SDLY BCF GPIO,XMTR_OUT MOVLW D'9' ;Low for 0.9mS CALL SDLY RETLW 0 BIT1 Boot value BSF GPIO,XMTR_OUT MOVLW D'9' ;High for 0.9mS CALL SDLY BCF GPIO,XMTR_OUT MOVLW D'3' ;Low for 0.3mS CALL SDLY RETLW 0 MOVWF OSCCAL ;Load the factory Internal oscillator calibration ; Initialize I/O ports MOVLW CFG_GP ;Select direction of GPIO bits TRIS GPIO ;Write selection to GPIO data ;direction register MOVLW INIT_GP ;Initialize GPIO MOVWF GPIO CLRF STATUS MOVLW OPTINI ;Initialize option register OPTION START ;The actual program starts here. BCF GPIO,LED ;Turn off LED. BTFSC GPIO,SIGNAL_IN ;Wait for signal input to go high. GOTO $+4 BTFSS GPIO,TST_IN ;Transmit if test button is pushed to GOTO TST ;test RF link. GOTO $-4 MOVLW GROAN_TIME ;1 second (31 counts) MOVWF LCVR3 MOVLW -D'126' ;128 max count if testing bit 7 for zero. -D'128'= mS CLRF TMR0 ;-126 was chosen to get exactly 1 second with 31 counts.

11 MOVWF TMR0 ;Actual TMR0 preset is 256-x (x is 126 in this case). GAP_DET BSF GPIO,LED ;Turn on LED MOVLW NARROW_GAP ;Minimum detectable audio-gap length in ms. BTFSS GPIO,GAP_SEL ;Test gap select switch. MOVLW WIDE_GAP ;Wider gap for patient with hoarse throat. MOVWF LCVR1 ;TMR0 is not part of this gap timer, but is constantly MOVLW D'141' ;being polled as the timer runs. TMR0 is being used MOVWF LCVR2 ;to count off the groan time in the background. BTFSS TMR0,7 ;TMR0 bit 7 went low, service timer. GOTO TMR_SRV BTS BTFSC GPIO,SIGNAL_IN ;Test input signal GOTO GAP_DET ;Input high, re-initialize gap detector. LCVR2,F GOTO $-5 LCVR1,F GOTO $-9 ;Audio gap too long, start over. TMR_SRV ;Timer service routine. MOVLW -D'126' CLRF TMR0 ;Clear TMR0 and prescaler MOVWF TMR0 ;Re-initialize TMR0. LCVR3,F ;Decrement GROAN_TIME counter. GOTO BTS ;Continue testing input signal. TST CALL BEEP XMIT MOVLW D'10' ;Number of times data word is MOVWF LCVR3 ;to be transmitted. SYNC BSF GPIO,XMTR_OUT ;High portion of sync pulse (2.4mS) MOVLW D'24' CALL SDLY BCF GPIO,XMTR_OUT ;Low portion of sync pulse (2.4mS). MOVLW D'24' ;Call short delay subroutine. CALL SDLY ;0.1mS increments. CALL BIT1 ;Send bits CALL BIT0 CALL BIT1 ;Alternating ones and zeros to CALL BIT0 ;avoid a DC component in the CALL BIT1 ;received data stream. CALL BIT0 CALL BIT1 CALL BIT0 CALL BIT1 CALL BIT0

12 CALL BIT1 CALL BIT0 CALL BIT1 CALL BIT0 CALL BIT1 CALL BIT0 LCVR3,F GOTO SYNC ;Repeat END ; Groan receiver.asm source code ; Created ; Last modified ; Remote alarm receiver for groan detector. Receiver will emit ; a loud pulsating beep when it receives a valid signal from ; the transmitter. The alarm will sound for one minute if not ; muted. The mute mode will time out in 10 minutes. Pressing ; the MUTE button again will unmute the device. ; The radio receiver used in this project cannot tolerate a ; DC component in the data stream. Manchester encoding is too ; complex for this project, since only one code will ever be ; transmitted. A bipolar sync pulse, followed by a series ; of alternating ones and zeros, forms the data stream. ; Written by: ; Andrew R. Morris ; morr3763@bellsouth.net ; This code was written for a PIC10F200 or PIC10F202 LIST P=10F202 #include P10F202.INC errorlevel -302 ;suppress message 302 from list file CONFIG _CP_OFF & _MCLRE_OFF & _WDT_OFF & _IntRC_OSC ;Register equates LCVR1 EQU 10 ;Loop count variable register 1 LCVR2 EQU 11 ;Loop count variable register 2 LCVR3 EQU 12 ;Loop count variable register 3 LCVR4 EQU 13 ;Loop count variable register 4 LCVR5 EQU 14 ;Loop count variable register 5

13 LCVR6 EQU 15 ;Loop count variable register 6 LCVR7 EQU 16 ;Loop count variable register 7 STAT EQU 17 ;STAT register ;Initialization equates INIT_GP EQU B' ' ;Initialize GPIO CFG_GP EQU B' ' ;Configure GPIO OPTINI EQU B' ' ;Initialize option register ;STAT register equates BIT EQU 0 ;1 if incoming bit is high VERIFY EQU 1 ;Valid data detected once. ;Parameter equates ALARM_PITCH EQU D'165' ;1 KHz tone ALARM_DURATION EQU D'10' ;Tone duration, 100mS at 1KHz ALARM_PERIOD EQU D'2' ;Time between tones, 0.1 second increments. ALARM_TIME EQU D'200' ;Time alarm sounds (0.3 x 200 = 60 sec.) MUTE_TIME EQU D'10' ;Mute time in minutes. ;I/O pin equates ;GPIO MUTE_IN EQU 0 ;Mute button (active low), pin 5 DATA_IN EQU 3 ;Data input from RF module, pin 8 AUDIO_OUT EQU 1 ;Audio output to speaker, pin 4 LED EQU 2 ;"Power" and "muted" LED, pin 3 ; ORG 0 ;Reset vector rolls over to here GOTO Boot ;Go to beginning of program ;Subroutines BITST ;Tests incoming bits for 1 or 0 BTFSS GPIO,DATA_IN ;Wait for data input to go high GOTO $-1 BCF STAT,BIT MOVLW D'9' ;Wait for data input to stay HIGH for 0.6mS. MOVWF LCVR1 MOVLW D'13' MOVWF LCVR2 BTFSS GPIO,DATA_IN RETLW 0 LCVR2,F GOTO $-3 LCVR1,F GOTO $-7

14 BSF STAT,BIT BTFSC GPIO,DATA_IN ;Wait for data input to go low GOTO $-1 RETLW 0 DLY ;Delay subroutine MOVWF LCVR1 ;D'10' in the W register when this routine LP1 MOVLW D'78' ;is called sets the delay to 1 sec. MOVWF LCVR2 ;i.e. delay is in 0.1 sec increments. LP2 MOVLW D'255' MOVWF LCVR3 LP3 BTFSS GPIO,MUTE_IN GOTO MUTE LCVR3,F GOTO LP3 LCVR2,F GOTO LP2 LCVR1,F GOTO LP1 GOTO LP6 REL_DLY ;100mS Release delay (mute button debounce) MOVLW D'78' ;Button must have been released for 100mS MOVWF LCVR1 ;in order to leave routine. MOVLW D'255' MOVWF LCVR2 BTFSS GPIO,MUTE_IN GOTO $-5 LCVR2,F GOTO $-3 LCVR1,F GOTO $-7 RETLW 0 FREQ_GEN MOVLW ALARM_DURATION MOVWF LCVR1 ALP1 MOVLW D'10' MOVWF LCVR2 ;Frequency generator for alarm tone. ALP2 BSF GPIO,AUDIO_OUT ;This counts the time that the AUDIO MOVLW ALARM_PITCH ;output is high for the tone. MOVWF LCVR3 LCVR3,F GOTO $-1 NOP ;NOPs to compensate for looping delay NOP ;to maintain a square wave.

15 BCF GPIO,AUDIO_OUT ;This counts the time that the AUDIO MOVLW ALARM_PITCH ;output is low for the tone. MOVWF LCVR3 LCVR3,F GOTO $-1 LCVR2,F ;This block counts off the duration of GOTO ALP2 ;the alarm tone. LCVR1,F GOTO ALP1 RETLW 0 Boot value MOVWF OSCCAL ;Load the factory Internal oscillator calibration ; Initialize I/O ports MOVLW CFG_GP ;Select direction of GPIO bits TRIS GPIO ;Write selection to GPIO data ;direction register MOVLW INIT_GP ;Initialize GPIO MOVWF GPIO CLRF STATUS CLRF TMR0 ;Reset TMR0 and prescaler CLRWDT ;Reset watchdog timer MOVLW OPTINI ;Initialize option register OPTION START ;The actual program starts here. BSF GPIO,LED ;Turn LED back on. CALL REL_DLY ;Wait for MUTE button to be released. BCF STAT,VERIFY ;Reset verify status bit SYNC BTFSS GPIO,MUTE_IN GOTO MUTE MOVLW D'14' ;Wait for data from RF module to stay low for 1.8mS. MOVWF LCVR1 ;This is the point where the decoder is LP4 MOVLW D'25' ;synchronized to the transmitter. MOVWF LCVR2 LP5 BTFSC GPIO,DATA_IN GOTO SYNC ;Start over if high detected, but LCVR2,F ;don't clear verify status. GOTO LP5 LCVR1,F GOTO LP4 ;Start testing incoming bits. BTFSS STAT,BIT ;Bit must be "1"

16 BTFSC STAT,BIT ;Bit must be "0" BTFSS STAT,BIT ;Bit must be "1" BTFSC STAT,BIT ;Bit must be "0" BTFSS STAT,BIT ;Bit must be "1" BTFSC STAT,BIT ;Bit must be "0" BTFSS STAT,BIT ;Bit must be "1" BTFSC STAT,BIT ;Bit must be "0" BTFSS STAT,BIT ;Bit must be "1" BTFSC STAT,BIT ;Bit must be "0" BTFSS STAT,BIT ;Bit must be "1" BTFSC STAT,BIT ;Bit must be "0" BTFSS STAT,BIT ;Bit must be "1" BTFSC STAT,BIT ;Bit must be "0" BTFSS STAT,BIT ;Bit must be "1" BTFSC STAT,BIT ;Bit must be "0" BTFSC STAT,VERIFY ;Valid data word, test verify bit

17 GOTO ALARM ;Verified, activate alarm BSF STAT,VERIFY ;Set verify bit GOTO SYNC ;Test data word a second time. ALARM MOVLW ALARM_TIME ;Alarm routine. MOVWF LCVR4 CALL FREQ_GEN MOVLW ALARM_PERIOD GOTO DLY ;Can't call DLY, because program can leave LP6 LCVR4,F ;the subroutine without returning, causing GOTO $-4 ;a stack error. DLY is not used elsewhere. MUTE CALL REL_DLY ;Wait for MUTE button to be released. MOVLW MUTE_TIME ;Mute time in minutes MOVWF LCVR5 LP7 MOVLW D'60' ;Sixty seconds per minute MOVWF LCVR6 LP8 MOVLW D'31' ;31 TMR0 overflows per second MOVWF LCVR7 LP9 MOVLW -D'126' CLRF TMR0 ;Clear TMR0 and prescaler MOVWF TMR0 ;Re-initialize TMR0. LP10 BTFSS GPIO,MUTE_IN ;Go out of mute mode if MUTE button is pressed. BTFSC TMR0,7 ;Check for TMR0 bit 7 going low (overflow). GOTO LP10 BCF GPIO,LED ;Flash LED at 1 Hz rate by looking at bit 4 BTFSC LCVR7,4 ;of LCVR7 while mute timer is running. BSF GPIO,LED LCVR7,F GOTO LP9 LCVR6,F GOTO LP8 LCVR5,F GOTO LP7 END

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