Integrating LPG Gas Sensor Module with RN-42 Bluetooth Module

KyleALindsay · 2014-04-06 14:42

I am working with a Basic Stamp 2.

I would like to use the LPG Gas Sensor Module with RN-42 Bluetooth Module to take gas readings wirelessly.

I have the example program for both but am having trouble combining these together.

Any help would be appreciated.

This is what i have so far.

'GAS SENSOR #1 - PROPANE

HSW PIN 6 ' Heater Switch Control
ALR PIN 7 ' Alarm Input Sense

index VAR Word ' Counter Variable

RX PIN 0 ' RX of the Easy Bluetooth
TX PIN 2 ' TX of the Easy Bluetooth

Baud CON 84 ' Baud set at 9600

myByte VAR Byte ' Byte to establish connection & used for workspace

PAUSE 250 ' Waits 1/4 second
SERIN RX, Baud, [myByte] ' Waiting for byte
myByte = 0 ' Clear the byte value

SEROUT TX, Baud, [ CLS] ' Send instructions to the Debug Terminal

DO
DO UNTIL myByte > 0 ' Wait until byte is valid
SERIN RX, Baud, [myByte] ' Receive byte
LOOP
HIGH HSW ' Turn Heater ON
FOR index = 59 TO 0 ' Count Down 60 Seconds
SEROUT TX, Baud, ["PURGE MODE...", DEC2 index, " "]
myByte = 0
PAUSE 1000 ' 1 Second Pause
NEXT
index = 1710 ' Approximately 90 Seconds
DO ' Of Iterations On BS2
SEROUT TX, Baud, ["SENSE MODE...", DEC2 index / 19]
myByte = 0
HIGH HSW ' Turn Heater ON
PAUSE 15 ' For 15 mS
LOW HSW ' Turn Heater OFF
PAUSE 3 ' For 3 mS
index = index - 1 ' Decrement Counter
IF ALR = 1 THEN ' Check For Alarm Condition
DEBUG " ***ALARM***" ' Display Alarm Condition
FREQOUT 4, 2000, 3000
ELSE
DEBUG " " ' Clear Alarm Condition
ENDIF
LOOP UNTIL index = 0 ' End Of Sense Mode Loop
LOOP

Chris Savage · 2014-04-07 11:41

Welcome to the forums! Please define, "Take readings wirelessly"? The Gas Sensor Board allows you to set a trip point and know when it has been reached/exceeded, but you're not getting raw sensor readings. That would require an ADC and some calibration against a known source.

KyleALindsay · 2014-04-07 13:33

Chris Savage wrote: »

Welcome to the forums! Please define, "Take readings wirelessly"? The Gas Sensor Board allows you to set a trip point and know when it has been reached/exceeded, but you're not getting raw sensor readings. That would require an ADC and some calibration against a known source.

Hello Chris,

Thank you for your prompt response.

Yes, perhaps I chose my words incorrectly.

I have been able to test the gas sensor but only via serial connection. I would like to use the gas sensor with the RN-42 Bluetooth module (which i have also tested RX/TX capabilities independently). Basically, I would like for the information shown in the debug screen of the Gas Sensor program above to be displayed via bluetooth connection (similar to the Test Bluetooth file above but the RN-42 will only be transmitting and not receiving I think).

Eventually, I am planning to add three more gas sensor boards as well (alcohol, methane, co2) and ideally will see on the laptop debug screen if any are in "ALARM" mode.

Thank you,
Kyle

Chris Savage · 2014-04-08 09:55

To send the DEBUG data over the Bluetooth you literally just change the DEBUG statements to SEROUT as you have started to do. On the Bluetooth Module connected RTS to CTS and whatever I/O pin you use for the SEROUT to the Bluetooth Module will connect to the RX pin on the Bluetooth Module. Everything else is just a function of the sync and connection of the Bluetooth on the PC to the RN-42 Bluetooth Module. When connected you can open the PST to the COM port assigned to your PC Bluetooth Adapter. For more information see the following article...

http://learn.parallax.com/project/rn-42-bluetooth-pc-demo

KyleALindsay · 2014-04-08 17:50

Hello Chris,

Thanks for your help. I was a bit confused about what to include along with SEROUT. I was able to get it to work replacing "DEBUG HOME," with "SEROUT TX, Baud, [..."

I am now attempting to display the status of all four gas sensors in the debug screen at the same time. I have also added an audio signal for the alert.

Here is my code:

HSW1 PIN 6 ' Heater 1 Switch Control
ALR1 PIN 7 ' Alarm 1 Input Sense

HSW2 PIN 8 ' Heater 2 Switch Control
ALR2 PIN 9 ' Alarm 2 Input Sense

HSW3 PIN 10 ' Heater 3 Switch Control
ALR3 PIN 11 ' Alarm 3 Input Sense

HSW4 PIN 12 ' Heater 4 Switch Control
ALR4 PIN 13 ' Alarm 4 Input Sense

TX PIN 2 ' RX of the Easy Bluetooth

index VAR Word ' Counter Variable
Baud CON 84 ' Baud set at 9600

Main:

DO
HIGH HSW1 ' Turn Heater 1 ON
HIGH HSW2 ' Turn Heater 2 ON
HIGH HSW3 ' Turn Heater 3 ON
HIGH HSW4 ' Turn Heater 4 ON
FOR index = 10 TO 0 ' Count Down 10 Seconds
SEROUT TX, Baud, [CLS, "ALCOHOL PURGE MODE...", DEC2 index,CR,
"CO2 PURGE MODE...", DEC2 index,CR,
"PROPANE PURGE MODE...", DEC2 index,CR,
"METHANE PURGE MODE...", DEC2 index]
PAUSE 1000 ' 1 Second Pause
NEXT

index = 1710 ' Approximately 90 Seconds
DO ' Of Iterations On BS2
SEROUT TX, Baud, [CLS, "ALCOHOL SENSE MODE...", DEC2 index / 19, CR,
"CO2 SENSE MODE...", DEC2 index / 19, CR,
"PROPANE SENSE MODE...", DEC2 index / 19, CR,
"METHANE SENSE MODE...", DEC2 index / 19]
HIGH HSW1 ' Turn Heater 1 ON
HIGH HSW2 ' Turn Heater 2 ON
HIGH HSW3 ' Turn Heater 3 ON
HIGH HSW4 ' Turn Heater 4 ON
PAUSE 15 ' For 15 mS
LOW HSW1 ' Turn Heater 1 OFF
LOW HSW2 ' Turn Heater 2 OFF
LOW HSW3 ' Turn Heater 3 OFF
LOW HSW4 ' Turn Heater 4 OFF
PAUSE 3 ' For 3 mS
index = index - 1 ' Decrement Counter

IF ALR1 = 1 THEN ' Check For Alarm Condition
SEROUT TX, Baud, [" ***ALCOHOL ALARM*** "] ' Display Alarm Condition
FREQOUT 4, 2000, 2000 ' Play audible alarm
PAUSE 5000 ' 5 Second Pause
ELSE
SEROUT TX, Baud, [CLS, " "] ' Clear Alarm Condition
ENDIF

IF ALR2 = 1 THEN ' Check For Alarm Condition
SEROUT TX, Baud, [" ***CO2 ALARM*** "] ' Display Alarm Condition
FREQOUT 4, 2000, 3000 ' Play audible alarm
PAUSE 5000 ' 5 Second Pause
ELSE
SEROUT TX, Baud, [CLS, " "] ' Clear Alarm Condition
ENDIF

IF ALR3 = 1 THEN ' Check For Alarm Condition
SEROUT TX, Baud, [" ***PROPANE ALARM*** "] ' Display Alarm Condition
FREQOUT 4, 2000, 4000 ' Play audible alarm
PAUSE 5000 ' 5 Second Pause
ELSE
SEROUT TX, Baud, [CLS, " "] ' Clear Alarm Condition
ENDIF

IF ALR4 = 1 THEN ' Check For Alarm Condition
SEROUT TX, Baud, [" ***METHANE ALARM*** "] ' Display Alarm Condition
FREQOUT 4, 2000, 5000 ' Play audible alarm
PAUSE 5000 ' 5 Second Pause
ELSE
SEROUT TX, Baud, [CLS, " "] ' Clear Alarm Condition
ENDIF
LOOP UNTIL index = 0 ' End Of Sense Mode Loop
LOOP

Purge mode is working correctly, but for some reason the sense mode is appearing for only a brief second before disappearing and looping back to purge mode. Any idea why this is? Also, would it be possible to display multiple "alarms" at once?

Thank you!

Chris Savage · 2014-04-09 10:06

The reason things are disappearing is you're clearing the screen before each item displayed is my guess. But I didn't analyze all the code because I got hung up on something. It appears you're using multiple sensors and you're trying to define sense and purge modes for all of them, but the only one that has that requirement is the CO Gas Sensor. The others you just turn the heater on, wait a few seconds and then test the ALM pin. I can't even guess on what the output of the other sensors will be turning the heater on/off like that. I would guess you would get false readings.

KyleALindsay · 2014-04-20 17:03

Hello Chris,

Thank you for the information, I did not realize that ONLY the CO gas sensor needed to be purged.

I have now been able to get all four gas sensors to work and send alarm simultaneously via Bluetooth.

I am now trying to make the Boe-Bot use the PING sensor for movement / obstacle avoidance while it transmits whether each gas sensor is in alarm condition via Bluetooth.

I feel like I am very close but when I add the code for the PING sensor, the CO gas sensor stops alerting me when the alarm condition is reached but the other gas sensors continue to work.

Here is my code:

' {$STAMP BS2}
' {$PBASIC 2.5}
'
' I / O
' =========================================================================

HSW1 PIN 6 ' Heater 1 Switch Control -- ALCOHOL
ALR1 PIN 7 ' Alarm 1 Input Sense

HSW2 PIN 8 ' Heater 2 Switch Control -- PROPANE
ALR2 PIN 9 ' Alarm 2 Input Sense

HSW3 PIN 10 ' Heater 3 Switch Control -- METHANE
ALR3 PIN 11 ' Alarm 3 Input Sense

HSW4 PIN 12 ' Heater 4 Switch Control -- CO
ALR4 PIN 13 ' Alarm 4 Input Sense

TX PIN 2 ' RX of the Easy Bluetooth

Ping PIN 15
PingServo PIN 14
LeftServo PIN 13
RightServo PIN 12

' VARIABLES
' =========================================================================

index VAR Word ' Counter Variable

Baud CON 84 ' Baud set at 9600

rawDist VAR Word
sweepcount VAR Word
x VAR Byte
pulseCount VAR Byte

' MAIN
' =========================================================================

Main:

DO

HIGH HSW1 ' Turn Heater 1 ON
HIGH HSW2 ' Turn Heater 2 ON
HIGH HSW3 ' Turn Heater 3 ON
HIGH HSW4 ' Turn Heater 4 ON

FOR index = 10 TO 0 ' Count Down 10 Seconds

SEROUT TX, Baud, [CR,CR, "ALCOHOL SENSE MODE "]
IF ALR1 = 1 THEN ' Check For Alarm Condition
SEROUT TX, Baud, [" *** ALCOHOL ALARM *** ", CR] ' Display Alarm Condition
FREQOUT 4, 2000, 2000 ' Play audible alarm
ELSE
SEROUT TX, Baud, [" ", CR] ' Clear Alarm Condition
ENDIF

SEROUT TX, Baud, ["METHANE SENSE MODE "]
IF ALR2 = 1 THEN ' Check For Alarm Condition
SEROUT TX, Baud, [" *** METHANE ALARM *** ", CR] ' Display Alarm Condition
FREQOUT 4, 2000, 3000 ' Play audible alarm
ELSE
SEROUT TX, Baud, [" ", CR] ' Clear Alarm Condition
ENDIF

SEROUT TX, Baud, ["PROPANE SENSE MODE "]
IF ALR3 = 1 THEN ' Check For Alarm Condition
SEROUT TX, Baud, [" *** PROPANE ALARM *** ", CR] ' Display Alarm Condition
FREQOUT 4, 2000, 4000 ' Play audible alarm
ELSE
SEROUT TX, Baud, [" ", CR] ' Clear Alarm Condition
ENDIF

SEROUT TX, Baud, ["CO PURGE MODE...", DEC2 index]

PAUSE 1000
NEXT

HIGH HSW1 ' Turn Heater 1 ON
HIGH HSW2 ' Turn Heater 2 ON
HIGH HSW3 ' Turn Heater 3 ON

FOR index = 10 TO 0 ' Count Down 10 Seconds

SEROUT TX, Baud, [CR,CR, "ALCOHOL SENSE MODE "]
IF ALR1 = 1 THEN ' Check For Alarm Condition
SEROUT TX, Baud, [" *** ALCOHOL ALARM *** ", CR] ' Display Alarm Condition
FREQOUT 4, 2000, 2000 ' Play audible alarm
ELSE
SEROUT TX, Baud, [" ", CR] ' Clear Alarm Condition
ENDIF

SEROUT TX, Baud, ["METHANE SENSE MODE "]
IF ALR2 = 1 THEN ' Check For Alarm Condition
SEROUT TX, Baud, [" *** METHANE ALARM *** ", CR] ' Display Alarm Condition
FREQOUT 4, 2000, 3000 ' Play audible alarm
ELSE
SEROUT TX, Baud, [" ", CR] ' Clear Alarm Condition
ENDIF

SEROUT TX, Baud, ["PROPANE SENSE MODE "]
IF ALR3 = 1 THEN ' Check For Alarm Condition
SEROUT TX, Baud, [" *** PROPANE ALARM *** ", CR] ' Display Alarm Condition
FREQOUT 4, 2000, 4000 ' Play audible alarm
ELSE
SEROUT TX, Baud, [" ", CR] ' Clear Alarm Condition
ENDIF

SEROUT TX, Baud, ["CO SENSE MODE...", DEC2 index]

HIGH HSW4 ' Turn Heater 4 ON
PAUSE 15 ' For 15 mS
LOW HSW4 ' Turn Heater 4 OFF
PAUSE 3 ' For 3 mS

IF ALR4 = 1 THEN ' Check For Alarm Condition
SEROUT TX, Baud, [" *** CO ALARM *** "] ' Display Alarm Condition
FREQOUT 4, 2000, 5000 ' Play audible alarm
ELSE
SEROUT TX, Baud, [" "] ' Clear Alarm Condition
ENDIF

PAUSE 1000
NEXT
LOOP

' SUBROUTINES
' =========================================================================

GetSonar:
LOW Ping
PULSOUT Ping, 5
PULSIN Ping, 1, rawDist

IF (rawDist < 600) THEN
IF (sweepcount < 750) THEN
GOSUB Turn_Left
ELSEIF (sweepcount > 750) THEN
GOSUB Turn_Right
ELSE
GOSUB Back_Up
ENDIF
ELSE
GOSUB Forward_Pulse
ENDIF

RETURN

Forward_Pulse:
FOR pulsecount = 0 TO 5
PULSOUT LeftServo, 850
PULSOUT RightServo, 650
PAUSE 20
NEXT
RETURN

Turn_Left:
FOR pulseCount = 0 TO 10
PULSOUT LeftServo, 650
PULSOUT RightServo, 650
PAUSE 20
NEXT
RETURN

Turn_Right:
FOR pulseCount = 0 TO 10
PULSOUT LeftServo, 850
PULSOUT RightServo, 850
PAUSE 20
NEXT
RETURN

Back_Up:
FOR pulseCount = 0 TO 3
PULSOUT LeftServo, 750
PULSOUT RightServo, 750
PAUSE 20
NEXT

FOR pulseCount = 0 TO 7
PULSOUT LeftServo, 650
PULSOUT RightServo, 850
PAUSE 20
NEXT
RETURN

I want to insert the code below after the second FOR statement above so that the Boe-Bot explores using PING sensor only when all gas sensors are in SENSE mode.

FOR sweepcount = 350 TO 1150 STEP 200
FOR x = 0 TO 5
PULSOUT 14, sweepcount
PAUSE 20
NEXT
GOSUB GetSonar
NEXT

FOR sweepcount = 950 TO 550 STEP 200
FOR x = 0 TO 5
PULSOUT 14, sweepcount
PAUSE 20
NEXT
GOSUB GetSonar
NEXT

For some reason when I add the code for the PING sensor, the CO gas sensor stops alerting me when the alarm condition is reached but the other gas sensors continue to work.

Thank you!

Chris Savage · 2014-04-21 09:56

Once you start using the PING))) you have a window of up to 20 ms where nothing else can happen. This means you cannot effectively PWM the CO sensor. You may have to use another method of controlling the heater voltage on it such as a DAC or some other way to achieve the two voltages require for its sense/purge modes.

Integrating LPG Gas Sensor Module with RN-42 Bluetooth Module

Comments