Humidity Sensor

[faiq18]

I just want to know the sensitivity of this sensor.high or low?what about their response?

[robosang]

Which humidity sensor? Don you have the part number or model name? And don the sensor come with datasheet or document?

[kl84]

Hey, have u read the user manual? Should have mentioned there.

[ober]

Hi, assuming you are asking about humidity sensor on Cytron site: SN-HMD.

The User's Manual, there is a graph on page 5 showing the relationship between the voltage and humidity, in %RH and another table showing the similar data.

[royalstorm7]

yes..manual stated all the detail...base on my experiences...SN-HMD... gave a very good response.....have fun

royalstorm7@yahoo.com

[shahrul]

yes..manual stated all the detail...base on my experiences...SN-HMD... gave a very good response.....have fun

SN-HMD temperature reading give some delay response, LM35 give more faster response for temperature.

[Bridget Tham]

Hi,

Anyone here know how to convert the analog output of the HSM-20G humidity sensor to the actual humidity value in %RH?
Can someone show me the calculation here?
Thanks.

[shahrul]

Hi,

Anyone here know how to convert the analog output of the HSM-20G humidity sensor to the actual humidity value in %RH?
Can someone show me the calculation here?
Thanks.

In the datasheet, was given graph output voltage vs humidity.
You can do 2 ways.
1. Every 2 point assume as straight line and do linear equation for every 2 points. Ex like distance sensor.
2. From the tabulated data, you can find best fit equation. I'm using software Maple and it's called Curve Fitting. Ex like current sensor, ACS712.

[Bridget Tham]

Hi,

Thanks for the reply. I tried and put in the linear equation given by the graph, but I still can't get the accurate value.
The following is the modified sample code for IAR Embedded Workbench MSP430 and I'm using the eZ430-RF2500 boards from Texas Instrument. FYI, the ADC pin that I'm using is Channel A0 which is pin 3 on the target board. While the humidity sensor that I'm using is HSM-20G. The modified code is in red color which is to sense for the humidity parameter. Can someone help me? Since I'm not familiar to this. Thanks.

#include "bsp.h"
#include "mrfi.h"
#include "nwk_types.h"
#include "nwk_api.h"
#include "bsp_leds.h"
#include "bsp_buttons.h"
#include "vlo_rand.h"

/*------------------------------------------------------------------------------
* Defines
*----------------------------------------------------------------------------*/
/* How many times to try a TX and miss an acknowledge before doing a scan */
#define MISSES_IN_A_ROW 2

/*------------------------------------------------------------------------------
* Prototypes
*----------------------------------------------------------------------------*/
static void linkTo(void);
void createRandomAddress(void);
__interrupt void ADC10_ISR(void);
__interrupt void Timer_A (void);

/*------------------------------------------------------------------------------
* Globals
------------------------------------------------------------------------------*/
static linkID_t sLinkID1 = 0;
/* Temperature offset set at production */
volatile int * tempOffset = (int *)0x10F4;
/* Initialize radio address location */
char * Flash_Addr = (char *)0x10F0;
/* Work loop semaphores */
static volatile uint8_t sSelfMeasureSem = 0;

/*------------------------------------------------------------------------------
* Main
*----------------------------------------------------------------------------*/
void main (void)
{
addr_t lAddr;

/* Initialize board-specific hardware */
BSP_Init();

/* Check flash for previously stored address */
if(Flash_Addr[0] == 0xFF && Flash_Addr[1] == 0xFF &&
Flash_Addr[2] == 0xFF && Flash_Addr[3] == 0xFF )
{
createRandomAddress(); // Create and store a new random address
}

/* Read out address from flash */
lAddr.addr[0] = Flash_Addr[0];
lAddr.addr[1] = Flash_Addr[1];
lAddr.addr[2] = Flash_Addr[2];
lAddr.addr[3] = Flash_Addr[3];

/* Tell network stack the device address */
SMPL_Ioctl(IOCTL_OBJ_ADDR, IOCTL_ACT_SET, &lAddr);

/* Initialize TimerA and oscillator */
BCSCTL3 |= LFXT1S_2; // LFXT1 = VLO
TACCTL0 = CCIE; // TACCR0 interrupt enabled
TACCR0 = 12000; // ~ 1 sec
TACTL = TASSEL_1 + MC_1; // ACLK, upmode

/* Keep trying to join (a side effect of successful initialization) until
* successful. Toggle LEDS to indicate that joining has not occurred.
*/
while (SMPL_SUCCESS != SMPL_Init(0))
{
BSP_TOGGLE_LED1();
BSP_TOGGLE_LED2();
/* Go to sleep (LPM3 with interrupts enabled)
* Timer A0 interrupt will wake CPU up every second to retry initializing
*/
__bis_SR_register(LPM3_bits+GIE); // LPM3 with interrupts enabled
}

/* LEDs on solid to indicate successful join. */
BSP_TURN_ON_LED1();
BSP_TURN_ON_LED2();

/* Unconditional link to AP which is listening due to successful join. */
linkTo();

while(1);
}

static void linkTo()
{
uint8_t msg[4];
#ifdef APP_AUTO_ACK
uint8_t misses, done;
#endif

/* Keep trying to link... */
while (SMPL_SUCCESS != SMPL_Link(&sLinkID1))
{
BSP_TOGGLE_LED1();
BSP_TOGGLE_LED2();
/* Go to sleep (LPM3 with interrupts enabled)
* Timer A0 interrupt will wake CPU up every second to retry linking
*/
__bis_SR_register(LPM3_bits+GIE);
}

/* Turn off LEDs. */
BSP_TURN_OFF_LED1();
BSP_TURN_OFF_LED2();

/* Put the radio to sleep */
SMPL_Ioctl(IOCTL_OBJ_RADIO, IOCTL_ACT_RADIO_SLEEP, 0);

while (1)
{
/* Go to sleep, waiting for interrupt every second to acquire data */
__bis_SR_register(LPM3_bits);

/* Time to measure */
if (sSelfMeasureSem) {
volatile long temp,a;
int degC, volt;
int humidity;
int results[3];

#ifdef APP_AUTO_ACK
uint8_t noAck;
smplStatus_t rc;
#endif

/* Get temperature */
ADC10CTL1 = INCH_10 + ADC10DIV_4; // Temp Sensor ADC10CLK/5
ADC10CTL0 = SREF_1 + ADC10SHT_3 + REFON + ADC10ON + ADC10IE + ADC10SR;
/* Allow ref voltage to settle for at least 30us (30us * 8MHz = 240 cycles)
* See SLAS504D for settling time spec
*/
__delay_cycles(240);
ADC10CTL0 |= ENC + ADC10SC; // Sampling and conversion start
__bis_SR_register(CPUOFF + GIE); // LPM0 with interrupts enabled
results[0] = ADC10MEM; // Retrieve result
ADC10CTL0 &= ~ENC;

/* Get voltage */
ADC10CTL1 = INCH_11; // AVcc/2
ADC10CTL0 = SREF_1 + ADC10SHT_2 + REFON + ADC10ON + ADC10IE + REF2_5V;
__delay_cycles(240);
ADC10CTL0 |= ENC + ADC10SC; // Sampling and conversion start
__bis_SR_register(CPUOFF + GIE); // LPM0 with interrupts enabled
results[1] = ADC10MEM; // Retrieve result

/* Stop and turn off ADC */
ADC10CTL0 &= ~ENC;
ADC10CTL0 &= ~(REFON + ADC10ON);

/* Get humidity */
ADC10CTL1 = INCH_0 + ADC10DIV_4; // Humidity Sensor ADC10CLK/5
ADC10CTL0 = SREF_1 + ADC10SHT_3 + REFON + ADC10ON + ADC10IE + ADC10SR;
__delay_cycles(240);
ADC10CTL0 |= ENC + ADC10SC; // Sampling and conversion start
__bis_SR_register(CPUOFF + GIE); // LPM0 with interrupts enabled
results[2] = ADC10MEM; // Retrieve result
ADC10CTL0 &= ~ENC;

/* oC = ((A10/1024)*1500mV)-986mV)*1/3.55mV = A10*423/1024 - 278
* the temperature is transmitted as an integer where 32.1 = 321
* hence 4230 instead of 423
*/
temp = results[0];
degC = ((temp - 673) * 4230) / 1024;
if( (*tempOffset) != 0xFFFF )
{
degC += (*tempOffset);
}

/* message format, UB = upper Byte, LB = lower Byte
-------------------------------
|degC LB | degC UB | volt LB |
-------------------------------
0 1 2
*/
temp = results[1];
volt = (temp*25)/512;
a = results[2];
humidity = (a-0.379)/0.032;
msg[0] = degC&0xFF;
msg[1] = (degC>>8)&0xFF;
msg[2] = volt;
msg[3] = humidity;


/* Get radio ready...awakens in idle state */
SMPL_Ioctl( IOCTL_OBJ_RADIO, IOCTL_ACT_RADIO_AWAKE, 0);

#ifdef APP_AUTO_ACK
/* Request that the AP sends an ACK back to confirm data transmission
* Note: Enabling this section more than DOUBLES the current consumption
* due to the amount of time IN RX waiting for the AP to respond
*/
done = 0;
while (!done)
{
noAck = 0;

/* Try sending message MISSES_IN_A_ROW times looking for ack */
for (misses=0; misses < MISSES_IN_A_ROW; ++misses)
{
if (SMPL_SUCCESS == (rc=SMPL_SendOpt(sLinkID1, msg, sizeof(msg), SMPL_TXOPTION_ACKREQ)))
{
/* Message acked. We're done. Toggle LED 1 to indicate ack received. */
BSP_TURN_ON_LED1();
__delay_cycles(2000);
BSP_TURN_OFF_LED1();
break;
}
if (SMPL_NO_ACK == rc)
{
/* Count ack failures. Could also fail becuase of CCA and
* we don't want to scan in this case.
*/
noAck++;
}
}
if (MISSES_IN_A_ROW == noAck)
{
/* Message not acked */
BSP_TURN_ON_LED2();
__delay_cycles(2000);
BSP_TURN_OFF_LED2();
#ifdef FREQUENCY_AGILITY
/* Assume we're on the wrong channel so look for channel by
* using the Ping to initiate a scan when it gets no reply. With
* a successful ping try sending the message again. Otherwise,
* for any error we get we will wait until the next button
* press to try again.
*/
if (SMPL_SUCCESS != SMPL_Ping(sLinkID1))
{
done = 1;
}
#else
done = 1;
#endif /* FREQUENCY_AGILITY */
}
else
{
/* Got the ack or we don't care. We're done. */
done = 1;
}
}
#else

/* No AP acknowledgement, just send a single message to the AP */
SMPL_SendOpt(sLinkID1, msg, sizeof(msg), SMPL_TXOPTION_NONE);

#endif /* APP_AUTO_ACK */

/* Put radio back to sleep */
SMPL_Ioctl( IOCTL_OBJ_RADIO, IOCTL_ACT_RADIO_SLEEP, 0);

/* Done with measurement, disable measure flag */
sSelfMeasureSem = 0;
}
}
}

void createRandomAddress()
{
unsigned int rand, rand2;
do
{
rand = TI_getRandomIntegerFromVLO(); // first byte can not be 0x00 of 0xFF
}
while( (rand & 0xFF00)==0xFF00 || (rand & 0xFF00)==0x0000 );
rand2 = TI_getRandomIntegerFromVLO();

BCSCTL1 = CALBC1_1MHZ; // Set DCO to 1MHz
DCOCTL = CALDCO_1MHZ;
FCTL2 = FWKEY + FSSEL0 + FN1; // MCLK/3 for Flash Timing Generator
FCTL3 = FWKEY + LOCKA; // Clear LOCK & LOCKA bits
FCTL1 = FWKEY + WRT; // Set WRT bit for write operation

Flash_Addr[0]=(rand>>8) & 0xFF;
Flash_Addr[1]=rand & 0xFF;
Flash_Addr[2]=(rand2>>8) & 0xFF;
Flash_Addr[3]=rand2 & 0xFF;

FCTL1 = FWKEY; // Clear WRT bit
FCTL3 = FWKEY + LOCKA + LOCK; // Set LOCK & LOCKA bit
}

/*------------------------------------------------------------------------------
* ADC10 interrupt service routine
*----------------------------------------------------------------------------*/
#pragma vector=ADC10_VECTOR
__interrupt void ADC10_ISR(void)
{
__bic_SR_register_on_exit(CPUOFF); // Clear CPUOFF bit from 0(SR)
}

/*------------------------------------------------------------------------------
* Timer A0 interrupt service routine
*----------------------------------------------------------------------------*/
#pragma vector=TIMERA0_VECTOR
__interrupt void Timer_A (void)
{
sSelfMeasureSem = 1;
__bic_SR_register_on_exit(LPM3_bits); // Clear LPM3 bit from 0(SR)
}