Satoru Yoshida
measure ohm of HS15P
Fork of
Frequency_counter
by 
Neel Shah
This test program measures ohm of HS15P, humidity sensor.
| C(micro F) with LMC555 | 0.1 | 0.15 | 0.22 | 0.33 | 0.47 | 0.68 | 1 |
| CONV_KILO_OHM | 0.0072 | 0.0048 | 0.0033 | 0.0022 | 0.0015 | 0.0011 | 0.00072 |
If you get 2500 microseconds as interrupt time interval , it means 18 kilo ohm when 0.1 micro F. ( = 2500 * 0.0072 )
- ohm of HS15P is calculated from pulse interval of LMC555.
- CONV_KILO_OHM will be used.
- this program reads interval time.between interrupt in the P8.
- takes ON the P9 to oscillate LMC555 as short as enough to measure interval time
- last several interval times will be used for calculation.
- the time is defined as READ_TIMER .
- In current circit, VDD of LMC555 is about 1.55V, AC 0.4V between pins of HS15P.
- LMC555 consumes 120 micro A while oscillation, 90 micro A when level of P9 is OFF. (reset is ON)
- Total 1-2mA is consumed in the circit.
Related nootbook : https://mbed.org/users/strysd/notebook/measure_humidity_with_hs15p_and_lmc555/
Diff: main.cpp
- Revision:
- 6:7f90a61e1a69
- Parent:
- 5:9be3080ca8ba
- Child:
- 7:42e7f18361c8
--- a/main.cpp Tue Jun 04 06:14:19 2013 +0000
+++ b/main.cpp Sun Aug 11 08:34:00 2013 +0000
@@ -1,14 +1,6 @@
+//see mbed.org/users/strysd/notebook/measure_humidity_with_hs15p_and_lmc555/
#include "mbed.h"
-
-//see mbed.org/users/strysd/notebook/measure_humidity_with_hs15p_and_lmc555/
-#define CONV_KILO_OHM 0.0072 //if use 0.1 micro F
-#define IN_TIMES 10 //interrupt times
-#define READ_TIMER 3 //rest times when reads timer
-#define WAIT_IN 1000 //wait interrupts in msec
-#define WAIT_NEXT 4000 //wait next measurement in msec
-#define MAX_INTERVAL 100000 // > 0.1 sec ( < 10 Hz) in microseconds
-#define MIN_INTERVAL 20 // < 20 micro sec ( > 50 kHz) in microseconds
-#define ONESEC_BY_MICRO 1000000// 1 sec in microseconds
+#include "main.h"
InterruptIn in(p8); //connect to the Discharge of 555
DigitalOut run555(p9);//connect to the Reset of 555
@@ -22,15 +14,14 @@
void flip(void)
{
- if(rest_in > 0){
- if(rest_in < READ_TIMER){
- my_interval = t1.read_us();// Get time since last interrupt
- }
- t1.reset();// Reset timer and wait for next interrupt
- rest_in--;
+ if(rest_in < READ_TIMER){
+ my_interval = t1.read_us();// Get time since last interrupt
}
- if(rest_in == 0){
+ t1.reset();// Reset timer and wait for next interrupt
+ rest_in--;
+
+ if(rest_in <= 0){
//No use interrupt
run555 = led = 0;
t1.stop();
@@ -41,7 +32,7 @@
run555 = led = 0;
// Set up the interrupt
in.mode(PullUp);
- in.fall(&flip);
+ in.rise(&flip);
printf("\rStarting measure\n");
@@ -52,14 +43,15 @@
rest_in = IN_TIMES;
run555 = led = 1;
wait_ms(WAIT_IN);
+ run555 = led = 0;//force stop
if (my_interval < MIN_INTERVAL || my_interval > MAX_INTERVAL){
printf("\r not ready\n");
} else {
my_freq = ONESEC_BY_MICRO / my_interval; // Convert to Hz
my_ohm = my_interval * CONV_KILO_OHM;// Convert to kilo ohm
- printf("\r %d Hz, %d micro sec, %4.1f kilo ohm \n",
- (int)my_freq, (int)my_interval, my_ohm);
+ printf("\r %.0f Hz, %.0f micro sec, %.1f kilo ohm \n",
+ my_freq, my_interval, my_ohm);
}
wait_ms(WAIT_NEXT);