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:
- 5:9be3080ca8ba
- Parent:
- 4:64d9c0bed75b
- Child:
- 6:7f90a61e1a69
--- a/main.cpp Mon Jun 03 15:04:08 2013 +0000
+++ b/main.cpp Tue Jun 04 06:14:19 2013 +0000
@@ -4,14 +4,14 @@
#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 200 //wait interrupts in msec
-#define WAIT_NEXT 4800 //wait next measurement in msec
+#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
InterruptIn in(p8); //connect to the Discharge of 555
-DigitalOut run555(p9);//connect to the Reset of 555
+DigitalOut run555(p9);//connect to the Reset of 555
DigitalOut led(LED1);
Timer t1;
@@ -29,7 +29,7 @@
t1.reset();// Reset timer and wait for next interrupt
rest_in--;
}
-
+
if(rest_in == 0){
//No use interrupt
run555 = led = 0;
@@ -39,11 +39,12 @@
int main() {
run555 = led = 0;
+ // Set up the interrupt
in.mode(PullUp);
- in.rise(&flip);// Set up the interrupt for rising edge
+ in.fall(&flip);
printf("\rStarting measure\n");
-
+
while (1) {
//Use interrupt
my_interval = 0;