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:
- 7:42e7f18361c8
- Parent:
- 6:7f90a61e1a69
--- a/main.cpp Sun Aug 11 08:34:00 2013 +0000
+++ b/main.cpp Wed Nov 06 07:38:20 2013 +0000
@@ -4,7 +4,8 @@
InterruptIn in(p8); //connect to the Discharge of 555
DigitalOut run555(p9);//connect to the Reset of 555
-DigitalOut led(LED1);
+DigitalOut led1(LED1);//running 555
+DigitalOut led2(LED2);//not ready
Timer t1;
float my_interval = 0;//between interrupts in microseconds
@@ -23,13 +24,13 @@
if(rest_in <= 0){
//No use interrupt
- run555 = led = 0;
+ run555 = led1 = 0;
t1.stop();
}
}
int main() {
- run555 = led = 0;
+ run555 = led1 = led2 = 0;
// Set up the interrupt
in.mode(PullUp);
in.rise(&flip);
@@ -41,12 +42,14 @@
my_interval = 0;
t1.start();
rest_in = IN_TIMES;
- run555 = led = 1;
+ run555 = led1 = 1;
+ led2 = 0;
wait_ms(WAIT_IN);
- run555 = led = 0;//force stop
+ run555 = led1 = 0;//force stop
if (my_interval < MIN_INTERVAL || my_interval > MAX_INTERVAL){
printf("\r not ready\n");
+ led2 = 1;
} else {
my_freq = ONESEC_BY_MICRO / my_interval; // Convert to Hz
my_ohm = my_interval * CONV_KILO_OHM;// Convert to kilo ohm