From the time I learned about relays, I wondered if they can be used to make an H-Bridge for motors, I asked my professor and he said that you can't because they are slow.
I never knew how slow, till today, so I wrote a small code on my AVR ATmega168 microcontroller
basically, the code send an ON -> delay(x) -> OFF -> delay(x)
where x is a value (in ms) changing every time a button is pressed going down from 15 ms to 1ms
I never knew how slow, till today, so I wrote a small code on my AVR ATmega168 microcontroller
basically, the code send an ON -> delay(x) -> OFF -> delay(x)
where x is a value (in ms) changing every time a button is pressed going down from 15 ms to 1ms
1: #include <avr/io.h>
2: #include <util/delay.h>
3: #include <USART.h>
4: #define SETBIT(ADDRESS,BIT) (ADDRESS |= (1<<BIT))
5: #define CLEARBIT(ADDRESS,BIT) (ADDRESS &= ~(1<<BIT))
6: int main(void)
7: {
8: init_uart();
9: SETBIT(DDRB,0); //Output pin (ON/OFF)
10: CLEARBIT(DDRB,1); //Input to change time
11: SETBIT(PORTB,1); //Enable Pull-Up resistor
12: for (;;)
13: {
14: for (uint16_t i=15; i>0; i--) //repeat 15 times going down, used as delay
15: {
16: printf("i=%d\n",i); //just to see whats the current delay value
17: _delay_ms(100); //give me time to release button
18: while ((PINB & 0x02)==0x02) //loop when I don't press button
19: {
20: SETBIT(PORTB,0); //ON
21: _delay_ms(i); //i value as delay
22: CLEARBIT(PORTB,0); //OFF
23: _delay_ms(i);
24: }
25: }
26: }
27: return 0;
28: }
And then connected the relay, driving it with a NPN
I found that min time is 2ms, at 1ms, no switching will occur ( i was getting highly rippled 5v)
and here is an awesome sound of 1~15ms switching, at 0:16 the time is 1ms
~2ms (500Hz) is the min time (max freq) u can switch a typical relay
