http://www.kpsec.freeuk.com/555timer.htm#dutycycle
I have a circuit to turn a buzzer on and off at regular intervals. I am using the above circuit (the one with a diode in parallel to R2). The formulas on the site state that:
Tm = 0.7 * R1 * C1
Ts = 0.7 * R2 * C1
Where R1 and R2 are in ohm and C1 is in Farads
I am using a 1000µF cap for C1 and 270Ω and 22000Ω resistors for R1 and R2 respectively.
According to the formulas above I should get:
Tm = 0.7 * 270 * 0.001 = 1.9 seconds
Ts = 0.7 * 22000 * 0.001 = 154.0 seconds
However I get:
Tm < 1 second
Ts ≈ 18 seconds
The circuit is being powered by 1 * 9v battery that is actually giving roughly 8.1 volts.
Can anyone explain where the error I have made could be? I have already tested both resistors and they are correct to within a few Ωs.
Thanks in advance!
I have a circuit to turn a buzzer on and off at regular intervals. I am using the above circuit (the one with a diode in parallel to R2). The formulas on the site state that:
Tm = 0.7 * R1 * C1
Ts = 0.7 * R2 * C1
Where R1 and R2 are in ohm and C1 is in Farads
I am using a 1000µF cap for C1 and 270Ω and 22000Ω resistors for R1 and R2 respectively.
According to the formulas above I should get:
Tm = 0.7 * 270 * 0.001 = 1.9 seconds
Ts = 0.7 * 22000 * 0.001 = 154.0 seconds
However I get:
Tm < 1 second
Ts ≈ 18 seconds
The circuit is being powered by 1 * 9v battery that is actually giving roughly 8.1 volts.
Can anyone explain where the error I have made could be? I have already tested both resistors and they are correct to within a few Ωs.
Thanks in advance!