# 555 timers

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#### jasona@wbeer

##### New Member
ive reserched this a bit and i think i got it figured out the only thing i dont understand is how will the capacitors affect my out put
and if i use 2 10k resistors my duty cycle is 2k now what will this look like if i put a light on the out put will it flash or is tthis too fast to see

any more info you think i might be able to use would be apreciated

#### Russlk

##### New Member
I think you mean frequency instead of duty cycle. Duty cycle is the ratio of on time to off time (or vice-versa), frequency is the number of cycles per second. At 2kc you will not see any blinking. The eye cannot see 60 Hz, so you would have to be lower than that. With 2 resistors in the standard circuit, the duty cycle is 33.3%.

#### audioguru

##### Well-Known Member
Since your timing resistors are both 10k ohms, a 47uF timing capacitor will cause the frequency to be about 1Hz and a 4.7uF capacitor about 10Hz.

#### demokesola

##### New Member
Russlk said:
I think you mean frequency instead of duty cycle. Duty cycle is the ratio of on time to off time (or vice-versa), frequency is the number of cycles per second. At 2kc you will not see any blinking. The eye cannot see 60 Hz, so you would have to be lower than that. With 2 resistors in the standard circuit, the duty cycle is 33.3%.

t1 = 0.693(R2)C
t2 = 0.693(R1 + R2)C

T = t1 + t2

f = 1/T

duty = t2/T x 100%

#### audioguru

##### Well-Known Member
The duty-cycle is 67% high and 33% low since the timing resistors have equal values. :lol:

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