Ok, I need to control a servomotor with this 555 timer. This is for a school assignment, as usual!
I'm using the 2 diodes version of the astable mode 555 schematic!
So, we were told to consider that the servomotor turns left for output pulses with tON = 1ms, centered for output pulses of tON= 1.5ms and it turns right for pulses with tON = 2ms and a frequency of 50Hz! We have a 100nF capacitor to work with!
So, as I'm using the 2 diodes version, to be able to get Duty Cycles under 50%, the formulas I'm using for tON and tOFF are:
tON = ln(2)xRaxC
tOFF = ln2xRbxC
So, for 50Hz we have 20ms period.
To get 1ms of tON:
1ms = ln(2)xRax100nF
Ra = 14.4kΩ
To get the tOFF time:
20ms  tON = ln (2)xRbx100nF
Rb = 274kΩ
I'm using a potentiometer for Ra and I'm setting it to 14.4kΩ. Rb is fixed at 274kΩ but I don't know why, I'm not even getting the 50Hz frequency I was expecting. Also tON is larger than expected as also the tOFF.
I'm using the 2 diodes version of the astable mode 555 schematic!
So, we were told to consider that the servomotor turns left for output pulses with tON = 1ms, centered for output pulses of tON= 1.5ms and it turns right for pulses with tON = 2ms and a frequency of 50Hz! We have a 100nF capacitor to work with!
So, as I'm using the 2 diodes version, to be able to get Duty Cycles under 50%, the formulas I'm using for tON and tOFF are:
tON = ln(2)xRaxC
tOFF = ln2xRbxC
So, for 50Hz we have 20ms period.
To get 1ms of tON:
1ms = ln(2)xRax100nF
Ra = 14.4kΩ
To get the tOFF time:
20ms  tON = ln (2)xRbx100nF
Rb = 274kΩ
I'm using a potentiometer for Ra and I'm setting it to 14.4kΩ. Rb is fixed at 274kΩ but I don't know why, I'm not even getting the 50Hz frequency I was expecting. Also tON is larger than expected as also the tOFF.
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