# how to multiply or divide frequency from 555

#### pheonix992

Joined Jun 23, 2013
21
I want to increase my frequency from 555 ic or decrease it
but by small ration
it means that I don't want to multiply or divide by number
I want by fraction so please how ???????

#### MrChips

Joined Oct 2, 2009
30,824
I assume you mean a fixed frequency oscillator and not necessarily a 555 circuit.
To multiply or divide by a small quantity you use a phase-locked loop.
A vfo (variable frequency oscillator) is used plus divide by n counters in the path of the vfo and the fixed frequency clock. A signal from a phase comparator followed by a low pass filter is used to send an error signal back to the vfo.

#### Bernard

Joined Aug 7, 2008
5,784
For small changes in 555 oscillator, put a pot in series with timing resistor. Multi turn pots seem to be more stable- from what I heard on AAC.

#### pheonix992

Joined Jun 23, 2013
21
I am making quadcopter without microcontroller
and I don't now any source of frequency I can adjust manually
except 555
and what is pot ?

#### MrChips

Joined Oct 2, 2009
30,824
Here is another example where I've been sent on a wild goose chase.
You must tell us on the opening post what you are attempting to do.

What does a 555 oscillator frequency have to do with a quadcopter?

A "pot" is short for "potentiometer" which is a voltage divider which can be implemented with a variable resistor.

Put a variable resistor in the 555 timer circuit to adjust the output frequency. You can do this to make both small and large changes in frequency.

#### pheonix992

Joined Jun 23, 2013
21
the quadcopter motor is brushless motor which need speed controller and its input
is frequency range from 460hz to 1.63khz
my problem is in the stability
I already used 4x (555) for each motor
so I use the accelerometer and I use it to increase gradually the frequency of the motor which need to increase its speed to make the copter stable
that's my idea

#### MrChips

Joined Oct 2, 2009
30,824
Are you controlling the 555 timer frequency manually or is this done by automatic control?
If the latter, a variable resistor will not work in this situation. You would need a voltage controlled oscillator (VCO).

#### Bernard

Joined Aug 7, 2008
5,784
What is the output of the accelerometers,[ tilt sensor? ] variable DC V or PWM, or other?? 555 frequency can be varied over a limited range by modulating pin 5, or wide range with an analog opto-coupler [ LED & light dependent resistor, LDR ].

#### pheonix992

Joined Jun 23, 2013
21
the output of sensor of accelerometers is analog and Tilt Sensor Module its output is short circuit or open circuit
put I use one source of frequency to the esc of 4 motors
but how to adjust the frequency for each motor
and how I use vco I think by pot also

#### pheonix992

Joined Jun 23, 2013
21
should use 4 (555) for my 4 esc
or I use one 555
and the esc is controlled by frequency only or with the amplitude of volt of frequency too

#### GopherT

Joined Nov 23, 2012
8,009
I think a frequency adjustment is not needed, you need a method to change the frequency to a triangle wave then use a quad comparitor to to create a pulse-width-modulation to drive each motor. The comparitor will monitor your sensor and your triangle wave generator to control the DUTY CYCLE that each motor will need to maintain position.

A triangle wave may not be perfect because the transfer function you need may not be linear but it will be a good start for you.

#### pheonix992

Joined Jun 23, 2013
21
but esc need square wave I guess
and I have new problem when I use one 555 for the 4 motor
they don't rotate fast I cannot reach their full power
but when I connect 555 with one motor only it works
why ???????

#### shortbus

Joined Sep 30, 2009
10,045
The comparators that GopherT mentioned ,compare the triangle wave to the sensor output and then give the result as a square wave.

#### pheonix992

Joined Jun 23, 2013
21
there is a pin in 555 its number is 5 and it is called voltage control to adjust the copter to right or left or any direction I
will make switch to input volt to it and to adjust its stability the same thing I do from the output of analog accelerometer
but now I tried to use one 555 it didn't fly the motors not fast enough
then I tried four 555 for each motor and the same problem
now I adjust z-axis by pot and x,y axis by input volt to pin 5 in 555
is there is any other source of frequency without processor or micro control
some one help me its my project in college

#### Bernard

Joined Aug 7, 2008
5,784
Is the test platform tethered with control & power supplied by umbilical cord?