# how to multiply or divide frequency from 555

Discussion in 'The Projects Forum' started by pheonix992, Jun 23, 2013.

1. ### pheonix992 Thread Starter New Member

Jun 23, 2013
21
0
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 ???????

2. ### MrChips Moderator

Oct 2, 2009
12,657
3,461
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.

3. ### Bernard AAC Fanatic!

Aug 7, 2008
4,248
424
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.

4. ### pheonix992 Thread Starter New Member

Jun 23, 2013
21
0
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 ?

5. ### MrChips Moderator

Oct 2, 2009
12,657
3,461
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.

6. ### pheonix992 Thread Starter New Member

Jun 23, 2013
21
0
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

7. ### MrChips Moderator

Oct 2, 2009
12,657
3,461
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).

8. ### Bernard AAC Fanatic!

Aug 7, 2008
4,248
424
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 ].

9. ### pheonix992 Thread Starter New Member

Jun 23, 2013
21
0
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

10. ### pheonix992 Thread Starter New Member

Jun 23, 2013
21
0
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

11. ### GopherT AAC Fanatic!

Nov 23, 2012
6,340
4,094
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.

12. ### pheonix992 Thread Starter New Member

Jun 23, 2013
21
0
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 ???????

13. ### shortbus AAC Fanatic!

Sep 30, 2009
4,098
1,698
The comparators that GopherT mentioned ,compare the triangle wave to the sensor output and then give the result as a square wave.

14. ### pheonix992 Thread Starter New Member

Jun 23, 2013
21
0
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

15. ### Bernard AAC Fanatic!

Aug 7, 2008
4,248
424
Is the test platform tethered with control & power supplied by umbilical cord?