Hi all,
As always get a lot of help here, I dare to hope that this time will be the same
So the issue is that I need to generate 1 to 255 Hz frequency and this have to be controlled by an arduino. I am playing with a 555 now and my first idea is to use it combined with a digital potentiometer to actually set the frequency. I found a lot of calculators on the internet but was not able to decide some values for the potentiometer in order to get steps for about 1Hz.
Do you have any idea how can I achieve this? Or maybe using 555 is not a good approach ?
Thank you very much

 

How do you intend to control it with the Arduino?
What do you want to control from the Arduino?

• frequency
• duty cycle
• pulse amplitude
• trigger input
• duration

1-255Hz is not considered fast. You don't need a 555-timer circuit for this. You can generate the signal entirely from the Arduino.
Do you want to generate square waves, 50% duty cycle, or some other kind of arbitrary waveform such as sine, triangle, saw-tooth?

 

Hi,
Square with 50%

 

Hi,
Square with 50%

Use the timer output-compare feature of the Arduino/ATmega

 

Hi all,
As always get a lot of help here, I dare to hope that this time will be the same
So the issue is that I need to generate 1 to 255 Hz frequency and this have to be controlled by an arduino. I am playing with a 555 now and my first idea is to use it combined with a digital potentiometer to actually set the frequency. I found a lot of calculators on the internet but was not able to decide some values for the potentiometer in order to get steps for about 1Hz.
Do you have any idea how can I achieve this? Or maybe using 555 is not a good approach ?
Thank you very much

Simple solution:
use an arduino timer interrupt
use the output from the potmeter converted to digital value to reset the timer register.

that's all.
good luck

Picbuster

 

Ok, I will rephrase because I think is not clear what I want to achieve :
I have a device that measure RPM and need a frequency input. What I want is to simulate an input for this device.(By default as input there is some sort of tahometer).
From my tests with arduino pwm :
If I generate 10Hz then device read - 1198RPM (somehow double the value, because normally on 10Hz I should have 600 RPM)
If I generate 11Hz then device read - 1318 RPM
and so on...
Basically step that I increase RPM on device is around 120RPM. I need to have step of about 10RPM or at least 50 RPM but I am not able to with arduino 10.5 HZ ro better 10.x Hz (where x to be from 0 to 9 ).

Ideea with 555 was to control it with arduino using a digital potentiometer.

So I am open on any suggestions / hints

Thanks

 

hi David,
Can you check, if your RPM reading tacho device is designed to read pulses edges.?, some do.
That would account for the doubled RPM reading.
Do you have a tacho spec sheet or link to post.?
E

 

Hi,
I am not able to get that info unfortunately but I did tests with many values and I am sure that the reading is doubled.
Is there any way to test somehow and answer to your question?

 

hi,
You could use a push switch as an input to the tacho.
And check if the tacho increments when the switch is closed and opened.
Do you know how to set that up.?
E

 

Thanks a lot for the idea but I am not sure I am able to understand that. You mean a like a push button which open 5v?

 

hi,
This would be a basic circuit.
If you don't have the components on the bench, tell me what you have and I will modify if possible.

E

 

I have them all. Will do the test now.
Thanks
L.E. - I just tried but nothing happen. So does not read anything even if I press super fast on switch or not...

 

Here is a link to an Arduino sketch that could be modified to do what you want. For just a square wave output you would not need to use the DAC. For just a square wave you could also output a higher frequency than 170 Hz.

Les.

 

But this is for due (which is not a problem cause I have a due also) but as far I can see from code the step is also around 1.hz, right/?

 

I was only suggesing it as a basis for writing your own code. I think it should be possible to change the resolution to 1 Hz. I am very poor at writing in "C" so I would use assembler.

Les.

 

hi D,
You say operating the switch does not count the tacho over.??

E

 

Yes, that s correct

 

Thats very strange.
As you say that you want to use the tacho 1Hz thru 255Hz, is it possible that your tacho has a minimum RPM restriction.?

 

If I feed it with 1Hz pwm from arduino I get around 118 RPM (double as it shout ) . I cannot go lower to test.

 

hi David,
If that switch test circuit has been built and connected correctly to the tacho, I do not a reason why it is not working.
Its a simple circuit that is often used to send a pulse into a circuit.
E