So the project I am trying to make right now requires a sawtooth wave to be generated (for an RF transmitter).
Anyways, the schematics call for a 555 Timer to pull this off.
My question is, why can't my Arduino generate that?
If it can, is there really any need for a 555 Timer?
Or can you think of any reasons why they would be kept separate?
Thanks!
555 is much cheaper and does not require programming.
To generate any kind of non-square waves on Arduino, you would need to output analog values from some sort of wave table (containing a definition of the wave). This would be one way. The other would be to calculate the values as they are to be generated as part of the wave.
Another limitation for the Arduino is the maximum frequency you can generated using these methods.
What are some common appliances I can bust open to find a 555 timer?
They cost next to nothing, but i you want to scavenge one, old joysticks with "autofire" frequently had a 555 to generate the fireing pulses.
The 555 does not generate a real sawtooth. There is an exponential voltage on a timing capacitor which could be treated as sawtooth.
For a "true" sawtooth you have to use a constant current source for charging / discharging.
To generate any kind of non-square waves on Arduino, you would need to output analog values
Not necessarily, you could use the arduino to charge and discharge a capacitor (through a resistor) through one half of a H-bridge or even from an output pin directly. You could either swap directions after a fixed time or when the capacitor voltage had reached a certain level. This would not be a true saw waveform as stated above but would be close. To get a true saw then you need to charge at a constant current. This is easily done by using an op amp and having a capacitor as the negative feedback path. You could then feed the positive input straight from the arduino pin.
However I would still use a NE555.
What exactly is the purpose of this saw tooth? Is it to act as a threshold for generating PWM? That is the normal use but you can generate PWM directly from the Arduino.