how to control 555 resisters with PIC

[Darrel Taylor]

"Anything you can do, I can do better". Said the PIC to the NE555.

I can see no reason to even attempt what you're proposing. The PIC can perform any function the 555 can do, without any external components. And do a bunch of other stuff at the same time.

It would be like using a 300hp car engine just to regulate how fast your electric can opener turns. Not that someone wouldn't try that either.
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[sayzer]

"Anything you can do, I can do better". Said the PIC to the NE555.

I can see no reason to even attempt what you're proposing. The PIC can perform any function the 555 can do, without any external components. And do a bunch of other stuff at the same time.

It would be like using a 300hp car engine just to regulate how fast your electric can opener turns. Not that someone wouldn't try that either.
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I have seen people using 12C508 direct drop in 555 place upside down (different supply pins ).

Compared to 555, 12C508 provides a better accuracy over a range of frequency they say. Thus, it comes to the cost at the end.

555 is about the same price of a single general purpose transistor!


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[Acetronics2]

Just play with voltage @ pin 5 ... see 555 Datasheet for that.

Other ( read complicated for the use ...) thing to do is use the " constant current config" and drive this current with the PIC.

Broadest freq range to be expected ...

Hi, Darrel

You're not right ... or right just for "classical" designs ...

Alain / ._ ._.. ._ .. _.

[KB3BYT]

I thought I made my reasons for wanting to learn how to
control the 555 resistor and capacitor rack.
This isn't a question of how to make a PIC do something better than a 555.
Its a specific question of how to control the resistors and capacitors aligned with the 555 to make the 555
do something variable.
And again....
I'm not an electronics engineer.
I am a retired computer programmer.
So I don't always understand some of the things the electronics engineers take for granted when
designing circuits so please tell me how to wire
with more detail. All my wiring I get from the PBP manual and you know how sparce that is.

[Acetronics2]

Soooo,

In your case ... I only see digital pots ( AD 7376 i.e. ) wired in parallell to existing resistors ... or instead them.

For capacitors ... small relays parallelling other values to those existing is the only easy way I see.

Of course, The PIC will drive both ... and you might get no scale-holes !!!

Sorry for the scheme ... but I consider you've to understand what you do !!!
That's it ...

Alain / ._ ._.. ._ .. _.

[KB3BYT]

I can do that.
Thankyou.

[skimask]

I had the same type of thing awhile back, thought I needed to use a 555 and a pot to generate a variable freq output. I used a 12F675 and 2 buttons to make a nice square wave, one button increased freq, the other decrease freq. 8 pins, 1 pin power, 1 pin ground, internal oscillator, 2 pins for buttons, 4 pins left over, 2 pins at main freq (inverted from each other), the other 2 pins running at 1/2 and 1/4 of the main freq. Was able to adjust it from 0hz up to around 200khz. Worked like a champ, took the same amount of board space, and I suspect took less time to program that PIC than it would've to calculate the correct values for a 555 to get a 50% duty cycle square wave.

My 2 cents....
JDG