Low voltage working and cutting it fine for a 555 unless I use the CMOS part.You don't want the simple 555 version?
http://www.discovercircuits.com/DJ-Circuits/simplepwm2.htm
Lots more out there.
Max.
Thanks - that's kinda the right direction. I just need the oscillator section and not the "slicing" bit, there's a build underway with a 4093 - might find out how it performs later.....Below is a comparator base circuit, write-up here.
And below is one using a Schmitt-trigger CMOS inverting buffer:
The gates are paralleled to give a lower-impedance drive for a MOSFET gate load.
View attachment 173191
Thanks - I'd forgotten them. Nothing for me this time round, but having been reminded could come in handy.There is quite a lot of material here: http://www.4qdtec.com/pwm-01.html It is covered in several sections. Also here: http://www.4qdtec.com/
4QD was my bible for the first PWM circuit I built. Sawtooth/trangle wave with comparator. That was more than 20 years ago and the site has changed, but the archives may still have that old stuff.
How much does "ctrl" shift the PWM on that one? My target is fixed, but trimmable PWM - 2 diodes & 2 pots is about where I'm at ATM.Here's another candidate :
View attachment 173198
Mostly just the oscillator from that style of PWM circuit. Fully adjustable frequency & ratio would've been nice, but not its not mission critical. accuracy would also be nice - if I knew for certain what frequency I need it to stay put on.What are the actual goals, accuracy, both duty cycle and freq ? Any other
desireables, like 3.3V vs 5V or power or other......
You constrained to do more elemental logic/analog approach ?
Regards, Dana.
3.93V <Ctrl < 5V ..... duty cycle=0%,How much does "ctrl" shift the PWM on that one?
That would do it - half built prototype of something on my bench, I'll finish that off and see how heavily that falls over first though.3.93V <Ctrl < 5V ..... duty cycle=0%,
Ctrl=3.93V, duty cycle = 8.8%,
Ctrl = 1.01V, duty cycle = 91.2%,
Ctrl < 1.01V, duty cycle =100%.
Bear in mind this is a simulation result with ideal components.
Yebbut - I'd have to go out and buy one of those...……...If you used ATTINY85 it will run down to 1.8V and over T and V its clock
accuracy +/- 1% if user calibration is invoked.
Can be programmed with Arduino IDE, both code writing and chip programming.
Or Bascom Basic. I think Arduino a better choice for code writing and IDE capability.
Note ATTINY has A/D so using that to adjust DC and or freq pretty straightforward.
Just a thought.
Regards, Dana.
Why are you preaching all this guff to a minimalist designer?!!!Just as an aside, future reference, here is a PSOC approach, also good down to
1.8V. One chip, just a small amount of overall capability used.
Here a SAR digitizes the pots and controls the PWM (16 bit, 2 channels, more if you
want).
And throw in a Wavedac to generate Sine, Tri, Ramp, User Arbitrary. Use same pots
to adjust freq and amplitude.
This is just a fraction of the capability you can get out of Mixed Signal processors these days.
Lots of fun, drag and drop onto canvas, and wire tool to do interchip wiring and routes to pins.
Write some code, in this example not too much, maybe 30 lines of code Add LCD (chip can
manage that as well) and you have an elemental sig gen. Add some more logic and do bursts
of waveforms, like burst 5 cycles of a sine.....All this single chip.
View attachment 173629
Regards, Dana.
The destination was an oscillator with adjustable mark space ratio - various hobby PWM circuits do that, but with limitations I wanted to find a way round. I ended up with a CMOS inverting gate oscillator, but I had to give each steering diode its own pot.Hello,
@crutschow , your circuit is like the circuit that SgtWookie posted 10 years ago:
Project: Simple PWM circuit
Bertus