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pls help: resistance-to-pwm converter

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grp1nidhlp

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hi! :D , i have a problem interpreting this circuit, the one that is in the attachment. ah, i don't know how the system really works, especially the RC oscillator. can somebody tell me why is there a need for the RC oscillator and what is the formula for it's frequency (or time). i just can't read the one in the article. is there somebody out there capable of explaning to me how each part of the circuit is interrelated. please help me...i really need to know. it's really important for our group...i'll be expecting your replies by tonight...thank you very much... :)
 

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Klaus

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Expecting replies by tonight, eh? Is that because the assignment is due by tomorrow? :wink:
Now, looking at this circuit, I'm sure you can work it out yourself, you get the credit for it, anyway.
I do not know what pwm stands for (do not expect anybody else to know the same acronym's as you do) but looking at it I could work out what the circuit does.
A few hints; the 555 is a timing/ oscillator chip, check up what exactly it does in that configuration.
The other chip is a binary counter with a tri state output (I looked that up with "google"). So, what does a binary counter do?
You'll also see it has a clock (CLK) input. Where does that clock pulse come from? An oscillator perhaps? So you have part of the inverter chip performing that function, the other part is conditioning the signal from the 555 output.
Over to you, have fun :lol:
Klaus
 

grp1nidhlp

New Member
sorry for my rudeness

actually pwm stands for pulse width modulation... sorry if i badly needed your replies, its just that there is a big chance that will fail if we're unable to complete our requirements, i know it's our problem but i know that you guys can give me the answers, your our last hope. ah, if you guys have any idea in how to derive the frequency of the RC oscillator...pls reply because i really can't read the one in the artticle. thank you, thank you, thank you very much!!! :)
 
Read the DATA Sheet of the 555 Timer and you get the calculation for the RC, remember T=RC, but in the case of the 555 Timer, there is a constant, a forgot that one Kabayan. You need the 555 to generate pulses, the T_LOW and T_HIGH will depend on the two resistors, but as I see in yoru circuit, it used a Trimmer Resistor, the trimmer will be adjusted to adjust the pulse width. :)
 
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