| T O P I C R E V I E W |
| n/a |
Posted - Mar 07 2004 : 9:32:42 PM
Does the PWM circuit on this website work?
Thanks
(Edit...Fix useless subject line)
Edited by - Aaron Cake on Mar 08 2004 10:25:04 AM |
| 15 L A T E S T R E P L I E S (Newest First) |
| audioguru |
Posted - Aug 12 2009 : 10:01:07 AM
quote:
Originally posted by kivdenn
What is the frequency of this oscilator?
The frequency of this Cmos oscillator is 0.455/RC.
with the 100k pot set to max the frequency is 455Hz.
With the pot set to minimum then the oscillator will be shorted and it will stop. The pot should have a resistor in series to prevent a short circuit.
Download Attachment:  Cmos oscillator Aaron.PNG
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| kivdenn |
Posted - Aug 12 2009 : 05:45:25 AM
What is the frequency of this oscilator? |
| boron |
Posted - Aug 03 2009 : 12:32:20 PM
Yes it will produce a square wave at its output. By definition an oscillator takes a smooth dc signal and, well, oscillates it to produce a repeating signal pattern, in this case a simple square wave.
What audioguru is telling you is that this circuit simply varies the frequency of the pulses and not the actual duty cycle. Since for true PWM to function the duty cycle must change this is not true PWM. It will still control motor speed to a certain extent, but less effectively. |
| kivdenn |
Posted - Aug 03 2009 : 12:07:52 PM
But can it change smooth DC to pulsed DC ?
Thanks |
| audioguru |
Posted - Jul 31 2009 : 12:48:05 PM
Guess what?
The "Pulse Width Modulation DC Motor Control" circuit on this site does not produce PWM.
It is simpoly a variable frequency Cmos oscillator.
Download Attachment: Cmos oscillator again.PNG
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| kivdenn |
Posted - Jul 31 2009 : 09:59:22 AM
I want to use this circuit to produce a pulsed DC that can be used with Cakes automatic charger to charge a 12V battery from a solar panel. Is that possible? If so, how can I change this circuit to work on 12v supply so that I can connect it on Cakes battery automatic battery charger. Thans
Dennis |
| Presbychuck |
Posted - Dec 12 2006 : 3:04:56 PM
Thanks, I have completed my 3 channel 555 steppeer motor controller and it works pretty well. |
| Aaron Cake |
Posted - Dec 03 2006 : 10:47:45 AM
http://www.discovercircuits.com also has alarge list of links to various PWM circuits. Most based on the dual 555. |
| Presbychuck |
Posted - Dec 03 2006 : 12:14:58 AM
OK Thanks anyway. I'm going back to a 555 controller. I know how to get that one going. |
| audioguru |
Posted - Dec 02 2006 : 10:14:33 PM
Sorry, no e-mailing. |
| Presbychuck |
Posted - Dec 02 2006 : 9:08:15 PM
Audioguru,
If you could send the sketch to presbychuck at hotmail dot com then I would have it. :) And I do have a few of 1N4148's on hand. Thanks a million. |
| audioguru |
Posted - Dec 02 2006 : 2:04:41 PM
The circuit here uses a 4 gate IC. It has both inputs joined so its input threshold voltage is not symmetrical. Only a single input should be used to make the inputs symmetrical.
A 4069 hex inverter IC will make 3 of these circuits.
The gates or inverters in this circuit operate at only a few mA when they are working hard. herefore any little diode would work. I use 1N914 and 1N4148 for little diodes.
If I could attach my sketch here showing how to connect the required diodes for it to make PWM then I would. |
| Presbychuck |
Posted - Dec 02 2006 : 12:33:16 PM
Thanks guru, that makes some sense even to my small mind. But can you offer me any clues as to WHAT diodes and from whence to insert them? If need be I can fall back on a 555 design I have used in the past, but this circuit, appearing so simple, was easier to wrangle for newbie me. I am trying to make a three channel controller. Since this one is done save this issue, I'd like to make it work. If I need to scrap it and get on with the 555 board, then so be it.
Thanks so much for your time and knowledge.
chuck |
| audioguru |
Posted - Dec 01 2006 : 11:53:52 PM
This circuit is an ordinary Cmos variable frequency oscillator. It doesn't produce Pulse Width Modulation, the pot just changes the frequency. The frequency changing changes the speed a little of some DC motors because their inductance causes them to slow down a little at high frequency. This circuit needs two diodes added and the ends of the pot connected to the diodes so that the duty-cycle of the pulses can be changed. Then Pulse Width Modulation will be produced to control the speed of a DC motor or the brightness of a DC lamp. The fixed circuit is in Don Lancaster's Cmos Cookbook but I couldn't find the circuit on the web.
A 555 oscillator can also produce Pulse Width Modulation if two diodes are added. |
| Presbychuck |
Posted - Dec 01 2006 : 9:03:51 PM
I need help with this circuit. I am trying to make a PWM controller to use for some electric motorcycle clothing. ANyway, I assembled the circuit as per the schematic and as a test, hooked it to a 12V light bulb to observe the functionality. What happens is that the lowest pot setting gives me about 60% power and the pot setting makes no difference until about 8 (on a 1-10 scale). Then from 8-10 the power increases to about 80% or so. I have constructed the circuit three times with identical results using all new components each time. I did deter from the schematic when I could not find the listed MOSFETs. I substituted IRF540's instead. Can you help me make this work or at least tell me when to give up? LOL
TIA
chuck |
