# PWM diagram



## canadianhorsepower (Jun 12, 2013)

Hi guys,
             I know CNC PWM have been a very common discussion
lately and allot of unsatisfied customers or members.

This link give you access to a very solid PWM diagram with all the parts description needed.

http://www.dprg.org/tutorials/2005-11a/

pin 8 state +3 to 18 volts 
now don't let this stop you a small addition and you could use this same circuit with 120 volt input and it will work

please enjoy


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## Tin Falcon (Jun 12, 2013)

Interesting have you or anyone you know built one . I have a motor that could use one. 
Tin


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## /// (Jun 12, 2013)

Yes Tin, it should work.

Back when I was in high school I needed a PWM motor control circuit for a school project. (I had built a Helium Neon laser and wanted to draw patterns with two motors and mirrors).
These were the days before the Internet and I was able to get hold of the 555 datasheet from the local component retailer, it was a photocopy of a photocopy of a photoccopy.... remember the quality of these? 
Studying the datasheet I was a but disheartened to find the 555 could not do what I wanted, which was 0 to 100% variable PWM, as far as I could tell, it could only do ~0 to 50% or ~50-100%.
Much studying and re-studying and brainstorming, I came up with an idea of adding a pair of diodes to allow 0-100% PWM... I thought I was so clever! haha (I was about 13 or 14 years old)

Anyway, the circuit worked as hoped and the project got made and I got a pass grade.
The teacher(who was an Electronic Engineer) was talking to me about it and was pretty surprised with my circuit, he told me to wait while he got something and walked away.
He came back with a large lever-arch file full of datasheets. He showed me an App Note for the 555 (I had never heard of an App Note back then) which had heaps of example circuits and uses for the 555.... including my circuit! Some of the component values were different(was a diferent oscillating freq) but otherwise identical.
I was so angry! hahahaha. I wish I had known about the App Note, it would have saved me so much time, I hate re-inventing the wheel.

I don't know if the circuit above is the same as the one I used ~25 years ago, too long ago to remember, but it looks similar. The 555 App Note should have the circuit anyway. (edit: this will depend on the manufacturer that publishes the datasheet/app note) 

The internet really has made the world a better place as far as accessibility to technical literature is concerned.
Component datasheets of decent quality were so hard to source before the mid 90's.

Addendum: That same teacher ended up addicted to lasers after my school project. I was told he later(after I had left school) that he had built/bought many lasers for personal and school use.
About 20 years later(5 years ago) I met up with the teacher again (He came into component store I was managing at the time), after chatting about old times he went back out to his car and came back into the store with his latest laser.... haha, Addict!


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## canadianhorsepower (Jun 13, 2013)

Tin Falcon said:


> Interesting have you or anyone you know built one . I have a motor that could use one.
> Tin


 
Tin,
              yes I did buid a few I must say and they work perfect
range from 5% to 95% of motor RPM.


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## Tin Falcon (Jun 13, 2013)

> pin 8 state +3 to 18 volts
> now don't let this stop you a small addition and you could use this same circuit with 120 volt input and it will work



My Machinex  5  has a 110/120 v dc motor  in runs full speed  simple circuit a switch and a bridge rectifier. 

I expect one would need a rectifier and a couple of caps to smooth out the input voltage if using wall  voltage to feed the circuit and power a 120v dc motor. 
Tin


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## Griffin (Jun 13, 2013)

Tin

I built one too, for my cnc router and mine worked OK as well, mines only 12v motor but it seems to be good, not used it now for a few years but was pleased with it

Mark


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## canadianhorsepower (Jun 13, 2013)

Tin Falcon said:


> My Machinex  5  has a 110/120 v dc motor  in runs full speed  simple circuit a switch and a bridge rectifier.
> 
> I expect one would need a rectifier and a couple of caps to smooth out the input voltage if using wall  voltage to feed the circuit and power a 120v dc motor.
> Tin


 
Correct me if I'm wrong 
You would like to use this circuit to drive a 120 volt DC motor
If that's the case I can do some modes and send it back in PM

cheers


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## Tin Falcon (Jun 13, 2013)

Luc you are correct. while it could be interesting for lower voltage say 12 for some application  the most useful app I can think of is for the little lathe . actually a two headed monster 3-1 machine. I would not mill on it but drilling could be useful at times. 
Tin


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## Tin Falcon (Jun 13, 2013)

Also guys thanks for the reviews. and verification. 
There is so much on the net and many self proclaimed experts. Do not always know what info to trust.
Tin


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## rythmnbls (Jun 14, 2013)

I have built the circuit above as well, I use it to control the fuel pump on my gas turbines. It works very well.

Steve.


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## /// (Jun 14, 2013)

canadianhorsepower said:


> range from 5% to 95%



Actually that is starting to ring some bells.
Seem to remember I wasn't able to achieve 0 to 100% range.

Been so long since I've used a 555 timer IC, I very quickly moved to PIC chips.


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## Tin Falcon (Jun 14, 2013)

When I was working on one of my cnc projects I went to the local harware store for some wire. they sell by the foot. 
The sales guy asks: What are you using it for?"
So I tell him I am powering a Pulse width modulator.  

I get (Long pause) the Uhhh Uhhh Uhhh  How many amps does it take? 
Call me mean but I sometime mes with hardware store sales people. 

Tin


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## albertorc19 (Jun 14, 2013)

I found this PWM controller on DX, it's inexpensive and it seems that it can handle up to 90 volts and 15A. It looks worth of trying provided you have a DC power source that matches your needs.

http://dx.com/p/dc-6v-90v-15a-pwm-motor-speed-control-switch-governor-green-black-160094


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## dnalot (Jun 14, 2013)

I have built this dc motor controller for use on model R.R. layouts. It is reversible and has exceptional control at the low end, down to 0 rpm. It would probably work very well for a small lathe.

http://home.roadrunner.com/~jimngage/TRACTRONICS/ARTICLES/Ccartcl/CCARTCL.HTM

Mark T


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