Reply by Phil Allison March 2, 20152015-03-02
Shithead Keith wrote:
> > Upon taking the fan out of the car, I discovered a few things. > > 1) Multimeter signal did squat. > 2) PWM is +12V potential > 3) grounding PWM w/ 0-~5kOhms will cause the fan to run but "pulse" every few seconds, turning itself on and off. >5kOhms = nothing. At the higher resistances, the fan cycles faster and draws less current over a narrow range, probably less than 2kOhms. > > So I was totally on the wrong track.
** Alouette, gentille alouette, Alouette, je te plumerai. ... Phil
Reply by amdx March 1, 20152015-03-01
Hi Keith,
  You sounded like you might have been exasperated in your last post,
I know the feeling.
  Here's some info about PWM that may help.

Here's a video showing the output wave form.
https://www.youtube.com/watch?v=IESHN5i-OFI

Here's a PWM circuit I have built, I used it to control a motor for 
winding a Tesla coil.
It uses a common LM324.

http://www.pcsilencioso.com/cpemma/pwm.html

  Then there is the 555 timer ic.
Google will deliver thousands of pages about 555 PWM circuits.

Here's one with some explanation of the 555 to help with the
understanding.

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


                     Mikek





Reply by amdx March 1, 20152015-03-01
On 3/1/2015 8:43 AM, S Keith wrote:
> Upon taking the fan out of the car, I discovered a few things. > > 1) Multimeter signal did squat. > 2) PWM is +12V potential > 3) grounding PWM w/ 0-~5kOhms will cause the fan to run but "pulse" every few seconds, turning itself on and off. >5kOhms = nothing. At the higher resistances, the fan cycles faster and draws less current over a narrow range, probably less than 2kOhms. > > So I was totally on the wrong track. > > Thanks to everyone for their help. > > Steve >
Sorry, But I don't know what to make of that, but I don't know that understand your statements either. > 1) Multimeter signal did squat. I don't understand, in car it did cause the motor to spin, out of car it didn't? > 2) PWM is +12V potential Meaning you measured 12V on the positive lead of the motor? There is a good explanation for that, but I need to know exactly where you leads were placed for the measurement. I grabbed the first site I saw, please view the first schematic drawing, the circuit on the left side. You can see that if you measured from the positive of the motor to ground, you would get 12V, with motor running or not. http://www.precisionmicrodrives.com/application-notes-technical-guides/application-bulletins/ab-001-discrete-driver-circuits-for-vibration-motors > 3) grounding PWM w/ 0-~5kOhms will cause the fan to run but "pulse" >every few seconds, turning itself on and off. >5kOhms = nothing. At >the higher resistances, the fan cycles faster and draws less current >over a narrow range, probably less than 2kOhms. Are you saying you can't get the motor to run at full speed out of the car? Hope that helps, Mikek
Reply by S Keith March 1, 20152015-03-01
Upon taking the fan out of the car, I discovered a few things.

1) Multimeter signal did squat.
2) PWM is +12V potential
3) grounding PWM w/ 0-~5kOhms will cause the fan to run but "pulse" every few seconds, turning itself on and off. >5kOhms = nothing.  At the higher resistances, the fan cycles faster and draws less current over a narrow range, probably less than 2kOhms.

So I was totally on the wrong track.

Thanks to everyone for their help.

Steve
Reply by Frnak McKenney February 28, 20152015-02-28
On Fri, 27 Feb 2015 12:44:05 -0800 (PST), whit3rd <whit3rd@gmail.com> wrote:
> On Wednesday, February 25, 2015 at 6:59:28 PM UTC-8, S Keith wrote: > >> I have a 12V PWM controlled fan. I don't know anything other than it >> takes 12V ~1.6A to run it and a 3V, 2mA signal to activate it. I'm >> trying to accomplish this. If I supply a higher current, I am >> concerned I might damage something. > > If the fan is on a fused automotive circuit, and you're bypassing that > power source, you might want to insert a similar fuse in your > 'alternate' power connection. As for the 'signal to activate', that > sounds like it might be TTL logic (and that means we cannot be sure > that it sinks 2 mA; it could as easily SOURCE 2 mA, the polarity DOES > matter). > > If the fan runs when the signal is at +3V, and does NOT run when the > signal pin is left open, and does NOT run when the signal pin is > grounded, then probably that signal pin has a pulldown resistor and > runs on 3V logic. The "PWM" feature could be implemented by putting a > variable duty cycle onto the signal pin, i.e. constant 3V drive makes > the motor run full speed. > > A two-resistor voltage divider, output 3V and impedance about 100 ohms, > would be suitable to arrange this ( +12V<--->360 ohms<--->120 > ohms<--->GND). If the 12V source is not regulated, some provision to > prevent overvoltage events on the logic signal pin is recommended. > Automotive +12 power is allowed to have occasional 60V spikes... a fan > doesn't usually care, but logic inputs will.
Is it possible that the OP's "motor" has an inboard transistor/FET? You all piqued my curiosity, and I had DuckDuckGo do a quick search on "computer fan 12V pwm speed control circuit". This turned up a circuit based on the Micrel MIC502 "Fan Management IC" (yup, they have a "hardware app" for that!): PWM Fan controller http://www.bit-tech.net/modding/2001/12/03/pwm_fan_controller/1 What's interesting is that this chip produces (at Vdd=12V) 3.75V PWM pulses out, intended to drive a transistor controlling a motor. There's also a "brother" chip, the MIC5021, which does a similar job and assumes it's driving a MOSFET controlling a motor. Does this shed any light on the subject? Frank McKenney -- ...[B]ecause his martyrdom is thus a power to the martyr, modern people think that any one who makes himself slightly uncomfortable in public will immediately be uproariously popular. ... The assumption is that if you show your sincerity (or even your political ambition) by being a nuisance to yourself as well as to other people, you will have the strength of the great saints who passed through the fire. -- G.K. Chesterton: The Modern Martyr (1908) -- Frank McKenney, McKenney Associates Richmond, Virginia / (804) 320-4887 Munged E-mail: frank uscore mckenney aatt mindspring ddoott com
Reply by ehsjr February 28, 20152015-02-28
On 2/27/2015 5:51 PM, S Keith wrote:
> On Friday, February 27, 2015 at 1:23:41 PM UTC-7, Tim Wescott wrote: >> As has been expressed to you before, nothing can, always and >> simultaneously, put out a given voltage at a given current, because the >> current at any given voltage (or voltage at any given current) depends on >> the load, not the source. > > I see contradiction in your statement. The VR suggested early in the thread puts out 3V/100mA (max).
There is NO contradiction in Tim's statement. And the 2950 VR would work fine for you, assuming that the 3V 2mA figure you measured was accurate. The 100mA current that the VR is CAPABLE of providing is NOT what it will provide to your load. At 3 volts, it will provide 2mA to your load - again, assuming your measurements are correct. With a fixed voltage supply, it is your load that determines how much current flows. Add an LED in series with a 100 ohm resistor from the 3V output of the supply to ground, so that when you switch the supply on to activate the fan the LED acts as an on/off indicator. Ed <snip>
Reply by Phil Allison February 27, 20152015-02-27
 Shithead Keith wrote:

 
> > Indeed, why is he here ?
** Why are YOU here ??? Your idiot Q is way off topic, it's got nothing to do with "basic electronics" and is not answerable. Only one explanation is possible - you are here to amuse yourself and that means you are TROLLING. What you don't have the brains to see is the ONLY person currently on this NG who is NOT trolling is me. .... Phil
Reply by S Keith February 27, 20152015-02-27
On Friday, February 27, 2015 at 1:23:41 PM UTC-7, Tim Wescott wrote:
> As has been expressed to you before, nothing can, always and=20 > simultaneously, put out a given voltage at a given current, because the=
=20
> current at any given voltage (or voltage at any given current) depends on=
=20
> the load, not the source.
I see contradiction in your statement. The VR suggested early in the threa= d puts out 3V/100mA (max). Would it be more accurately stated that I wish to produce a 3V, 2mA max pow= er supply? =20
> So in the context that you quote it, your "3V, 2mA output" is completely=
=20
> meaningless. Something else is happening, and I suspect that you want to=
=20
> know what that is.
Perhaps, but I definitely want to know what it is. =20
> > I do not know the components involved or their limitations. I only kno=
w
> > the "experimental" input and outcome. >=20 > From elsewhere I know that you learned the "3V, 2mA" figure from a meter=
=20
> data sheet. Here are some observations: >=20 > 1: That's a data sheet. Data sheets lie on rare occasions, commonly > obfuscate, and are often not written to be easy to understand for > the general public. So you don't want to trust your reading of one > unless it's been a close reading, and you're firm in your knowledge > of the subject. > > 2: You've been assured that it's physically impossible by more than > one person, the majority of whom have been calm and helpful about > it. >=20 > 3: A common practice, when one runs into questions on a data sheet, is > to MEASURE. Get another meter (or two), and measure the voltage > on the "3V, 2mA" input, and measure its current, too, if that floats > your boat.
Phil is the source of that assertion. I explicitly stated that I measured t= he output of one DMM with another DMM. The DMM that spun the motor MEASURE= D 3V, 2mA
> 4: Just because it works with 3V (or whatever) on the control input > doesn't mean that it won't suffer long-term damage. Your best bet > would be to measure what's going on at that input when the thing is > in a car, working. If you can get access to a car (even a junker) > and MEASURE, you'll know way better. It could be that the input is > supposed to be 12V, or 5V, or something, and that 3V just barely > turns it on, and leaves it sputtering on and off. It could be that > 3V is exactly right -- you don't know.
Agreed. As I mentioned before, the fan only runs when temperature hits cer= tain significant values. I am unable to create that environment reliably t= o get the fan to come on AND measure it. When Phoenix temps hit 110=B0F+, = then I can probably do exactly that. The values I have measured are consistent with 12V computer fan PWM specifi= cations. I realize that ultimately means nothing, but I choose to use it a= s supporting data. Thank you for your help. Steve
Reply by S Keith February 27, 20152015-02-27
On Friday, February 27, 2015 at 1:14:10 PM UTC-7, Tim Wescott wrote:
> On Thu, 26 Feb 2015 17:19:18 -0800, S Keith wrote: > > > On Thursday, February 26, 2015 at 4:28:35 PM UTC-7, Phil Allison wrote: > >> S Keith wrote: > >> > >> > >> > > > Thanks John G. While my ignorance is vast, I know V=IR. I need to > >> > > > supply 3V, 2mA > >> > > > >> > > ** You are being far to literal. > >> > > > >> > > 3V at 2mA MEANS with a voltage supply of 3V, the LOAD draws 2mA. > >> > > > >> > > > >> > > > I have a 12V PWM controlled fan. > >> > > > I don't know anything other than it takes 12V ~1.6A > >> > > > >> > > > >> > > ** That is a very big PWM fan. > >> > > > >> > > High time you supplied a link to the thing. > >> > > > >> > > > >> > > > to run it and a 3V, 2mA signal to activate it. > >> > > > >> > > > >> > > ** PWM fans normally require a PWM signal to control them. > >> > > > >> > > You are contradicting yourself not making sense. > >> > >> > >> > If I could link it for you, I would know more about it. It's the > >> > cooling fan for a Honda Civic Hybrid battery pack. > >> > >> > >> ** Figured it was something weird and automotive. > >> > >> How do you know it is a PWM fan ?? > >> > >> > >> > I "discovered" that I can activate the fan with a multimeter that > >> > puts out a 3V, 2mA current. > >> > >> > >> ** OK - so we FINALLY get to know where your 3V, 2mA nonsense came > >> from. > >> > >> The spec sheet for a DMM. > >> > >> And it does not mean what you assume. > >> > >> > >> I wish to duplicate this to drive the fan as I thought it would be a > >> simple solution compared to figuring out how to supply a PWM signal. > >> > >> ** You do not know what is needed. > >> > >> So neither do we. > >> > >> > >> .... Phil > > > > Phil, > > > > Since you're clearly not willing to read what I write as evidenced by > > your response (I said nothing of any DMM spec sheet), I'm going to > > disregard any of your future responses. > > > > I'm not sure what you're getting from your participation in a group > > labeled "basics". You remind me of why I stopped using Usenet back in > > the day (started in the late 80s). > > > > Simply put, you're an arrogant asshole. I've seen it time and time again > > in dozens of groups covering as many topics. Take comfort in your false > > sense of superiority. I'm far kinder to those ignorant of my areas of > > expertise. > > Steve, an essential USENET skill (any-"NET" for that matter) is to just > ignore the trolls. Phil oscillates between being a valuable resource on > audio circuits and an incensed troll. No amount of talk will get him down > from the trees when he's chosen to go there, so you need to just ignore > him. Or bait him on purpose, if it makes you feel better. But trust me > -- many people have tried talking sense to him, and all it does is get him > worked up. > > He's: > > --> very trustworthy on audio stuff > > --> less reliable on regulatory and "that'll burn your house down" stuff > > --> not at all reliable when you can tell that there's spittle hitting > the computer screen. > > -- > > Tim Wescott > Wescott Design Services > http://www.wescottdesign.com
Tim, Agreed. I have been away from usenet for the better part of 7-8 years, and I lost that skillset. My biggest regret is that plonking with Google Groups isn't an option. Lesson learned! Thanks, Steve
Reply by S Keith February 27, 20152015-02-27
On Friday, February 27, 2015 at 1:08:23 PM UTC-7, Ralph Mowery wrote:
> > I don't know the setup of your motor, but I was thinking that the supply is > the 12 volts and the lead with the 3 volts on it is the speed determing > wire. With a constant voltage on it,it is running full speed as it is a > 'pulse' of 100 % . If you fed that wire some pulses then the speed would > change. Just a guess.
That is exactly what I was thinking.
> When meters are fed pulses they can show many differant voltages depending > on the meter. Most will try and average them. Some will try to show a > true RMS value. Often depends if an analog or digital meter.
These are NOT precision instruments; however, the half dozen I have all correlate nicely with each other and other hardware. I'll find out what it does this weekend. :) Thanks, Steve