Whole house fan motor

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Hi Jamie,

Thanks for the info, I have been shutting off the breaker when working with this. I guess I'm surprised that the white wire would be used, I guess the A/C guys may have just twisted it up for safety. That must be the missing piece, I had tested both blacks to the one black (assuming the white was was wrapped up as it was not used).

And yes, the motor has some kind of arm attached to it w/ a spring.

the two wires are your 120 volt AC lines from the motor..

in your case, you can connect the black wires from the motor to the white and black wire that is capped off..

the green wire from the motor is the ground which is connected to the bare wire you see..

P.S. since there is a wire nut on the black wire, this tells me it could be alive or at some point may come alive... I would first kill the circuit that supplies that before attaching the last black lead from the motor to that one.

Also, this appears to be a single direction motor, this tells me that the shutter drive must not have a stop on it or it just keeps going around and around.. Most likely has an eccentric wheel or a wheel with an offset swing arm on it.

Jamie

When you say the white wire was wrapped, is it wrapped with black tape? If so it is probably a hot from the switch.

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Sorry, I should have been more precise. The white wire was not stripped, w as not in a wire nut, and was coiled up whereas the other 2 wires were stra ight (for lack of a better term). In other words, it looked like it wasn't being used, or this was done to prevent a short or something, although I w ould have thought having the dangling black and bare would be just as bad.

Back again for some more abuse.

I'm building a 12V battery charger that will be controlled by a small low-power microcontroller. I've not yet hooked up the microcontroller, but most of the code is written and I'm trying to finalize the charger electronics before I hook it up.

The circuit is very simple. An 18V 2A transformer, a bridge rectifier, and filter capacitor feeds a main power rail. A 5V regulator produces a few mA for the microcontroller, which I won't show here. The charger is more or less as follows, though I will leave out the resistor/divider taps which hook up to the ADC channels on the micro.

+18VDC ---------------------------+ Q1 c e | D1 R1 -----\_/--------->|----\/\/\--------+12(batt) b| | +------+ | | | +--+----------+ / Q2 e\_/c | R1 \ |b | / | e |c Q3 \ +--\/\/\------\_/ | R2 |b | | R3 SW1 LED1 \_/ +--\/\/\-- \-- +5V --- | | GND --------------+------------------------------------ GND(batt)

Q1 - MJE3055 D1 - 1N4004 R1 - .5 5W

Q2 - BC557 R2 - 200K

Q3 - 2N2222 R3 - 1K

The microcontroller will strobe R3 with PCM at about 488HZ with a duty cycle dependant on the charge profile. R1 is the sense resistor and permits measuring instantaneous charge current. I've got the battery attached and can watch the voltage rise (and settle) as I manually engage a switch attached as shown. The battery voltage as it came from Wallmart was about 12.7V. Charge current with this circuit is 1.4A at this point in its charge cycle. The heat-sink gets rather warm, but it isn't all that big and I'm going to target 3 or 4A as the peak charge current so I'll probably substitute a TO-3 package with a much beefier heat-sink when I put the project in an enclosure.

So far, so good. The output of Q1 shows .6V ripple. Attaching my scope to the base of Q1 shows an idle (SW off) voltage of 16mV and a

120Hz signal with a 70mVpp with a duty cycle of 17%. I'm not exactly sure where this signal is coming from, although its frequency suggests a causal relationship with the AC mains. There does not appear to be any ripple on the 5V rail, but my scope isn't good enough to really zoom in on it.

The other side of the coin is that the Q2/Q3 network seems to be rather sensitive. When I pass my hand over the breadboard the distortion described above doubles and I can get an amplitude of 1V on that distortion by standing up suddenly while sitting in front of the idle circuit. It is difficult to say what is happening because I can double the distortion by attaching the scope to a wall-wart USB charger, and I know I haven't yet calibrated the scope all that well either. (Scope shows 4.5V from the 5V regulator.) But the fact that I can affect the circuit just by moving things in the general vicinity is, um, rather shocking.

Besides installing the circuit in a metal case, are there any easy solutions to fix that 16mV idle voltage? Should I just change the BC557 to a 2n2222 and work out how many of what kind of resistors I need to supply the 3055 with the mA it needs to dump several amps into the battery? I like this version because it is easy to set up and has a low part count, but I'd really like to get rid of the noise and the sensitivity to movement.

Regards,

Uncle Steve

--
There should be a special word in the English language to identify 
people who create problems and then turn around and offer up their own 
tailor-made bogus non-solutions designed to completely avoid the root 
causes of the situation under consideration.  'Traitor' might be a 
good choice, but lacks the requisite specificity.  One of the problems 
with contemporary English is it lacks many such words that would 
otherwise categorically identify certain kinds of person, place, or 
thing -- making it difficult or impossible to think analytically about 
such objects.  These shortcomings of the English lexicon are 
representative of Orwellian linguistics at work in the real world.

Ah, sorry. R1 immediately above is 2.2K and it's the other R1 that is .5 ohms.

Regards,

Uncle Steve

-- There should be a special word in the English language to identify people who create problems and then turn around and offer up their own tailor-made bogus non-solutions designed to completely avoid the root causes of the situation under consideration. 'Traitor' might be a good choice, but lacks the requisite specificity. One of the problems with contemporary English is it lacks many such words that would otherwise categorically identify certain kinds of person, place, or thing -- making it difficult or impossible to think analytically about such objects. These shortcomings of the English lexicon are representative of Orwellian linguistics at work in the real world.

Start a new thread! This isn't even remotely related to fan motors!

--
My liberal friends think I'm a conservative kook. 
My conservative friends think I'm a liberal kook. 
Why am I not happy that they have found common ground? 

Tim Wescott, Communications, Control, Circuits & Software 
http://www.wescottdesign.com

Sorry. My newsreader crashes when I 'post' so I have to reply to something and then delete the references header, which I forgot to do in this case. What happens next is dependant on the newsreader you use.

Regards,

Uncle Steve

--
There should be a special word in the English language to identify 
people who create problems and then turn around and offer up their own 
tailor-made bogus non-solutions designed to completely avoid the root 
causes of the situation under consideration.  'Traitor' might be a 
good choice, but lacks the requisite specificity.  One of the problems 
with contemporary English is it lacks many such words that would 
otherwise categorically identify certain kinds of person, place, or 
thing -- making it difficult or impossible to think analytically about 
such objects.  These shortcomings of the English lexicon are 
representative of Orwellian linguistics at work in the real world.

R4 \ |b |

R4 - 2k

As suggested, I moved this out of the existing thread. It was an mistake that I did not remove the references header.

At any rate, I set up a separate pair of 2n2222, 10K resistor, and BC557 similar to the input stage above as well as a LED. Then I connected a small spool of insulated wire to the base of the 2n2222 and then let it out a couple of feet until the LED stayed onish without my hands being near the device.

The result is a strong 6-7MHz signal for a bunch of cycles and then some dead time. It looks like there could be some FM in there, and on the high part of the cycle there appears to be an additional small signal, but I can't resolve any detail with my equipment.

If I hold the spool in my hand the amount of on time changes considerably depending how much of my hand is in contact with the plastic and insulation. With palm open, there is one rise/fall cycle at about 6.5MHz when my hand is about 6in from the wire. As my hand gets closer, a second peak appears and so on until there is a train of several dozen cycles at or near the measured frequency.

Any idea what the hell that signal might be?

Regards,

Uncle Steve

--
There should be a special word in the English language to identify 
people who create problems and then turn around and offer up their own 
tailor-made bogus non-solutions designed to completely avoid the root 
causes of the situation under consideration.  'Traitor' might be a 
good choice, but lacks the requisite specificity.  One of the problems 
with contemporary English is it lacks many such words that would 
otherwise categorically identify certain kinds of person, place, or 
thing -- making it difficult or impossible to think analytically about 
such objects.  These shortcomings of the English lexicon are 
representative of Orwellian linguistics at work in the real world.

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 D1     R1

/\/\--------+12(batt)

-----+

      |        |      e  |c Q3

-\_/

        |b          |   R3     SW1       +--\/\/\-- \-- +5V

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ttdesign.com- Hide quoted text -

Yes a new thread is in order. The middle of the circuit is weird. (at least to me.) Your moving hand thing is a sure sign of electrostatic pickup.

George H.

I'm not making sense of your schematic. If Q2 is a PNP it should have its emitter to +18V and its collector to the base of Q1. (Q1 should have its collector _connected_!!). Q3 is configured to deliver current to the base of Q2, but it needs to pull current -- ?!?!?!?!

Could you be showing the emitters and collectors of Q2 and Q3 reversed?

If it's doing anything at all (which presumably it is) then amongst your various transistors you have tons of uncontrolled gain, so it's not surprising that its oscillating or doing other weird stuff.

What's your goal? A charge current that's proportional to the voltage at the SW1 end of R3?

I'd have to think about how to take that collection of transistors and make a stable circuit out of it, but if you're really building to that schematic then I suspect that you need to make some changes!

Note that if you're charging a lead-acid battery (gel or flood) the ideal charge profile is to limit both voltage and current. Voltage is limited to some magic number (which I can never remember -- look it up), and current is limited either by the charger's capabilities or the battery's. When the charge of the battery is low it accepts charge at the constant current, but then as it charges you must drop the current to hold the voltage constant.

--
My liberal friends think I'm a conservative kook. 
My conservative friends think I'm a liberal kook. 
Why am I not happy that they have found common ground? 

Tim Wescott, Communications, Control, Circuits & Software 
http://www.wescottdesign.com

I started doing that, but the path I went down is superficially similar to Larry Wall's story and I fear it will be a while yet before I have running code.

Regards,

Uncle Steve

-- There should be a special word in the English language to identify people who create problems and then turn around and offer up their own tailor-made bogus non-solutions designed to completely avoid the root causes of the situation under consideration. 'Traitor' might be a good choice, but lacks the requisite specificity. One of the problems with contemporary English is it lacks many such words that would otherwise categorically identify certain kinds of person, place, or thing -- making it difficult or impossible to think analytically about such objects. These shortcomings of the English lexicon are representative of Orwellian linguistics at work in the real world.

I don't think so. The arrangement is described as a Sziklai Pair, and is described at the following URL:

SW1 is a stand in for the TTL level output from a microcontroller pin and will operate at 488Hz PWM as described above.

The oscillation showing up at the base of Q1 may be the result of some sort of capacitance issue with Q2/Q3. I fiddled with a few small ceramic capacitors in a naive fashion, but I did not accomplish anything other than destroying a 2n2222. I simply haven't internalized enough information about how these things operate to figure out what I should do to eliminate the distortion.

I understand that. The preliminary figures I have suggest that the charge voltage should be 13.8V and the float voltage 13.5V.

The current strategy I'm working on will limit the average current over time with PWM, measuring instantaneous current when Q1 is on to drive a feedback loop to set PWM duty-cycle. I'll be reading supply voltage, and voltage at either side of the .5 Ohm sense resister at various times throughout the PWM cycle. The software will do ADC at about 125KHz so there's lots of room to average things nicely. I assume there's no real problem with allowing current to spike at short intervals if the battery naturally wants more amps than my PS will supply on a continual basis. I may be wrong, and it may be a simple matter to install a load resistor with the sense resistor. I'm still in larval stage so this stuff is still a little mysterious.

Regards,

Uncle Steve

--
There should be a special word in the English language to identify 
people who create problems and then turn around and offer up their own 
tailor-made bogus non-solutions designed to completely avoid the root 
causes of the situation under consideration.  'Traitor' might be a 
good choice, but lacks the requisite specificity.  One of the problems 
with contemporary English is it lacks many such words that would 
otherwise categorically identify certain kinds of person, place, or 
thing -- making it difficult or impossible to think analytically about 
such objects.  These shortcomings of the English lexicon are 
representative of Orwellian linguistics at work in the real world.

The white wire is the other power wire you need to connect one of the black wires on the motor to.

THe only reason it is not protected via a wire nut is because that wire ends up being the low side of the circuit, which should be near

0 volts. But don't take any chances to think it is just a ground wire, just because it does connect to the ground back to subpanel.

Jamie

Kind of curious how that LED is handling the current when you only have a .5 ohm R feeding it? Even if that bias on the base was current limited, you'll be suppressing the voltage to the battery no more than what the LED forward voltage is plus the 0.650 drop from the base and emitter.

As for the noise you maybe seeing, it's possible you are picking that up because of the wires hanging all over the place. You most likely have lights with ballast circuits in them, they can generate noise, putting your hands over the circuit is just using your body to convey the noise closer.

bjts are grate for acting as R.F. detectors...

Jamie

Look again -- I don't think you're there. One huge thing to note: your Sziklai pair is only going to work well when it's all the way off or all the way on -- PWM is good, but don't expect it to work in anything resembling a linear fashion.

+18V Q1 ___ battery o---------------- ------|___|-----o \ ^ --- | | .-. | | | | '-' | | |< .---| Q2 | |\ | | | | | | PWM |/ | o---------| Q3 | |> | | | | | === === GND GND (created by AACircuit v1.28.6 beta 04/19/05

--
My liberal friends think I'm a conservative kook. 
My conservative friends think I'm a liberal kook. 
Why am I not happy that they have found common ground? 

Tim Wescott, Communications, Control, Circuits & Software 
http://www.wescottdesign.com

I will consider that, but note that Q1 is NPN. What you propose suggests I was counting on current-limiting to occur in the wrong place.

The software feedback loop ought to allow the ideal pulse width to 'fly' automatically at the correct setting, assuming the ADC readings are reasonably accurate. Theoretically, I should also be able to detect collapse (?) of the transformer flux if the current draw grows too large, which would be a nice bonus.

Regards,

Uncle Steve

--
There should be a special word in the English language to identify 
people who create problems and then turn around and offer up their own 
tailor-made bogus non-solutions designed to completely avoid the root 
causes of the situation under consideration.  'Traitor' might be a 
good choice, but lacks the requisite specificity.  One of the problems 
with contemporary English is it lacks many such words that would 
otherwise categorically identify certain kinds of person, place, or 
thing -- making it difficult or impossible to think analytically about 
such objects.  These shortcomings of the English lexicon are 
representative of Orwellian linguistics at work in the real world.

[snip]

How is the charger "controlled"?

Do you mean that the output CURRENT from the charger will be a function of the "duty-cycle" from the micro-controller?

Or do you have some other algorithm in mind? ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
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