Troubleshooting a fan speed controller UPDATE

Thread Starter

Tonyr1084

Joined Sep 24, 2015
6,000
for that matter to the IGBT he is so in love with.
What'd I do to you? The PCB has rather thin wiring. There's a picture of it in post #12. Though I didn't take a picture of the dimmer, it's in a plastic housing with no room for a heatsink. The ONLY sinking of heat that has been provided is the riveted mount to the "Sink" pin of the dimmer.

Overkill is better than underkill. Under do it and I could be revisiting this thread. And the stuff I have is stuff I've had for close to 15 years. Haven't used it for anything else, so what's the harm in using it now? I COULD just throw it away and build the circuit the way you are convinced it should be done. But then what happens if it doesn't hold up? As has been said, the blower (eventually) will run with near no restriction, so the draw will be really close to what I measured. That's a lot of wattage moving through a FET with no heatsink. Yeah, it could be mounted externally, but then I'd be concerned with heat soak. Heat rises in the box and can't be dissipated without a fan or some unknown number (and size of) holes. The IGBT is just as easy to use as it is to disassemble and modify a working dimmer. But should something go wrong - it's likely going to be the Iggy. {edited from iggy to Iggy for Wolframore}

By now it should be clear I don't know as much as some of you long timers. My best experience can be described as a hobbiest and experimenter. I've built logic circuits that have worked - for a while. I've built things that are still working. I've also built things that never worked, and have never been able to figure them out so I abandoned them.

I once built a logic circuit for the car. You start the car, push a button then turn the key off and the engine continues to run. Step on the brake pedal and the circuit shuts off. If the key is not in the ignition and not turned to the run position then you can't steal the car. But if you put the key in the engine is already warm and you can then turn the heater on and have instant heat. But that circuit didn't last very long. So I rebuilt it using diode and relay logic. The circuit worked great. So there have been some accomplishments. Many more failures. And many more opportunities to learn.

Some people like mint ice cream, some don't. Doesn't mean mint ice cream is not good, it's just not the choice of everyone. Using the IGBT is my way of saying I don't care for the idea of modifying the dimmer or risking blowing it up.

Am I "IN LOVE" with the idea? No, not really. But it IS convenient. It gives me a sense of security. Even if it's overkill.
 
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Wolframore

Joined Jan 21, 2019
2,283
that's Iggy to you... iggy pops.... shaken not stirred.

Tony this isn't an attack, you are missing some issues with the IGBT in this situation and we keep bringing them up but you are married to the idea. Just do it... if it doesn't work then maybe we can continue.
 

MisterBill2

Joined Jan 23, 2018
8,808
At present, I've put together a perf board circuit that fits into a small box. The initial point of this build is to prove out a working circuit. But I'm likely going to have issues with heat. I probably will have to rethink the enclosure for the addition of heat-sinking abilities. Have scrounged several different heatsinks from computers and other stuff. The IGBT does not have a mounting hole but rather it's a clip design for mounting; so perhaps one of those scrounged heatsinks will do. If not - a scavenged LED lamp with aluminum housing and heatsink fins can probably be made to work well.

Over the four years I've been here I've learned a few things. Thank you all for that. Even the arguments and disagreements is a source of greater wisdom and critical thinking. This has probably been the best year so far for learning new things, and everyone's input has been greatly appreciated (least say the very few that I've put on the ignore list). So Happy New Year wherever you are. Today is the warm before the storm so I'll probably be busy pulling down Christmas decorations from on the house. My sleigh and reindeer with the frog driving - that's got to come down. Expecting 4 to 10 inches tomorrow (boy I wanted to say "next year").

Looking forward to an even better year; and I hope I've made a similar contribution to others. Again, thank you all. And Happy New Year.
We went from almost 50 degrees, sunny but windy to 30 degrees and snow falling all night. The trade-off between not dealing with snow versus not skiing is a really tough call.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
6,000
@Chris65536 I sure hope not. I don't see why it would. hard on and should be pretty hard off as well. But I'll be sure to check it when testing with the lamp. Just to be sure I'll also check the wave form when the motor is on the line.
 

shortbus

Joined Sep 30, 2009
8,594
What'd I do to you? The PCB has rather thin wiring. There's a picture of it in post #12. Though I didn't take a picture of the dimmer, it's in a plastic housing with no room for a heatsink. The ONLY sinking of heat that has been provided is the riveted mount to the "Sink" pin of the dimmer.
You did nothing to me. I am just trying to help you.
Tell me what the difference is between trying to make an IGBT work out side of your PWM module and putting the Mosfet outside? The PWM would work to do what you want, IF it was sourcing instead of sinking. You don't seem to understand, and I've tried every way I can think of to explain it, that if you have a gate voltage on the IGBT and try to sink it to turn it off it won't happen. as long as you still have the gate wired the way you have it shown the gate will be on. To turn it off you need to break the connection to the voltage that is now (as shown in your schematic) to be available to the gate. Like I said in another thread an optoisolator might work but...


You say, "The ONLY sinking of heat that has been provided is the riveted mount to the "Sink" pin of the dimmer." but I said to take the mosfet outside of the module and mount it to what ever your IGBT will be mounted to. The mosfet and IGBT use the same driver type to make them work so the only change is not using an IGBT, but they also need the same heat sinking..But you are getting so mad at me and listening to some one else, that you just pass over what I'm saying. What you have tried so far isn't working, you've proved that, but you won't even consider anything else because your new friend has convinced you he knows what he's doing. I get it.

I'll leave you out of my responses now, but will still respond to other members posting in this thread.
 

Chris65536

Joined Nov 11, 2019
270
that if you have a gate voltage on the IGBT and try to sink it to turn it off it won't happen. as long as you still have the gate wired the way you have it shown the gate will be on.
I don't understand this part. The positive voltage is through a resistor, and the MOSFET should easily pull the gate voltage down to zero. Why wouldn't the IGBT turn off in this scenario?
 

shortbus

Joined Sep 30, 2009
8,594
I don't understand this part. The positive voltage is through a resistor, and the MOSFET should easily pull the gate voltage down to zero. Why wouldn't the IGBT turn off in this scenario?
Why doesn't any one do it that way? I have my doubts, and so far he has proven it, that such a circuit is capable of completely turning the IGBT gate off. If it works there would be no need for a low side driver to be made. Look at the data sheets for low side drivers, they sink many times more than they source, to get the mosfet or IGBT to turn off, he is doing PWM, so it may almost be turned off when the next on pulse hits. That's why I say this.
 
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Thread Starter

Tonyr1084

Joined Sep 24, 2015
6,000
@shortbus - you're still my friend. And I haven't thrown you over for someone else. I still love you man! "J

Sorry if I'm being stubborn and pig headed. I can be that way. But I will consider your proposal. So far I'm not so far in this build that I can't change things up a bit. I've taken stock of my heat sinks and found my thermal compound, so it won't be a difficult thing to paste a MOSFET to the heatsink. As for the thin traces on the board - I suppose I can duplicate them outside the dimmer.

Are we still friends?
 

MisterBill2

Joined Jan 23, 2018
8,808
The reason that nobody in industry does things a certain way is usually because it costs more, if even only one cent. Especially in the auto and consumer junk industries, cutting costs is the primary aim, bar nothing else. So if adding another power device added two cents to the cost it would never be done.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
6,000
@shortbus has me thinking about modifications. Maybe I should remove the internal MOSFET and wire what was the controlling gate voltage to that FET and send it directly to my IGBT. Mount my IGBT to an aluminum housing, one I would have to construct. The bulk of the electronics will remain within the dimmer. Only external components would be a fuse to safeguard the dimmer, another for the Motor, the IGBT, the high current flyback diode and a controlling switch. It's not looking like it can be put into a plastic projects box. The changes are now under consideration. As I move forward I'll keep you all informed.

Looks like it's snowing again.
 

MisterBill2

Joined Jan 23, 2018
8,808
@shortbus has me thinking about modifications. Maybe I should remove the internal MOSFET and wire what was the controlling gate voltage to that FET and send it directly to my IGBT. Mount my IGBT to an aluminum housing, one I would have to construct. The bulk of the electronics will remain within the dimmer. Only external components would be a fuse to safeguard the dimmer, another for the Motor, the IGBT, the high current flyback diode and a controlling switch. It's not looking like it can be put into a plastic projects box. The changes are now under consideration. As I move forward I'll keep you all informed.

Looks like it's snowing again.
I suggest using the control module as it is, and understanding how it works. Wire it up with the IGBT and try it on a small 12 volt light. You will need a pull up resistor to turn on the IGBT, start with 220 ohms. That may not provide enough current but it is a safe value for starters.
Until you try it, most of the suggestions are guesses, some better than others. And as for modifying that controller, you may come up against unanticipated problems attempting to make changes. And since I don't think that you have a box of them, that could be the end of the project.
 

shortbus

Joined Sep 30, 2009
8,594
I suggest using the control module as it is, and understanding how it works. Wire it up with the IGBT and try it on a small 12 volt light. You will need a pull up resistor to turn on the IGBT,
As usual. Go back and read what he has done so far. See if that isn't what you just said and it isn't working.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
6,000
Feedback? OK, feedback.

The PWM Dimmer works. It's control output is a sink and not a source. It works. It dims an automotive lightbulb throughout the entire range. It pulses at about 385 Hz.

The IGBT: It works when the gate is tapped to positive. It lights up the auto lightbulb. As soon as the gate is disconnected from positive the lightbulb goes out. Just how fast? That I can't answer. But today I plan on adding the PNP transistor last drawn in circuit with an additional pulldown resistor to make sure the IGBT shuts off.

For those of you new to this thread - it's worth reading all the way through as you will see that these very questions have already been answered. As for the rest of the building and testing, you'll have to wait. I've been busy with family and the holidays. Things are settling down, but having to run the snowblower didn't speed anything up as far as this project. Life happens. Hobbies get done when they get done. And there's no hurry to get this up and running. It's winter and I'm not planning any fire pit tests anytime soon. But I can bench test with the light bulb. Please be patient. I'm not one of those guys who come here - ask a question - get an answer - and then never tell you the outcome of what I'm doing. That's not how I roll.
 

Wolframore

Joined Jan 21, 2019
2,283
A screenshot of the oscilloscope for the IGBT would be very informative. I'm sorry I know you did tests, I was hoping for more information so we can see what's going on. How much current is being passed and what's the drop on the IGBT... these are important values you will need to gauge how it will work with a motor.
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
6,000
Will see what I can do with my scope. It's old school. CRT and knobs. Not computer based; though I COULD hook up the Hantek, take a screen shot, transfer it to my Mac, edit it then upload the final picture.

Right now I'm going to build a spreadsheet with all the calculations on it so I can have a quick and reliable look at amps and calculate watts so I can decide what to use for a resistor. I only have a stock of quarter watt resistors, and if I go with 220Ω at 12 volts that'll require a 1 watt resistor. I'll have to scrounge my stock to find one - OR use at least 3 quarter watt resistors. (refer to last drawing) (post #71)
 

Thread Starter

Tonyr1084

Joined Sep 24, 2015
6,000
A little help please? I've found this 270Ω resistor (measured 271.8Ω) in an old LED Bulb (the kind you screw into your ceiling light fixture). Looks to me like it's definitely at least 1 watt, possibly 2 watts. Would like some confirmation please. CR2032 coin cell battery for size reference.

0.165" dia. max X (roughly) 0.450" long (body, not leads).

20200102AM.jpg
 
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Wolframore

Joined Jan 21, 2019
2,283
That sounds like 1 Watt... but there are some variations between manufacturers:

1577990373762.png

Here these are both 1/4 Watt but large differences in sizes... get used to working with mm

1577990446521.png
 
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