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Topic: Basic Transistor Question? (Read 3382 times) previous topic - next topic

sparkylabs

well yes some people pretend they can design airplanes and others believe them  :P

yes it's mid morning here I'll try and not spoil my day with thoughts of crashing airplanes  :~
My shop: www.sparkylabs.co.uk/shop

SamuelCB

So... What type of diode am I using, and where's it going?

Haha!  :smiley-red:

sparkylabs

1N4007 or similar. if you are doing PWM above 500Hz I'd suggest a schotky that can handle a few hundred mA, where you put it ? where ever you like just make sure it's in back to front or in one case the fan will never turn off and in the other you will short your transistor out.
My shop: www.sparkylabs.co.uk/shop

1oldfox

"Why I hate forums!!!" (see above)

To get back to the issue of this thread:

Look at it this way. The coil of the fan can be likened to the spark coil of any modern internal combustion engine. Anyone care to grab a spark plug wire with the motor running? I didn't think so.

Static electricity *will* blow a hole in the glass insulation inside a CMOS device. Unbelievable? Try going out to the desert with lowest humidity, wearing your nylon running clothes, and run for 100yds. Now pick up a known good CMOS device by the leads. After you feel the shock (maybe) put the device in the circuit and see if it still works. Or... Just skoot your feet across a carpet, wearing your fuzzy kitty slippers. Same thing.

The old 3 finger rule still applies. (MFC = motion, flux direction, current direction)
The inductive kick *is* in reverse *polarity* to the current that expanded the field in the first place.
That's because the *motion* direction changed by 180 degrees.
The coil starts looking like a source. (e.g. high voltage battery)

Well, that's my 2 cents worth. Now back to the kiddie playground.

sparkylabs

Care to tell us "where to stick it" ?  :P
My shop: www.sparkylabs.co.uk/shop

tack

The point of the snubber diode is to contain that back EMF to a closed loop containing the coil and diode. It's not shunting anything to ground. The field collapses and generates a high negative spike, dependent on field strength and the speed it collapses. The diode contains this to that mini circuit and the energy is dissipated as the circulating current and respective magnetic field decays. The rest of the circuit is thus protected from that spike.

sparkylabs


The point of the snubber diode is to contain that back EMF to a closed loop containing the coil and diode. It's not shunting anything to ground. The field collapses and generates a high negative spike, dependent on field strength and the speed it collapses. The diode contains this to that mini circuit and the energy is dissipated as the circulating current and respective magnetic field decays. The rest of the circuit is thus protected from that spike.


Thank you, now go ask the "aeroplane designer" which planes he meddled with and make sure you don't fly on them  ;)
My shop: www.sparkylabs.co.uk/shop

1oldfox

Samuel, did you get the answer you were looking for?
And sparky, why the rude comment? I was on your side.
-oldfox-

sparkylabs


Samuel, did you get the answer you were looking for?
And sparky, why the rude comment? I was on your side.
-oldfox-



Err I was trying to humorously capitalize on all of the arguments about should it go across the transistor or the load, wasn't meant as rude
My shop: www.sparkylabs.co.uk/shop

1oldfox

sparky, acceptable. No harm.

Retroplayer

#40
Mar 28, 2013, 10:40 pm Last Edit: Mar 28, 2013, 10:50 pm by Retroplayer Reason: 1

Thank you, now go ask the "aeroplane designer" which planes he meddled with and make sure you don't fly on them  ;)


Cute... not gonna bite, though. ;) Just wanted you to know I seen it. lol

BTW, I should make it clear that I don't actually *disagree* with you. It just really makes no difference either way except in some imaginary chicken little land. I just found your little diatribe quite humorous, that's all. I had this delightful picture of you in a superhero outfit running around with an oscilloscope probe. It was very enjoyable. We'll just chalk you up as 'passionate.' I'd love to draw it up if you'd like it for your avatar.

P.S. I really am an electrical engineer for an aerospace company. I suppose that is less funny given the current issues with batteries catching fire (not my product, btw.) Hmm, I wonder if they put the diode across the transistor.

You will be happy to know that I am not in charge of designing anything that would require a snubber diode. I deal with almost exclusively embedded and digital design (and some audio stuff.) The guys in the floods, taped up glasses, and nasaly voices design the power supplies and actuator controls.

So, not a programmer. In fact, I suck at programming aside from sucking at flyback diodes, apparently. ;) And the programmers probably think I suck at digital and embedded design and I think the programmers suck at programming my hardware. Oh, my...

Seriously, Sparky... no harm was intended. Just having a bit of fun.

(Ok, I guess I nibbled, didn't I?)

sparkylabs



Thank you, now go ask the "aeroplane designer" which planes he meddled with and make sure you don't fly on them  ;)


Cute... not gonna bite, though. ;) Just wanted you to know I seen it. lol

BTW, I should make it clear that I don't actually *disagree* with you. It just really makes no difference either way except in some imaginary chicken little land. I just found your little diatribe quite humorous, that's all. I had this delightful picture of you in a superhero outfit running around with an oscilloscope probe. It was very enjoyable. We'll just chalk you up as 'passionate.' I'd love to draw it up if you'd like it for your avatar.

P.S. I really am an electrical engineer for an aerospace company. I suppose that is less funny given the current issues with batteries catching fire (not my product, btw.) Hmm, I wonder if they put the diode across the transistor.

You will be happy to know that I am not in charge of designing anything that would require a snubber diode. I deal with almost exclusively embedded and digital design (and some audio stuff.) The guys in the floods, taped up glasses, and nasaly voices design the power supplies and actuator controls.

So, not a programmer. In fact, I suck at programming aside from sucking at flyback diodes, apparently. ;) And the programmers probably think I suck at digital and embedded design and I think the programmers suck at programming my hardware. Oh, my...

Seriously, Sparky... no harm was intended. Just having a bit of fun.

(Ok, I guess I nibbled, didn't I?)


your sure welcome to draw me in said fashion and we'll see what you think i look like ;) I'm glad the fantasy gave you so much pleasure, I mean whatever floats your boat right ?  :D

OK so I feel more able to fly again now  ]:D thank you for the reassurance. All taken in fun
My shop: www.sparkylabs.co.uk/shop

Retroplayer


your sure welcome to draw me in said fashion and we'll see what you think i look like ;)


You're one of the flood wearing, taped glasses, nasal voicers, aren't you? lol

sparkylabs

Well my day job is 3D CAd modelling (Technical cartoonist). I do my electronics at home where I'll start on an orderly bench and end up in a mess. Work let me do some electronics but as soon as they realized it wasn't a grown ups version of lego and required development and equipment to prototype with they gave up.
My shop: www.sparkylabs.co.uk/shop

mjkzz

Use N-channel MOSFET BS170 and save yourself trouble.
Search for "mjkzz" on eBay :-)

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