Pages: 1 2 [3] 4   Go Down
Author Topic: Basic Transistor Question?  (Read 3174 times)
0 Members and 1 Guest are viewing this topic.
Northants - UK
Offline Offline
Sr. Member
****
Karma: 1
Posts: 258
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

well yes some people pretend they can design airplanes and others believe them  smiley-razz

yes it's mid morning here I'll try and not spoil my day with thoughts of crashing airplanes  smiley-confuse
Logged


0
Offline Offline
Full Member
***
Karma: 0
Posts: 212
Arduino rocks
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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

Haha!  smiley-red
Logged

Northants - UK
Offline Offline
Sr. Member
****
Karma: 1
Posts: 258
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged


Offline Offline
Newbie
*
Karma: 0
Posts: 23
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

"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.
Logged

Northants - UK
Offline Offline
Sr. Member
****
Karma: 1
Posts: 258
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Care to tell us "where to stick it" ?  smiley-razz
Logged


UK
Offline Offline
God Member
*****
Karma: 17
Posts: 569
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged

Northants - UK
Offline Offline
Sr. Member
****
Karma: 1
Posts: 258
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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  smiley-wink
Logged


Offline Offline
Newbie
*
Karma: 0
Posts: 23
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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

Northants - UK
Offline Offline
Sr. Member
****
Karma: 1
Posts: 258
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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
Logged


Offline Offline
Newbie
*
Karma: 0
Posts: 23
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

sparky, acceptable. No harm.
Logged

Offline Offline
God Member
*****
Karma: 27
Posts: 829
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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

Cute... not gonna bite, though. smiley-wink 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. smiley-wink 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?)
« Last Edit: March 28, 2013, 04:50:08 pm by Retroplayer » Logged

Northants - UK
Offline Offline
Sr. Member
****
Karma: 1
Posts: 258
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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

Cute... not gonna bite, though. smiley-wink 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. smiley-wink 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 smiley-wink I'm glad the fantasy gave you so much pleasure, I mean whatever floats your boat right ?  smiley-grin

OK so I feel more able to fly again now  smiley-twist thank you for the reassurance. All taken in fun
Logged


Offline Offline
God Member
*****
Karma: 27
Posts: 829
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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

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

Northants - UK
Offline Offline
Sr. Member
****
Karma: 1
Posts: 258
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

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.
Logged


Offline Offline
Full Member
***
Karma: 1
Posts: 135
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Use N-channel MOSFET BS170 and save yourself trouble.
Logged

Search for "mjkzz" on eBay :-)

Pages: 1 2 [3] 4   Go Up
Jump to: