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ngdbud
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Lord Garth
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 Posted:
Sun Dec 11, 2005 9:35 am Post subject:
Re: Transistor question |
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"ngdbud" <ngdbud@hotmail.com> wrote in message
news:1134287817.718059.155520@o13g2000cwo.googlegroups.com...
The schematic is correct...
A positive voltage on the base will cause current to flow from the base to
the emitter
and into ground. When this happens, a large current will also flow from the
12 volt
supply through the coil and transistor and into ground.
Think about the circuit using conventional current, from + to - rather than
electron
flow.
PS. heat sink that 2N3055 very well! |
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Pooh Bear
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Sun Dec 11, 2005 4:35 pm Post subject:
Re: Transistor question |
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ngdbud wrote:
Yes.
The collector is indeed positive wrt the emitter. See that " + " before the 12V ?
It would be conventional practice to say that the emitter is connected to ground and the positive suply
is connected to the collector load btw.
Graham
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Paul Burridge
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Sun Dec 11, 2005 5:07 pm Post subject:
Re: Transistor question |
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On 10 Dec 2005 23:56:57 -0800, "ngdbud" <ngdbud@hotmail.com> wrote:
The little arrow in the symbol always points in the direction of
*conventional current flow* which is (historically) from positive to
negative. This is the opposite of electron flow, which is what we are
*really* concerned with. So the arrows in these symbols basically
point the 'wrong' way.
--
"What is now proved was once only imagin'd" - William Blake |
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John Popelish
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| Posted:
Mon Dec 12, 2005 1:35 am Post subject:
Re: Transistor question |
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ngdbud wrote:
| Quote: | Thnks, I have a small peltier cooler and a heat sink should use both?
P.S. the peltier is just a small 1.5v one, should i use a voltage
divider or is there some better way to divide the voltage by eight?
Since a peltier is run on current, a series resistor is the simplest |
way to regulate the current. But you will be wasting 7/8ths of the
power that way. A more efficient way (but a more complicated one)
would be to use a buck switching regulator, that converts power to
power. So, for example 8 volts @ .1 amp (.8 watt) in, would become
1.5 volts @ 5.333 amps out, minus switch and inductor losses. Losses
might be 10 to 20% of the output power. There are some integrated
circuits that do most of the work for this sort of thing. You just
add and inductor, a couple capacitors, and, perhaps a Schottky diode.
See simple switchers under switching regulators at:
http://www.national.com/catalog/0,4567,74,00.html
Here is a tutorial on buck switching regulators:
http://www.national.com/appinfo/power/files/f5.pdf |
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ngdbud
Guest
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| Posted:
Mon Dec 12, 2005 1:35 am Post subject:
Re: Transistor question |
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Thnks, I have a small peltier cooler and a heat sink should use both?
P.S. the peltier is just a small 1.5v one, should i use a voltage
divider or is there some better way to divide the voltage by eight? |
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neon
Joined: 25 Feb 2006
Posts: 579
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Sat Feb 25, 2006 2:51 pm Post subject:
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| the answer to your qestion which way current will flow usualy pos to neg. and while electron go one way the holes go the other way. now thru this device 2n3055 if saturated current can flow both ways. turn this guy around and see. |
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