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 Posted: Mar 21, 2012 - 03:37 PM |
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Joined: Feb 02, 2012
Posts: 15
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Before switch:
A---B
C---D
After switch:
A---D
C---B
It can be implemented by 2 common switches. But I need only one so user can operate it easily.
OR I need a IC to implement this?
Thanks,
Fan |
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Posted: Mar 21, 2012 - 03:45 PM |
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Joined: Feb 12, 2005
Posts: 16329
Location: Wormshill, England
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This is a regular DPDT switch.
You could make it with wafers but this would be bulky.
Or design a suitable wafer yourself.
You could also do it with regular gates or in software.
It all depends on what you want to switch.
David. |
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Posted: Mar 21, 2012 - 03:46 PM |
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Joined: Dec 11, 2007
Posts: 6856
Location: Cleveland, OH
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Well,
This looks like a simple DPDT toggle switch application. Double Pole Double Throw
Feed A and C into the two central terminals.
Flip the switch left and A and C go to B and D.
On the other set of terminals you have B and D flipped, so if the switch is clodsed in that direction A nd C now connect to D and B.
So a single switch can be used, but internally it switches two poles in each of two directions.
JC
Cross posted with David... |
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Posted: Mar 21, 2012 - 04:33 PM |
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Joined: Nov 22, 2002
Posts: 12055
Location: Tangent, OR, USA
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Is this power or small signal? Analog or logic?
Jim |
_________________
Jim Wagner
Oregon Research Electronics, Consulting Div.
Tangent, OR, USA
"The only thing standing between us and victory is defeat" P.G.Wodhouse in Wooster & Jeeves series
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Posted: Mar 21, 2012 - 04:34 PM |
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Joined: Feb 02, 2012
Posts: 15
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Thanks for quick response. I search the "DPDT" and it should fill my requirement.
But the size of one DPDT looks a little big for SMD board... Anyway It is not a big problem.
And @David, what't the "regular gate" and "software way", can you give more details? I am quite new guy:)
Thanks,
Fan |
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Posted: Mar 21, 2012 - 04:36 PM |
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Joined: Feb 02, 2012
Posts: 15
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ka7ehk wrote:
Is this power or small signal? Analog or logic?
Jim
it carry PWM signal, should be logic. |
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Posted: Mar 21, 2012 - 05:46 PM |
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Joined: Nov 02, 2009
Posts: 3239
Location: Zelenograd, Russia
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Posted: Mar 21, 2012 - 06:30 PM |
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Joined: Nov 22, 2002
Posts: 12055
Location: Tangent, OR, USA
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DPDT switches come in a huge range of sizes. At one extreme, big ones will handle kilowatts. At the other end, little ones will handle microwatts. Methinks you need a little one.
Jim |
_________________
Jim Wagner
Oregon Research Electronics, Consulting Div.
Tangent, OR, USA
"The only thing standing between us and victory is defeat" P.G.Wodhouse in Wooster & Jeeves series
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Posted: Mar 22, 2012 - 06:41 AM |
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Joined: May 02, 2007
Posts: 3022
Location: Nieuwegein, Netherlands
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make sure you also select the right variant.
make before break, or break before make.
That might keep you from getting nasty surprises....
and think about what will happen during the switching period, wich in your eyes is short, but for your processor might take a long time with a lot of unforseen issues that then appear. |
_________________
1)Datasheet and application notes checked?
2)tutorial forum
3)Newbie start here
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Posted: Mar 22, 2012 - 03:27 PM |
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Joined: Feb 02, 2012
Posts: 15
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Posted: Mar 22, 2012 - 03:48 PM |
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Joined: Nov 22, 2002
Posts: 12055
Location: Tangent, OR, USA
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If it is really a logic signal, then why not CD4051, 74C4051, 74HC4051, or other variants. Readily available. Low cost.
Jim |
_________________
Jim Wagner
Oregon Research Electronics, Consulting Div.
Tangent, OR, USA
"The only thing standing between us and victory is defeat" P.G.Wodhouse in Wooster & Jeeves series
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Posted: Mar 22, 2012 - 04:08 PM |
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Joined: Feb 12, 2005
Posts: 16329
Location: Wormshill, England
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Shirley, you can use your existing AVR PORT pins.
You can either send PWM out on a different OC pin or simply gate it with other GPIO pins.
You can add extra chips if you like, but this seems untidy to me.
David. |
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Posted: Mar 24, 2012 - 09:16 AM |
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Joined: Feb 02, 2012
Posts: 15
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ka7ehk wrote:
If it is really a logic signal, then why not CD4051, 74C4051, 74HC4051, or other variants. Readily available. Low cost.
Jim
I checked the page http://ics.nxp.com/products/hc/switches/, looks 4051 is just a SP4T. So If I want a dpdt, I need a 3*spdt chip like 74hct4053, is it correct?
I am wondering why there are not DPDT chip. Maybe they want you to use 2*SPDT to build a DPDT. |
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Posted: Mar 24, 2012 - 09:18 AM |
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Joined: Feb 02, 2012
Posts: 15
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david.prentice wrote:
Shirley, you can use your existing AVR PORT pins.
You can either send PWM out on a different OC pin or simply gate it with other GPIO pins.
You can add extra chips if you like, but this seems untidy to me.
David.
For my application, all PWM ports are used. But what's your meaning of "gate it"? |
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Posted: Mar 24, 2012 - 09:24 AM |
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Joined: Feb 12, 2005
Posts: 16329
Location: Wormshill, England
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Yes. Any chip is going to be configured as the 'most useful'. e.g. SPDT.
Why not say exactly what you want to do?
Describe in English.
I doubt that you need any external chips at all.
David. |
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Posted: Mar 24, 2012 - 09:44 AM |
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Joined: Feb 02, 2012
Posts: 15
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I am building a PC Fan controller. I use PWM to control speed of fan. It is simple. But fan has 2 kinds: 3pin and 4pin. For 3pin, I use PWM to driver a voltage bulk to control voltage of fan. For 4pin fan, PWM signal drivers fan directly.
So I want to one PWM signal to driver fan whatever it is 3pin or 4pin. Of course you need software configuration.
Now my plan is to use 2 74HCT4053(I need a TTL enabled one?). 3*SPDT * 2 = 3 DPDT. And use a avr chip to drive the 2 4053(need 3 ports of avr chip). Does my solution work?
Thanks,
Fan |
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Posted: Mar 24, 2012 - 10:00 AM |
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Joined: Feb 12, 2005
Posts: 16329
Location: Wormshill, England
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I presume you are using a Tiny25 or similar 8-pin AVR.
Adding two 4053 chips looks overkill.
I do not know what a 'voltage bulk' is.
I presume it is a 'charge pump' that creates a variable DC voltage.
You want a 3-pin fan to connect to one header, and the 4-pin fan to connect to a different header. Or perhaps the 3-pin just uses 3 of the 4 pins on a single 4-pin header.
Post your schematic. It makes life a lot easier.
David. |
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Posted: Mar 24, 2012 - 01:48 PM |
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Joined: Feb 02, 2012
Posts: 15
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Yes David, I want 3-pin use 3 of 4 pin on single 4-pin header. So the header can be reused.
And I use a "buck converter": UDN2981. This chip also need PWM to drive it.
Before switching:
OCRB1 pwm---->4pin of fan header
PB1 HIGH--->buck convert--->12v ---->3-pin of fan header
after switching(for 3pin fan):
OCRB1 pwm---->buck convert--> (0v~12v)-->3-pin of fan header
PB1 --> N/A
I hadn't draw schematic for this approach. |
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Posted: Mar 26, 2012 - 12:50 AM |
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Joined: Mar 18, 2012
Posts: 8
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Switching a couple of SPDT? Consider:
http://www.ti.com/lit/ds/symlink/sn74lvc1g3157.pdf
Sub $1 parts. SOT23-6 package. Smaller that 4051's.
Plugging a 3 ping connector onto a 4 pin header may lead to many incorrect connections. The extra circuity to protect against incorrect connections may justify the second header anyway? |
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