Maker Pro
Maker Pro

Momentary Switch to Toggle Fan.

I'm having a bit of trouble here. I am a sophomore Computer
Engineering student at Psu. I recently bought a new computer case,
and the front has an 80cm fan with LED's and what-not. The problem is
that it is very loud. To make matters worse, it runs on a four-pin
molex, and the speed isn't variable. Additionally, I share the room
with a roomate, and the lights are kinda bright, esp. when its dark.
The case is acrylic, and the side panels are screw-on, so I can't
even unplug it.

Now my Idea is to use the 'reset' button, which is useless with a
'power' button above it, to change the speed, as well as turn it off.

My plan is to us a binary-output counter (SN74LS163), and tie the
one's and two's places into a 2 to four DMUX (Say an SN74LS139A).
I'll then use the momentary switch(reset button) as the clock for the
counter. This will let me cycle between four different circuits:
Unmodified, 80%, 40%, and off.

Now implementing the logic is no problem. The issue I have is using
the 5v logic outputs to actually control the 12v fan. I looked into
Tri-State buffers, but even if I was able to find one that took 5 and
12 volt inputs, none have the necessary 150 mA capacity. Now I talked
to an EE buddy of mine and he suggested that I could use a few
transistors to switch it. Alas, transistors aren't one of my strong
points, and I dont know how to use them, or even what type to get. I
pretty much need to use a 5v, 20 mA max low/high signal to start/stop
a 12v current that may go up to 250mA, without frying any ICs, and can
last for at least two years of continuous use.

I tried searching the internet for a few hours, but couldn't find the
info I needed. I eventually found this group, and I'm hoping somebody
here can help.

Cheers.
 
G

Gibbo

Jan 1, 1970
0
I'm having a bit of trouble here. I am a sophomore Computer
Engineering student at Psu. I recently bought a new computer case,
and the front has an 80cm fan with LED's and what-not. The problem is
that it is very loud. To make matters worse, it runs on a four-pin
molex, and the speed isn't variable. Additionally, I share the room
with a roomate, and the lights are kinda bright, esp. when its dark.
The case is acrylic, and the side panels are screw-on, so I can't
even unplug it.

Now my Idea is to use the 'reset' button, which is useless with a
'power' button above it, to change the speed, as well as turn it off.

My plan is to us a binary-output counter (SN74LS163), and tie the
one's and two's places into a 2 to four DMUX (Say an SN74LS139A).
I'll then use the momentary switch(reset button) as the clock for the
counter. This will let me cycle between four different circuits:
Unmodified, 80%, 40%, and off.

Now implementing the logic is no problem. The issue I have is using
the 5v logic outputs to actually control the 12v fan. I looked into
Tri-State buffers, but even if I was able to find one that took 5 and
12 volt inputs, none have the necessary 150 mA capacity. Now I talked
to an EE buddy of mine and he suggested that I could use a few
transistors to switch it. Alas, transistors aren't one of my strong
points, and I dont know how to use them, or even what type to get. I
pretty much need to use a 5v, 20 mA max low/high signal to start/stop
a 12v current that may go up to 250mA, without frying any ICs, and can
last for at least two years of continuous use.

I tried searching the internet for a few hours, but couldn't find the
info I needed. I eventually found this group, and I'm hoping somebody
here can help.

Cheers.

Several hundred people here can show you, very simply, exactly what you
need to do with the output of yout TTL IC to feed your fan so it goes on
and off as you dictate.

But ask yourself one question..........

Why do you think the fan is there in the first place? Just to annoy your
roommate?
 
K

kell

Jan 1, 1970
0
I'm having a bit of trouble here. I am a sophomore Computer
Engineering student at Psu. I recently bought a new computer case,
and the front has an 80cm fan with LED's and what-not. The problem is
that it is very loud. To make matters worse, it runs on a four-pin
molex, and the speed isn't variable. Additionally, I share the room
with a roomate, and the lights are kinda bright, esp. when its dark.
The case is acrylic, and the side panels are screw-on, so I can't
even unplug it.

Now my Idea is to use the 'reset' button, which is useless with a
'power' button above it, to change the speed, as well as turn it off.

My plan is to us a binary-output counter (SN74LS163), and tie the
one's and two's places into a 2 to four DMUX (Say an SN74LS139A).
I'll then use the momentary switch(reset button) as the clock for the
counter. This will let me cycle between four different circuits:
Unmodified, 80%, 40%, and off.

Now implementing the logic is no problem. The issue I have is using
the 5v logic outputs to actually control the 12v fan. I looked into
Tri-State buffers, but even if I was able to find one that took 5 and
12 volt inputs, none have the necessary 150 mA capacity. Now I talked
to an EE buddy of mine and he suggested that I could use a few
transistors to switch it. Alas, transistors aren't one of my strong
points, and I dont know how to use them, or even what type to get. I
pretty much need to use a 5v, 20 mA max low/high signal to start/stop
a 12v current that may go up to 250mA, without frying any ICs, and can
last for at least two years of continuous use.

I tried searching the internet for a few hours, but couldn't find the
info I needed. I eventually found this group, and I'm hoping somebody
here can help.

Cheers.

Get a quieter fan, maybe. allelectronics.com has an 80 mm fan, part
number cf-257 for $3.50. Says it's 21.0 dBA...
 
D

Don Lancaster

Jan 1, 1970
0
I'm having a bit of trouble here. I am a sophomore Computer
Engineering student at Psu. I recently bought a new computer case,
and the front has an 80cm fan with LED's and what-not. The problem is
that it is very loud. To make matters worse, it runs on a four-pin
molex, and the speed isn't variable. Additionally, I share the room
with a roomate, and the lights are kinda bright, esp. when its dark.
The case is acrylic, and the side panels are screw-on, so I can't
even unplug it.

Now my Idea is to use the 'reset' button, which is useless with a
'power' button above it, to change the speed, as well as turn it off.

My plan is to us a binary-output counter (SN74LS163), and tie the
one's and two's places into a 2 to four DMUX (Say an SN74LS139A).
I'll then use the momentary switch(reset button) as the clock for the
counter. This will let me cycle between four different circuits:
Unmodified, 80%, 40%, and off.

Now implementing the logic is no problem. The issue I have is using
the 5v logic outputs to actually control the 12v fan. I looked into
Tri-State buffers, but even if I was able to find one that took 5 and
12 volt inputs, none have the necessary 150 mA capacity. Now I talked
to an EE buddy of mine and he suggested that I could use a few
transistors to switch it. Alas, transistors aren't one of my strong
points, and I dont know how to use them, or even what type to get. I
pretty much need to use a 5v, 20 mA max low/high signal to start/stop
a 12v current that may go up to 250mA, without frying any ICs, and can
last for at least two years of continuous use.

I tried searching the internet for a few hours, but couldn't find the
info I needed. I eventually found this group, and I'm hoping somebody
here can help.

Cheers.

There's rumored to be a CMOS COOKBOOK with the circuits you need in it.


--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email: [email protected]

Please visit my GURU's LAIR web site at http://www.tinaja.com
 
H

Homer J Simpson

Jan 1, 1970
0
I'm having a bit of trouble here. I am a sophomore Computer
Engineering student at Psu. I recently bought a new computer case,
and the front has an 80cm fan with LED's and what-not. The problem is
that it is very loud.

Buy a quiet fan.
 
Several hundred people here can show you, very simply, exactly what you
need to do with the output of yout TTL IC to feed your fan so it goes on
and off as you dictate.

Several hundred perhaps, but can you?
But ask yourself one question..........

Why do you think the fan is there in the first place? Just to annoy your
roommate?

I live with Mike Tyson. He'll bite my face off.


This is one of those little pet-projects that I want to do regardless
of the neccessity. There are two other molex fans in the case,
withought lights, and I've aready ordered three-pin replacents, as
well as a green cold cathode strip light. But the front fan is
special. I want to be able to build a little board with a female
molex and some pins soldered on, and I can just plug everything in an
have it work. The only hurdle left is what transistors to use, and how
to connect them. Additionally, is there a better way to implement the
switching besides a counter+dmux? This design is simpler, and has
less wiring than a J-K solution, so I'm thinking its the best choice,
esp. as I have all of the neccessary parts.
 
Found an excellent resource:

http://www.winpicprog.co.uk/pic_tutorial_extras.htm

This page seems to clear up a lot of the uncertainty about the
outputs. I'm going to draft up a schematic and run it past another EE
buddy.

Keep in mind that other people with the same situation may come
through here on a google search, and it would be good to have clear,
concise, solutions. I may post up a schematic, and let ya'll know how
it goes.
 
A

amdx

Jan 1, 1970
0
Don Lancaster said:
You obviously have never met his roommate.

--
Don, your humor has been showing lately.
I liked your answer to the guy that wanted to melt ice off the driveway.
"The obvious solution is to move the driveway to where there is no
ice."

From sunny Florida,
Mike
P.S. I don't miss winter in Michigan
 
M

Michael A. Terrell

Jan 1, 1970
0
I live with Mike Tyson. He'll bite my face off.


Then you need to chose your boyfriends with more care. he would
probably bite the computer, too.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
M

Michael A. Terrell

Jan 1, 1970
0
Don said:
There's rumored to be a CMOS COOKBOOK with the circuits you need in it.


He just copied some guys TTL COOKBOOK. ;-)


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
M

me

Jan 1, 1970
0
[email protected] wrote in @j27g2000cwj.googlegroups.com:
Found an excellent resource:

http://www.winpicprog.co.uk/pic_tutorial_extras.htm

This page seems to clear up a lot of the uncertainty about the
outputs. I'm going to draft up a schematic and run it past another EE
buddy.

Keep in mind that other people with the same situation may come
through here on a google search, and it would be good to have clear,
concise, solutions. I may post up a schematic, and let ya'll know how
it goes.

You could also look here http://www.cpemma.co.uk/index.html
 
J

John Fields

Jan 1, 1970
0
Several hundred perhaps, but can you?


I live with Mike Tyson. He'll bite my face off.


This is one of those little pet-projects that I want to do regardless
of the neccessity. There are two other molex fans in the case,
withought lights, and I've aready ordered three-pin replacents, as
well as a green cold cathode strip light. But the front fan is
special. I want to be able to build a little board with a female
molex and some pins soldered on, and I can just plug everything in an
have it work. The only hurdle left is what transistors to use, and how
to connect them. Additionally, is there a better way to implement the
switching besides a counter+dmux?

---
Yes.

I've emailed you a schematic since you can't access
alt.binaries.schematics.electronic from Google groups and posted it
there as well for anyone else who might be interested.
 
I've emailed you a schematic since you can't access
alt.binaries.schematics.electronic from Google groups and posted it
there as well for anyone else who might be interested.

I got your email, however it was all garbled. I saw the words
'Fanspeed.pdf' So I assume you meant to send it as an attatchment,
not as ascii text. I'm interested in seeing what your version looks
like, and how it compares to my own.

I don't have access to a scanner right now, but the general layout is
a four-bit counter with the 1's and 2's places fed into a 2-to-4
Dmux. The first three Dmux outputs each go to a PNP transistor, which
mediate the current to the fan, while the fourth goes to ground,
disabling (or rather, not enabling) the fan. As each output is
selected, the output goes from high to low, allowing the 12v current
to pass through the Transistor(s).

Total # of parts: Two ICs, Seven resistors, three PNP transistors, a
capacitor (used to stabilize clock), and various wires and
connectors. Done properly, it'll take up less space than a saltine
cracker, and depending on the quality of the ICs, last for years.
Total cost: less than 5 bucks, esp. since I can get most of the parts
for free.
 
J

John Fields

Jan 1, 1970
0
I got your email, however it was all garbled. I saw the words
'Fanspeed.pdf' So I assume you meant to send it as an attatchment,
not as ascii text. I'm interested in seeing what your version looks
like, and how it compares to my own.

---
OK. I think I know what happened. I sent the post to abse as an
attachment and to you in the same post, but I think Agent defaults
email attachments to inline text, so that's what it sounds like from
your description. I'll send it to you again as an attachment and
we'll see what happens.
---
I don't have access to a scanner right now, but the general layout is
a four-bit counter with the 1's and 2's places fed into a 2-to-4
Dmux. The first three Dmux outputs each go to a PNP transistor, which
mediate the current to the fan, while the fourth goes to ground,
disabling (or rather, not enabling) the fan. As each output is
selected, the output goes from high to low, allowing the 12v current
to pass through the Transistor(s).

---
No need to scan it, I know exactly how it works, and I think you're
going to have a problem because the TTL part won't be able to pull
the transistor bases up to 12V to turn them off, since its Vcc is
+5V.
---
Total # of parts: Two ICs, Seven resistors, three PNP transistors, a
capacitor (used to stabilize clock), and various wires and
connectors. Done properly, it'll take up less space than a saltine
cracker, and depending on the quality of the ICs, last for years.
Total cost: less than 5 bucks, esp. since I can get most of the parts
for free.

---
Mine has one chip (an HC4017) three 2N4401 NPN transistors, five
1/4watt resistors, three power resistors to slow the fan, and a
diode and a capacitor to debounce the switch. Take a look at a 4017
data sheet:

http://focus.ti.com/lit/ds/symlink/cd74hc4017.pdf

and you'll see that it has the decoded outputs coming out,
eliminating the need for the demux. Plus, its out outs are positive
true so you can drive NPNs and get away from the PNP level shifting
problems.
 
Mine has one chip (an HC4017) three 2N4401 NPN transistors, five
1/4watt resistors, three power resistors to slow the fan, and a
diode and a capacitor to debounce the switch. Take a look at a 4017
data sheet:

http://focus.ti.com/lit/ds/symlink/cd74hc4017.pdf

and you'll see that it has the decoded outputs coming out,
eliminating the need for the demux. Plus, its out outs are positive
true so you can drive NPNs and get away from the PNP level shifting
problems.


Awesome. Data sheets=good! I don't know if I'll be able to get one of
those chips or not, but do you have a schematic for this design?
 
K

kell

Jan 1, 1970
0
I'm having a bit of trouble here. I am a sophomore Computer
Engineering student at Psu. I recently bought a new computer case,
and the front has an 80cm fan with LED's and what-not. The problem is
that it is very loud. To make matters worse, it runs on a four-pin
molex, and the speed isn't variable. Additionally, I share the room
with a roomate, and the lights are kinda bright, esp. when its dark.
The case is acrylic, and the side panels are screw-on, so I can't
even unplug it.

Now my Idea is to use the 'reset' button, which is useless with a
'power' button above it, to change the speed, as well as turn it off.

My plan is to us a binary-output counter (SN74LS163), and tie the
one's and two's places into a 2 to four DMUX (Say an SN74LS139A).
I'll then use the momentary switch(reset button) as the clock for the
counter. This will let me cycle between four different circuits:
Unmodified, 80%, 40%, and off.

Now implementing the logic is no problem. The issue I have is using
the 5v logic outputs to actually control the 12v fan. I looked into
Tri-State buffers, but even if I was able to find one that took 5 and
12 volt inputs, none have the necessary 150 mA capacity. Now I talked
to an EE buddy of mine and he suggested that I could use a few
transistors to switch it. Alas, transistors aren't one of my strong
points, and I dont know how to use them, or even what type to get. I
pretty much need to use a 5v, 20 mA max low/high signal to start/stop
a 12v current that may go up to 250mA, without frying any ICs, and can
last for at least two years of continuous use.

I tried searching the internet for a few hours, but couldn't find the
info I needed. I eventually found this group, and I'm hoping somebody
here can help.

Cheers.

There's just one thing I don't get. After you turn the fan down,
what's going to keep your computer from overheating?
 
J

John Fields

Jan 1, 1970
0
Awesome. Data sheets=good! I don't know if I'll be able to get one of
those chips or not, but do you have a schematic for this design?
 
Still nothing, john.

I managed to scan the schematic that I designed, and touched it up a
little. Does it look electrically sound to everyone? I'm pretty sure
about the logic, its the transistors I'm worried about. Will a five
volt High signal block the current? And if it goes low, will current
be allowed to pass? What model of transistor should I get? I
calcultae that it will need to provide at least 150 mA at 12v to power
the fan, so a >=2W tran. is required. A link to the image that (I
hope) works is here:

http://allyoucanupload.webshots.com/v/2002723092834367425
 
J

John Fields

Jan 1, 1970
0
Still nothing, john.

I managed to scan the schematic that I designed, and touched it up a
little. Does it look electrically sound to everyone? I'm pretty sure
about the logic, its the transistors I'm worried about. Will a five
volt High signal block the current?

---
Current will pass through all the transistors all the time.
---
What model of transistor should I get? I
calcultae that it will need to provide at least 150 mA at 12v to power
the fan, so a >=2W tran. is required.

---
No. With the transistor fully saturated the voltage drop across the
collector-to emitter junction will be about 100mV, so since:


P = IE, P = 0.125A * 0.1V = 0.0125 watt


Even if there was a volt across the transistor the power it would be
dissipating would only be 1/8 watt.


A link to the image that (I hope) works is here:

http://allyoucanupload.webshots.com/v/2002723092834367425

---
That won't work, for the reason stated earlier.

what you can do to fix it is this: (View in courier)

+12
|
+-------+
| |K
[MOTOR] [DIODE]
| |
+-------+-->TO OTHER DRIVERS
+5V |
| [R]
[1K] |
+5V | C
| +-----B 2N4401
[10K] | E
| C |
FROM DEMUX>---+----B 2N3904 GND
E
|
GND


Just duplicate the circuit for each demux output.
 
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