Voltage controlled rheostat?

[Jonathan Busby]

I'm no analog electronics expert by any definition of the word so I
apologize if this question is stupid. I'm looking for a device
( preferably no assembly required ) that functions as the hypothetical
device in the subject : something that takes a control voltage of 0-12
volts and adjusts the output from a voltage source ( a power supply )
from 0-24 volts linearly w.r.t the control voltage while handling up
to 80 watts of power.

Is there any device out there that will do this?

Thanks,

Jonathan Busby

 

[John Fields]

I'm no analog electronics expert by any definition of the word so I
apologize if this question is stupid.

---
This is sci.electronics.basics, where there is no such thing as a
stupid question.
---

I'm looking for a device
( preferably no assembly required ) that functions as the hypothetical
device in the subject : something that takes a control voltage of 0-12
volts and adjusts the output from a voltage source ( a power supply )
from 0-24 volts linearly w.r.t the control voltage while handling up
to 80 watts of power.

Is there any device out there that will do this?

---
Yes. The device is itself a power supply with a voltage sensitive
control input which can be used to control the output voltage.

Finding exactly what you need might involve a huge amount of
legwork, but the best place to start might be by Googling:

"Voltage programmable power supply" with and without the quotes.

Most likely you'll find something with a 0 to 5V or a 0 to 10V input
which will do the adjusting, and if you do, post back and one of us
will tell you how to make it work with your 0 to 12V control
voltage.

 

[Jonathan Busby]

Heh. Yeah. That was the first thing I thought of. I did many extensive
Google searches but came up with nothing that really fit my needs.
( or my wallet )

Finding exactly what you need might involve a huge amount of
legwork, but the best place to start might be by Googling:

"Voltage programmable power supply" with and without the quotes.

Thanks. I was using "voltage controlled" power supply. Maybe I'll get
more
relevant results with this.

Most likely you'll find something with a 0 to 5V or a 0 to 10V input
which will do the adjusting, and if you do, post back and one of us
will tell you how to make it work with your 0 to 12V control
voltage.

Many thanks.

Jonathan

 

[Bob Masta]

I'm no analog electronics expert by any definition of the word so I
apologize if this question is stupid. I'm looking for a device
( preferably no assembly required ) that functions as the hypothetical
device in the subject : something that takes a control voltage of 0-12
volts and adjusts the output from a voltage source ( a power supply )
from 0-24 volts linearly w.r.t the control voltage while handling up
to 80 watts of power.

Is there any device out there that will do this?

Thanks,

Jonathan Busby

While the voltage-controlled power supply already
mentioned will fill the bill, we might be able to
suggest a different (less expensive, etc) approach
if you gave us the "big picture" of what you are
trying to do.

Best regards,


Bob Masta

DAQARTA v3.50
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, FREE Signal Generator
Science with your sound card!

 

[JeffM]

I'm looking for a device ( preferably no assembly required )
[...]that takes a control voltage of 0-12 volts
and adjusts the output from a voltage source[...]
from 0-24 volts linearly w.r.t the control voltage
while handling up to 80 watts of power.

While the voltage-controlled power supply already
mentioned will fill the bill,

....especially the *no assembly required* part...

we might be able to suggest a different (less expensive

Ah. The magic phrase.

, etc) approach
if you gave us the "big picture" of what you are trying to do.

Yup.
There's lots of ways to skin a cat--if you have details of the cat.
http://groups.google.com/group/sci....tage-values+PWM+*-divider+LPF-*-*-*+FET-array

 

[Jonathan Busby]

---
This is sci.electronics.basics, where there is no such thing as a
stupid question.
---



---
Yes. The device is itself a power supply with a voltage sensitive
control input which can be used to control the output voltage.

Finding exactly what you need might involve a huge amount of
legwork, but the best place to start might be by Googling:

"Voltage programmable power supply" with and without the quotes.

Most likely you'll find something with a 0 to 5V or a 0 to 10V input
which will do the adjusting, and if you do, post back and one of us
will tell you how to make it work with your 0 to 12V control
voltage.

I've done numerous Google searches with many variants on "voltage
programmable power supply" but almost all the results are irrelevant
as they're "high voltage -- programmable power supply" . When
excluding "high" there are only a few hits, mostly patents, that refer
to "voltage controlled power supply" but don't specify any model. The
only real info I got was from this message :

http://groups.google.com/group/sci.electronics/msg/2a98c55165d4d60a?hl=en
:

"I'd look at something like a used HP 6266B, which will give you 0 to
40V at 5 Amps. You can program it from an external voltage or current
source (or resistance source, with opt. 002). Programming speed isn't
too fast, but it is sufficient for most ATE apps. "

When I looked at the specs of said supply on eBay, it indicated it was
"analog programmable" and had "sense" inputs. So, I searched again but
this time I used "analog programmable" -- got a truckload of hits.
Unfortunately when the search is restricted to only those hits that
have a service manual, then it's down to only a few hundred. Even in
the service manuals though, I've yet to find a complete description of
the "analog programming" process, only a mention that the device
supports "analog programming" .

So, is this what I'm looking for?

Thanks,

Jonathan Busby

 

[Jonathan Busby]

While the voltage-controlled power supply already
mentioned will fill the bill, we might be able to
suggest a different (less expensive, etc) approach
if you gave us the "big picture" of what you are
trying to do.

I have an automatic DC fan controller that can vary the voltage
depending on a temperature sensor between 0 and 12 volts while
being able to handle 20 watts of power. The problem is that the fan I
need uses 24 volts and over 70 watts at max voltage.

Hope this clarifies things.

Jonathan Busby

 

[Jonathan Busby]

I'm looking for a device ( preferably no assembly required )
[...]that takes a control voltage of 0-12 volts
and adjusts the output from a voltage source[...]
from 0-24 volts linearly w.r.t the control voltage
while handling up to 80 watts of power.

While the voltage-controlled power supply already
mentioned will fill the bill,

...especially the *no assembly required* part...

Well, it's just that I hate soldering. Although solder paste and an
oven I can tolerate.

 

[John Fields]

I've done numerous Google searches with many variants on "voltage
programmable power supply" but almost all the results are irrelevant
as they're "high voltage -- programmable power supply" . When
excluding "high" there are only a few hits, mostly patents, that refer
to "voltage controlled power supply" but don't specify any model. The
only real info I got was from this message :

http://groups.google.com/group/sci.electronics/msg/2a98c55165d4d60a?hl=en
:

"I'd look at something like a used HP 6266B, which will give you 0 to
40V at 5 Amps. You can program it from an external voltage or current
source (or resistance source, with opt. 002). Programming speed isn't
too fast, but it is sufficient for most ATE apps. "

When I looked at the specs of said supply on eBay, it indicated it was
"analog programmable" and had "sense" inputs. So, I searched again but
this time I used "analog programmable" -- got a truckload of hits.
Unfortunately when the search is restricted to only those hits that
have a service manual, then it's down to only a few hundred. Even in
the service manuals though, I've yet to find a complete description of
the "analog programming" process, only a mention that the device
supports "analog programming" .

So, is this what I'm looking for?

---
Maybe.

What 'analog programming' is referring to is that the supply's
output voltage can be controlled by (instead of cranking the knob(s)
on its front panel) connecting a voltage source, a current source,
or a resistance to some terminal blocks on the rear panel of the
supply.

From your more recent post:

"I have an automatic DC fan controller that can vary the voltage
depending on a temperature sensor between 0 and 12 volts while
being able to handle 20 watts of power. The problem is that the fan
I need uses 24 volts and over 70 watts at max voltage."

and from an earlier post:

I'm looking for a device ( preferably no assembly required ) that
functions as the hypothetical device in the subject : something that
takes a control voltage of 0-12 volts and adjusts the output from a
voltage source ( a power supply ) from 0-24 volts linearly w.r.t the
control voltage while handling up to 80 watts of power.

It appears that what you'd like to be able to do is use the 0 to 12V
output from the controller as a control signal to drive the larger
power supply needed to drive the 70 watt fan.

Something Like this: (View in Courier)

MAINS>----------------------+
|
+----------+ |
MAINS?>--| | |
| | |
+----| | +---+---+ +---+
| | |---| +|---|+ |
[SENSOR] |CONTROLLER| |SUPPLY | |FAN|
| | |---| -|---|- |
+----| | +---+---+ +---+
| | |
MAINS?>--| | |
+----------+ |
|
MAINS>----------------------+

where the connections to the supply voltage control terminals are
the outputs from the controller?

 

[Jonathan Busby]

I've done numerous Google searches with many variants on "voltage
programmable power supply" but almost all the results are irrelevant
as they're "high voltage -- programmable power supply" . When
excluding "high" there are only a few hits, mostly patents, that refer
to "voltage controlled power supply" but don't specify any model. The
only real info I got was from this message :

"I'd look at something like a used HP 6266B, which will give you 0 to
40V at 5 Amps. You can program it from an external voltage or current
source (or resistance source, with opt. 002). Programming speed isn't
too fast, but it is sufficient for most ATE apps. "

When I looked at the specs of said supply on eBay, it indicated it was
"analog programmable" and had "sense" inputs. So, I searched again but
this time I used "analog programmable" -- got a truckload of hits.
Unfortunately when the search is restricted to only those hits that
have a service manual, then it's down to only a few hundred. Even in
the service manuals though, I've yet to find a complete description of
the "analog programming" process, only a mention that the device
supports "analog programming" .

So, is this what I'm looking for?

---
Maybe.

What 'analog programming' is referring to is that the supply's
output voltage can be controlled by (instead of cranking the knob(s)
on its front panel) connecting a voltage source, a current source,
or a resistance to some terminal blocks on the rear panel of the
supply.

From your more recent post:

"I have an automatic DC fan controller that can vary the voltage
depending on a temperature sensor between 0 and 12 volts while
being able to handle 20 watts of power. The problem is that the fan
I need uses 24 volts and over 70 watts at max voltage."

and from an earlier post:

I'm looking for a device ( preferably no assembly required ) that
functions as the hypothetical device in the subject : something that
takes a control voltage of 0-12 volts and adjusts the output from a
voltage source ( a power supply ) from 0-24 volts linearly w.r.t the
control voltage while handling up to 80 watts of power.

It appears that what you'd like to be able to do is use the 0 to 12V
output from the controller as a control signal to drive the larger
power supply needed to drive the 70 watt fan.

Something Like this: (View in Courier)

MAINS>----------------------+
|
+----------+ |
MAINS?>--| | |
| | |
+----| | +---+---+ +---+
| | |---| +|---|+ |
[SENSOR] |CONTROLLER| |SUPPLY | |FAN|
| | |---| -|---|- |
+----| | +---+---+ +---+
| | |
MAINS?>--| | |
+----------+ |
|
MAINS>----------------------+

where the connections to the supply voltage control terminals are
the outputs from the controller?

Yes that's basically it.


Jonathan Busby

 

[Jonathan Busby]

Finding exactly what you need might involve a huge amount of
legwork, but the best place to start might be by Googling:

"Voltage programmable power supply" with and without the quotes.

Most likely you'll find something with a 0 to 5V or a 0 to 10V input
which will do the adjusting, and if you do, post back and one of us
will tell you how to make it work with your 0 to 12V control
voltage.

I've done numerous Google searches with many variants on "voltage
programmable power supply" but almost all the results are irrelevant
as they're "high voltage -- programmable power supply" . When
excluding "high" there are only a few hits, mostly patents, that refer
to "voltage controlled power supply" but don't specify any model. The
only real info I got was from this message :

http://groups.google.com/group/sci.electronics/msg/2a98c55165d4d60a?h...
:

"I'd look at something like a used HP 6266B, which will give you 0 to
40V at 5 Amps. You can program it from an external voltage or current
source (or resistance source, with opt. 002). Programming speed isn't
too fast, but it is sufficient for most ATE apps. "

When I looked at the specs of said supply on eBay, it indicated it was
"analog programmable" and had "sense" inputs. So, I searched again but
this time I used "analog programmable" -- got a truckload of hits.
Unfortunately when the search is restricted to only those hits that
have a service manual, then it's down to only a few hundred. Even in
the service manuals though, I've yet to find a complete description of
the "analog programming" process, only a mention that the device
supports "analog programming" .

So, is this what I'm looking for?

Thanks,

Jonathan Busby

Brain Fart. Replace "Service Manual" with "Data Sheet" .


Jonathan Busby

 

[G. Duchene]

I've done numerous Google searches with many variants on "voltage
programmable power supply" but almost all the results are irrelevant
as they're "high voltage -- programmable power supply" . When
excluding "high" there are only a few hits, mostly patents, that refer
to "voltage controlled power supply" but don't specify any model. The
only real info I got was from this message :

http://groups.google.com/group/sci.electronics/msg/2a98c55165d4d60a?hl=en
:

"I'd look at something like a used HP 6266B, which will give you 0 to
40V at 5 Amps. You can program it from an external voltage or current
source (or resistance source, with opt. 002). Programming speed isn't
too fast, but it is sufficient for most ATE apps. "

When I looked at the specs of said supply on eBay, it indicated it was
"analog programmable" and had "sense" inputs. So, I searched again but
this time I used "analog programmable" -- got a truckload of hits.
Unfortunately when the search is restricted to only those hits that
have a service manual, then it's down to only a few hundred. Even in
the service manuals though, I've yet to find a complete description of
the "analog programming" process, only a mention that the device
supports "analog programming" .

So, is this what I'm looking for?

Thanks,

Jonathan Busby

Please allow me to stimulate some other ideas out there:

If you really need an "analog" output to drive your fan motor, you might
want to consider
using a power op-amp (Apex at http://www.apexmicrotech.com/ is a good
source).
They can be used just like regular op-amps (i.e. be configured as voltage
followers,
or with a DC gain of 2 -- to convert your 0-12V input into a 0-24V output.
Bear in mind that the op-amp supply voltage would probably need to be a few
volts
higher than the required op-amp output voltage.
Apex apps or sales engineers could probably suggest an appropriate device
and circuit.

However, your existing DC fan motor might be happy being driven via a "PWM"
(pulse width modulator) driver. PWM drivers are more compact, require a much
smaller heat sink (i.e. are much more efficient), and would be much cheaper.
If your motor can be driven via PWM, that is probably the most sensible way
to go.
The easiest approach is to simply buy an appropriate "motor driver",
available from
most motor distributers. Many will accept a DC control signal of 0-10V
(which can
easily be derived from your 0-12V signal via a resistor or two.)

G. Duchene

 

[John Fields]

Something Like this: (View in Courier)

MAINS>----------------------+
|
+----------+ |
MAINS?>--| | |
| | |
+----| | +---+---+ +---+
| | |---| +|---|+ |
[SENSOR] |CONTROLLER| |SUPPLY | |FAN|
| | |---| -|---|- |
+----| | +---+---+ +---+
| | |
MAINS?>--| | |
+----------+ |
|
MAINS>----------------------+

where the connections to the supply voltage control terminals are
the outputs from the controller?

Yes that's basically it.

---
OK, what do you want to do now, and how much money do you have
available to throw at getting the problem solved? Material, that
is. As long as I don't have to start wielding a soldering iron
I'll be happy to help you for free,

BTW, do you have a schematic or a link to the controller's data
sheet?

 

[Jonathan Busby]

Something Like this: (View in Courier)
MAINS>----------------------+
|
+----------+ |
MAINS?>--| | |
| | |
+----| | +---+---+ +---+
| | |---| +|---|+ |
[SENSOR] |CONTROLLER| |SUPPLY | |FAN|
| | |---| -|---|- |
+----| | +---+---+ +---+
| | |
MAINS?>--| | |
+----------+ |
|
MAINS>----------------------+
where the connections to the supply voltage control terminals are
the outputs from the controller?

Yes that's basically it.

I think my price cap is around a hundred bucks.

As long as I don't have to start wielding a soldering iron
I'll be happy to help you for free,

Nah. But I want you to come over to my house and complete the
construction
of my 20 ft tall Tesla coil -- I have completed the first steps :
ordering the plans.

BTW, do you have a schematic or a link to the controller's data
sheet?
http://www.t-balancer.com/english/produkt_tban_bigng.htm

http://www.t-balancer.com/download/bng.pdf

Thanks a lot for all your help!

Jonathan

 

[Jonathan Busby]

Something Like this: (View in Courier)
MAINS>----------------------+
|
+----------+ |
MAINS?>--| | |
| | |
+----| | +---+---+ +---+
| | |---| +|---|+ |
[SENSOR] |CONTROLLER| |SUPPLY | |FAN|
| | |---| -|---|- |
+----| | +---+---+ +---+
| | |
MAINS?>--| | |
+----------+ |
|
MAINS>----------------------+
where the connections to the supply voltage control terminals are
the outputs from the controller?

I think my price cap is around a hundred bucks.

As long as I don't have to start wielding a soldering iron
I'll be happy to help you for free,

Nah. But I want you to come over to my house and complete the
construction
of my 20 ft tall Tesla coil -- I have completed the first steps :
ordering the plans.

BTW, do you have a schematic or a link to the controller's data
sheet?
http://www.t-balancer.com/english/produkt_tban_bigng.htm

http://www.t-balancer.com/download/bng.pdf

Thanks a lot for all your help!

Jonathan

Oops. Forgot the fan :

http://www.delta.com.tw/product/cp/dcfans/download/pdf/FFB/FFB120x120x38mm.pdf

Part # : FFB1224XHE :
http://www.delta.com.tw/product/cp/...ure_unit=2&air_pressure=&noise=&order=m3 desc
( The one at the top )


Jonathan

 

[John Fields]

Something Like this: (View in Courier)

MAINS>----------------------+
|
+----------+ |
MAINS?>--| | |
| | |
+----| | +---+---+ +---+
| | |---| +|---|+ |
[SENSOR] |CONTROLLER| |SUPPLY | |FAN|
| | |---| -|---|- |
+----| | +---+---+ +---+
| | |
MAINS?>--| | |
+----------+ |
|
MAINS>----------------------+

where the connections to the supply voltage control terminals are
the outputs from the controller?
Yes that's basically it.

I think my price cap is around a hundred bucks.

As long as I don't have to start wielding a soldering iron
I'll be happy to help you for free,

Nah. But I want you to come over to my house and complete the
construction
of my 20 ft tall Tesla coil -- I have completed the first steps :
ordering the plans.

BTW, do you have a schematic or a link to the controller's data
sheet?
http://www.t-balancer.com/english/produkt_tban_bigng.htm

http://www.t-balancer.com/download/bng.pdf

Thanks a lot for all your help!

Jonathan

Oops. Forgot the fan :

http://www.delta.com.tw/product/cp/dcfans/download/pdf/FFB/FFB120x120x38mm.pdf

Part # : FFB1224XHE :
http://www.delta.com.tw/product/cp/...ure_unit=2&air_pressure=&noise=&order=m3 desc
( The one at the top )

---
OK, since it's a brushless fan it's not really designed to be
pulse-width modulated and since you've got a $100 cap on the
project, here's what I'd do: (View in Courier)


A1
+-----+
120AC>-+------|~ +24|-----+
| | | |
120AC>-|-+----|~ -24|--+ |
| | +-----+ | |
| | | |
| | +-----------+ |
| | | A2 |
| | | +-----+ |
+-|-|--|~ -12|-----+-----------------+
| | | | |
+-|--|~ +12|--+ |
| +-----+ | |
| | LT |
0-12VDC>---|--[4K7]---|+ \1636 D
| +---|S >--+-[1000]-+---G IRFZ34E
| | +-|- / | |K S
| | | | [10K] [1N4744A] |
+------+-|--+ | | |
| +--------+ +-----+
| | |+
| [10K] [FAN]
| | |
GND>-------+-----------------+--------------+

A1 is a Kepco RKW 24-4.5K, $79, (or an RKW 24-6.5K for $99) from
Kepco at:

http://www.kepcopower.com/specs/rkw-openspecs2.pdf

http://www.kepcopower.com/rkwo-buy.htm

A2 can be pretty much any 12V wall-wart you might have laying around
as long as its output stays under 15V under high line and no load
conditions.

You'll probably need a heat sink for the MOSFET, but I haven't got a
good handle on what current VS voltage looks like for a brushless
motor. However, assuming that the relationship is roughly linear
means that with 24V across the fan pulling 3.25A through it, 14V (at
the low end of its range) will pull:


14V
----- = 0.583 of 3.25A,
24V


So:

0.583 * 3.25A = 1.89A.


With the supply at 24V and the fan at 14V means the MOSFET is
dropping 10 volts with 1.89 amps through it, so it's dissipating:


P = IE = 1.89A * 10V = 18.9W

Quite a bit of power.

From IR's thermal data for the MOSFET we have:

Tj max = 150C

Rtjc = 2.2C/W


From:

Tj - Ta
Pd = --------------------
Rtjc + Rtcs + Rtsa

we rearrange to solve for the thermal resistance of the heatsink
surface to air:

Tj - Ta
Rtsa = --------- - (Rtjc + Rtcs)
Pd



150C - 50C 2.2C 0.5C
= ------------ - ( ------ + ------ )
18.9W W W



= 2.59C/W

Which is a pretty substantial convection-only heatsink.

Here's an example:

http://www.aavidthermalloy.com/cgi-...gth=3&airflow=57.2&CType=Natural&AirUnits=LFM

Finally, here's a little simulation so you can see how the thing
works:

Version 4
SHEET 1 880 832
WIRE -224 112 -944 112
WIRE -512 192 -832 192
WIRE -464 240 -608 240
WIRE -336 240 -384 240
WIRE -512 272 -512 192
WIRE -224 272 -224 112
WIRE -608 320 -608 240
WIRE -544 320 -608 320
WIRE -336 352 -336 240
WIRE -336 352 -400 352
WIRE -272 352 -336 352
WIRE -544 384 -704 384
WIRE -512 464 -512 432
WIRE -464 464 -464 432
WIRE -464 464 -512 464
WIRE -224 464 -224 368
WIRE -944 512 -944 112
WIRE -832 512 -832 192
WIRE -704 512 -704 384
WIRE -608 512 -608 320
WIRE -944 640 -944 592
WIRE -832 640 -832 592
WIRE -832 640 -944 640
WIRE -704 640 -704 592
WIRE -704 640 -832 640
WIRE -608 640 -608 592
WIRE -608 640 -704 640
WIRE -512 640 -512 464
WIRE -512 640 -608 640
WIRE -224 640 -224 544
WIRE -224 640 -512 640
WIRE -944 704 -944 640
FLAG -944 704 0
SYMBOL voltage -944 496 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 24
SYMBOL voltage -704 496 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 24 104 Invisible 0
SYMATTR Value PULSE(0 12 0 .1)
SYMATTR InstName V2
SYMBOL res -240 448 R0
SYMATTR InstName R5
SYMATTR Value 8
SYMBOL nmos -272 272 R0
SYMATTR InstName M1
SYMATTR Value IRF1312S
SYMBOL Opamps\\LT1636 -512 352 R0
SYMATTR InstName U1
SYMBOL res -624 496 R0
SYMATTR InstName R1
SYMATTR Value 10k
SYMBOL res -480 256 R270
WINDOW 0 69 58 VTop 0
WINDOW 3 69 56 VBottom 0
SYMATTR InstName R2
SYMATTR Value 15k
SYMBOL voltage -832 496 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value 36
TEXT -856 672 Left 0 !.tran .2

 

[Jonathan Busby]

On Dec 31 2007, 3:01 pm, John Fields <[email protected]>
wrote:
(View in Courier)
MAINS>----------------------+
|
+----------+ |
MAINS?>--| | |
| | |
+----| | +---+---+ +---+
| | |---| +|---|+ |
[SENSOR] |CONTROLLER| |SUPPLY | |FAN|
| | |---| -|---|- |
+----| | +---+---+ +---+
| | |
MAINS?>--| | |
+----------+ |
|
MAINS>----------------------+
where the connections to the supply voltage control terminals are
the outputs from the controller?
--
JF
Yes that's basically it.
---
OK, what do you want to do now, and how much money do you have
available to throw at getting the problem solved? Material, that
is.
I think my price cap is around a hundred bucks.
As long as I don't have to start wielding a soldering iron
I'll be happy to help you for free,
Nah. But I want you to come over to my house and complete the
construction
of my 20 ft tall Tesla coil -- I have completed the first steps :
ordering the plans.
BTW, do you have a schematic or a link to the controller's data
sheet?
http://www.t-balancer.com/english/produkt_tban_bigng.htm
http://www.t-balancer.com/download/bng.pdf

Oops. Forgot the fan :

Part # : FFB1224XHE :
http://www.delta.com.tw/product/cp/dcfans/dcfans_prod_sch.asp?act=sch...
( The one at the top )

---
OK, since it's a brushless fan it's not really designed to be
pulse-width modulated and since you've got a $100 cap on the
project, here's what I'd do: (View in Courier)

A1
+-----+
120AC>-+------|~ +24|-----+
| | | |
120AC>-|-+----|~ -24|--+ |
| | +-----+ | |
| | | |
| | +-----------+ |
| | | A2 |
| | | +-----+ |
+-|-|--|~ -12|-----+-----------------+
| | | | |
+-|--|~ +12|--+ |
| +-----+ | |
| | LT |
0-12VDC>---|--[4K7]---|+ \1636 D
| +---|S >--+-[1000]-+---G IRFZ34E
| | +-|- / | |K S
| | | | [10K] [1N4744A] |
+------+-|--+ | | |
| +--------+ +-----+
| | |+
| [10K] [FAN]
| | |
GND>-------+-----------------+--------------+

A1 is a Kepco RKW 24-4.5K, $79, (or an RKW 24-6.5K for $99) from
Kepco at:

http://www.kepcopower.com/specs/rkw-openspecs2.pdf

http://www.kepcopower.com/rkwo-buy.htm

A2 can be pretty much any 12V wall-wart you might have laying around
as long as its output stays under 15V under high line and no load
conditions.

You'll probably need a heat sink for the MOSFET, but I haven't got a
good handle on what current VS voltage looks like for a brushless
motor. However, assuming that the relationship is roughly linear
means that with 24V across the fan pulling 3.25A through it, 14V (at
the low end of its range) will pull:

14V
----- = 0.583 of 3.25A,
24V

So:

0.583 * 3.25A = 1.89A.

With the supply at 24V and the fan at 14V means the MOSFET is
dropping 10 volts with 1.89 amps through it, so it's dissipating:

P = IE = 1.89A * 10V = 18.9W

Quite a bit of power.

From IR's thermal data for the MOSFET we have:

Tj max = 150C

Rtjc = 2.2C/W

From:

Tj - Ta
Pd = --------------------
Rtjc + Rtcs + Rtsa

we rearrange to solve for the thermal resistance of the heatsink
surface to air:

Tj - Ta
Rtsa = --------- - (Rtjc + Rtcs)
Pd

150C - 50C 2.2C 0.5C
= ------------ - ( ------ + ------ )
18.9W W W

= 2.59C/W

Which is a pretty substantial convection-only heatsink.

Here's an example:

http://www.aavidthermalloy.com/cgi-bin/exdisp.pl?Pnum=60050&LengthUni...

Finally, here's a little simulation so you can see how the thing
works:

Version 4
SHEET 1 880 832
WIRE -224 112 -944 112
WIRE -512 192 -832 192
WIRE -464 240 -608 240
WIRE -336 240 -384 240
WIRE -512 272 -512 192
WIRE -224 272 -224 112
WIRE -608 320 -608 240
WIRE -544 320 -608 320
WIRE -336 352 -336 240
WIRE -336 352 -400 352
WIRE -272 352 -336 352
WIRE -544 384 -704 384
WIRE -512 464 -512 432
WIRE -464 464 -464 432
WIRE -464 464 -512 464
WIRE -224 464 -224 368
WIRE -944 512 -944 112
WIRE -832 512 -832 192
WIRE -704 512 -704 384
WIRE -608 512 -608 320
WIRE -944 640 -944 592
WIRE -832 640 -832 592
WIRE -832 640 -944 640
WIRE -704 640 -704 592
WIRE -704 640 -832 640
WIRE -608 640 -608 592
WIRE -608 640 -704 640
WIRE -512 640 -512 464
WIRE -512 640 -608 640
WIRE -224 640 -224 544
WIRE -224 640 -512 640
WIRE -944 704 -944 640
FLAG -944 704 0
SYMBOL voltage -944 496 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 24
SYMBOL voltage -704 496 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 24 104 Invisible 0
SYMATTR Value PULSE(0 12 0 .1)
SYMATTR InstName V2
SYMBOL res -240 448 R0
SYMATTR InstName R5
SYMATTR Value 8
SYMBOL nmos -272 272 R0
SYMATTR InstName M1
SYMATTR Value IRF1312S
SYMBOL Opamps\\LT1636 -512 352 R0
SYMATTR InstName U1
SYMBOL res -624 496 R0
SYMATTR InstName R1
SYMATTR Value 10k
SYMBOL res -480 256 R270
WINDOW 0 69 58 VTop 0
WINDOW 3 69 56 VBottom 0
SYMATTR InstName R2
SYMATTR Value 15k
SYMBOL voltage -832 496 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value 36
TEXT -856 672 Left 0 !.tran .2

Man! I don't know what to say or how to thank you! You went through
all this effort ( actually it probably took you 5 minutes ) and what
did I do? I thank you very much. You're the type of person that
still keeps me on Internet forums -- most have degenerated into
cesspits of off-topic messages, spam, trolls, idiots, flamewares, and
of course assholes. Speaking of such things, I'm currently the
target of a flamewar in another newsgroup. Anyway. I tested the
circuit ( not that I thought it wouldn't work and it works
perfectly. There's only one minor and really insignificant detail :
when the control voltage is varied there seems to be around a 30ms lag
before the output responds. I don't know if this is just a property of
the circuit or the simulator. It doesn't matter anyway. I had to
replace the V2 voltage source with a an arbitrary behavioral voltage
source for testing. I'm running ltspice under Wine on top of Kanotix
Linux in LiveCD mode out of a RAM disk. heh. Anyway, here's a link to
a screen capture of the simulator with your circuit running :
http://i209.photobucket.com/albums/bb286/wqo2/snapshot3.png .

Thanks for all your help.

Regards,

Jonathan

 

[Bob Monsen]

On Dec 31 2007, 3:01 pm, John Fields <[email protected]>
wrote:

On Dec 29, 5:53 pm, John Fields <[email protected]>
wrote:
Something Like this: (View in Courier)

MAINS>----------------------+
|
+----------+ |
MAINS?>--| | |
| | |
+----| | +---+---+ +---+
| | |---| +|---|+ |
[SENSOR] |CONTROLLER| |SUPPLY | |FAN|
| | |---| -|---|- |
+----| | +---+---+ +---+
| | |
MAINS?>--| | |
+----------+ |
|
MAINS>----------------------+

where the connections to the supply voltage control terminals are
the outputs from the controller?
Yes that's basically it.

I think my price cap is around a hundred bucks.

As long as I don't have to start wielding a soldering iron
I'll be happy to help you for free,

Nah. But I want you to come over to my house and complete the
construction
of my 20 ft tall Tesla coil -- I have completed the first steps :
ordering the plans.

BTW, do you have a schematic or a link to the controller's data
sheet?


Thanks a lot for all your help!

Oops. Forgot the fan :

Part # : FFB1224XHE :
http://www.delta.com.tw/product/cp/dcfans/dcfans_prod_sch.asp?act=sch...
( The one at the top )

---
OK, since it's a brushless fan it's not really designed to be
pulse-width modulated and since you've got a $100 cap on the
project, here's what I'd do: (View in Courier)

A1
+-----+
120AC>-+------|~ +24|-----+
| | | |
120AC>-|-+----|~ -24|--+ |
| | +-----+ | |
| | | |
| | +-----------+ |
| | | A2 |
| | | +-----+ |
+-|-|--|~ -12|-----+-----------------+
| | | | |
+-|--|~ +12|--+ |
| +-----+ | |
| | LT |
0-12VDC>---|--[4K7]---|+ \1636 D
| +---|S >--+-[1000]-+---G IRFZ34E
| | +-|- / | |K S
| | | | [10K] [1N4744A] |
+------+-|--+ | | |
| +--------+ +-----+
| | |+
| [10K] [FAN]
| | |
GND>-------+-----------------+--------------+

A1 is a Kepco RKW 24-4.5K, $79, (or an RKW 24-6.5K for $99) from
Kepco at:

http://www.kepcopower.com/specs/rkw-openspecs2.pdf

http://www.kepcopower.com/rkwo-buy.htm

A2 can be pretty much any 12V wall-wart you might have laying around
as long as its output stays under 15V under high line and no load
conditions.

You'll probably need a heat sink for the MOSFET, but I haven't got a
good handle on what current VS voltage looks like for a brushless
motor. However, assuming that the relationship is roughly linear
means that with 24V across the fan pulling 3.25A through it, 14V (at
the low end of its range) will pull:

14V
----- = 0.583 of 3.25A,
24V

So:

0.583 * 3.25A = 1.89A.

With the supply at 24V and the fan at 14V means the MOSFET is
dropping 10 volts with 1.89 amps through it, so it's dissipating:

P = IE = 1.89A * 10V = 18.9W

Quite a bit of power.

From IR's thermal data for the MOSFET we have:

Tj max = 150C

Rtjc = 2.2C/W

From:

Tj - Ta
Pd = --------------------
Rtjc + Rtcs + Rtsa

we rearrange to solve for the thermal resistance of the heatsink
surface to air:

Tj - Ta
Rtsa = --------- - (Rtjc + Rtcs)
Pd

150C - 50C 2.2C 0.5C
= ------------ - ( ------ + ------ )
18.9W W W

= 2.59C/W

Which is a pretty substantial convection-only heatsink.

Here's an example:

http://www.aavidthermalloy.com/cgi-bin/exdisp.pl?Pnum=60050&LengthUni...

Finally, here's a little simulation so you can see how the thing
works:

Version 4
SHEET 1 880 832
WIRE -224 112 -944 112
WIRE -512 192 -832 192
WIRE -464 240 -608 240
WIRE -336 240 -384 240
WIRE -512 272 -512 192
WIRE -224 272 -224 112
WIRE -608 320 -608 240
WIRE -544 320 -608 320
WIRE -336 352 -336 240
WIRE -336 352 -400 352
WIRE -272 352 -336 352
WIRE -544 384 -704 384
WIRE -512 464 -512 432
WIRE -464 464 -464 432
WIRE -464 464 -512 464
WIRE -224 464 -224 368
WIRE -944 512 -944 112
WIRE -832 512 -832 192
WIRE -704 512 -704 384
WIRE -608 512 -608 320
WIRE -944 640 -944 592
WIRE -832 640 -832 592
WIRE -832 640 -944 640
WIRE -704 640 -704 592
WIRE -704 640 -832 640
WIRE -608 640 -608 592
WIRE -608 640 -704 640
WIRE -512 640 -512 464
WIRE -512 640 -608 640
WIRE -224 640 -224 544
WIRE -224 640 -512 640
WIRE -944 704 -944 640
FLAG -944 704 0
SYMBOL voltage -944 496 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 24
SYMBOL voltage -704 496 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 24 104 Invisible 0
SYMATTR Value PULSE(0 12 0 .1)
SYMATTR InstName V2
SYMBOL res -240 448 R0
SYMATTR InstName R5
SYMATTR Value 8
SYMBOL nmos -272 272 R0
SYMATTR InstName M1
SYMATTR Value IRF1312S
SYMBOL Opamps\\LT1636 -512 352 R0
SYMATTR InstName U1
SYMBOL res -624 496 R0
SYMATTR InstName R1
SYMATTR Value 10k
SYMBOL res -480 256 R270
WINDOW 0 69 58 VTop 0
WINDOW 3 69 56 VBottom 0
SYMATTR InstName R2
SYMATTR Value 15k
SYMBOL voltage -832 496 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value 36
TEXT -856 672 Left 0 !.tran .2

Man! I don't know what to say or how to thank you! You went through
all this effort ( actually it probably took you 5 minutes ) and what
did I do? I thank you very much. You're the type of person that
still keeps me on Internet forums -- most have degenerated into
cesspits of off-topic messages, spam, trolls, idiots, flamewares, and
of course assholes. Speaking of such things, I'm currently the
target of a flamewar in another newsgroup. Anyway. I tested the
circuit ( not that I thought it wouldn't work and it works
perfectly. There's only one minor and really insignificant detail :
when the control voltage is varied there seems to be around a 30ms lag
before the output responds. I don't know if this is just a property of
the circuit or the simulator. It doesn't matter anyway. I had to
replace the V2 voltage source with a an arbitrary behavioral voltage
source for testing. I'm running ltspice under Wine on top of Kanotix
Linux in LiveCD mode out of a RAM disk. heh. Anyway, here's a link to
a screen capture of the simulator with your circuit running :
http://i209.photobucket.com/albums/bb286/wqo2/snapshot3.png .

Thanks for all your help.

Regards,

Jonathan

Here is a variation that does not require the additional 12V wart. It is
somewhat more complicated, needing 4 transistors and a few more resistors
instead of the opamp. It uses a p-channel mosfet instead of the n-channel.
FWIW. John's heat sink calculations are all the same, since the dissipation
is identical for the pass element. I also think that a diode parallel to the
fan would be a good idea, to prevent a spike from taking out the mosfet.

Thanks to Genome for original circuit.

Version 4
SHEET 1 880 832
WIRE -688 32 -944 32
WIRE -480 32 -688 32
WIRE -224 32 -480 32
WIRE -688 48 -688 32
WIRE -480 48 -480 32
WIRE -688 160 -688 128
WIRE -480 160 -480 128
WIRE -576 208 -624 208
WIRE -544 208 -576 208
WIRE -576 272 -576 208
WIRE -480 272 -480 256
WIRE -480 272 -576 272
WIRE -944 288 -944 32
WIRE -224 288 -224 32
WIRE -688 304 -688 256
WIRE -272 304 -688 304
WIRE -688 416 -688 304
WIRE -480 416 -480 272
WIRE -832 464 -864 464
WIRE -368 464 -416 464
WIRE -320 464 -368 464
WIRE -224 464 -224 384
WIRE -224 464 -240 464
WIRE -864 512 -864 464
WIRE -688 528 -688 512
WIRE -592 528 -688 528
WIRE -480 528 -480 512
WIRE -480 528 -592 528
WIRE -224 528 -224 464
WIRE -592 544 -592 528
WIRE -368 544 -368 464
WIRE -944 640 -944 368
WIRE -864 640 -864 592
WIRE -864 640 -944 640
WIRE -592 640 -592 624
WIRE -592 640 -864 640
WIRE -368 640 -368 624
WIRE -368 640 -592 640
WIRE -224 640 -224 608
WIRE -224 640 -368 640
WIRE -944 656 -944 640
FLAG -944 656 0
SYMBOL voltage -944 272 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 24V
SYMBOL voltage -864 496 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 16 99 Left 0
SYMATTR Value PULSE(0 12 0 .1)
SYMATTR InstName V2
SYMBOL res -240 512 R0
SYMATTR InstName R5
SYMATTR Value 8
SYMBOL pmos -272 384 M180
SYMATTR InstName M1
SYMATTR Value FDS4465
SYMBOL res -224 448 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R1
SYMATTR Value 10k
SYMBOL res -352 640 R180
WINDOW 0 36 76 Left 0
WINDOW 3 36 40 Left 0
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL npn -752 416 R0
SYMATTR InstName Q1
SYMATTR Value 2N2222
SYMBOL npn -416 416 M0
SYMATTR InstName Q2
SYMATTR Value 2N2222
SYMBOL res -608 528 R0
SYMATTR InstName R3
SYMATTR Value 10k
SYMBOL res -736 448 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R4
SYMATTR Value 4.7k
SYMBOL pnp -624 256 R180
SYMATTR InstName Q3
SYMATTR Value 2N3906
SYMBOL pnp -544 256 M180
SYMATTR InstName Q4
SYMATTR Value 2N3906
SYMBOL res -704 32 R0
SYMATTR InstName R6
SYMATTR Value 10
SYMBOL res -496 32 R0
SYMATTR InstName R7
SYMATTR Value 10
TEXT -888 672 Left 0 !.tran .2

Regards,
Bob Monsen

 

[John Fields]

Here is a variation that does not require the additional 12V wart.

 

[Jonathan Busby]

01 pm, John Fields <[email protected]>
wrote:
53 pm, John Fields <[email protected]>
wrote:
Something Like this: (View in Courier)
MAINS>----------------------+
|
+----------+ |
MAINS?>--| | |
| | |
+----| | +---+---+ +---+
| | |---| +|---|+ |
[SENSOR] |CONTROLLER| |SUPPLY | |FAN|
| | |---| -|---|- |
+----| | +---+---+ +---+
| | |
MAINS?>--| | |
+----------+ |
|
MAINS>----------------------+
where the connections to the supply voltage control terminals are
the outputs from the controller?
--
JF
Yes that's basically it.
---
OK, what do you want to do now, and how much money do you have
available to throw at getting the problem solved? Material, that
is.
I think my price cap is around a hundred bucks.
As long as I don't have to start wielding a soldering iron
I'll be happy to help you for free,
Nah. But I want you to come over to my house and complete the
construction
of my 20 ft tall Tesla coil -- I have completed the first steps :
ordering the plans.
BTW, do you have a schematic or a link to the controller's data
sheet?
http://www.t-balancer.com/english/produkt_tban_bigng.htm
http://www.t-balancer.com/download/bng.pdf
--
JF
Thanks a lot for all your help!
Jonathan
Oops. Forgot the fan :
http://www.delta.com.tw/product/cp/dcfans/download/pdf/FFB/FFB120x120....
Part # : FFB1224XHE :
http://www.delta.com.tw/product/cp/dcfans/dcfans_prod_sch.asp?act=sch...
( The one at the top )
---
OK, since it's a brushless fan it's not really designed to be
pulse-width modulated and since you've got a $100 cap on the
project, here's what I'd do: (View in Courier)
A1
+-----+
120AC>-+------|~ +24|-----+
| | | |
120AC>-|-+----|~ -24|--+ |
| | +-----+ | |
| | | |
| | +-----------+ |
| | | A2 |
| | | +-----+ |
+-|-|--|~ -12|-----+-----------------+
| | | | |
+-|--|~ +12|--+ |
| +-----+ | |
| | LT |
0-12VDC>---|--[4K7]---|+ \1636 D
| +---|S >--+-[1000]-+---G IRFZ34E
| | +-|- / | |K S
| | | | [10K] [1N4744A] |
+------+-|--+ | | |
| +--------+ +-----+
| | |+
| [10K] [FAN]
| | |
GND>-------+-----------------+--------------+
A1 is a Kepco RKW 24-4.5K, $79, (or an RKW 24-6.5K for $99) from
Kepco at:
http://www.kepcopower.com/specs/rkw-openspecs2.pdf
http://www.kepcopower.com/rkwo-buy.htm
A2 can be pretty much any 12V wall-wart you might have laying around
as long as its output stays under 15V under high line and no load
conditions.
You'll probably need a heat sink for the MOSFET, but I haven't got a
good handle on what current VS voltage looks like for a brushless
motor. However, assuming that the relationship is roughly linear
means that with 24V across the fan pulling 3.25A through it, 14V (at
the low end of its range) will pull:
14V
----- = 0.583 of 3.25A,
24V
So:
0.583 * 3.25A = 1.89A.
With the supply at 24V and the fan at 14V means the MOSFET is
dropping 10 volts with 1.89 amps through it, so it's dissipating:
P = IE = 1.89A * 10V = 18.9W
Quite a bit of power.
From IR's thermal data for the MOSFET we have:
Tj max = 150C
Rtjc = 2.2C/W
From:
Tj - Ta
Pd = --------------------
Rtjc + Rtcs + Rtsa
we rearrange to solve for the thermal resistance of the heatsink
surface to air:
Tj - Ta
Rtsa = --------- - (Rtjc + Rtcs)
Pd
150C - 50C 2.2C 0.5C
= ------------ - ( ------ + ------ )
18.9W W W
= 2.59C/W
Which is a pretty substantial convection-only heatsink.
Here's an example:
http://www.aavidthermalloy.com/cgi-bin/exdisp.pl?Pnum=60050&LengthUni....
Finally, here's a little simulation so you can see how the thing
works:
Version 4
SHEET 1 880 832
WIRE -224 112 -944 112
WIRE -512 192 -832 192
WIRE -464 240 -608 240
WIRE -336 240 -384 240
WIRE -512 272 -512 192
WIRE -224 272 -224 112
WIRE -608 320 -608 240
WIRE -544 320 -608 320
WIRE -336 352 -336 240
WIRE -336 352 -400 352
WIRE -272 352 -336 352
WIRE -544 384 -704 384
WIRE -512 464 -512 432
WIRE -464 464 -464 432
WIRE -464 464 -512 464
WIRE -224 464 -224 368
WIRE -944 512 -944 112
WIRE -832 512 -832 192
WIRE -704 512 -704 384
WIRE -608 512 -608 320
WIRE -944 640 -944 592
WIRE -832 640 -832 592
WIRE -832 640 -944 640
WIRE -704 640 -704 592
WIRE -704 640 -832 640
WIRE -608 640 -608 592
WIRE -608 640 -704 640
WIRE -512 640 -512 464
WIRE -512 640 -608 640
WIRE -224 640 -224 544
WIRE -224 640 -512 640
WIRE -944 704 -944 640
FLAG -944 704 0
SYMBOL voltage -944 496 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 24
SYMBOL voltage -704 496 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 24 104 Invisible 0
SYMATTR Value PULSE(0 12 0 .1)
SYMATTR InstName V2
SYMBOL res -240 448 R0
SYMATTR InstName R5
SYMATTR Value 8
SYMBOL nmos -272 272 R0
SYMATTR InstName M1
SYMATTR Value IRF1312S
SYMBOL Opamps\\LT1636 -512 352 R0
SYMATTR InstName U1
SYMBOL res -624 496 R0
SYMATTR InstName R1
SYMATTR Value 10k
SYMBOL res -480 256 R270
WINDOW 0 69 58 VTop 0
WINDOW 3 69 56 VBottom 0
SYMATTR InstName R2
SYMATTR Value 15k
SYMBOL voltage -832 496 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value 36
TEXT -856 672 Left 0 !.tran .2

Man! I don't know what to say or how to thank you! You went through
all this effort ( actually it probably took you 5 minutes ) and what
did I do? I thank you very much. You're the type of person that
still keeps me on Internet forums -- most have degenerated into
cesspits of off-topic messages, spam, trolls, idiots, flamewares, and
of course assholes. Speaking of such things, I'm currently the
target of a flamewar in another newsgroup. Anyway. I tested the
circuit ( not that I thought it wouldn't work and it works
perfectly. There's only one minor and really insignificant detail :
when the control voltage is varied there seems to be around a 30ms lag
before the output responds. I don't know if this is just a property of
the circuit or the simulator. It doesn't matter anyway. I had to
replace the V2 voltage source with a an arbitrary behavioral voltage
source for testing. I'm running ltspice under Wine on top of Kanotix
Linux in LiveCD mode out of a RAM disk. heh. Anyway, here's a link to
a screen capture of the simulator with your circuit running :
http://i209.photobucket.com/albums/bb286/wqo2/snapshot3.png.

Thanks for all your help.

Jonathan

Here is a variation that does not require the additional 12V wart. It is
somewhat more complicated, needing 4 transistors and a few more resistors
instead of the opamp. It uses a p-channel mosfet instead of the n-channel.
FWIW. John's heat sink calculations are all the same, since the dissipation
is identical for the pass element. I also think that a diode parallel to the
fan would be a good idea, to prevent a spike from taking out the mosfet.

Thanks to Genome for original circuit.

Version 4
SHEET 1 880 832
WIRE -688 32 -944 32
WIRE -480 32 -688 32
WIRE -224 32 -480 32
WIRE -688 48 -688 32
WIRE -480 48 -480 32
WIRE -688 160 -688 128
WIRE -480 160 -480 128
WIRE -576 208 -624 208
WIRE -544 208 -576 208
WIRE -576 272 -576 208
WIRE -480 272 -480 256
WIRE -480 272 -576 272
WIRE -944 288 -944 32
WIRE -224 288 -224 32
WIRE -688 304 -688 256
WIRE -272 304 -688 304
WIRE -688 416 -688 304
WIRE -480 416 -480 272
WIRE -832 464 -864 464
WIRE -368 464 -416 464
WIRE -320 464 -368 464
WIRE -224 464 -224 384
WIRE -224 464 -240 464
WIRE -864 512 -864 464
WIRE -688 528 -688 512
WIRE -592 528 -688 528
WIRE -480 528 -480 512
WIRE -480 528 -592 528
WIRE -224 528 -224 464
WIRE -592 544 -592 528
WIRE -368 544 -368 464
WIRE -944 640 -944 368
WIRE -864 640 -864 592
WIRE -864 640 -944 640
WIRE -592 640 -592 624
WIRE -592 640 -864 640
WIRE -368 ...

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You guys are great! Thanks a lot! -- works perfectly in the simulator,
as usual. Again I would also like to thank John Fields, Bob
Monsen, G. Duchene, and everyone else who contributed in this thread.

Thanks again,

Jonathan Busby