Today's Message Index:
----------------------
1. 06:53 AM - Re: 5 Volt Dimmer (Robert L. Nuckolls, III)
2. 08:08 AM - Re: 5 Volt Dimmer (John Coloccia)
3. 09:01 AM - Re: 5 Volt Dimmer (Robert L. Nuckolls, III)
4. 04:38 PM - Re: 5 Volt Dimmer (Don Vs)
5. 05:48 PM - transponder antenna ground plane (Douglas Holub)
Message 1
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| Subject: | Re: 5 Volt Dimmer |
At 06:03 AM 5/18/2007 -0800, you wrote:
>
>Don,
>
>Check out the LC-40 panel dimmer from Van's.
Some thoughts on the task of crafting a dimmer
suited for 5v lighting circuits:
First, the device cited above appears to be a
variable duty cycle control device that delivers
full bus voltage pulses of energy to the lamps
but controls the average current in the lamps
by setting the ON/OFF ratio. For example, if
you switch a 14 volt supply on for 10 milliseconds
and then off for 90 milliseconds, a device connected
downstream of that switch will experience and
average of Oout = Ein (Ton/Toff+Ton)
= 14.0 * (10/90+10) = 1.4 Volts.
This product appears to offer a full range of
control for the purpose of controlling 14 volt
lamps. When installing this style of controller
for a 5v lighting system, the controlling
potentiometer and associated resistors would
want to be tailored such that max clockwise
for the potentiometer produces a maximum duty
cycle of 5/14 or 36%.
The product cited appears to use strip-m-and-
mash-em screw terminals once used by Vision
Microsystems, recently recommended by BMA
(See page 41 of
http://www.aeroelectric.com/articles/richter/response_1.pdf )
These are not the best we know how to do (BWKHTD)
for bringing wires off an assembly and into an aircraft wire
bundle. I understand Vision Microsystems went to
D-sub connectors for their products. I use D-sub
connectors for ALL of my products where ever their
capabilities are commensurate with the task.
One might also consider pure linear dimmer controls
like those once sold from my website but now offered
from B&C's site at:
http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?10X358218#dim30-14
These too are 4 to 12 volt controllers and would
require modification of their control circuitry
to provide the more useful 1.5 to 5 volt output
range. Further, a pure linear controller has to toss
off about 65 percent of total energy fed to the dimmer
when the lamps are on full bright. Hence the need for
heatsinks. However, these are dimming REGULATORS. Unlike
most variable duty cycle controllers, these devices will
maintain a constant output voltage irrespective of
perturbations of the bus voltage that might cause
visible fluctuations in the light produced by lamps
downstream.
A regulating dimmer isolates the lighting system from
such perturbations.
The BWNHTD mirrors methodologies but not the technology
in years past to provide an efficient step down of
bus voltage to the desired 1.5 - 5 volt output
range by use of inductors, capacitors and smart
transistors. These are a members of a large family
of switchmode power supplies. The device I was considering
was a commercial off the shelf product that didn't
match it's marketing hype. One can consider a scratch
built approach that is typified by this part.
http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,P1915
One takes a 1.8v fixed output version of this part
and adds the potentiometer to the feedback circuit
to achieve a 1.8 to 5.0 volt output. Or perhaps
a fully adjustable version will be necessary to get
a lower min output of say 1.0 to 5 volts.
This approach would be VERY efficient. The lost energy
is so low that the package could be quite small and
heat losses easily managed.
I thought I had a quick-turn solution to offer but
it didn't work out. So I've had to back-burner the
project.
Food for thought.
Bob . . .
Message 2
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| Subject: | Re: 5 Volt Dimmer |
Or you can use a PIC to drive a MOSFET and make a dirt cheap, simple and
effecient switching regulator. I've been using this approach to dim a
bank of LEDs.
-John
>
>
Message 3
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| Subject: | Re: 5 Volt Dimmer |
At 08:07 AM 5/19/2007 -0700, you wrote:
>
>Or you can use a PIC to drive a MOSFET and make a dirt cheap, simple and
>effecient switching regulator. I've been using this approach to dim a
>bank of LEDs.
Yes, but do you close the loop to make it regulate?
I've used PICs for some exceedingly simplistic tasks
like generate a square wave with off-delays between
half cycles to prevent shoot-through on totem-pole
output transistors. A 555 with 2 capacitors, a diode
two resistors and a pot can be arranged to provide
an open loop, adjustable duty cycle square wave . . .
but the best we know how to do suggests we close
the loop to prevent bus perturbations from making
it through the dimmer circuit and causing the
lights to visibly vary.
If you want to write the code for a 12F683 chip
that provides a closed loop, variable duty cycle
controller, we could market programmed chips . . .
or I'd market a dimmer and pay a royalty. I have
several products in the works now being developed
by others who will get a slice of the pie for the
market life of that product. You could use one
pin as an input to strap the functionality for
both 12v and 5v dimmers. I think the 683 has
enough snort to do a dual dimmer with a lookup
table that would cause filament lamps and LEDs
to track each other for apparent intensity.
Pretty cool product . . . but close the loop so
that the output is regulated.
If interested, let's develop a Product Function
Specification and see what we can cook up.
Bob . . .
----------------------------------------
( "Physics is like sex: sure, it may )
( give some practical results, but )
( that's not why we do it." )
( )
( Richard P. Feynman )
----------------------------------------
Message 4
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Bob,
I could put up with the strip and mash connectors as I use ferrules that
give insulation support for this type of connector and, not the nest, but
adequate electrical connection. Can you provide a wire diagram for the
needed support parts if I use one Pot ? Thanks in advance.
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com]On Behalf Of Robert
L. Nuckolls, III
Sent: Saturday, May 19, 2007 7:53 AM
Subject: Re: AeroElectric-List: 5 Volt Dimmer
<nuckollsr@cox.net>
At 06:03 AM 5/18/2007 -0800, you wrote:
>
>Don,
>
>Check out the LC-40 panel dimmer from Van's.
Some thoughts on the task of crafting a dimmer
suited for 5v lighting circuits:
First, the device cited above appears to be a
variable duty cycle control device that delivers
full bus voltage pulses of energy to the lamps
but controls the average current in the lamps
by setting the ON/OFF ratio. For example, if
you switch a 14 volt supply on for 10 milliseconds
and then off for 90 milliseconds, a device connected
downstream of that switch will experience and
average of Oout = Ein (Ton/Toff+Ton)
= 14.0 * (10/90+10) = 1.4 Volts.
This product appears to offer a full range of
control for the purpose of controlling 14 volt
lamps. When installing this style of controller
for a 5v lighting system, the controlling
potentiometer and associated resistors would
want to be tailored such that max clockwise
for the potentiometer produces a maximum duty
cycle of 5/14 or 36%.
The product cited appears to use strip-m-and-
mash-em screw terminals once used by Vision
Microsystems, recently recommended by BMA
(See page 41 of
http://www.aeroelectric.com/articles/richter/response_1.pdf )
These are not the best we know how to do (BWKHTD)
for bringing wires off an assembly and into an aircraft wire
bundle. I understand Vision Microsystems went to
D-sub connectors for their products. I use D-sub
connectors for ALL of my products where ever their
capabilities are commensurate with the task.
One might also consider pure linear dimmer controls
like those once sold from my website but now offered
from B&C's site at:
http://www.bandc.biz/cgi-bin/ez-catalog/cat_display.cgi?10X358218#dim30-14
These too are 4 to 12 volt controllers and would
require modification of their control circuitry
to provide the more useful 1.5 to 5 volt output
range. Further, a pure linear controller has to toss
off about 65 percent of total energy fed to the dimmer
when the lamps are on full bright. Hence the need for
heatsinks. However, these are dimming REGULATORS. Unlike
most variable duty cycle controllers, these devices will
maintain a constant output voltage irrespective of
perturbations of the bus voltage that might cause
visible fluctuations in the light produced by lamps
downstream.
A regulating dimmer isolates the lighting system from
such perturbations.
The BWNHTD mirrors methodologies but not the technology
in years past to provide an efficient step down of
bus voltage to the desired 1.5 - 5 volt output
range by use of inductors, capacitors and smart
transistors. These are a members of a large family
of switchmode power supplies. The device I was considering
was a commercial off the shelf product that didn't
match it's marketing hype. One can consider a scratch
built approach that is typified by this part.
http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,P1915
One takes a 1.8v fixed output version of this part
and adds the potentiometer to the feedback circuit
to achieve a 1.8 to 5.0 volt output. Or perhaps
a fully adjustable version will be necessary to get
a lower min output of say 1.0 to 5 volts.
This approach would be VERY efficient. The lost energy
is so low that the package could be quite small and
heat losses easily managed.
I thought I had a quick-turn solution to offer but
it didn't work out. So I've had to back-burner the
project.
Food for thought.
Bob . . .
Message 5
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| Subject: | transponder antenna ground plane |
Regarding the size of the ground plane for a transponder antenna,
Nuckolls says in his book, "5 1/2" in diameter is sufficient." I thought
that's what I did, but after I installed it I found that mine was only
5.22" in diameter. I understand that the length of the radius is
important for resonance at the transponder frequency. Can someone tell
me how much antenna degradation I can expect by being off by .18"? If
it's 10%, I'll reinstall the ground plane. If it's only 2 or 3 percent,
I'll probably just leave it the way it is.
Doug Holub
building a Velocity
Irving, Texas
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