Heading Hold Gyro.

[Brian Whatcott]

I expect, like me, you thought you knew what heading hold gyros were all
about? If you haven't been around model helicopter enthusiasts lately,
you have no idea! Try googling 'heading hold gyro'.
It turns out, that radio control modelers stick a heading hold gyro on
their model helicopter and hook it to a fast servo that modulates the
tail rotor pitch. The device takes over when a rotate ("pirouette')
command stops, and stops the tail dead on that heading - fast, and holds
it against wind-drift and weather cock effects.
The HH gyro runs $40 to $150 and a fast (digital) servo might add
another $40 on it.

Think of the possibilities for a heading stabilize function in a homebuilt!
A HH gyro driving a big servo, controlling a servo tab on the rudder.
Something similar could be arranged for pitch hold (a sort of super
cheap altitude hold/augment?)

Brian W

[Peter Dohm]

"brian whatcott" > wrote in message
...
>I expect, like me, you thought you knew what heading hold gyros were all
>about? If you haven't been around model helicopter enthusiasts lately, you
>have no idea! Try googling 'heading hold gyro'.
> It turns out, that radio control modelers stick a heading hold gyro on
> their model helicopter and hook it to a fast servo that modulates the tail
> rotor pitch. The device takes over when a rotate ("pirouette') command
> stops, and stops the tail dead on that heading - fast, and holds it
> against wind-drift and weather cock effects.
> The HH gyro runs $40 to $150 and a fast (digital) servo might add another
> $40 on it.
>
> Think of the possibilities for a heading stabilize function in a
> homebuilt!
> A HH gyro driving a big servo, controlling a servo tab on the rudder.
> Something similar could be arranged for pitch hold (a sort of super cheap
> altitude hold/augment?)
>
> Brian W

One of the avionics makers, Bendix IIRC, had a system available about 25 or
so years ago that used an air stream across a pair of resistance elements,
or two pairs of resistance elements for a two axis autopilot. Basically,
each pair of elements was an uninsulated resistor on each side of the
airstream for heading hold and top and bottom for pitch hold--not really the
same thing as altitude hold but possibly usefull in smooth VFR conditions.
AFAIK, the system worked because the resistance of each element (for most
materials) tends to increase with rising temperature and decrease with
falling temperature--so that the system can work by comparing the
resistances with little regard for the actual resistance values. My best
recollection is that the device could also maintain a standard rate turn.

I only vaguely recall that there may have been an article in one of the
homebuilding magazines--possibly in the early 1980s.

Peter

[cavelamb[_2_]]

Peter Dohm wrote:
> "brian whatcott" > wrote in message
> ...
>> I expect, like me, you thought you knew what heading hold gyros were all
>> about? If you haven't been around model helicopter enthusiasts lately, you
>> have no idea! Try googling 'heading hold gyro'.
>> It turns out, that radio control modelers stick a heading hold gyro on
>> their model helicopter and hook it to a fast servo that modulates the tail
>> rotor pitch. The device takes over when a rotate ("pirouette') command
>> stops, and stops the tail dead on that heading - fast, and holds it
>> against wind-drift and weather cock effects.
>> The HH gyro runs $40 to $150 and a fast (digital) servo might add another
>> $40 on it.
>>
>> Think of the possibilities for a heading stabilize function in a
>> homebuilt!
>> A HH gyro driving a big servo, controlling a servo tab on the rudder.
>> Something similar could be arranged for pitch hold (a sort of super cheap
>> altitude hold/augment?)
>>
>> Brian W
>
> One of the avionics makers, Bendix IIRC, had a system available about 25 or
> so years ago that used an air stream across a pair of resistance elements,
> or two pairs of resistance elements for a two axis autopilot. Basically,
> each pair of elements was an uninsulated resistor on each side of the
> airstream for heading hold and top and bottom for pitch hold--not really the
> same thing as altitude hold but possibly usefull in smooth VFR conditions.
> AFAIK, the system worked because the resistance of each element (for most
> materials) tends to increase with rising temperature and decrease with
> falling temperature--so that the system can work by comparing the
> resistances with little regard for the actual resistance values. My best
> recollection is that the device could also maintain a standard rate turn.
>
> I only vaguely recall that there may have been an article in one of the
> homebuilding magazines--possibly in the early 1980s.
>
> Peter
>
>
>

Electro-Fluidic Autopilot.
Sport Aviation -


May '78
Preliminary Report-Development of a Poor Man's VFR Autopilot/Don Hewes

March '79
Update On The Poorman's Autopilot... by Donald E. Hewes

February '80
Autopilot System For Homebuilt Airplanes... by Don Hewes

August '80
Fine Tuning The Electro-Fluidic Autopilot.. . by Doug Garner

April '81
Muscle For Your Homebuilt Autopilot... by Don Hewes

November '81
A Magnetic Heading Reference For The Electro Fluidic Autopilot,Part I
by Doug Garner

December '81
Magnetic Heading Performance For The Electro Fluidic Autopilot
Part 11 . . , by Doug Garner

--

Richard Lamb

[Brian Whatcott]

Peter Dohm wrote:
> "brian whatcott" > wrote in message
> ...
>> I expect, like me, you thought you knew what heading hold gyros were all
>> about? If you haven't been around model helicopter enthusiasts lately, you
>> have no idea! Try googling 'heading hold gyro'.
>> It turns out, that radio control modelers stick a heading hold gyro on
>> their model helicopter and hook it to a fast servo that modulates the tail
>> rotor pitch. The device takes over when a rotate ("pirouette') command
>> stops, and stops the tail dead on that heading - fast, and holds it
>> against wind-drift and weather cock effects.
>> The HH gyro runs $40 to $150 and a fast (digital) servo might add another
>> $40 on it.
>>
>> Think of the possibilities for a heading stabilize function in a
>> homebuilt!
>> A HH gyro driving a big servo, controlling a servo tab on the rudder.
>> Something similar could be arranged for pitch hold (a sort of super cheap
>> altitude hold/augment?)
>>
>> Brian W
>
> One of the avionics makers, Bendix IIRC, had a system available about 25 or
> so years ago that used an air stream across a pair of resistance elements,
> or two pairs of resistance elements for a two axis autopilot. Basically,
> each pair of elements was an uninsulated resistor on each side of the
> airstream for heading hold and top and bottom for pitch hold--not really the
> same thing as altitude hold but possibly usefull in smooth VFR conditions.
> AFAIK, the system worked because the resistance of each element (for most
> materials) tends to increase with rising temperature and decrease with
> falling temperature--so that the system can work by comparing the
> resistances with little regard for the actual resistance values. My best
> recollection is that the device could also maintain a standard rate turn.
>
> I only vaguely recall that there may have been an article in one of the
> homebuilding magazines--possibly in the early 1980s.
>
> Peter
>
>
>
I remember this project well, it was the brainchild of a research
engineer at one of the NASA labs - NASA Ames, if I remember.
I was so intrigued, I called him up to talk about it.
A few people scratch built the device, the "gyros" were four thermistors
on a circle, with a little tube blowing air into the center of the
circle. Rotation in either axis shielded one from the air jet, and
ventilated the other, of each pair. Thermistors generate a little heat,
and their resistance varies dramatically with temperature. Each pair fed
an operational amplifier as differential inputs.
A weakness of the design was the little motor and fan involved.
These days, a two axis (piezo) gyro is more stable, more sensitive and
more reliable, not to mention using much less power. And you can buy it
off the shelf!

Regards

Brian W

[Peter Dohm]

"cavelamb" > wrote in message
m...
> Peter Dohm wrote:
>> "brian whatcott" > wrote in message
>> ...
>>> I expect, like me, you thought you knew what heading hold gyros were all
>>> about? If you haven't been around model helicopter enthusiasts lately,
>>> you have no idea! Try googling 'heading hold gyro'.
>>> It turns out, that radio control modelers stick a heading hold gyro on
>>> their model helicopter and hook it to a fast servo that modulates the
>>> tail rotor pitch. The device takes over when a rotate ("pirouette')
>>> command stops, and stops the tail dead on that heading - fast, and holds
>>> it against wind-drift and weather cock effects.
>>> The HH gyro runs $40 to $150 and a fast (digital) servo might add
>>> another $40 on it.
>>>
>>> Think of the possibilities for a heading stabilize function in a
>>> homebuilt!
>>> A HH gyro driving a big servo, controlling a servo tab on the rudder.
>>> Something similar could be arranged for pitch hold (a sort of super
>>> cheap altitude hold/augment?)
>>>
>>> Brian W
>>
>> One of the avionics makers, Bendix IIRC, had a system available about 25
>> or so years ago that used an air stream across a pair of resistance
>> elements, or two pairs of resistance elements for a two axis autopilot.
>> Basically, each pair of elements was an uninsulated resistor on each side
>> of the airstream for heading hold and top and bottom for pitch hold--not
>> really the same thing as altitude hold but possibly usefull in smooth VFR
>> conditions. AFAIK, the system worked because the resistance of each
>> element (for most materials) tends to increase with rising temperature
>> and decrease with falling temperature--so that the system can work by
>> comparing the resistances with little regard for the actual resistance
>> values. My best recollection is that the device could also maintain a
>> standard rate turn.
>>
>> I only vaguely recall that there may have been an article in one of the
>> homebuilding magazines--possibly in the early 1980s.
>>
>> Peter
>>
>>
>>
>
> Electro-Fluidic Autopilot.
> Sport Aviation -
>
>
> May '78
> Preliminary Report-Development of a Poor Man's VFR Autopilot/Don Hewes
>
> March '79
> Update On The Poorman's Autopilot... by Donald E. Hewes
>
> February '80
> Autopilot System For Homebuilt Airplanes... by Don Hewes
>
> August '80
> Fine Tuning The Electro-Fluidic Autopilot.. . by Doug Garner
>
> April '81
> Muscle For Your Homebuilt Autopilot... by Don Hewes
>
> November '81
> A Magnetic Heading Reference For The Electro Fluidic Autopilot,Part I
> by Doug Garner
>
> December '81
> Magnetic Heading Performance For The Electro Fluidic Autopilot
> Part 11 . . , by Doug Garner
>
> --
>
> Richard Lamb
>
>

Thanks, Richard, I had forgotten where I saw it--and completely forgotten
that there were really a series of articles!

Peter

[Peter Dohm]

"brian whatcott" > wrote in message
...
> Peter Dohm wrote:
>> "brian whatcott" > wrote in message
>> ...
>>> I expect, like me, you thought you knew what heading hold gyros were all
>>> about? If you haven't been around model helicopter enthusiasts lately,
>>> you have no idea! Try googling 'heading hold gyro'.
>>> It turns out, that radio control modelers stick a heading hold gyro on
>>> their model helicopter and hook it to a fast servo that modulates the
>>> tail rotor pitch. The device takes over when a rotate ("pirouette')
>>> command stops, and stops the tail dead on that heading - fast, and holds
>>> it against wind-drift and weather cock effects.
>>> The HH gyro runs $40 to $150 and a fast (digital) servo might add
>>> another $40 on it.
>>>
>>> Think of the possibilities for a heading stabilize function in a
>>> homebuilt!
>>> A HH gyro driving a big servo, controlling a servo tab on the rudder.
>>> Something similar could be arranged for pitch hold (a sort of super
>>> cheap altitude hold/augment?)
>>>
>>> Brian W
>>
>> One of the avionics makers, Bendix IIRC, had a system available about 25
>> or so years ago that used an air stream across a pair of resistance
>> elements, or two pairs of resistance elements for a two axis autopilot.
>> Basically, each pair of elements was an uninsulated resistor on each side
>> of the airstream for heading hold and top and bottom for pitch hold--not
>> really the same thing as altitude hold but possibly usefull in smooth VFR
>> conditions. AFAIK, the system worked because the resistance of each
>> element (for most materials) tends to increase with rising temperature
>> and decrease with falling temperature--so that the system can work by
>> comparing the resistances with little regard for the actual resistance
>> values. My best recollection is that the device could also maintain a
>> standard rate turn.
>>
>> I only vaguely recall that there may have been an article in one of the
>> homebuilding magazines--possibly in the early 1980s.
>>
>> Peter
>>
>>
>>
> I remember this project well, it was the brainchild of a research engineer
> at one of the NASA labs - NASA Ames, if I remember.
> I was so intrigued, I called him up to talk about it.
> A few people scratch built the device, the "gyros" were four thermistors
> on a circle, with a little tube blowing air into the center of the circle.
> Rotation in either axis shielded one from the air jet, and ventilated the
> other, of each pair. Thermistors generate a little heat,
> and their resistance varies dramatically with temperature. Each pair fed
> an operational amplifier as differential inputs.
> A weakness of the design was the little motor and fan involved.
> These days, a two axis (piezo) gyro is more stable, more sensitive and
> more reliable, not to mention using much less power. And you can buy it
> off the shelf!
>
> Regards
>
> Brian W

Some very good points there, especially regarding the advances in some of
the components that are now available, which also remind me of a problem
that could be either general or local in nature.

Most of the sources that I used to know about have dissappeared from the
local business landscape--so I not not sure were one would buy solid state
gyros, abolute pressure sensors, mass flow sensors, thermistors, or any of
the resistors and SSI and LSI components that used to be so common.

Peter

[Brian Whatcott]

Peter Dohm wrote:
>...regarding the advances in some of
> the components that are now available, which also remind me of a problem
> that could be either general or local in nature.
>
> Most of the sources that I used to know about have dissappeared from the
> local business landscape--so I not not sure were one would buy solid state
> gyros, abolute pressure sensors, mass flow sensors, thermistors, or any of
> the resistors and SSI and LSI components that used to be so common.
>
> Peter
>
>
>

Sad but true. The source these days is the Internet via Google, and
originating usually in China or Taiwan.

Brian W

[RogerN]

"brian whatcott" > wrote in message
...
>I expect, like me, you thought you knew what heading hold gyros were all
>about? If you haven't been around model helicopter enthusiasts lately, you
>have no idea! Try googling 'heading hold gyro'.
> It turns out, that radio control modelers stick a heading hold gyro on
> their model helicopter and hook it to a fast servo that modulates the tail
> rotor pitch. The device takes over when a rotate ("pirouette') command
> stops, and stops the tail dead on that heading - fast, and holds it
> against wind-drift and weather cock effects.
> The HH gyro runs $40 to $150 and a fast (digital) servo might add another
> $40 on it.
>
> Think of the possibilities for a heading stabilize function in a
> homebuilt!
> A HH gyro driving a big servo, controlling a servo tab on the rudder.
> Something similar could be arranged for pitch hold (a sort of super cheap
> altitude hold/augment?)
>
> Brian W

The heading hold gyros are rate gyros and use a microcontroller integrate
the error. They hold heading real well but drift over time. Most of the
time we can trim out the drift well enough to not be a problem but remember
most model helicopter flights last no more than 15 minutes and if a constant
heading was held for an entire 5 minutes it would be a long and boring time
for the pilot.

But gyros in model helicopters do make a world of difference. When I
started trying to learn to fly model helicopters (1981) gyros weren't very
common. I tried for years and was never able to hover out a tank of fuel
before a crash. After purchasing a simple mechanical rate gyro, I flew some
70 full tanks of fuel before crashing, and that crash was a result of
getting too far away and losing orientation (the heli turned black in the
bright sky!).

On my larger model helicopters I have gyro's that once sold for nearly $400
and a servo that sells for $130, I bought most of my stuff used and
sometimes crashed. By that time I had so much experience rebuilding crashes
that I would buy heli's needing work for a fraction of the new cost. I have
my own home machine shop and make most of the shafts simply by cutting drill
rod to length and cross drilling the holes for the bolts, a $20 main shaft
costs me about $2 + 10 minutes.

RogerN

[Brian Whatcott]

RogerN wrote:
/snip/
>> Think of the possibilities for a heading stabilize function in a
>> homebuilt!
>> A HH gyro driving a big servo, controlling a servo tab on the rudder.
>> Something similar could be arranged for pitch hold (a sort of super cheap
>> altitude hold/augment?)
>>
>> Brian W
>
> The heading hold gyros are rate gyros and use a microcontroller to integrate
> the error. They hold heading real well but drift over time. Most of the
> time we can trim out the drift well enough to not be a problem but remember
> most model helicopter flights last no more than 15 minutes and if a constant
> heading was held for an entire 5 minutes it would be a long and boring time
> for the pilot. /snip/
> RogerN
>
>
Good thought. Gyros drift.
When I consider my personal heading hold, cross country, I drift way
more than any gyro I could buy, I reckon :-)

Moreover (as I find to my cost) a mini rate gyro won't drive a torquey
servo, unless I beef up the output signal.
It's pretty to watch a little scrap of gyro stretching and shrinking a
1.5 millisecond pulse repeated at 50Hz when I rotate the gyro.
I needed to slap together a pretend receive signal which pulses at 1.5
ms per 20 ms with a pot to vary the pulse from 1 ms to 2 ms to provide a
command signal. That's one 556 chip and a few Rs and Cs. Next step is
a heading hold - which I should have bought initially, and some mini
servos that can use this mini rate servo.

Brian W

[Peter Dohm]

"RogerN" > wrote in message
m...
>
> "brian whatcott" > wrote in message
> ...
>>I expect, like me, you thought you knew what heading hold gyros were all
>>about? If you haven't been around model helicopter enthusiasts lately, you
>>have no idea! Try googling 'heading hold gyro'.
>> It turns out, that radio control modelers stick a heading hold gyro on
>> their model helicopter and hook it to a fast servo that modulates the
>> tail rotor pitch. The device takes over when a rotate ("pirouette')
>> command stops, and stops the tail dead on that heading - fast, and holds
>> it against wind-drift and weather cock effects.
>> The HH gyro runs $40 to $150 and a fast (digital) servo might add
>> another $40 on it.
>>
>> Think of the possibilities for a heading stabilize function in a
>> homebuilt!
>> A HH gyro driving a big servo, controlling a servo tab on the rudder.
>> Something similar could be arranged for pitch hold (a sort of super cheap
>> altitude hold/augment?)
>>
>> Brian W
>
> The heading hold gyros are rate gyros and use a microcontroller integrate
> the error. They hold heading real well but drift over time. Most of the
> time we can trim out the drift well enough to not be a problem but
> remember most model helicopter flights last no more than 15 minutes and if
> a constant heading was held for an entire 5 minutes it would be a long and
> boring time for the pilot.
>
> But gyros in model helicopters do make a world of difference. When I
> started trying to learn to fly model helicopters (1981) gyros weren't very
> common. I tried for years and was never able to hover out a tank of fuel
> before a crash. After purchasing a simple mechanical rate gyro, I flew
> some 70 full tanks of fuel before crashing, and that crash was a result of
> getting too far away and losing orientation (the heli turned black in the
> bright sky!).
>
> On my larger model helicopters I have gyro's that once sold for nearly
> $400 and a servo that sells for $130, I bought most of my stuff used and
> sometimes crashed. By that time I had so much experience rebuilding
> crashes that I would buy heli's needing work for a fraction of the new
> cost. I have my own home machine shop and make most of the shafts simply
> by cutting drill rod to length and cross drilling the holes for the bolts,
> a $20 main shaft costs me about $2 + 10 minutes.
>
> RogerN
>
>
As a matter of fact, I really allowed myself to get way off track early on
in this thread--along with nearly everyone else.

Basically IIRC the rate gyro systems are traditionally called wing levelers,
while a real heading gyro is just that--and frequentle slaved to a flux
gate--so that an autopilot on heading hold will really continue to follow
the same magnetic heading. The rate gyro allows the autopilot to intersept
a new course or heading without commanding an acrobatic maneuver to
accomplish it.

Peter

[RogerN]

"Peter Dohm" > wrote in message
...
> "RogerN" > wrote in message
> m...
>>
>> "brian whatcott" > wrote in message
>> ...
>>>I expect, like me, you thought you knew what heading hold gyros were all
>>>about? If you haven't been around model helicopter enthusiasts lately,
>>>you have no idea! Try googling 'heading hold gyro'.
>>> It turns out, that radio control modelers stick a heading hold gyro on
>>> their model helicopter and hook it to a fast servo that modulates the
>>> tail rotor pitch. The device takes over when a rotate ("pirouette')
>>> command stops, and stops the tail dead on that heading - fast, and holds
>>> it against wind-drift and weather cock effects.
>>> The HH gyro runs $40 to $150 and a fast (digital) servo might add
>>> another $40 on it.
>>>
>>> Think of the possibilities for a heading stabilize function in a
>>> homebuilt!
>>> A HH gyro driving a big servo, controlling a servo tab on the rudder.
>>> Something similar could be arranged for pitch hold (a sort of super
>>> cheap altitude hold/augment?)
>>>
>>> Brian W
>>
>> The heading hold gyros are rate gyros and use a microcontroller integrate
>> the error. They hold heading real well but drift over time. Most of the
>> time we can trim out the drift well enough to not be a problem but
>> remember most model helicopter flights last no more than 15 minutes and
>> if a constant heading was held for an entire 5 minutes it would be a long
>> and boring time for the pilot.
>>
>> But gyros in model helicopters do make a world of difference. When I
>> started trying to learn to fly model helicopters (1981) gyros weren't
>> very common. I tried for years and was never able to hover out a tank of
>> fuel before a crash. After purchasing a simple mechanical rate gyro, I
>> flew some 70 full tanks of fuel before crashing, and that crash was a
>> result of getting too far away and losing orientation (the heli turned
>> black in the bright sky!).
>>
>> On my larger model helicopters I have gyro's that once sold for nearly
>> $400 and a servo that sells for $130, I bought most of my stuff used and
>> sometimes crashed. By that time I had so much experience rebuilding
>> crashes that I would buy heli's needing work for a fraction of the new
>> cost. I have my own home machine shop and make most of the shafts simply
>> by cutting drill rod to length and cross drilling the holes for the
>> bolts, a $20 main shaft costs me about $2 + 10 minutes.
>>
>> RogerN
>>
>>
> As a matter of fact, I really allowed myself to get way off track early on
> in this thread--along with nearly everyone else.
>
> Basically IIRC the rate gyro systems are traditionally called wing
> levelers, while a real heading gyro is just that--and frequentle slaved to
> a flux gate--so that an autopilot on heading hold will really continue to
> follow the same magnetic heading. The rate gyro allows the autopilot to
> intersept a new course or heading without commanding an acrobatic maneuver
> to accomplish it.
>
> Peter

The problem with sensing magnetic heading in model helicopters is that they
want them to hold the heading relative to the model. For example if you
were heading north and did a loop you would be heading south at the top of
the loop, that would be interesting if it tried to auto correct magnetic
heading during a loop or other aerobatics.

But for stabilizing an aircraft that wasn't performing aerobatics perhaps a
rate gyro, magnetic heading, and perhaps an accelerometer might be able to
do the job.

RogerN

[RogerN]

"brian whatcott" > wrote in message
...
> RogerN wrote:
> /snip/
>>> Think of the possibilities for a heading stabilize function in a
>>> homebuilt!
>>> A HH gyro driving a big servo, controlling a servo tab on the rudder.
>>> Something similar could be arranged for pitch hold (a sort of super
>>> cheap altitude hold/augment?)
>>>
>>> Brian W
>>
>> The heading hold gyros are rate gyros and use a microcontroller to
>> integrate the error. They hold heading real well but drift over time.
>> Most of the time we can trim out the drift well enough to not be a
>> problem but remember most model helicopter flights last no more than 15
>> minutes and if a constant heading was held for an entire 5 minutes it
>> would be a long and boring time for the pilot. /snip/
>> RogerN
>>
>>
> Good thought. Gyros drift.
> When I consider my personal heading hold, cross country, I drift way more
> than any gyro I could buy, I reckon :-)
>
> Moreover (as I find to my cost) a mini rate gyro won't drive a torquey
> servo, unless I beef up the output signal.
> It's pretty to watch a little scrap of gyro stretching and shrinking a 1.5
> millisecond pulse repeated at 50Hz when I rotate the gyro.
> I needed to slap together a pretend receive signal which pulses at 1.5 ms
> per 20 ms with a pot to vary the pulse from 1 ms to 2 ms to provide a
> command signal. That's one 556 chip and a few Rs and Cs. Next step is a
> heading hold - which I should have bought initially, and some mini servos
> that can use this mini rate servo.
>
> Brian W

The transmitter frames are about 50Hz but some of the more expensive
gyro/servo combinations are able to update the servo a few times between
transmitter frames. If I'm not mistaken larger servos don't put a higher
drain on the signal lines but they do pull more amps through the power
wires, that are often routed through the gyro. It's been years since I
looked but I think they have wiring harnesses to deliver servo power more
directly through the battery and the signal wire comes through the receiver
or gyro, as opposed to the power being routed through the receiver or gyro.

Instead of

Power > switch > receiver > gyro > servo

they have

Power > switch > servo
and
Power > switch > receiver > gyro > signal from gyro > servo

Back maybe 15 years ago I flew with one of the gyro manufacturers and at the
time they were using Tokin gyros, and AVR microcontrollers. I think some of
the newer gyro sensors have less drift problem than the Tokin did. The
drift was at least partially caused by change in gyro output due to change
in temperature. When the model heli is setting in the sun, the gyro gets
hot, when they start flying around the air flow helps cool it off and it
seems to be a good bit of drift during the first few minutes of a flight.
They fought this problem using a thermistor and compensating.

I know it would be more expensive but I thought it would be interesting to
use 2 sensors mounted 180 degrees to each other. That way they should both
drift in temperature together, giving nearly 0 differential output but the
actual signal from motion should be doubled.

RogerN

[Brian Whatcott]

RogerN wrote:

>> Moreover (as I find to my cost) a mini rate gyro won't drive a torquey
>> servo, unless I beef up the output signal.
>> Brian W
>
> /snip/ If I'm not mistaken larger servos don't put a higher
> drain on the signal lines but they do pull more amps through the power
> wires /snip/
> RogerN
>
>
I tried driving a Futaba S3010 with a GWS PG-03 rate sensor.
From a 6 volt cad stack.
The servo drives well with my dummy receiver signal - but just sits
there with the PG-03 in line.
But a scope demonstrates the GW-03 is reshaping the pulse with angular
rate....
So I ordered a Futaba 251 HH...

Brian W