https://rotorwayforums.com/ Sun, 18 Oct 2026 19:22:06 +0000 MyBB https://rotorwayforums.com/thread-251.html Fri, 25 Sep 2026 13:01:21 -0500 Jon Davis]]> https://rotorwayforums.com/thread-251.html Hi all,

It was actually Graeme Smith from Australia that started this whole story back in the late 90’s, and much of the credit should go to his foresight.   

I had been an ardent RC model helicopter enthusiast for several years and read a series of articles in a RC helicopter magazine by ventriloquist Jeff Dunham about building a Rotorway kit.  I was totally hooked.

I purchased a Rotorway EXEC 90 kit in 1994, one of the first in Australia.  A few years later Graeme was appointed as  the new Australian distributor (not sure of the date but must have been around 1996),  and as many of you would know, Graeme has for many decades been involved in experimental classification helicopters and has researched and implemented many new innovations and upgrades, particularly with the RotorWay helicopters.

Westach produce some great cost effective gauges for experimental and amateur built aircraft and a lot of their gauges were supplied in the RW kits. , However their analog rotortach always had some noticeable shortcomings, such has poor needle tracking, poor RPM accuracy, the need for calibration before use, drift with temperature, and it was often affected when the radio transmit button was pressed. As an person that  grew up and learnt electronics in the 60’s and 70’s analog era I would be the first to admit that analog circuitry is not an ideal or easy solution for this type of application that demands high repeatable accuracy and negligible affect  from environmental conditions.  But digital solutions were less readily available in the 80’s and 90’s .

The original Westberg tacho is a pure analog device and as such is obviously very susceptible to RF interference. Whilst shielded cables and using correct grounding techniques can sometimes help alleviate these problems, a digital tacho has a very much higher level of immunity to this problem. A slight amount of RF induced onto the signal cables, or directly radiated through the plastic tacho case (only a few millivolts of interference) onto the PCB is likely to affect the reading of an analog tacho. With a digital device, a small amount of superimposed RF signal will have no effect until its amplitude comes close to the amplitude of the digital signal (about 3 - 4 volts, ie. a thousand times higher)

 Also the gauge readings would vary with temperature. Owners may experiences temp changes from -40 to +100F. Whilst in Australia we don't experience temperature changes of that magnitude, and  the digital tacho there is (by definition) no drift with temperature on a digital device. Temperature  drift is an "analog thing" and can only occur in analog circuits. A digital tacho is all digital except where it interfaces to the meter movement where the digital signal is converted back to analog. ie 98% of the device is digital. The analog components that are used to drive the meter operate at unity gain and hence will have negligible temperature drift.

A digital tacho is also inherently very precise (using mathematical algorithms) and hence capable of very accurate tracking of rotor and engine speed.

Knowing that I owned an electronics design and manufacturing company ( mainly working at that time in the industrial and  oil/coal exploration fields), and was also a RotorWay owner, around 1998 he approached me to see if I was interested in designing a new improved rotortach that would overcome the shortfalls in the existing unit.

We decided that the best option would be for us to develop completely new circuitry based on digital microprocessor electronics to replace the original analog circuit board, but retain the existing case and meter movements etc.  That way we could offer cost effective upgrades to anyone with an existing rotortach, by simply replacing the circuit board, and without the need and high costs involved in a total product redesign and associated plastic injection moldings for new case components etc.

In 1999,  we had a successful prototype PCB working.  Even though we could design a  microcontroller digital circuit with optically isolate engine and rotor signal inputs with crystal controlled RPM accuracy that would never require customer calibration (eliminating the need for the optical rotor blade  RPM measuring tool that was supplied with the RW kit)  we did come a bit unstuck with the meter movements - as you will soon see.    

For the original prototype unit we carefully “characterised” /  calibrated the engine and rotor meters such that we knew the exact relationship of meter voltage to RPM reading on the dial. And this relationship in the form of a digital look-up table was programed in to the code that went in to the microcontroller.  So, all good, and the result was perfect.  Absolute accuracy and precise tracking of engine and rotor display over the full range – just what we were after.

However, the meter movements themselves are inherently analog devices and as such every individual meter movement is just slightly different in its sensitivity.  We hadn’t actually considered that at the time (silly us!).

So,  when we assembled our second prototype for testing, with another set of new meter movements, the result was disappointing as the meter readings were both slightly out in accuracy, and they did not track perfectly.

What this meant was that every tacho we were to manufacture would clearly require it’s own individual custom calibration look up table that would need to be downloaded in to the firmware when it was manufactured.  At the time that was certainly not good news. Every tacho manufactured would  need to be unique and custom programmed to suit it's particular meter movements – and that hasn’t changed to this date.  Hence the important serial number on the back of every tacho, and this relates back to its own manufacturing file with it’s unique calibration data.  For every tacho that has been manufactured since 1999, we keep all it’s details on file in case we ever need to refer to it for repairs etc.

However fortunately we found a way to simplify this onerous task and speed up the measuring and calibrating of every individual meter movement.  We developed a separate program (using MATLAB) that could interpolate and generate a full look up table covering the 45% to 114% dial range based on twelve spot measurements.  It still takes time to do each one but the end result is perfect accuracy and tracking of both needles.

And that is how we came to start modifying and upgrading RW rotortachs with an effective digital solution.

Sadly I do not have a photo of the original digital circuit board.  But soon after releasing the new digital RW upgrade we got approached by Russ Gerrish around  2002 who had heard about our rotortach and was after one to suit the Jet Exec.  And that started a whole new interesting chain of developments of the product that continues to this day.  That will all be covered in my Part 2 of the story.  Attached is a photo of the revised circuit from 2002 that was resigned to suit both the standard RW and also the Jet Exec. That’s 24 years ago!  I just can’t believe where all the years have gone.


]]> Hi all,

It was actually Graeme Smith from Australia that started this whole story back in the late 90’s, and much of the credit should go to his foresight.   

I had been an ardent RC model helicopter enthusiast for several years and read a series of articles in a RC helicopter magazine by ventriloquist Jeff Dunham about building a Rotorway kit.  I was totally hooked.

I purchased a Rotorway EXEC 90 kit in 1994, one of the first in Australia.  A few years later Graeme was appointed as  the new Australian distributor (not sure of the date but must have been around 1996),  and as many of you would know, Graeme has for many decades been involved in experimental classification helicopters and has researched and implemented many new innovations and upgrades, particularly with the RotorWay helicopters.

Westach produce some great cost effective gauges for experimental and amateur built aircraft and a lot of their gauges were supplied in the RW kits. , However their analog rotortach always had some noticeable shortcomings, such has poor needle tracking, poor RPM accuracy, the need for calibration before use, drift with temperature, and it was often affected when the radio transmit button was pressed. As an person that  grew up and learnt electronics in the 60’s and 70’s analog era I would be the first to admit that analog circuitry is not an ideal or easy solution for this type of application that demands high repeatable accuracy and negligible affect  from environmental conditions.  But digital solutions were less readily available in the 80’s and 90’s .

The original Westberg tacho is a pure analog device and as such is obviously very susceptible to RF interference. Whilst shielded cables and using correct grounding techniques can sometimes help alleviate these problems, a digital tacho has a very much higher level of immunity to this problem. A slight amount of RF induced onto the signal cables, or directly radiated through the plastic tacho case (only a few millivolts of interference) onto the PCB is likely to affect the reading of an analog tacho. With a digital device, a small amount of superimposed RF signal will have no effect until its amplitude comes close to the amplitude of the digital signal (about 3 - 4 volts, ie. a thousand times higher)

 Also the gauge readings would vary with temperature. Owners may experiences temp changes from -40 to +100F. Whilst in Australia we don't experience temperature changes of that magnitude, and  the digital tacho there is (by definition) no drift with temperature on a digital device. Temperature  drift is an "analog thing" and can only occur in analog circuits. A digital tacho is all digital except where it interfaces to the meter movement where the digital signal is converted back to analog. ie 98% of the device is digital. The analog components that are used to drive the meter operate at unity gain and hence will have negligible temperature drift.

A digital tacho is also inherently very precise (using mathematical algorithms) and hence capable of very accurate tracking of rotor and engine speed.

Knowing that I owned an electronics design and manufacturing company ( mainly working at that time in the industrial and  oil/coal exploration fields), and was also a RotorWay owner, around 1998 he approached me to see if I was interested in designing a new improved rotortach that would overcome the shortfalls in the existing unit.

We decided that the best option would be for us to develop completely new circuitry based on digital microprocessor electronics to replace the original analog circuit board, but retain the existing case and meter movements etc.  That way we could offer cost effective upgrades to anyone with an existing rotortach, by simply replacing the circuit board, and without the need and high costs involved in a total product redesign and associated plastic injection moldings for new case components etc.

In 1999,  we had a successful prototype PCB working.  Even though we could design a  microcontroller digital circuit with optically isolate engine and rotor signal inputs with crystal controlled RPM accuracy that would never require customer calibration (eliminating the need for the optical rotor blade  RPM measuring tool that was supplied with the RW kit)  we did come a bit unstuck with the meter movements - as you will soon see.    

For the original prototype unit we carefully “characterised” /  calibrated the engine and rotor meters such that we knew the exact relationship of meter voltage to RPM reading on the dial. And this relationship in the form of a digital look-up table was programed in to the code that went in to the microcontroller.  So, all good, and the result was perfect.  Absolute accuracy and precise tracking of engine and rotor display over the full range – just what we were after.

However, the meter movements themselves are inherently analog devices and as such every individual meter movement is just slightly different in its sensitivity.  We hadn’t actually considered that at the time (silly us!).

So,  when we assembled our second prototype for testing, with another set of new meter movements, the result was disappointing as the meter readings were both slightly out in accuracy, and they did not track perfectly.

What this meant was that every tacho we were to manufacture would clearly require it’s own individual custom calibration look up table that would need to be downloaded in to the firmware when it was manufactured.  At the time that was certainly not good news. Every tacho manufactured would  need to be unique and custom programmed to suit it's particular meter movements – and that hasn’t changed to this date.  Hence the important serial number on the back of every tacho, and this relates back to its own manufacturing file with it’s unique calibration data.  For every tacho that has been manufactured since 1999, we keep all it’s details on file in case we ever need to refer to it for repairs etc.

However fortunately we found a way to simplify this onerous task and speed up the measuring and calibrating of every individual meter movement.  We developed a separate program (using MATLAB) that could interpolate and generate a full look up table covering the 45% to 114% dial range based on twelve spot measurements.  It still takes time to do each one but the end result is perfect accuracy and tracking of both needles.

And that is how we came to start modifying and upgrading RW rotortachs with an effective digital solution.

Sadly I do not have a photo of the original digital circuit board.  But soon after releasing the new digital RW upgrade we got approached by Russ Gerrish around  2002 who had heard about our rotortach and was after one to suit the Jet Exec.  And that started a whole new interesting chain of developments of the product that continues to this day.  That will all be covered in my Part 2 of the story.  Attached is a photo of the revised circuit from 2002 that was resigned to suit both the standard RW and also the Jet Exec. That’s 24 years ago!  I just can’t believe where all the years have gone.


]]> https://rotorwayforums.com/thread-244.html Thu, 10 Sep 2026 12:52:00 -0500 Jon Davis]]> https://rotorwayforums.com/thread-244.html TESTING THE 720-12R WESTACH ROTOR SHAFT HALL EFFECT SENDER UNIT.

This sender can be simply yet accurately tested either in situ in the helicopter or as a “bench test”.  If in situ then it can be tested whilst connected to the rotortach and I’ll do a separate post for that that also includes testing the rotortach itself.

However this thread is for testing the hall effect sender when it is NOT connected to the rotortach.  It is a simple but important  fundamental test of the sender itself, and I think this is a particularly useful test when there appears to be some problem with the rotor speed display and there is a difficulty identifying whether the problem is actually with the sender, the rotortach, or the wiring.

All you will need is a multimeter, a resistor, a magnet, and a voltage source - anything between 5V – 12V.

NOTE:  the sender unit expects to see the South pole of a magnet.  It won't work with a North pole.

A few comments relating to the alignment of the magnet ring :-
1/  The active part of the hall effect sender is dead centre in the middle of the threaded barrel.  Ensure that your magnet ring is vertically aligned so that the centre of it passes over the centre of the sender. If it is too high or low then the sensor in the sender may not “see” the magnet.  There have been a couple of different styles of magnet rings over the decades, but the same theory holds.
2/  Don’t adjust the sender so that it is almost touching the magnets.  It’s not necessary.  The actual hall effect sensor semiconductor used in the sender is extremely sensitive to shock or any impact. If a magnet hits or touches the epoxy face of the sender it is likely to damage it. Typically 1.5-2.0mm gap should work fine.

Instructions are in the drawing.  Let me know your comments and if anyone has any questions.




  Hall Effect Sender test circuit.pdf (Size: 10.01 KB / Downloads: 22) ]]> TESTING THE 720-12R WESTACH ROTOR SHAFT HALL EFFECT SENDER UNIT.

This sender can be simply yet accurately tested either in situ in the helicopter or as a “bench test”.  If in situ then it can be tested whilst connected to the rotortach and I’ll do a separate post for that that also includes testing the rotortach itself.

However this thread is for testing the hall effect sender when it is NOT connected to the rotortach.  It is a simple but important  fundamental test of the sender itself, and I think this is a particularly useful test when there appears to be some problem with the rotor speed display and there is a difficulty identifying whether the problem is actually with the sender, the rotortach, or the wiring.

All you will need is a multimeter, a resistor, a magnet, and a voltage source - anything between 5V – 12V.

NOTE:  the sender unit expects to see the South pole of a magnet.  It won't work with a North pole.

A few comments relating to the alignment of the magnet ring :-
1/  The active part of the hall effect sender is dead centre in the middle of the threaded barrel.  Ensure that your magnet ring is vertically aligned so that the centre of it passes over the centre of the sender. If it is too high or low then the sensor in the sender may not “see” the magnet.  There have been a couple of different styles of magnet rings over the decades, but the same theory holds.
2/  Don’t adjust the sender so that it is almost touching the magnets.  It’s not necessary.  The actual hall effect sensor semiconductor used in the sender is extremely sensitive to shock or any impact. If a magnet hits or touches the epoxy face of the sender it is likely to damage it. Typically 1.5-2.0mm gap should work fine.

Instructions are in the drawing.  Let me know your comments and if anyone has any questions.




  Hall Effect Sender test circuit.pdf (Size: 10.01 KB / Downloads: 22) ]]> https://rotorwayforums.com/thread-207.html Thu, 20 Aug 2026 12:31:22 -0500 Jon Davis]]> https://rotorwayforums.com/thread-207.html Hi everyone,

I am the designer and manufacturer of the digital rotortach that has been used in Rotorway helicopters since late 1999,  which replaced the original Westach analog units, and became standard equipment supplied in RW kits for very many years.

I was one of the original Rotorway owner/builders in Australia and purchased and built an Exec 90 in 1994, which is how I got involved in the new rotortach in the first place. Conveniently  I just happened to also own an electronic design and manufacturing company! 

I sold the company and moved to the UK in 2021 but retained the rotortach business, where I continue to manufacture them, not just to suit Rotorway, but just about every experimental class helicopter.  Aside from being the approved supplier to RW for many years they continue to be the standard factory supplied rotortachs for Cicare and Safari, and are used extensively by the Helicycle community.             

Since the original digital rotortach some twenty six years ago,  I have continued to update and refine the design as new microcontroller and electronic component technology has advanced. 

The Rotorway version with the round style front is an exact  drop-in replacement for the old Westach analog units – same mounting and identical pin out and electrical connections (with the addition of a sounder horn on Pin 1). However we also offer them in the standard square aircraft style case.

Whilst every rotortach is assembled to order because of the large number of different versions we offer,  delivery time is still typically only 7 working days.

There is a pretty interesting background story to how the digital rotortach originally came about in the first place.   Also many of you technical guys I am sure will be interested in some of the rather unusual and very unique aspects of the electronic design which I am happy to share. I will cover these in more detail in further posts.

In the meantime please contact me if you have any questions.

Jon Davis
Digilin LEDtechnics
Brickfields
Hillis Gate Road
Cowes
Isle of Wight PO31 8NA
UK

ph +44 1983 282332
Mob +44 771765 78933
email jon.digilin@gmail.com




]]> Hi everyone,

I am the designer and manufacturer of the digital rotortach that has been used in Rotorway helicopters since late 1999,  which replaced the original Westach analog units, and became standard equipment supplied in RW kits for very many years.

I was one of the original Rotorway owner/builders in Australia and purchased and built an Exec 90 in 1994, which is how I got involved in the new rotortach in the first place. Conveniently  I just happened to also own an electronic design and manufacturing company! 

I sold the company and moved to the UK in 2021 but retained the rotortach business, where I continue to manufacture them, not just to suit Rotorway, but just about every experimental class helicopter.  Aside from being the approved supplier to RW for many years they continue to be the standard factory supplied rotortachs for Cicare and Safari, and are used extensively by the Helicycle community.             

Since the original digital rotortach some twenty six years ago,  I have continued to update and refine the design as new microcontroller and electronic component technology has advanced. 

The Rotorway version with the round style front is an exact  drop-in replacement for the old Westach analog units – same mounting and identical pin out and electrical connections (with the addition of a sounder horn on Pin 1). However we also offer them in the standard square aircraft style case.

Whilst every rotortach is assembled to order because of the large number of different versions we offer,  delivery time is still typically only 7 working days.

There is a pretty interesting background story to how the digital rotortach originally came about in the first place.   Also many of you technical guys I am sure will be interested in some of the rather unusual and very unique aspects of the electronic design which I am happy to share. I will cover these in more detail in further posts.

In the meantime please contact me if you have any questions.

Jon Davis
Digilin LEDtechnics
Brickfields
Hillis Gate Road
Cowes
Isle of Wight PO31 8NA
UK

ph +44 1983 282332
Mob +44 771765 78933
email jon.digilin@gmail.com




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