Wireless Rotor tach.

gyrojake

Gyro Rehab Candidate
Joined
Jan 1, 2007
Messages
2,313
Location
E-City, Florida
Aircraft
Gyroplanes
Total Flight Time
A few hours
Decided to build a wireless rotor tach.

This is just dead bugged on the wire for now and will be put on a PCB board once the design is complete.

This is a crystal controlled F.M. transmitter, so the frequency is very stable and Yes, I can modulate a crystal in F.M.

A phased lock loop will take too much power to operate.

The transmitter is powered by a generator supplied by the ring gear teeth and a magnetic pickup, just like the pickup you use on the red lion tach.

This will work with a programmable tach like red lion or one that delivers one pulse per rev.

The upper unit will not need power since the rotation of the rotor head powers the transmitter.

It will be smaller than a one-inch square and one half inch tall.

A small F.M. receiver will be hooked to the tach and BINGO wireless rotor tach.

Not bad for a drunk, pot smoking, swamp rat !!

Should be able to market this device with no problem.

Here's a vid to demo and explain
 
now my question is will you build us one?
in canada it's the law to have a rotor rpm gauge
 
Once I'm finished with the design I am going to have them commercially produced to accommodate different models of gyros. Some count 108, some count 4 and some count 1 Per Rev.
Thanks for noticing. I felt this would have gotten a much larger response because none of the engineers or geniuses came up with it. Hopefully, the Chinese will see this and have them on the market next week for $12 and save me some design work and investment money !!
Also thanks for the likes :)
 
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Great idea Jake!

I feel a wireless system as you describe would be a very nice thing to have.

The wiring to the pickup I use now is fragile and located in a place with lots of wind, vibration and movement.

I have lost the rotor tachometer twice on Autogyro products and following the wiring from the sender to the tachometer is troublesome.

I have replaced the rotor tachometer twice on The Predator.

Part of my preflight on every gyroplane I fly is to check the condition of the wiring to the pickup.

I would prefer an analog rotor tachometer so I can more quickly get a feel for when the rotor rpm is approaching my decision/action points; especially when I am waiting for the rotor to stop decelerating and start to accelerate when I am doing stop and goes.
 
Great input Vance.
Never thought of the analog guys !!
I can devise the receiver to put out a voltage for an analog tach and pulses for digital tachs.
Positive and negative input always helps me see in different perspectives, thank you for your input.
With my limited technical abilities, I need all the help I can get :)
 
Jake, every couple of months you throw something out there that makes me say to myself "damn, why didn't I think of that!" Keep using your imagination medicine (if you know whet I mean). You make the gears in my head start turning every now and then.
 
Jake, cool idea! Is the transmitter on the FM broadcast band? Or maybe somewhere in the 433- or 900-MHz bands where stuff like wireless weather stations operate?

There was a guy a couple years ago trying to use wi-fi to bring a bunch of remote sensors in to a Raspberry Pi computer, for display on a small HD TV used as an instrument panel. It sounded to me like it would require too much power, but the idea of wireless senders is cool.

Once you perfect the wireless rotor tach, see if you can also obsolete thermocouple wiring. It will be a major contribution to mental health!
 
PW_Plack;n1127131 said:
Jake, cool idea! Is the transmitter on the FM broadcast band? Or maybe somewhere in the 433- or 900-MHz bands where stuff like wireless weather stations operate?

There was a guy a couple years ago trying to use wi-fi to bring a bunch of remote sensors in to a Raspberry Pi computer, for display on a small HD TV used as an instrument panel. It sounded to me like it would require too much power, but the idea of wireless senders is cool.

Once you perfect the wireless rotor tach, see if you can also obsolete thermocouple wiring. It will be a major contribution to mental health!

The FCC allows us to use Specific frequencies in the F.M. broadcast band.I choose 88.1mhz for simplicity in the project. My tx power is low enough to pass the regulations, plus it's an unused frequency.
Now I can use products that are readily available for the project.
My only problem was a transmitter that would operate at 1 volt. I couldn't find one , so I had to design one.
The receiver can use battery power from the aircraft and the tx will use the ring gear and pickup for power.
As for your thermal-couple wiring problem; always remember that with J or K types, RED is always negative and an enclosed wiring harness must use a twisted J or K type wire all the way to the instrument.
You can use #14 tinned wire in exposed installations.
To tx static analog voltages is a complicated endeavor, Digital is the way to go for that.
The RPM analog would be easier because it starts out as an alternating current which can be used for the analog RPM gauges.
Thermal-couples are always putting out a small D.C. voltage which is hard to translate in modulating RF. so a pulse width modulator can convert a D.C. voltage to pulses that then can be modulated into the RF.
I think ? !!!
 
AirCommandPilot;n1127107 said:
Jake, every couple of months you throw something out there that makes me say to myself "damn, why didn't I think of that!" Keep using your imagination medicine (if you know whet I mean). You make the gears in my head start turning every now and then.

Sometimes you can't see the woods because of the forest.
I burn the weeds and could see the big picture clearly !! Haha :)
 
gyrojake;n1127146 said:
I choose 88.1mhz for simplicity in the project. My tx power is low enough to pass the regulations, plus it's an unused frequency. Now I can use products that are readily available for the project. My only problem was a transmitter that would operate at 1 volt. I couldn't find one , so I had to design one...

Unused? There's a bunch of stations on 88.1 in Florida, and even three here in sparsely-populated Utah. It will be interesting to see if the improved FM reception you get in the air produces too much interference.

Your method of powering the transmitter is novel and cool. I always wondered how much power was available from a pickup. I guess the rotor tach schemes which use magnets on the ring gear could be capable of providing a higher power budget, but your approach is pretty neat!

gyrojake;n1127146 said:
Thermal-couples are always putting out a small D.C. voltage which is hard to translate in modulating RF. so a pulse width modulator can convert a D.C. voltage to pulses that then can be modulated into the RF. I think ? !!!

The EGT thermocouples on the 582 I'm flying produce in the range of 20 mV at room temp, so it would probably take an op-amp to scale it up to something useful. But it would be worth the hassle of providing it some power..
 
Paul,
I'm only using 88.1in my experiment for convenience and in my area it is unused. The closest tx is 150 miles away.
If I produce these commercially I will use the 400 mhz commercial band with a DTMF tx and rx .
With DTMF a receiver will not accept reception without a specific tone in the carrier.
I'm using the ring gear for simplicity also. I'm sure I could add ten pounds of magnets and twenty pounds of coils to produce a Kilowatt of power but this is not needed.
On the EGT probes, pulse width modulation could be achieved with one component and no extra amplification.
Thanks for the input, Kinnda keeps me on my toes to see or hear other ideas.
 
Its a great project Jake. Are you using the same pickup coil for power and RPM sensing? Are you rectifying the pickup coil with the diodes, then charging a capacitor for powering the oscillator and also using the pickup coil AC voltage to Frequency Modulate the 88.1?

You might want to keep in mind any noise generated that might mess with an airband transciever.

Great work!
 
Hmm...DTMF stands for "dual-tone multi-frequency." Better known as "touch tone" in the telephone world. I think what you're thinking of is CTCSS, or "PL" as Motorola called it (for "Private Line"). That's an OK way to go for audio, but probably overkill for getting pulses over a four-foot path. I've seen prices on low-power digital data transfer stuff coming down a bunch lately. The advantage there is it inherently listens only for its paired partner.

There won't be a frequency in the 400 MHz band you can use legally in the US. You'll probably want to go to 915 MHz. Or, 46/49 MHz is still out there, although the little walkie-talkies and baby monitors for that band have been out of production for years. That band would actually lend itself to really simple pulse transmitters like you're using.
 
Seems like you got some google talents going on Paul.

"That's an OK way to go for audio, but probably overkill for getting pulses over a four-foot path."
How does this make any sense?

Keep in mind, this is a prototype and I am using parts that I have available to me from my junk pile.
A DTMF is used regularly for secure radio connections and controlling items with a radio. I'm sure today's technology has many other options.
DTMF is not only for phones. I'm sure you have used pliers as a hammer ! and I use many things in an unorthodox manner to achieve my goals.
The tone or tones are used as an analog code for the receiver to only accept the information I'm transmitting.
I am making this simple. Using tones to activate the receiver is cheap and simple, plus keeps information from other sources out.
This is a prototype and I am not going through the expense of high dollar technology.
I have a problem with explaining or teaching someone that already thinks they know.
If you have Ideas, share them but NEVER tell me how I should do my project unless you have the skills to achieve the same goal.
I'm gonna give you a chance to participate, build one and show me what you have.
Beat me to the outcome and I'll buy one from you :)
410420
This band is used in the Industrial/Business Radio Service. This band is allocated for both Federal and Non-Federal use. Operation of unlicensed Part 15 Devices is permitted between 410 and 420 MHz.


 
Wasn't trying to start a pissing contest Jake. Just wondered how DTMF would work in a low-parts-count, pulse-modulated application. I'll be content to watch and see what you come up with. If your junkbox is complete enough to include a spectrum analyzer, maybe it includes an 8870 and some logic chips.

The Google comment was cute. DTMF and I go back a ways. I mounted a Western Electric DTMF pad in the dash of my '64 Chevy to access ham radio autopatches on VHF, and spent a lot of years building and maintaining ham repeaters in Florida and the Carolinas.

I stand corrected on the low end of 400 MHz. I forgot there was Part 15 down there. The US is being flooded with 433-434 MHz stuff from China which is legal in Europe and other places, but not here. Carry on!
 
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