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Old 06-24-2011, 04:19 PM   #1 (permalink)
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Default Hyperion Phase Sensor on the CGY750

As regular visitors to this forum may have noticed I have been experimenting with using the CGY750 governor on a 500ESP, as reported HERE.

This first involved fitting magnets to the autorotation gear, and then to the main gear, using the supplied hall effect sensor. Whilst reasonably good results were obtained, I felt that a phase sensor was more appropriate for an electric heli, and couldn't resist the temptation to give that a try. Ultimately the results have been worthwhile as reported below.

Before continuing though I'd like to thank ollie2893 and Dr.Ben in particular for their input and enthusiasm.

V-BAR user have reported some success with the Hyperion Phase Sensor which is very cheap. It seemed the obvious basis for the project, available HERE in the US, and HERE in the UK for under a very modest sum.

Upon arrival mine looked thus:


And out of the packet:


And, heatshrink removed:


Unfortunately the output pulse rate from the phase sensor is too high for the CGY750. Using a 14T pinion with a 162T main gear, and with the sensor giving 3 pulses per revolution of the motor, the motor-pulse:head-speed ratio is 34.71, higher than the 30.00 max of the CGY750 governor. It was therefore necessary to pre-scale these pulses. Dividing by two would allow a ratio of 17.36:1. The Rsen connection to the CGY750 provides a regulated 3V output, so any circuitry attached to it, unless sourcing power from elsewhere, needs to be able to operate at this voltage. Fortunately the 74HC logic family operates on 2 to 6V. In order to pre-scale the signal by 2, 4, or 8 times I selected a 74HC93 device as shown below:


As can be seen this consists of a 1 stage and 3 stage ripple counter. I chose to use only the 3 bit counter as this would give me the flexibility in output pulse rate I sought.

As can be seen below, the phase sensor fortunately has no components on the rear.


I was therefore able to mount the 74HC93 on the rear of the board without obstruction. To mount it I removed the solder resist from the ground plane adjacent to where pins 2, 3, 6, 7, 13 and 14 would sit. This provided for secure mounting of the device using n/c pins, and unused inputs which needed to be grounded. The board was then tinned:


And with all other pins straightened so eliminate any shorting to the ground plane, the device mounted:


I then superglued an 0805 2K7 resistor to the top of the chip and wired the output signal from the phase sensor to one end of the resistor and on to pin 1, the input to the 3 bit counter section. I also fitted a 1210 0.1uF decoupler cap across the 0V/3V connections and ran the 3V line to the other end of the resistor and on to pin 5, the power input.


Next I added a ground wire to pin 10, which was too close to the single (3V) track on the back of the PCB to simply connect it to the ground plane.

I also connected the output of the divide by two stage of the counter (pin 9) to the output lead. NOTE THAT THIS SUBSEQUENTLY WAS MOVED to pin 8, see below.


For those who find battery connections hard to solder, see below the modified board next to a servo connector for scale!


I then potted both sides of the board in epoxy to protect the wiring:



Installation was simple. The red sense wire was connected to one of the ESC leads to the motor:


The sense wire was run, protected by braiding, past the motor to the phase sensor, now enclosed in heatshrink and cable-tied to the inside of the frame at the top of the 'X':


And the output cable was then run into the Rsen input of the CGY750.


Alas first results were not good! The RPM display on the CGY750 peaked at 2091 rpm and refused to read any higher. I checked the signal of an oscilloscope and it looked perfect, a 50:50 duty cycle square wave, but clearly the CGY750 didn't like it. The supplied hall effect sensor waveform is a sequence of relatively short positive spikes, so for a given frequency the low period of the input signal to the CGY750 would be much longer. Also considering that I'm running at the top end of the RPM range (2720rpm), I figured that this low period was perhaps too short, output from my divide by two counter. I therefore removed the heatshrink and drilled into the epoxy to move the output wire from pin 9 to pin 8, turning the pre-scaler into a divide by four.

Changing the gear ratio from 17.36 to 8.68, the CGY750 was then happy over the full RPM range. Initial testing was hampered by me leaving the LLmt_Hov and LLmtIdup gov advanced settings too high, so the gov wouldn't regulate at a low speed. I checked the headspeed using a laser tacho and this agreed with that shown on the CGY750 display.

On to the flight tests and I found that the tail wagged and gov hunted. Most disappointing. I tried Quick/Middle/Moderate settings etc to no avail. I then checked the gov basic menu and found that the servo type was set to analog, not DG:1520. Changing that made all the difference, and suddenly everything started working as hoped/expected.

Now I'm running the gov using the following settings:

ServoTyp: DG:1520
Wrk.Mode: Governor
Rv.Disp: Rotor
Response: Quick
Gv.Gain: 20%
THR.Mode: Tx.Curve
Rv.UpDly: 8Frm
Rv.DnDly: 10Frm
StartDly: 5St
On.Revo: 60%
LLmt_Hov: 80%
LLmtIdup: 80%


At takeoff with a full battery there's a little hunting lasting maybe 5s and then the flight was perfect. Punch-outs had no audible dip in head-speed, nor fluttering.

I've only had one proper flight before it started to rain, but I believe the slight hunting at the start of the flight is probably due to the Rv.DnDly being too low, my reasoning being that this governor is designed for use with IC engines which have engine braking. Unless I turn on the braking function in the ESC, the electric motor is unbraked and so won't respond very quickly to a reduction in throttle input. A large Rv.DnDly should go some way to address this. I'll report back.

Steve

PS Sticky worthy?
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Last edited by Steve Evans; 06-24-2011 at 06:19 PM.. Reason: Attachments vanished!
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Old 06-27-2011, 01:37 PM   #2 (permalink)
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Wow! this is incredible. So for 10 pole motors can you wire it to divide by 5?

Exactly what we need for CGY750 and EP heli's.
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Old 06-27-2011, 02:29 PM   #3 (permalink)
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No, the 74HC93 is a binary counter, so it can divide by 2, 4, 8 or 16. For a 10 pole motor you'd get 5 pulses per revolution, which probably wouldn't work at the same head-speed (2720) using divide by four, but you could wire up the output to pin 11 to get divide by eight. Of course this all depends on your gearing and head-speed.

Steve
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Old 06-27-2011, 03:24 PM   #4 (permalink)
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A quick bit of hovering in the garden with a couple of fully charged batteries has led me to the following settings:

Rv.UpDly: 14Frm
Rv.DnDly: 18Frm


There's a very slight hunt on takeoff, but this very quickly vanishes.

Hoping for a better fly at the park tomorrow lunchtime.

Incidentally, note that the Maximum RPM display on the CGY750 gets somewhat confused by the startup beeps from the ESC, so if you want to use that, be sure to reset it after poweron. For the record I see an overspeed to about 2810rpm before the head-speed settles down to the desired 2720.

Steve
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Old 06-27-2011, 03:52 PM   #5 (permalink)
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I want two of these! But I think the soldering work is a little over my capability.

If anyone is going to make some of these keep me in mind.

Great work Steve
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Old 06-29-2011, 08:42 AM   #6 (permalink)
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Great job Steve!

If Futaba could come up with a cheap sensor for EP I'm sure they would gain market share!

Meanwhile, can you enter mass production and sell me 2 of those?
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Old 06-29-2011, 02:51 PM   #7 (permalink)
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The trouble is it would cost more than the phase sensor!

Steve
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Old 06-29-2011, 05:41 PM   #8 (permalink)
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Well done, Steve! I am very impressed by your tenacity (and engineering skills). Being a lesser mortal myself, I simply bought the vbar
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Old 06-30-2011, 09:33 AM   #9 (permalink)
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Thanks for sharing this info, Steve. I'm going to have to give this a try.
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Old 06-30-2011, 10:04 AM   #10 (permalink)
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I would like to do so too, given Steve doesn't wish to become a billionnaire selling those

Steve, my soldering habilities ARE limited to soldering bullets and deans

Do you care to share what type of equipment is needed for this kind of job (soldering iron size, magnifying glass, type of solder, crocodile pliers to hold the stuff, type of epoxy?). That would be very appreciated!
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Old 06-30-2011, 01:06 PM   #11 (permalink)
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I used a 15W cheapo soldering iron and a pair of no. 7 tweezers and that's about it. Epoxy was normal araldite (24 hour variety).

I wish Futaba would update the CGY750 software to accept the signal from the phase sensor directly (requiring only a pullup resistor which is very easy to add) and then this wouldn't be necessary!

Steve
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Old 07-06-2011, 06:08 AM   #12 (permalink)
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Quote:
Originally Posted by Steve Evans View Post
The trouble is it would cost more than the phase sensor!

Steve
How much would one cost? I'd love to try one on a 450 Pro if it would work.

I am fairly confident I have the soldering ability, it's the electronics know how that I lack. I am barely able to comprehend what you've done. Great job, btw!
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Old 07-09-2011, 11:14 AM   #13 (permalink)
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The phase sensor is about 10, the 74HC93 was about 5 delivered for a one off. Then there were a couple of discrete components, wire, heatshrink, epoxy, solder and about an hour's effort. I used a different servo lead custom for my 500ESP, but the original would normally be used. I also put the sense wire in braid to prevent issues where it passes past frame edges which wouldn't be a standard offering.

Sundry bits were probably not more than 2, so just to order the bits, assemble and post would be about 20. Labour and testing is the issue which would jack the price up. I tested on my heli, but I'd not do that on every one I made if I started mass production! A signal generator is something j don't possess although I do have an oscilloscope. I suppose eBay is a good place to get such things.

Anybody fitting one of these would have so connect the sense wire to a motor wire.

How much would people be prepared to pay for such a sensor, considering how much the standard Furaba sensor costs?

Steve
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Old 07-10-2011, 02:28 AM   #14 (permalink)
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Hi Steve,

Hard to say what people would be willing to pay. I think what scares some off is the messing around with settings in the CGY750...I know it's something I'm thinking about as I don't have a lot of spare time or the patience to persevere. Have to give you a ton of credit for keeping at it!

I went back and studied your modification. I actually think I understand how it's wired up now. The scare for me is not knowing what parts to order. I input your part descriptions at www.digikey.com and www.mouser.com and a bunch of parts come up that look similar but not sure if it's critical on which one you decide to use?
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Old 07-10-2011, 04:53 AM   #15 (permalink)
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Hi,

For the correct datasheet, see HERE. Note that it is the HC device that is needed, package choice being down to soldering skills.

By way of a little background, there is a "standard" set of logic functions that was defined when TTL (Transistor-Transistor Logic) was first introduced, known as the 74xx series. There were a number of manufacturers all producing compatible parts which could be used to construct systems requiring AND, OR, NAND, XOR etc gates, counters, buffers, multiplexers and so on. See HERE for more background.

As time progressed the advances in chip fabrication led to improvements in speed and power consumption, so the original 7400 quad NAND gate, for example evolved into the 74S00, then 74LS00 etc., each functionally equivalent. Most such devices ran at 5V, with some later devices designed for 3.3V. The High-speed CMOS (HC) family is of particular use though because it will operate using a supply voltage anywhere from 2V to 6V.

So, armed with the above knowledge I selected a 7493 device functionality (4 bit counter) from the HC series; a 74HC93. Next was package choice. Basically you have two choices, DIP (Dual In-line Package) or SMD (Surface Mount Device), both of which have the same (14 pin) pinout. DIP is much easier to solder as it's huge by comparison. I wanted to mount the device on the rear of the phase sensor PCB, so SMD made more sense. There are two SMD packages; SOP (Small Outline Package) and SSOP (Shrunk Small Outline Package). SOP is more readily available and small enough (SSOP being approx half the length), so that's what I used.

Hope that makes sense. Just do an eBay search for "74HC93 SMD" and you'll find what you need.

Steve
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Old 07-11-2011, 01:18 PM   #16 (permalink)
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Hi Steve,
Thanks for the additional info. Is it important to choose the correct capacitor and resistor type? There are so many different types!
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Old 07-11-2011, 01:45 PM   #17 (permalink)
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A tantalum cap would be best, and is only there for decoupling, so the value isn't critical. The resistor dissipates so little power that any size will be fine. The resistor should be no less than 1K and probably no more than 4K7.

Steve
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Old 07-12-2011, 07:45 PM   #18 (permalink)
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Looking at the pics further, I don't quite understand what the resistor is for. I understand that the phase signal goes to pin 1 and 3v+ goes to pin 5. However, it seems to me that pin 1 is pulsed (I have no idea if it's AC or on/off DC) and now you're providing it with positive 3v (minus a little from the loss through the resistor) all the time. I don't get it. This confusion is, no doubt, caused by my lack of electronics understanding. Steve, can you explain a bit?
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Old 07-13-2011, 01:54 AM   #19 (permalink)
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The purpose of the pullup resistor is to give a good logic high on the input to the counter. I'd read online that some sensors, such as Align's require a pullup when used with Futaba product, indicating that they have open collector outputs. Not knowing what the output of the Hyperion Phase Sensor is I simply played safe and assumed it was open collector.

It is common for devices to have what are called "open collector" outputs which pull the output low to indicate a logic 0 but don't drive high for a logic 1. The resistor is literally "pulling up" the output to 3V to indicate a logic 1 all the time, but only a small amount of current flows, which the output driver in the phase sensor can easily overcome to achieve a logic 0 when required. This is why the pullup shouldn't be less than about 1K as otherwise a good logic 0 low level might not be achieved.

See HERE for a nice explanation of what a pullup is for.

Steve
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Old 07-27-2011, 10:11 AM   #20 (permalink)
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I've finished adding a binary counter to one of the phase sensors that I purchased last week. After a quick test flight in my TRex 450S with the sensor installed and the governor still off, it seems that my CGY750 is able to read the headspeed; it recorded 3500 rpm and 3900 rpm in idle 1 and 2 respectively. Note that I did not have my gear ratio set correctly (default was set at 8:1). Using the gear ratio of my 450, the 2221-8 motor pole count and the chosen output from my binary counter, I can calculate the actual ratio:

(150T main / 12T pinion) * (6 pole motor) * (1 pulse in / 8 pulses out) = 9.375

I can calculate my actual headspeeds as:

3500 rpm * ( 8 / 9.375 ) = 2990 rpm
3900 rpm * ( 8 / 9.375 ) = 3330 rpm

This however presents a problem; once I enable the governor, 3000 rpm will be the maximum that I can set. I get around this I can fool the CGY750. If I increase the ratio by 25%, this will decrease the headspeed that the CGY750 reads by 25%. My ratio then becomes:

9.375 * 1.25 = 11.72

and I can use the following chart to convert the headspeed set in my 8FG/CGY750 to the actual headspeed of the helicopter:

8FG/CGY750____Actual
2000 rpm * 1.25 = 2500 rpm
2080 rpm * 1.25 = 2600 rpm
2160 rpm * 1.25 = 2700 rpm
2240 rpm * 1.25 = 2800 rpm
2320 rpm * 1.25 = 2900 rpm
2400 rpm * 1.25 = 3000 rpm
2480 rpm * 1.25 = 3100 rpm
2560 rpm * 1.25 = 3200 rpm
2640 rpm * 1.25 = 3300 rpm
2720 rpm * 1.25 = 3400 rpm

It's a little awkward but I believe that I can make it work. Hopefully, the next update to the CGY750 will increase the maximum governed headspeed so I can avoid this conversion. I'll report back with photos of my sensor and a flight report. Thanks, Steve, for providing the information about adding the binary counter to the phase sensor. If anyone is interested I can list the exact electronic components that I purchased from Mouser; I was a little daunted by all the choices.
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