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DX8 telemetry RPM pickup for Gas engines - SOLVED!!

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Old 07-21-2012, 11:58 AM
  #26
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

Correct.

The gear ratio setting might come in handy if you were to use an optical sensor to pick up the prop, or a magnetic sensor with a 2-cylinder engine.

Andy
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Old 07-23-2012, 10:32 AM
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

Confirmed it works when the engine is running
Thanks

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Old 10-31-2012, 02:45 AM
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

I could not get it to work... (But I didn't look to see if the light was blinking)  but in re-reading the thread, I noticed that there was some setting that was set to inh.   Previously I had the RPM sensor working off the normal crankcase sensor and I didn't change anything but the motor.  Is it improtant to set the inh when using this set up.  What I did was install a "Y" connector on the electonic ignition, and tap the yellow signal wire sending it to signal on the TM1000 and leaving the TM1000 red and black  off ( I cut the old RPM input lead and just used the yellow) 

What am I missing.  I did check the spark plug, and I am getting good spark when the magnet passes the pickup, so the signal should be there.


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Old 10-31-2012, 05:57 AM
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

Too bad the Tach Output from the CDI boxes do not work. I personally am uncomfortable adding an extra connector in the ignition circuit on $3500+ planes. It introduces another potential failure mechanism very near the source of all vibration. The Y adapter is however good for initial testing to figure out what is needed for each type setup, though. That is an excellent idea. Maybe once it is all working on the bench, one should remove the Y and just solder in and re-insulate a tap on the needed wires? However, this too has it own disadvantages in that solder makes wires stiff and more suspetable to breaking.

I suspect that the different experiences seen with the need or not for a ground wire has to do with the various ground paths already on each different plane. For a signal circuit to be reliable, one has to have a complete circuit (i.e. a ground and a signal.) Also, multiple ground paths can also introduce its own set of problems. So, I suspect the differences that are being seen from plane to plane may just be grounding related. I needed the ground wire and a signal wire, probably because I have isolated the CDI circuits from the Receiver/Servo circuit. Anyone else done any significant testing on aircraft circuit grounding?

Last but not least; Usually, we take great pains (e.g. separate ignition batteries, fiber-optic kill switches, non-conductive throttle linkages, etc.) to ensure the CDI circuits and the Receiver circuits are physically isolated. This helps to preclude RF and other stray voltage from the CDI module impacting the Receiver and Servo circuits. RPM Telemetry seems to preclude this protective design feature. One can't help wondering if adding telemetry undermines the basic design of a well designed aircraft's isolated electrical systems. Maybe the manufacturers are buffering the telemetry? Maybe the need for electrically isolating the CDI from the Receiver is over-hyped by the various manufacturers? Maybe not! Guess we would have to look at the post-flight receiver data to be sure. Anyone else with telemetry and a isolated CDI system testing and/or monitoring this?
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Old 10-31-2012, 06:29 AM
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

I realized that I mistakenly indicated the engine I'm working on is a DA 20 but in fact it is a copy of a DLE-20, actually
it is a RCG-20
http://www.hobbyking.com/hobbyking/s...dproduct=15381

and I'm not certain it is quite identical.  the DLE-20 ignition system has 1 high voltage line and 3 wires for input/outputs
1 wire is for power, one is for the Hall sensor, and 1 wire is for the optional tach.

I'm not certain the RCG ignition box has the tach option.  I don't recall when I buried it in the plane and will have to dig it back out.

I have been testing using a "Y" that taps the signal on the Hall effect output line.  Just connecting the yellow signal line doesn't work.
I did get some readings when I used the original crankcase designed sensor and placed it at a 45 degree angle over the magnet
that is embedded in the crankshaft, but it was so critical, a millimeter of movement would cause it to stop working.

From reading the thread, it appears that using the Hall effect from the ignition system may or may not require ground going to the TM1000,
I wish folks would post more pictures, as this really helps.  Also we need to really pay attention to what leads are being used.  I totally overlooked the fact that some ignition systems have an actual 3rd lead dedicated to Tach function.

Right now I am leaning towards just going optical.  I have had such great success on electric motors just painting the can black or using black electrical tape, and putting the silver dot supplied with the SPM 1452 sensor.  On my engine, last night I placed a ring of black electrical tape on the collar leaving a strip open where the magnet is located.  Still, I would prefer an electrical pick-up if it is possible.

KKKKFL
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Old 10-31-2012, 12:11 PM
  #31
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

Update,
Pulled the TM1000 out of the plane where I could see it clearly, connected signal and black lead up to the CDI unit using a "Y". Now I have the TM1000 actually blink each time the magnet passes the sensor but no reading. Here's what I have on the DX8 when I open the RPM settings, and it looks just like this:


Display:ACT Alarm
RPM Min: 100 Inh
MAX: 10000 Inh
Ratio: 1.00 : 1
Poles: 2

I tried Inh on the Poles, no joy

I think the Inh under the alarm correspond to the min max numbers

I'm thrilled that the TM1000 is actually blinking, cuz I think that means it is getting and transmitting data WRT RPM otherwise it wouldn't blink. I also moved the ratio from 1 to 1 but that didn't make a difference.

Any Ideas group? One final bit of info, I had the RPM previously working with the normal crank sensor in the back of my SuperTigre .91 I'm using Telemetry ch1 (Not that it should matter) I am spinning the prop with an electric starter motor and it is turning 6 or 700 RPM this is fast enough for the crank sensor that HH sells to output data from the TM1000. Does anyone think it needs to be running over 2000 RPM to read on the
DX8?




Thanks

KKKKFl


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Old 10-31-2012, 12:45 PM
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

Update number two...

SUCCESS!!!!!

Here's what I did to get it to work...  I was pretty sure that from the aircraft side things were operating, leaving the DX8 suspect...   Now don't scream
at me Andy, but when all else fails one of my early experiences told me do a RE-BIND.  So, I re-assigned RPM from channel 1 to channel 6 prolly
has nothing to do with the problem, but then I did a re-bind.   BINGO,,,  by the way the electric starter turns the engine at 1350 RPM but key is to
see the TM1K blink when the magnet passes the sensor.

Now to sum this up for those following the thread. 

I am using an RCG engine that is a copy of a DLE-20, However the ignition module does NOT have the Tach wire (grey).  I cut the wire from the original Hall Effect sensor that HH sells. (Andy help me with the designator SPMA xxxx)  Next I used a "Y" connector plugging the sensor in one leg of the "Y" and sending black and signal to the TM1000 with the remaining leg going to the Electronic ignition.  When I re-assigned the RPM channel to 6 from 1, I let the DX8 pick the default settings.  One final note.  Spinning with the starter motor, you do NOT see immediate RPM readings, they jumped in after a second and a half of the motor spinning.

I could post a picture but there's not much to see, apart from the cable coming from the TM1000 with 3 leads 2 of which now have black and yellow attached.

KKKKFL
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Old 11-01-2012, 05:04 AM
  #33
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

What "channels" are you talking about? Telemetry devices don't have any channels. Binding doesn't make any difference - if it's already bound, power cycling the rx is the way to add new XBUS devices but doesn't do anything for the internal ones (V, RPM, Flight Log, temperature).

Is this the sensor you used? SPMA9569 - http://www.horizonhobby.com/products...acket-SPMA9569

I think your solution deserves a thread of its own with photographs.

You are correct, RPM needs to see continuous data for a while so it can filter properly.

Andy
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Old 11-01-2012, 05:31 AM
  #34
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

Yup that's what I refer to as the Crankcase sensor SPMA9569.  Unfortunately, it will not work on gas engines since the carb intake is at the rear of the engine.  As for the channels, when you go to the telemetry page there are a number of slots/(channels) and you can go through them and assign various sensors. 

I had hooked up the wires as mentioned in other threads, using yellow signal, and black but still did not see readings on the DX8.  I did see that everytime the magnet on the shaft went past the sensor, the TM1000 blinked.  This, I interpreted as "good sense".   I spun the motor up using the electric starter, but despite seeing the TM1000 rapidly flashing got no readings on the DX-8.

At this point I was at wit's end.  I had power cycled the Rx numerous times, I did have some concerns with the DX-8 settings in the Telemetry page.  Clicking on the first slot where RPM had been assigned, I  saw gear ratio, min/max settings for alarms, and poles.  I tried changing each with no luck, finally, in desperation I made the first slot EMPTY, and took another slot and assigned it to RPM.  Then as a final Genuflection, I put everything in "Bind" mode, and pressing the bind button on the DX8, hit the power.  Once everything bound, I again spun the motor with the electric starter.  Viola!  RPM readings on the iPhone, and on the DX8.

Don't shoot the messager, its the process I went through.   Might be I just needed to re-assign the slot.  As others go down the path, we might gain better knowledge.

KKKKFL
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Old 11-01-2012, 10:45 AM
  #35
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

This goes with the other thread, but Andy really wanted pictures so here goes. first the motor, not the magnet in the collar behind the prop


Next a shot of the Hall effect sensor, Note that I was about to give up on the RPM electronic and go optical so there's tape around the collar except for the magnet


I had to pull everything out of the fuselage and see the blinking on the TM1000 its a little dark here


Finally, the ignition "Y" with white and black  temporarily twisted will solder and put everything back together


Hope this helps...

KKKKFL
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Old 11-01-2012, 11:19 AM
  #36
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

We just call those "telemetry slots" and it doesn't make any difference which one you use for any sensor.

Andy
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Old 11-01-2012, 12:19 PM
  #37
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

If I change RPM from slot 1 to slot 6 do I need to re bind?  I did just to pay homage to the DX Gods 
And that's when everything started working
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Old 11-01-2012, 05:44 PM
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

No. You only need to bind for two reasons:

1) Establish initial connection to the Rx for setting up the aircraft, and
2) Set the failsafe mode properly after configuring the model

That's it. Period. Finito!

Note that 2 also includes if you want to change a failsafe setting, of course.

Andy
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Old 11-01-2012, 06:22 PM
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

So, ... Andy:

1.  Is the telemetry system buffered to preclude engine "electrical noise" and stray RF from the CDI system from getting back into the receiver? W/O some sort of buffering, to me it seems that telemetry being directly connected to the engine's CDI circuit and the receiver has the potential to forgo all the other design we put into place to isolate the receiver circuits from the ignition circuit (e.g. Separate batteries for ignition, Fiber-optic Kill Switch, non-conductive throttle linkage, etc.). I am sure you guys must have already thought this issue out.

2. Why doesn't the Tach output circuit from a typical CDI unit (e.g. DLE 111, etc.) work? Seems like that is the ideal spot to pick up a signal. Can an interface be fabbed to convert the CDI's Tach Output signal to a usable Telemetry signal and still buffer the CDI from the Receiver? Or, .. could NOT working only related to a transmitter setup issue?
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Old 11-02-2012, 05:50 AM
  #40
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

1) No. Perhaps there's a reason we don't provide a direct connection solution like you made ...

2) Don't know. We don't sell DLE.

Andy
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Old 11-02-2012, 06:03 AM
  #41
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

Todd,
I'm not sure that your concerns are valid WRT the ignition pick-up.  The TM-1000 seems quite happy to recognize the pulse coming from the Hall effect sensor that feeds the CDI.  The CDI unit is well shielded and sits up in the fuel tank compartment, well away from the Receiver, and even further away from the Satellite Rx which I have mounted as far towards the aft of the aircraft as possible.  I'll be the first one to post any problems that I see in flying this weekend.  That said, I do have a backup plan in that I have ordered several SPM 1452 Optical sensors and it should be fairly easy to have a black strip with the appropriate white space behind the propeller on the motor collar.  If you have not yet experimented with the Optical sensor, give it a shot.  They are ~ 6 bucks and changing the connector is a snap.  As far as I'm concerned it is the ONLY way to go for electrics.


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Old 11-02-2012, 10:50 AM
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

Andy;

After testing on the bench, I took the telemetry back off the plane. Without knowing whether or not the system was buffered, I was not willing to risk the undermining of the other design features that I put in place to isolate the CDI from the receiver. As I understand it,depending on certain conditions presented by the CDI, the receiver could be impacted. Seems likethis is a potential weakness of telemetry andone must be willing to take the added risk to use it. I also believe in KISS.

Are you saying that one should not do the above describedmod. and stick to the Spectrum RPM Sensor becausethe Spectrum Sensoris electrically insulated/isolated from the engine? Or are you saying either way, one takes the risk of the CDI interfering with the receiver. Or, ... are you saying there is no risk?

Speaking ofreceiver failures, ...my relatively new AR 9210 failed in the air today. I sent itback to HH for replacement. Fortunately the receivers still were working and the Hitec HV Servos could take the full voltage of the 2S LiPos. I think the Voltage regulation went out. ?? All 6 on-board LEDS were lit. Rudder twitching was the airborne tip-off of a problem. Fortunetely, the Failsafe Evolution Power System/Reciever is truely failsafe! I landed the plane safely w/o incident! I had a spare AR 9210, which I inserted and it works just fine,so it's back to the airport for me shortly.
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Old 11-02-2012, 04:07 PM
  #43
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

WOW, I've never heard of something like that! Amazing recovery - the chips in the receivers are only able to work to 3.3V, so I doubt the innermost regulator failed.

The TM1000 does not include any isolation circuitry. If you connect to your ignition system, you are providing a direct connection from the ignition to your receiver. We provide magnetic sensors to make that unnecessary.

We have had one or two reports of people who had the spark plug lead close to the TM1000 and it DID cause issues for them. There was no electrical connection, but apparently the long wires to the TM1000 and the unshielded plug wire didn't like each other very much. He solved his problem by relocating the TM1000.

If we had an interface to the ignition circuit, it would mean we had done extensive testing in that configuration (we have guys like Seth, QQ, and McConville to fly them). I have to recommend sticking with a system we have.

That said, as a modeler and "tinkerer" myself, I don't have any problem with what you and Franco have done. I just can't give a "Spektrum approved this" sticker to you.

Andy
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Old 11-03-2012, 07:11 AM
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

Andy;

Thanks for the information. It is very helpful when you take the time necessary to help us with such details, etc.
 I appreciate that.

Yah, yesterday's experience was one of those crazy things that happen. Bottom  Line: If the plane's rudder starts twitching ever so gently, or more, the plane is trying to tell you something (i.e. It is time to land me!)

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Old 11-05-2012, 03:09 AM
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!



I did run several tanks Friday and Saturday, and I realize my comments are a little like saying  "All indians walk in a straight line, at least the one I saw did!"  I have not experienced any twitch, glitch or indication of interference using the "Y" connector between the CDI and the supplied Hall effect sensor. feeding the TM1K.  That said, last week I ordered some extra SPM1452 optical pickups since someone scared me into thinking that they were going to disappear from HH inventory.  If you want isolation, go Optical.  However, you are still going to have the threat of RFI from the high voltage line. Make sure the braided shielding is all in good condition.


KKKKFL

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Old 11-05-2012, 06:42 AM
  #46
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!



Andy seems to think if we stick with their designed telemetry equipment that we will not have an isolation problem. They have apparently tested this equipment fairly significantly.  Andy did mention that you need to stay away from the spark plug harnesses.

I am putting the telemetry back in to monitor Receiver Voltage and Engine Temp. I have the DLE RPM indicator on the plane. For now, that is all I need.  But, I have to fab up or order a couple extensions to get the Telemetry module exactly where I want it. Also, I took all the receiver and servo current and voltage measurements, including end-points, etc., yesterday. Now I have a good baseline for post telemetry installation.

On a side note:

I am kind of glad that I did not have telemetry in when my Rxer died last week. I would have been suspicious of it. On the flip-side, had I been monitoring the Rxer voltage a bit closer with telemetry before lift off, I may have seen the problem I had before committing to the air. But then, who knows. Maybe I had a high voltage condition and the voltage alarm on the DX8 would not have sounded anyway, etc.  Maybe the problem initiated after I took off? That is when the rudder started twitching. But once the hatch was closed, problem indication was limited (i.e. I had not installed the two remote problem indicating LEDs. But, they are in there now!) Also, doing the final hatch closing, after warming up  the plane, now seems to make sense. That would allow a visual check of the receiver's/power system's problem LEDs one of the last things I do before take off. Jeez, it is almost like you got to have a sequential checklist to get one of these things safely in the air! Maybe I'll go back to my foamies and helis?

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Old 11-05-2012, 07:14 AM
  #47
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

Last month, I had a twitching rudder on my 1/4 scale EAA Biplane(ThunderTiger 1.20 2 stroke engine).  Everyone at the field swore that it was RFI, some donated those ferrite donuts but the twitching continued. 

On returning home, I did a "wire shake" test and sure enough the rudder twitched.  Thinking there was a bad solder joint, I changed the connectors from a point that was right inside the case.  Hooked everything up and Lo and behold, the rudder still twitched when the wire was jostled.  I took the servo back out, and this time hooked it to a test receiver.  What I eventually found was the the bad solder joint was on one of the spider legs of the micro-chip.  pushing down on the chip I had solid performance.  Now this was not a high priced Futaba servo, more like a mid range knock off of a HiTec standard servo, but it sure served as an eye opener.

KKKKFL
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Old 11-05-2012, 08:03 AM
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

In my case the receiver/power system actually went haywire. Once I replace it, the problem went away.

The receiver/power system has "battery condition LEDs" and all 6 LEDs were lit indicating a major problem. But before, I opened the hatch to find the LEDS all lit, I was suspicious of the rudder servo and or cable. It is a Hitec 7945TH. I opened the tail and removed and cleaned the connections, still had the twitch. So, ... I opened the hatch to find the all 6 LEDS lit. I repositioned and checked all battery and servo connections. All seemed good.  The 2S LiPo battery voltages were 8.19 and 8.18 VDC respectively, which was good. So, ... I quit flying and put it on the bench when I got back home. After further testing and still having all 6 LEDs still lighting, I replaced the receiver/power system with a new one that I had for a new build I am currently doing. With the new unit, the problem(s) no longer existed. I plugged the old unit back in and the problem was back. My problem was clearly in the power distribution system, which I will add still allowed me to fly the plane in w/o any incident other than the intermittent subtle tail twitching. The redundancy and power safe features they have in these expensive systems apparently really do work!

But enough for my hijacking. Lets get back to telemetry. OR,  you can PM me if you like, too.
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Old 11-20-2012, 09:03 AM
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

Update: The AR 9210 tested good at HH. They had to provide all the wiring and attachments, etc as all I sent was the main unit. Consequently, after my close inspection of the involved EC3 to MPX adapters, I have come to the conclusion that possibly both MPX connectors must have not been making consistent contact. ?? Some of the female pins in the MPX side of the adapters were spread apart, some of the pins were made from thinner metal, & some of the pins were in the molded plug further. I replaced the EC3 to MPX adapters. The new ones looked a lot better and took a lot more pressure to fully seat and get "clipped in." Also, instead of mounting the AR9210 as suggested in the book, I sandwiched a piece of 1/4 receiver foam between two plywood boards and mounted the AR on top of that. I also ran a support beam across the plane's cockpit above the AR to wire tie the adapters to. I think the arrangement of these adapters coming out of the top of the AR, the tiny vibration isolators on the AR and the quality of the adapters made the unit's battery connections susceptible to the vibrations in my plane. I have tested the returned/involved AR on the bench several hours w/o incident. The EC3 to MPX adapters were the closest thing I could find to a "smoking gun." However, seeing how they both apparently went at the same time still leaves me a bit worried, though. Got to do some more bench testing before this unit goes back in a plane. In the meantime, I have over 5 hours of stick time on the AR 9210 that I replaced it with. With the vibration mods and new adapters, it seems to be working just fine.

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Old 11-30-2012, 08:46 AM
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Default RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!

Is an extension ok instead of a Y cable?
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