kevenoco

My Feedback: (1)

I read in a Model Aviation article that the columnist was able to tap into the CDI to hall effect sensor connection in order to read the RPM for the telemetry system TM1000 for the Spektrum DX8. Does anyone have any specific instructions on how to do this? I am flying with a YS 170 DZ CDI but I think the setup would be the same for any CDI system motor.

SkidMan

My Feedback: (17)

It works very well for me with a RCEXL CDI. I just put a Y-cable inline with the hall effect to CDI cable and only connect the "signal" wire (no ground or power) to the TM1000.I just crimped a servo connector to a cut off Spektrum satellite receiver cable. (The satellite receiver cables are the same connector that the TM1000 uses. I had a couple inexpensive "Brand X" cables so it didn't cost much to sacrifice one)

Of course, YMMV. It works great for me.

Len Todd

My DLE 111 has a cable off the CDI for a remote tach display that has a servo connector on its end. I was wondering if I could justuse that CDI's tach outputas input to the telemetry module. Anyone done this for the DLE?

SkidMan

My Feedback: (17)

The smaller DLE's use the RCXL CDI. If the 111 does as well I would try what is shown above.

YMMV - I crossed my fingers that I wouldn't blow anything up when I first hooked it up.

Paul

Len Todd

Guess this winter I'll get the O-scope out and take a look at the signals from the Sensor to the CDI and theCDI to the Tachto see if they are similar. If they are similar, then Imay be able to use the CDI to Tach signal circuit. I would probably also use the ground provided in the signal wire's connector.

The reasons toNOT try what is being suggested are:

I personally do not like adding unnecessary connectors in the engine's critical circuits. Adding a Y introduces more potential failure mechanisms in one of the primary inputs to the CDI. Guess the old N-Plant Engineering is coming out here.

For me there is too much invested in the plane, that I would like to use telemetry on,to take unnecessary risks with unknown potential consequences.

Using the suggested tap, the signal from the Hall Effect Sensor and CDI would be tied indirectly to the receiver via the Telemetry module. I am a little hesitant to do this seeing how I went to great pains to isolate the 3 receivers from the CDI circuit. However, no matter whereone taps in, one is tying the Engine to the Receiver. I wonder if the telemetry module has some sort of buffering? I wonder if Spectrum's RPM sensor is electrically isolated from theengine when mounted?

Not to mention, from an electrical standpoint, a Y opens the potential to divideany voltage on a circuit andit could also parallel any resistance, etc. both of which could also negatively affect all the involved circuits.Circuit impedance is critical to avoid undesirable RF paths, etc.. Also, a single wire couldcause some weird grounding path. Electrical signals need a complete circuit for reliable use. One wire does not a reliable circuit make.

I am sure there may be circumstances where what is being suggested works. I'd just rather figure it out on the bench before I tried it in a plane. Too busy flying. I can wait till winter to figure this out.

Franco2fly

So, what's the consensus?  Can I just tap into the CDI using a "Y"?

Thanks

KKKKFL

Franco2fly

Answer is yes,
To tap into the RCG-20 CDI one needs to use the signal wire (Yellow) and the Black (ground) wire tied into the RPM input lead that goes to the RPM port on the TM1K

KKKKFL

boosted180

My Feedback: (8)

i tried this and it did NOT work. my telemetry module stopped working also (not sure when it stopped working), and i *may* damaged it trying to hook it up to the lead coming off of the dle-111 cdi?? horizon replaced it for me and i was too scared to try again. it also could have been the module being defective and had nothign to do with trying the tach telemetry. but in any case, it did NOT work for me. i also connected all the leads as-is (red, black and signal). could that have been why it didnt work??

Len Todd

I did quite a bit of testing on this. It will not work. I also tried slipping a "Y" in the Hall Effect circuit w/o success. I am currently testing some of the optical options. Should know more about that in the next few days.

Franco2fly

I thought I covered this, maybe I was chatting in the wrong thread.
Optical works great and its dead easy just paint the back of the spinner and mount the sensor.  Here's a shot of my Tucano with a 90 4 stroke the back mounted hall effect sensor is not possible.

http://www.rcuniverse.com/forum/m_10...40/key_/tm.htm

KKKKFL

Len Todd

I think you are right, you have it covered. I have just been to darned busy to make this work on my two gas powered Giants. I am real close though. I have the Optical reader mounted and Just have to place the target and I should be ready for testing. Thanks for the info.

Franco2fly

Once you are ready, just observe the light in the TM1000.  If on passing the silver stripe the orange light comes on and blinks when you rock the spinner past the pickup you are good to go.  If it doesn't blink, move the sensor closer.  You may also find that you need to tinker with orientations.  The key is to get the orange light to blink.  Don't worry about "read outs" initially, just get it blinking and you'll be good.  I found it easier than tinkering with the Magnetic pick up in the well of the Nitro motors.

KKKKFL

dlinares126

I tried the hall sensor on my DLE 55 connecting all three wires to the TM 1000 and spinning the motor with a drill and the spark plug off, it seemed to give me a reading between 900- 1600 rpm which is approximately what the drill was spinning. What I did is order a DLE hall sensor from ebay and I'm going to double stick tape the hall sensor to the engine right next to the existing sensor and run the engine to see what I get, I'll keep you informed!

Len Todd

I got optical sensors from HH for about $7 and put one of its foil targets on the spinner backplate. Then I glued the sensor out by the backplate on a 3/8" x 3/8" balsa stick mounted off the cowl. Works like a champ, can't see it when looking at the plane and is cheap to boot. It is also lighter than the DLE Hall sensors. HH# SPM1452. I cut off the JR connector and soldiered on an extension for a remote receiver and it plugged right in directly to the TM-1000. Wiring = Ground to ground (BRN) , VDC to VDC (RED), Signal to Signal (YEL). Set the senor back about 1/16th of an inch from the target to allow for the engine's axial end-play.

BigD_S2K

If you CDI box has a tach out put lead that should work. I have scoped this lead and find t is a negative going pulse that is sinuous with the ignition spark pulse. That is it follows the advance curve of the engine spark. The hall sensor is also a negative going pulse. Measurements taken from Rcexl Model A-01 CDI.

Len Todd

On the DLE 111's, I was not able to get the tach output from the CDI Box to work consistently. Thus I went the Optical Sensor sensor route.

BigD_S2K

My research of the hall sensor is based on looking at a sample of 3 units. If one was to place a 1000 ohm resistor in series with the lead to the TM device that minimize the risk of the TM dragging down the engine hall effect sensor. My research show the typical hall sensor to be provide a maximum of 11 milliamp. Also I do not understand not connecting reference ground between the units. No ground reference leads to noise and unreliable signal transfer. I have built a hall timing circuit and draw about 4 milliamp to light a LED and have not experienced any problem/issue with the sensor.

Franco2fly

I just purchased a new DLE 20 and the CDI had a tachometer lead that I tried to use. After about 90 seconds the TM 1K froze. I've seen this before, and guessed that the ignition noise was the culprit. A brain fart lead me to try damping the noise with a ferrite coil from an old ESC



just cut the wire removed the green doughnut and then put it on the RPM lead about 4 inches from the TM1000. Drive way testing was successful with no lockups, but will have to wait until Saturday's field experience to be 100% sure.

The DLE sure is a sweet engine right out of the box.

KKKKFL

Len Todd

Any direct electrical connection of the CDI to the RXer (e.g. Tach output to TM 1000 and then to the Rxer) should be avoided. This is a good way to get RFI on the Rxer. A torroid may work to choke off RF at certain frequencies. But various frequencies use differing torroid materials and the numbers of turns through the torroid. You may stumble on a combination that will work for your particular situation. Then again you may not. Also, the RF may vary with RPM. I just totally avoid all direct connections from the CDI to the Rxer. KIS.

Franco2fly

Weekend testing revealed that the tachometer lead provided by DLE works well so long as the torrid coil was installed. I will also say that RFI from the CDI's has impacted all RPM techniques whether from the lead provided or Optical pickups or even hall effect pickups. Only my Zehoah engine with the magnito gives good results using an optical pick up with the back of the spinner black and white. Evolution motors provide a lead off their CDI and they are the exception. although, only the 15 through 20. I have an early 10cc and it too would lock up telemetry unless a ferrite core was used. RPM is not really all that important, but it did show me that the DLE 20cc was unloading significantly more than I had anticipated when in the air. Idle is usually around 2600, turning a 16x6. but I was surprised that it unloaded to 11,000 in the air since on the ground it was just tickling 10,k.

KKKKFL