Hi guys
After power on (rotor still in static) the hand data terminal(HDT) show that the speed of the turbine are 5000-8300 rpm instead of 0 rpm normally .....Thanks in advance for any inputs..

Cheers,
Ivan

Hi Ivan,
Try degaussing the Hall sensor on the rpm sensor board on the front of the turbine. Simply wipe a refrigerator magnet (really low power magnet) across the face of the sensor. That usually restores it to normal. The Halls are very sensitive and can be magnetized easily by spurious signals and tools coming close to it. I had one customer that would screw on the sensor with a really strongly magnetized hex wrench and screw up the sensor every time!

Len Gladstone

Ivan

There are two things that can cause this.

1. Transmitter to close to the ECU.
2. Servo’s in a bind. Digital worse.

Not all see this so installation counts.

My fix took care of the two things I wanted.

I wanted to be able to reboot my ECU without rebooting the receiver or work on the jet with ECU off.

I installed a switch and a small Rx battery for the ECU.


Small Rx battery + to the ECU. Switched.

Signal wire from ECU to receiver.

All grounds together.


I made a harness with a switch build in.


Let me know if I could help more

Johnny

disclaimer:
I do R&D electronic work for the DOD –FAA so I thrust my work.

What I am trying to say is do good solder work.

Hi Len,
Try wipe a refrigerator magnet across the face of the sensor but the HDT still show 5000-8000rpm. Should i do it when ECU power on or off ? any other method?...........Thanks

Hi Johnny
Check though the setting, no servo in binding and TX is away from ECU also. Looking at Wren ECU there is only one port for receiver channel 1 which for both ECU power and signal. So in my case how should i go about it.......Thanks

Ok

Let’s clarify remove each servo from the receiver one at a time

Until the count goes away you’re picking up 300-500khz.

Johnny

Hi Johnny,
Yes! you are right, just did a test on a spare receiver, only channel 1 connected to ECU and the rest of channel without servo. HDT display back to normal showing 0 RPM. later will remove each servo from the receiver one at a time to identify the problem servo. Thank you very much.....

Ivan

Hey Ivan,

The round tank on the left in your picture, is that your header tank? What is the white cylinder in front of it? Just curious how you have things plumbed.

Thanks,


Jerry

Hi Jerry,
Yes,the round tank on you mention is a header tank and i have two air tanks in front for retract and air brake.

Cheers,
Ivan

I had the same problem on mine and it is nothing to worry about. The answer I got back from Gaspar (who is on this forum) said the system search's for a signal and ampifies a small signal so what it is doing is picking a signal from a near by servo or servo wire, but as soon as it picks a stronger signal up from the magnet in the rpm sensor it reduces its sensitivity and at that point it does not pick up the servo signal at all.

so don't worry just fly!


jason

infact heres the email he sent me as he explains it better.

Hello Jason,

Usually the noise is picked by the magnetic sensor, not the cables. All of
the servo cables that are near of the sensor radiate magnetic fields, and
the only solution is to move them far from the hall pick-up.

As a test, you can disconnect the servos from the receiver, and this should
stop the noise. Then, connect one by one to see what cables are inducing the
noise.

When the engine is running the sensor is fine because the system have a
automatic gain control for the amplifier. As soon as the pulses from the
magnet are sensed, the gain is reduced and the noise don't affect.

Hi

Ivan

Is this the Ivan that assembled a tjt 3000 at superman 2 years ago?


Hi

Jason

Gaspar makes a great ECU I have both the rpm Eco and the autostart.

I had a midrange problem and eliminated the ghost rpm with the first post.

The ECU had nothing to do with the midrange problem.

Getting the kink out of the fuel line fixed the midrange problem. Duh!@


Johnny

Hi Johnny,
I'm not the guy............

Hi Jason,
Thanks for the useful info.....can you tell me what are the value of the RPM cause by the noise on your hall sensor.

Ivan

Hello Ivan,

I'm sorry to arrive a bit late to read the thread about your troubles with the speed sensor. Hope that now this is fixed, if not, don't hesitate to ask me directly at [email protected]

A common cause of RPM reading in steady state is that the voltage on the power from the receiver is unstable, usually caused by weak voltage regulators in the presence of big power loads, like digital servos, or 4,8V packs with thin wires or trough isolating diodes that cause that the voltage drop below 4V.

If the problem persist, please e-mail me directly with the details of your setup.

Regards,

Gaspar

Hi,
Due to the above mention problem, decided to use redundant parallel fight packs with two separate switch set up. Currently i have one 2000 mah battery on the roo, can some one tell what are recommended battery capacity if using two batteries in parallel operation (one to batt port the other to extra channel)?Thanks......

Ivan

Ivan

use my first post it will work great.

isolate the positive receiver from the positive ECU.

or you can just try it last.

johnny

I use two 1400 mah 6 volt Electrodynamics NiCad packs with two of Andy's beefy switches into the two independant battery ports on the MPX 12 ch receiver. Works great and the receiver automatically draws from the strong pack.

Hi woketman



I never considered using 6v with regulators.

I bet that works great.

Johnny

I believe that the isolation circuit inside the MPX 12 ch receiver is a zener diode circuit. There is a significant voltage drop across the diodes so when you use this feature of that receiver, you must use 6 volt packs. You can, of course, simply use a 4.8 volt pack instead. Been flying this for 1.5 years without a single glitch. Works perfectly.

Hi Johnny,

Can i just ues a 'y' extension on channel 1, one end to ECU the other to a small battery and on the lead to receiver just cut away the red wire? Thanks in advance.......

Ivan

hi
Ivan



"Can i just use a 'y' extension on channel 1, one end to ECU the other to a small battery and on the lead to receiver just cut away the red wire? Thanks in advance....... "

yes just remove the red wire on ch1

also you may want a switch to charge\reboot the ECU

let me know how it turned out.

johnny

Hi Johnny,
I appreciate you replies.Now the ECU is working fine,no more unwanted reading .............again thanks

Ivan

ive got a similar problem. It reads zero rpm when it should, but ive been testing the electric motor and it will spoolup to 9000 rpm then when spooling down the rpm will jump around and even jump to 40000 just for half a second.

Ive tried deguassing it with a weak fridge magnet, but with the cowling on so im not sure how much effect it will have.

I dont have any servos attached so thats not it.

The transmitter is far enough away.

Ill try recharging the reciever battery and try again.

Any other suggestions???


PS it says in the instructions to do a manual start before attempting a full auto start. Can someone tell me what the harm in that would be given i can just shut it down with the throttle trim?