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Old Sep 17, 2011, 05:42 PM
Registered User
United States, CA, Sonoma
Joined Jan 2009
29 Posts
Question
on board tachometer

i just ordered a dle on board tachometer for my dle engine.tower hobbies sent me an rcexl tach,,which i cant even find on thier website.i went to the rcexl.com website,,and it says not to use thier tach while in flight,where as you can use the dle tach in flight.does anyone know if i need to send this back,,or if it will be ok in flight.thanx guys
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Old Sep 18, 2011, 09:47 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,698 Posts
Quote:
Originally Posted by markysonoma View Post
i just ordered a dle on board tachometer for my dle engine.tower hobbies sent me an rcexl tach,,which i cant even find on thier website.i went to the rcexl.com website,,and it says not to use thier tach while in flight,where as you can use the dle tach in flight.does anyone know if i need to send this back,,or if it will be ok in flight.thanx guys
As I understand it, that sensor has to be installed between the Hall Sensor and the motor to work. And very few motors have external sensors any more, they almost all use back EMF sensors to monitor RPM now.

You don't say what you are using it on but if you want to get more power systems data, both in static testing on the ground and in flight, the Eagle Tree eLogger and it's accessory Brushless RPM sensor are hard to beat. With accessory Power Panel display you can see all the data on a real time basis and, assuming you're not going to be on the plane when it is flying, it also records the in flight data for later analysis on a PC.

There are a couple of guys selling the Eagle Tree stuff on eBay but there is not much of a savings there...

Jack
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Old Sep 18, 2011, 10:00 AM
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United States, CA, Sonoma
Joined Jan 2009
29 Posts
thanks jack,,im using it on a DLE-30 engine.it plugs into the CDI unit that has an extra plug for that purpose.it doesnt go between the sensor and the CDI unit,,,i hope im explaing this right,,all i know is that it plugs into the CDI unit for an "on board tach",,and am not sure if the RCEXL tach can be used since they say not to use it in flight (which means on-board)
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Old Sep 18, 2011, 10:30 AM
Jack
USA, ME, Ellsworth
Joined May 2008
16,698 Posts
OK, I didn't know what a "dle" motor was when I replied, I assumed some kind of electric motor.

The manual for the RCEXL is written in Chinglish, it says:

"Connection tachometer is not recommended after the use of flight"

That is not very clear, it may mean that they do not recommend that you leave the tach connected when the motor is shut down for any period of time.

If you just want to use it just for ground run ups a handheld tach would be a easier and faster, maybe cheaper too:

http://tinyurl.com/67prkrb

If you want inflight data, the tach signal from that motor may work for the sensor on the eLogger too. The eLogger can use a Hall effect RPM sensor pickup with a magnet mounted where it will rotate, an optical sensor, or it can use the brushless one where you stick a pin into one of the three leads to the brushless motor.

The brushless motor pin sensor counts the pulses and divides that by the number of magnets settings to get the RPM. The brushless sensor works reliably over a wide range of voltages as the voltage goes up and down with the throttle movements.

Since you're not primarily interested in the electrical power data (volts, amps, etc.) you could power up the elogger off of your ignition battery and it would record the RPM changes for an entire flight of up to four hours or more.

Jack
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Old Sep 18, 2011, 01:24 PM
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United States, CA, Sonoma
Joined Jan 2009
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thanks for your time jack,,think ill have to make some calls monday and talk to a chinglish interpretur at rcexl,,,or tower hobbies,,they are the ones that made the mistake
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