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Old Jan 13, 2013, 10:16 PM
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Question
Optical RPM sensor

Is there a trick to using this sensor?
I have it installed on my Furion 6 600 size flybarless helicopter.
Installed on the boom looking up at the sky as indicated in the instructions.

Setup for 2 blades in the Tx sensor settings...

But I get readings all over the place, from 1900 to 2400 to 3000... I even saw 4000 a few time and I know its not going 4000 rpm.

My rpm is somewhere between 2000 and 2350, but I would like to know its actual speed.
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Old Jan 14, 2013, 04:17 AM
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Quote:
Originally Posted by dpelletier View Post
Is there a trick to using this sensor?
I have it installed on my Furion 6 600 size flybarless helicopter.
Installed on the boom looking up at the sky as indicated in the instructions.
Setup for 2 blades in the Tx sensor settings...
But I get readings all over the place, from 1900 to 2400 to 3000... I even saw 4000 a few time and I know its not going 4000 rpm.
My rpm is somewhere between 2000 and 2350, but I would like to know its actual speed.
Extract from the original instruction sheet:
"HTS-ORPM (RPM Sensor)
The Optical RPM sensor was made to be used with larger, outdoor, use helicopters.
Installation is simple, attach it to the boom and connect it to the sensor station.
It can read from 0 to 50,000 RPM.
- The readout can be inaccurate and influenced by the weather condition
- For a more accurate reading, install the sensor as far away from the y bar paddles as possible."

Given that your model does not have paddles, any other reflective item such as a large disc or
highly polished CF blades, which reflect light in various directions, could be a cause of poor readings.
Same problem when trying to tach large GP models.

A copy of the recently released HRS_SS Manual is attached.
This includes the latest HTS-MRPM & HTS-ORPM instructions and pictures.
Perhaps a small piece of chrome reflective tape, or a small dot of white
paint, nail polish or similar, be affixed in line with sensor will assist.

Alan T.
Alan's Hobby, Model & RC FAQ Web Links
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Old Jan 14, 2013, 08:50 AM
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Originally Posted by A.T. View Post
Given that your model does not have paddles, any other reflective item such as a large disc or
highly polished CF blades, which reflect light in various directions, could be a cause of poor readings.
Same problem when trying to tach large GP models.

Perhaps a small piece of chrome reflective tape, or a small dot of white
paint, nail polish or similar, be affixed in line with sensor will assist.

Alan's Hobby, Model & RC FAQ Web Links
Hi Alan thanks for the reply.

Do I want reflective or non reflective?
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Old Jan 14, 2013, 02:36 PM
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Originally Posted by dpelletier View Post
Hi Alan thanks for the reply.
Do I want reflective or non reflective?
Reflective.
On GP models, black props typically have white tips in order the blade be seen or a thin strip of
polished self adhesive chrome tape wrapped around blade say 3/4" from tip so as not to be easily flung off.
Need to overcome the problem of light being reflected from wrong sources
e,g, the sides of nearby structures, metallic RV parked close by and as mentioned post #2:
"highly polished CF blades, which reflect light in various directions, could be a cause of poor readings."
From the instructions of another hand held Opto Tach:
"Optical Tachometer
Use the digital optical model to take non contact speed measurements of rotating objects (rpm measurements).
Tachometer uses a reflective mark and an integral light beam to provide precise readings."

Alan T.
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Old Jan 14, 2013, 04:07 PM
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Thanks again.
I'll see what I can rig up.
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Old Jan 17, 2013, 10:54 PM
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I installed some metal tape under the rotor blades, the type of tape used in duct work, though not exactly chrome it is very reflective.

This however did not seem to work very well, while flying head speeds indicated ranged from 0 to 250 to 1800 to 2500.

Should I just use white?
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Old Jan 18, 2013, 03:23 AM
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Originally Posted by dpelletier View Post
I installed some metal tape under the rotor blades, the type of tape used in duct work, though not exactly chrome it is very reflective.
This however did not seem to work very well, while flying head speeds indicated ranged from 0 to 250 to 1800 to 2500.
Should I just use white?
Certainly worth a try, otherwise am out of ideas except for a comparison test
with another type of optical unit and the notes below.

Own two hand held (GloBee & Hobbico) optical units, for GP Acro models, do give varying results
jumping Hi Lo or jittering, depending upon weather and daylight, which is the same as extract
from HTS-ORPM instruction sheet:
"- The readout can be inaccurate and influenced by the weather condition"

Other notes regarding Optical Tach, from own Tach FAQ file:
1. Separation distance - Majority advise min 4" max 12"
3. Hold steady. Perhaps the boom or blades are vibrating to much?
2. Optical Tachometer Test:
Hold unit near a fluorescent light tube (which flickers at 60Hz in USA & 50Hz in Europe & NZ)
with unit set to two blade.
Given a good power supply and good fluorescent tube, a speed of 3600 in USA or
3000 in Europe & NZ should be displayed.
(Just checked the GloBee and noted under a coiled Fluro, which local greenies are insisting we replace
our incandescent bulbs with, do fluctuate - no doubt coil effect, yet rock steady 3000 under a good tube.
Results varied in a room with several lights unless unitheld near to one avoiding conflict from the others.)


Otherwise suggest email direct to service centre:
Hitec Warranty & Service - homepage.
Note: Hitec USA only services North/South America and Canada.
"Hitec USA customer service department is available Monday through Friday*
from 7am- 4:30 pm Pacific time. Reach us at 858.748.8440 or
service@hitecrcd.com any time you have a question"
If you are from a country that is outside North and South America, please contact the
Hitec distributor in your country for service.


Alan T.
Alan's Hobby, Model & RC FAQ Web Links
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