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Old 04-18-2020, 10:31 PM
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Futaba s.bus rpm and ignition signal

Has anyone taken the magnetic signal lead from a gas engine and added it to Futaba’s SBS-01RM Magnetic RPM Telemetry Sensor?

It seems that the magnetic signal is same whether it comes the stock engine sensor or the Futaba magnetic pickup so why not y-cable the stock pickup wire - one to the electronic ignition module and the other with just the signal wire back to the SBS-01RM? This would be a beautiful solution for Futaba telemetry, you would still need the SBS-01RM but just not use the Futaba pickup but instead a y-cable.

Maybe two solutions: (never use red or black from Ignition or Pick-Up to Futaba SBS-01RM!)
1. Use the signal wire from Ignition Tachometer RPM Signal Output to the Futaba SBS-01RM
2. Use the signal wire from the Ignition Pick-Up Sensor Wire to the Futaba SBS-01RM

Wonder if this will work with DLE and/or DA? Telemetry without the sensor would be neat.
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Old 04-18-2020, 11:10 PM
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Worth a try I guess. Not heard of anyone doing that.
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Old 04-18-2020, 11:55 PM
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Unless someone comments back in a day or so I am going to buy the Futaba magnetic sensor and give it a try. I have the Futaba optical sensor but donít think it will work since I canít intercept the pulse signal. The white wire is output sensor s-bus communication and not a pulse signal.

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Worth a try I guess. Not heard of anyone doing that.
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Old 04-19-2020, 12:43 AM
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One potential issue is the magnet polarity. I recall when I was flying nitro helis that getting magnet on the governor in correctly was important.
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Old 04-19-2020, 02:44 AM
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I will just use the signal wire coming from the DLE OEM pickup so hopefully it is just a pulse into the Futaba telemetry s.bus counter/converter.

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One potential issue is the magnet polarity. I recall when I was flying nitro helis that getting magnet on the governor in correctly was important.
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Old 04-19-2020, 05:04 AM
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What? Lower? OK!
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Certainly I would not connect the output of the hall sensor from the ignition to the Futaba s.bus rpm sensor unless I was absolutely sure that the sensor has an optically isolated input. And I have a lot of doubt about that.
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Old 04-19-2020, 06:39 AM
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What? Lower? OK!
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Quote:
Originally Posted by Judge View Post
One potential issue is the magnet polarity. I recall when I was flying nitro helis that getting magnet on the governor in correctly was important.
Yes of course, some engines have south pole outside, others have north pole outside. Some sensors could be really sensitive, they will work even if 180 degrees rotated to solve the problem with the opposite magnet orientation.
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Old 04-19-2020, 06:48 AM
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What magnetic polarity signal does the Futaba RPM sensor require to work?
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Old 04-19-2020, 10:49 AM
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What magnetic polarity signal does the Futaba RPM sensor require to work?
No idea. Sorry.
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Old 04-19-2020, 04:03 PM
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Hi William,

The Hall sensor is simply picking up the magnet and providing a pulse every time the magnet passes the hall sensor. As long as the Futaba SBUS module is powered by the receiver, I would think it's likely to work.

The easiest is always with an ignition that has a tach out lead. I have several Rcexl ignitions like that and they worked great feeding my AT-V1 FrSky rpm telemetry sensor. If you have a tach output lead on your ignition (most DA ignitions don't have these, DLE Rcexl's usually do), it might work plugging directly into that. Or not. It won't break anything. Just test it on the ground.

Unfortunately, I also have DA's with no tach out lead. I first tried the Y-connection as you described. The telemetry sensor developer told me to try it as he's had people with DA's work fine with the Y-connector off the pickup. It did not work in my case. On my DA100L, I connected an RCXP aftermarket pickup directly into the AT-V1 FrSky rpm sensor. The DA100L had a spare set of holes to mount the retrofit RCXP pickup 180 degrees away from the DA pickup. It works very well.

I have just done something similar with my Jeti on a DA60, using an inexpensive Rcexl universal pickup to connect to the Jeti MRPM Hall telemetry sensor. Like Futaba, the Jeti rpm sensor comes with its own hall pickup, but does not come with a convenient way to mount it. Unfortunately, the DA60 doesn't have extra holes for a 2nd pickup. I carefully drilled/tapped some 3mm holes on the hub, opposite the DA pickup and mounted the RCexl universal pickup. Just make sure the hub's magnet passes under the pickup if you go this route. Jeti also make an MRPM AC sensor that is typically used with an ignition that has a tach output lead. I've got that setup on a DLE and it works well, too.
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Old 04-19-2020, 06:05 PM
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Thank-you for your reply. Making this work with DLE will be a nice feature but this all started with me preparing to add a Futaba Optical RPM sensor on a DA70. I will reply once I receive the magnetic tach.
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