Signal for knowing when the engine has stopped
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Thread: Signal for knowing when the engine has stopped

  1. #1

    Default Signal for knowing when the engine has stopped


    I'm tinkering with a keyless ignition system for my m90 (very similar to digital guarddogs). And I was wondering how to make the bike stay running if the fob is too far, but not be able to start if the bikes motor has stopped for any reason. I would need a signal voltage from somewhere that the engine is running that would keep the relay active (would be driven into a pic/arduino so there is very little load). What would the most practical / sensible way of getting that voltage. From injection it seems like it might interfere with the injection system, same with the sparks. Any ideas?

    The easiest way is to use the normal electronic signals that kill the engine (killswitch, side stand, etc) but those wont give a signal if the fuel runs out or the engine stalls from incorrect clutch usage.

    Any help would be greatly appreciated.


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  3. #2
    Very Active Member NoSetFine's Avatar
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    Apr 2017
    Ontario, Canada


    Hello, friend.
    I did this on my 109 - I would hope it is similar on a 90.
    How much progress have you made with this?
    There are a couple of bridges to span when doing this, as you are discovering.

    • Consider using passive RFID instead of active RF. RFID are battery free but don't allow "proximity". RF allows proximity but then you have 2 new problems: 1/ The bike needs to be constantly probing for the fob, leading to battery issues on the bike. 2/ The fob will require batteries, and if it dies when you are riding, you need to ensure the bike stays running and you can get new batteries to get home!
    • Allow the keyed ignition to override the keyless as a backup system.
    • The silly "anti theft" resistor... I think 330ohm on the 109? Without the resistor, the bike will wakeup but not start without the key.
    • The Kill Switch override - I use this as my system wakeup trigger. I think this is your primary question. Like this: The Kill Switch provides the circuit necessary to keep your relays (or MOSFET's) alive, once they have power (which comes from my proximity sensor). Once the switch is OFF, the primary relay dies and cannot wake without a fresh FOB presentation, but will *latch* on once the bike is running.
    • System tilt override - Consider a tilt sensor to shut the entire system off to protect from parasitic drain on your battery.

    I did it with 3 relays total, and a prefab proximity RFID reader box.
    This winter I am considering redoing the entire setup using a microcontroller and mosfet's instead of relays. We'll see if I have time for that or not...

  4. #3


    Thank you very much for your input. I'm sure that the 109 and 90 are quite similar in this matter.

    I'm still in the planning stage of the project. I am using a BLE (bluetooth low energy) beacon and a microcontroller for the switching. That way I can set the distance of the fob pretty accurately (from 1cm (0.2")to 6m (18feet). By using the deep sleep mode of the microcontroller I can limit the power drainage of the unit (80mA ish when active 5uA when sleeping). The unit will try to scan 5 times (takes about 0.3s) and sleep for 2sec. that way the active time is reduced and power usage is also manageable. I've calculated that the unit would drain a 18Ah battery in about a month. I would ofc remove the battery if I am not driving for months.

    I've some experience with rfid but the reading distances and power usages are far inferior to BLE. Not to mention the possible security risks. I will also, in the future, implement a gps to the microcontroller to send a sms to me containing the location and time if the bike is shut off without the fob.

    Using the killswitch as a trigger would not trigger when the bike runs out of gas or if it's shut off manually with the clutch.
    One thing I am considering is to use the ignition signal from the ECU to the ignition coils and separate that with resistors so that they draw very little current from the signal (I dont want to mess up with that one) -> reduce the voltage with resistor division to be usable in the microcontroller and use a RC circuit to make the PWM constant so it can be used as a digital input.

    I was planning on using the key as a "master switch" that will shut off the engine and the microcontroller and the key needs to be "on" for the microcontroller and starting the bike. Planning on doing one of those key hiding mods also, so nobody gets any ideas about the keys being in the ignition.

    Thank you for mentioning mosfets, will use those instead of relays. I wonder how much amperage would it need. Any knowledge?

    I need to look into that anti theft resistor. Makes sense for it to have that so that the bike cant be just hotwired.

    There are a lot of things to consider as I dont want to get stranded because of some dumb thing I didn't think about. I have lots of time now that winter is here. There's no driving a M90 during finnish winters

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  6. #4
    Very Active Member NoSetFine's Avatar
    Join Date
    Apr 2017
    Ontario, Canada


    Sounds like you are well on your way to some good solutions! No riding in Canadian winters either - I only have names for TWO seasons in Canada: RIDING season and MODDING season... hahaha!

    I would agree, BLE is certainly the best of the FOB options, especially with a 5uA sleep mode cycle - I considered that also, but RFID was cheap and plentiful for me (although 100ma sleep, and why I needed a tilt switch), so I didn't pursue BLE. You could extend that even further with a tilt sensor, so the entire system is powered off when on the stand (?) - I chose this method over a mechanical or keyed "master switch" so I never need to touch or worry about keys for power. I agree the RFID isn't best for range, but my controller is programmable, and I have coded a silicone wrist band to authenticate. Yes security isn't "great" but if you are going to go to the trouble of cloning or scanning my RFID wrist band just to steal my bike, you probably deserve it. Hahaha. My RFID antenna has about a 1" range so I hid it behind RF-friendly plastic so I can just sit on the bike (tilt wakes system) and swipe my wrist to wake ignition, flip kill switch, and hit start. Jumping off the bike is just as impressive - hit kill switch... walk away. :)

    GPS + SMS would be a nice add on also, although Canada has one of the most expensive cell service rates in the world... so no SIM toys for me. :)

    My kill switch acts as the latch for my "Master" relay. Ignition cycle on the master relay is like this for me: Kill switch "on" (no power). Tilt-to-wake RFID module. RFID auth powers master relay coil for 7 seconds, which allows bike to start. Start bike, RFID power shuts off but kill switch feed is now hot while running, latching the relay ON. Relay will stay latched with no RFID present (so I can start and walk away without worry, or lose my fob while riding and not shut down), until kill switch is off. Then RFID is required again to wake the master relay coil and repeat the cycle. If the bike ran out of gas or other fault while kill switch was ON and HOT... I'm not actually sure what would happen! Ha. Never tested that. I *think* I would need to present the RFID again? I'm not sure if Kill Switch stays hot if the bike dies while powered. :)

    I suspect tapping into the ECU line would actually be the same or similar as the Kill Switch line because the kill switch is only powered when the bike is running (although not sure if it dies if out of gas). I don't know if the ignition signal is logic-level, but you would certainly want to clean it up if you are using it as a digital input - have you considered an opto-coupler for that? Using resistor division could work but would be a very dirty signal from the stator.

    I have some DMT10H010LPS mosfets (100V/100A) and 20A screw-terminals. Given the main bike fuse is "only" 30A... I'm hoping that individual 20A lines should be more than sufficient to individual circuits. I hope to test this setup this winter, using TLP281-4 opto's to handle the inputs. Fingers crossed... ha.

    The anti-theft resistor is silly but effective - if your ignition is the same as the 109 (probably?) then they "hid" a resistor inside the key mechanism module - you will get an FI error (C42 on 109) if you try to start without it. If the ECU doesn't see a specific resistance across... I would need to check which two lines - then it will not allow the bike to start, will produce an FI error code, although it WILL fully power-cycle and wake up. That stumped me for awhile when I first wired it up. :)

    Took me an entire winter to get it working, but now have proven it over 2 seasons and very happy with it. Looking to migrate to a digital solution, but because it is already working "as-is", it has fallen lower on my to-do list.

    I look forward to your success with your project!

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