Manual Transmission Gear sensor

[Ben] bought a remote starter for his car but needed a way to make sure the manual transmission was in neutral when starting. He built this infrared sensor frame to detect the position of the stick. It uses four beam paths which will tell him the exact gear or neutral position of the shifter. For this project he just needs to detect neutral but exact gearing is apparently necessary information for his next hacking project. We initially were worried about sunlight interfering with the sensor readings but he’s building this to go under the collar that is used to cover up the mechanical joint at the base of the stick.

57 thoughts on “Manual Transmission Gear sensor

  1. This can be easy accomplished using 2 switches on the gearbox levers, everything you do with the shifters ends up in 2 “levers” on the gearbox, so there’s no need for this kind of complex sensor.

    Sorry about my english, i’m spanish :)

    1. Hello Jorge.

      Is it possible if you could please elaborate this concept as I am not familiar with the field of gear mechanics. I am a Computer Engineering student and working on a project that requires a sensor which tells you when the car gear is neutral and when not.

      Thank you.

  2. Interesting project. I’d go with Jorge’s point – I’d rather pick off the data from underneath – or maybe there’s a signal somewhere heading to the ignition computer from which the data could be plucked. Depends on the make and model, I guess.

    This solution won’t work with some vehicles – I had a Ford Ranger (pickup) once which *required* the clutch to be depressed to run the starter, regardless of where the gearshift was positioned.

    Ford had some cars a few decades ago that had problems starting up and suddenly shifting into gear so all of their modern (at least USA) cars have some sort of interlock.

    Mike Y
    Dallas, Texas

  3. Don’t most cars with manual transmissions and cruise control have a neutral switch that serves this purpose? If not, I would suppose if you had cruise control on and you pushed the gear switch to neutral that the engine would race as the car slowed.

  4. @derek
    The point in leaving the car in gear is for safety, in case the handbrake fails, and when parking on slopes. It’s happened to my friend once, and I’ve kept my car in gear when parking ever since.
    Actually, the typical advice I hear is to get used to leaving it *in* gear and after a while it will become a good habbit, as opposed to the other way around.

  5. @derek – Yup, that’s how you’re meant to drive. Loads of people don’t though, and it also leaves a problem when you need to leave the car in gear on steep slopes (something you’re advised to do).

    None of the cars I’ve worked on with CC have a neutral switch, they all have clutch switches and if you dip the clutch they disengage the CC.

    As said above though, 2 switches on the gearbox housing end would make it easier, but I suppose often harder to get to on modern cars.

  6. did this over 15 years ago when remote starts first hit the market (in my area). As a professional installer, I’d use two microswitches to sense whether the stick was in the middle based on the fact that if it were in any gear, it would never be in the center position.

    As for the clutch issue noted above, that’s a simple bypass of the clutch switch.

    Never thought of using IR to sense stick position though – neat concept.

  7. I built something similar to this on my automatic Charger to control my ground effect and under grill lighting. In most states, it is perfectly legal to have this lighting but 100% illegal to be driving with it on. After the $300 ticket for forgeting to turn off my undergrill lights, I wired up a microswitch that was only closed when the shifter was in park. No more tickets for me!

  8. To the previous questions:

    1) Most cars do NOT have a neutral switch on a manual transmission. You have to press the clutch for it to start. These devices usually trick the clutch switch into thinking that the clutch is pressed when it’s not.

    2) For cruise control (@Nate), if the cruise is on and you push the shifter into neutral, the engine WILL race. I’ve done this before and it scared the hell out of me!

    Also, this method is much simpler than adding microswitches because most people don’t have easy access to their transmissions!

  9. This is a rather complicated approach…
    I did the same a couple of years back with a magnetic switch and two wires to the starter circuit.
    The only gears one should be worried about are 1st and 2nd which would possibly cause the car to move forward if the remote start is triggered; all others will just result in the car stalling.
    The engine would not be able to generate enough power to actually move the car.

    The way I did it was basically putting the magnetic switch’s wired end where the neutral position on the driver’s side(USDM) and the free piece on the shifter shaft (all this underneath the shift boot).
    That way when both components of the switch were aligned the car would start, but anywhere off would keep the remote start from activating by just cutting the power to the circuit.

    @Colin: you can do a clutch switch bypass for the remote start with a relay, which will take care of not being able to start because clutch isn’t pressed.

  10. Many aftermarket cruise controls have no neutral or clutch inputs. They sense the rapid increase in rpm as an indication of either a clutch press or a knock of the stick into neutral and turn off. They do have brake inputs, since the brakes effect on rpm is much more gradual.

  11. @Everybody saying “Too complex. Mount it on the shift linkage” That won’t work on a rear wheel drive vehicle as the shift lever goes directly into the transmission. There is no linkage.

  12. Just read this:
    “The only gears one should be worried about are 1st and 2nd which would possibly cause the car to move forward if the remote start is triggered; all others will just result in the car stalling.”

    I don’t remember being able to even start my car in-gear w/o pressing the clutch.

    Is there some kind of trick?

  13. xrazorwirex: with a powerful engine you can just about start in first or second, especially if the car is pointing downhill. It tends to work because as you start a car it revs the engine a bit to get it going, and some cars will sense that the engine isn’t turning, assume its too cold, and pump more fuel in.

  14. This type of assembly in a dangerous device is only valid in a development protoype (in use < a week at most).

    The opportunity for a critical fail is enormous.
    Sensors must be designed for fail-safe – not fail to some-other-mode.

    Any one or more LED pair failing, open-circuit wiring, mis-alignment, sunlight etc – should all render a void output.

    Also, ask someone that is unfamiliar that doesn;t know it's fitted (blind test) to perform your testing cycle to uncover any 'unexpected' differences in the way they use the device.

    and – Tell us where you live so we can keep our kids away (:-)

  15. I’m not particularly automotive savvy but I know of one vehicle that you never left in gear while parked. The military’s old multifuel M35 trucks will start on its own if left in gear and something bumps it. The engine runs just fine in reverse, too. So that makes parking on a hill and leaving it in first gear a particularly bad idea. There is an ancient technology used to secure cars with manual transmissions. It is called a wheel chock.

  16. pottymouth: I haven’t actually looked at how he fail-safes it, I would have thought it’d be best to go for a differential approach: Flash the led on and off, sense for any difference in input. That will sense broken leds, broken sensors etc

  17. Hi guys, thanks for all the feedback on the project. I will try and respond as much as possible.

    Most people I know with manual cars have older vehicles and there are no factory neutral safety switch. This device just tricks the car to thinking the clutch is pushed in when autostarted.

    A manual car should normally be parked in gear. That being said, in winter it is so freaking cold I would rather leave the car in neutral and use the autostart. This makes sure I didn’t forget to leave the car in neutral. Plus if a shop is working on the car or a friend is borrowing it no worries!

    A few people have also mentioned that really only 1st and 2nd are a threat, I felt the autostart repeatedly trying to start the car against the parking brake would be best avoided in all cases!

    @Jorge: Thanks for the info, I will look into that.

    @pottymouth: You do bring up a valid safety concern, and safety was a priority in this design.

    1. The detectors only have a <12 (maybe even 6) Deg viewing angle and they are pointed under the dash and at a door. I was unable to get a false start even on a sunny day with the car as open as possible.

    2. The sensors must read high signals to start, open sensor does nothing. In my PIC controlled version (coming soon) the LEDs with be pulsed and the PIC will verify the transmitted and detected pulses match. This is meant to be a very basic design for people who don't want to go nuts with triple fail safes and micro-controllers.

    3. Most people now just short out the clutch sensor and hope they don't forget to leave the car in gear. I feel this is 100% better than that. (I know people who have had accidents because of this)

    Keep the comments coming!

  18. Just about the sunlight concerns…

    modulated the LEDs with X kHz, set a bandpass-filter behind the IR dectors and this problem (if there was any at all) is gone. Similar different frequencies would help to match pairs of senders and receivers, just in case any kind of strange reflection might give you a false.

    Just my thoughts

  19. im a profesional installer. newer remote start units like the vipers by dei. have a manual transmision mode. ties into the ebrake, and door trigger. you press foot brake, engage ebrake, realease footbrake. remote start the car with the fob (take the key out, the car will still be running). open the door, get out, shut door, then lock. upon lock, the car shuts off.

    sounds like alot, but its second nature after a week. i have it like this on my car.

  20. To most of the people that have replied so far, please stop making assumptions based on one type of car. No most cars dont have neutral switches (in their manual transmission variants) and no not all front wheel drive transmissions have levers on the top. Many hondas have rods going to the back of the transmission instead of cables to the top.

    Compustar alarms are easier than the DEI/viper kevin listed above. Pull the ebrake up and take the key out, engine will still run. Hit the brake to turn the car off, or get out and close the door. The car will shut off on its own, the doors lock and it will allow you to remote start until the next time a door is opened.

  21. @ Ben

    Thanks for all those answers, but you didn’t cover mine – why so many sensors for that job?
    I still cannot understand the need for two or three of those four units.

  22. I did forget to mention the autostart this project was done with does have a manual transmission mode, but that requires you to do the arming sequence that Kevin mentioned earlier. It is a solid solution, but it seemed like a huge hassle that could be easily (and hopefully safely) hacked around.

    As for reflections, the power of the infrared LEDs is just enough to turn on the phototransistors(which have a 8 Deg viewing angle) so I doubt a reflected beam would have enough power to trigger a false positive. That being said it is a concern and I intend to do more testing to verify this is not an option.

    @TorstenL: I absolutely agree. Already implementing this on my PIC controlled final version.

    You guys have got me curious as to what it would take for sunlight to trigger a false positive.(even though the sensor isn’t exposed) I will do some tests this week.

  23. Sorry about that stunmonkey, You are correct, technically I could get by with only one horizontal sensor in the middle, if it was blocked I could say the stick was in neutral. This solution would not be safe as a disconnect or emitter failure would act like a positive reading. Requiring two positive horizontal reading allows me to safely assume the stick is in the neutral position.

    The reason I have two vertical sensors in addition to two horizontal ones is it allows my PIC (on a new project) to not only determine if the car is in neutral, but which gear it is in. This will then be displayed on the instrument cluster as I shift though gears.

    So long story short, for this particular project you are correct, only the horizontal sensors are needed.

  24. this, while good effort, is bad design, have you thought about dust or dirt getting on the sensors and giving false readings, or blocking the sensors… you should use some mechanical switches instead, that way its only the contacts you have to worry about, which will last a lonngggg time if you dont make then switch anything big. i reckon this one will start to play up after 6months to a year

  25. also, to some of the other posters, depends on how strong your starter motor is, and how your gearing is, 4th gen prelude can move from starter motor in 5th, but not start, and the starter motor can get the car running and rolling from 1st and second. If i park the car on something slippery, like wet grass, it can crawl along with the back wheels slipping. so maybe someone needs to put a car movement sensor in?

  26. I would be interested to know in how he has achieved functional safety in this project.

    If the sensor or circuit to fail in some way, it would be very likely for the car to zoom off and mow some people down.

    Does he use some kind of dual channel redundancy, majority voting etc?

    In my opinion, this modification could be a potential killer if not done properly.

  27. I noticed many VW/Audi manual gearboxes have a provision for a microswitch for each gear via a cam on the selector shaft and a matrix of small pushrods. I have never seen anything other than reverse and top gear switches actually fitted though and always wondered what the rest were for.

    If this fails as a safety lockout, as a final resort what about an accelerometer to detect if the car moves unexpectedly the instant after the starter is engaged.

  28. This seems a bit silly, you want to make sure the car is in neutral for safety, yet you have remote that starts up a car from a distance?

    Just get into a habit of leaving your car in neutral, if you park on a steep slope, then dont use the remote startup lol, you shouldn’t be starting it up anyway, unless you can at least see the car.

    Imho just get a mercury switch and wire it to the reciever, if it is on a slope, the remote won’t work.

  29. As a cautionary tale, after an interview a guy nearly killed one of my supervisors with an auto start. Tried to start it in gear. It jumped the curb and hit a little tree before it stopped. Came within two feet of coming through the floor to ceiling glass that made up his office. Do I have to say he didn’t get the job? I think the neutral parking option is a must. In fact, I would probably pull an actuator off of an old treadmill and have the car pull the parking break before start….

  30. Why not simply tap into the sensor that is ALREADY on the transmission? the neutral switch? Also I’d wire it in to also only work if the parking brake was on. Remote start on a manual is pure dumb without a ton of safeties. it’S why you cant get them installed anywhere.. To further enhance that stupidity, I saw a motorcycle with remote start. The poser that was all “that” went to show off his “fly” Ninja and went to start it, it lurched foreward and fell over. All of us laughed non stop as he picked up the bike, picked up the pieces of his fairing and then tried to start the bike to leave.

  31. Even my 24 year old Mazda RX7 has a neutral switch. It doesn’t disengage the starter. It just notifies the ECU that the transmission is out of gear. I’d be surprised if newer vehicles didn’t have a similar sensor.

  32. None of my 3 current vehicles (’91 toyota, 2001 Peugeot and ’96 Renault) have a neutral sensor. There is no need in a manual, you’re assumed to have at least half a brain and not start it in gear.

  33. Neutral + Parking break, then bypass the neutral safety switch for starting. If you want safety to prevent starting in gear, use the door ajar sensors to detect when the door is opened, then closed. Wire the iginition to remain running when the key is removed, engine is killed when doors are closed. Car is “cocked” and ready to start via remote. If doors are subsequently opened, it breaks the “cock” and cannot be started. This way, you must leave the car in neutral, set the brake, remove key, exit vehicle, close doors, engine stops, alarm arms and is ready to start.

  34. A clutch exists for a reason, you should use the clutch when starting the car anyways as the starter doens’t need to rotate the gear box that way.

    Then you don’t need to worry about the gear cause you just shift into first or leave it if it’s there.

  35. @Jake
    Name one :P

    Mercury switches wont work on hills and aren’t eco friendly.

    Magnetic and mechanical switches are much less reliable in this type of sensing IMHO.

    My car does not appear to have any factory sort of gear sensing or neutral safety switch.

    Total cost of the project was less than $20 and can be completed in a day and requires little actual electronic knowledge. I’m pretty happy with it :)

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