Detecting when vehicle is running. - Page 1
Forum section: electronics / beginners

author: PoDuck
author_rank: Regular Contributor
timestamp: April 13, 2022, 08:08:22 pm
content: I am trying to make a circuit that turns power on to the device when a vehicle is off, and turn the device off when the vehicle is running. I decided to try using a zener diode to accomplish this. I figure that if the voltage is above 13 volts, the vehicle is running. The range of voltages that a running vehicle can have is roughly between 13.7 volts and 14.7 volts, but it is conceivably possible that it could drop below 13.7V. Voltage should usually be around 12.6V without the alternator running, but it can conceivably be higher. I don't ever want the device on while the vehicle is on. I may be wrong thinking that this can work.On the schematic below, I have an IRFH7914TRPBF with a vgs max threshold of 2.35V. If this were all that I needed to worry about, I would be fine, but I'm looking at the vgs min threshold of 1.35V and thinking that if I use a 10.7V zener, which would fully saturate the fet when the power is above 13V, it would still be above the minimum threshold when the vehicle is off, as 12.6V - 1.35V is 11.25V, which is .5V higher than minimum threshold after accounting for the diode drop. Looking at this, and my specifications in terms of what I'm trying to detect, it appears I would need a mosfet where the difference in minimum and maximum vgs threshold are no more than 0.4 volts, otherwise the fet will always be in some stage of being on.Is there a better way to do what I'm trying to do? Is there a better mosfet/zener combination to accomplish this?

author: sahko123
author_rank: Frequent Contributor
timestamp: April 13, 2022, 08:19:43 pm
content: If you have access to the power going to the radio it would be as simple as power or no power. Or you can have it come from the ignition directly.There's a lot of uncertainty when measuring directly from the battery since there could be temperature variations differences in how long it's been since the vehicle was last driven or even degrading battery or whatever other variations.

author: Benta
author_rank: Super Contributor
timestamp: April 13, 2022, 08:21:05 pm
content: I expect you're talking about an internal combustion engine?Sensing battery voltage is doomed to fail. It's temperature dependent, battery state dependent and, and, and. In short: completely unpredictable.Your best bet is tapping into the crankshaft sensor, or alternatively the cam angle sensor.Both will deliver an AC signal that can be amplified to your needs. Analog post-processing is needed. This will work for both Diesel and petrol engines.For petrol engines, you can also place a capacitive sensor on one of the ignition leads.

author: PoDuck
author_rank: Regular Contributor
timestamp: April 13, 2022, 08:29:38 pm
content: Quote from: sahko123 on April 13, 2022, 08:19:43 pmWell, the power going to the radio isn't good either, because the radio can be on without the vehicle running.Quote from: Benta on April 13, 2022, 08:21:05 pmI know that a properly running vehicle with lower than 13 volts at the battery is not running. The only time it will be higher than 13 volts is when the alternator is on. If all I had to deal with is that, I wouldn't be having any trouble. It is not wanting it to be my fault that it is running while the vehicle is running that I would be concerned about.It is conceivable that a vehicle with a bad alternator would still be lower than 13 volts, and in that case, I am not terribly concerned, because it is a bad alternator causing the problem, not my device.

author: Benta
author_rank: Super Contributor
timestamp: April 13, 2022, 08:35:11 pm
content: Quote from: PoDuck on April 13, 2022, 08:29:38 pmWrong. Try jump starting a car with a flat battery and run it. It will be way below 13 V until the battery is up again, and we're talking a 15..30 min. drive here.And if it's cold?

author: PoDuck
author_rank: Regular Contributor
timestamp: April 13, 2022, 08:42:35 pm
content: Quote from: Benta on April 13, 2022, 08:35:11 pmI'm not too worried about that. If a vehicle is old enough to be using a generator that would have that problem, instead of an alternator, they will have no use to install my device.

author: themadhippy
author_rank: Super Contributor
timestamp: April 13, 2022, 08:52:00 pm
content: stick a mercury switch to the cylinder block,vibration from the engine will keep the switch open,engine off no vibration so switch will close

author: bdunham7
author_rank: Super Contributor
timestamp: April 13, 2022, 08:54:32 pm
content: Could you elaborate on the range of vehicles you have in mind and the precise definition of 'running'?

author: Benta
author_rank: Super Contributor
timestamp: April 13, 2022, 09:03:17 pm
content: Quote from: PoDuck on April 13, 2022, 08:42:35 pmWhere did I say anything about a generator? You'll have the issue with an alternator as well.

author: bill_c
author_rank: Regular Contributor
timestamp: April 13, 2022, 09:04:39 pm
content: Quote from: PoDuck on April 13, 2022, 08:08:22 pmThen let us know how well it works or if it failsYou haven't explained what this thing will do, you have conflicting requirements, and conflicting statements. How will this work on an electric vehicle? What about 24V systems? What happens if I turn off the engine or it stalls while going 80 down the highway?

author: inse
author_rank: Super Contributor
timestamp: April 13, 2022, 09:09:39 pm
content: Some time ago, I had a self developed device in my Ford Fiesta, which had been powered from the always-on cigarette lighter.I determined the thresholds specifically for this car with a multimeter, minimum voltage in idle with all electrical consumers turned on.And the drop of the battery voltage after turning off the engine.The voltage was monitored by the microcontroller and there was a switch-off delay in case I would turn off the motor at a traffic light.Do you want to implement your device to different cars?This might get even more complicated nowadays as modern cars may employ energy management to keep the battery in a controlled charge state.So the board net voltage might vary even when the engine is running.Above that the MOSFET zener diode approach is far from reliable, maybe not even functional.The threshold voltage is usually specified at 100uA drain current which most probably will not be sufficient for your voltage regulator.So you will run the MOSFET in linear operation resulting in a undefined output voltage.

author: sw2022
author_rank: Contributor
timestamp: April 13, 2022, 09:11:37 pm
content: There might be an output from the engine management already present that does what you want without any further circuitry. Though it might be speed sensor based. Though you’d have to research your individual vehicle. On one vehicle I have the output is used to control things that need to know whether the vehicle is moving.Steve

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 13, 2022, 09:16:15 pm
content: I have not been in a generator equipped vehicle for several decades, but have observed battery voltages below 13 V in a running car on many occasions. The most obvious is when the charging circuit is weak or failing, but other conditions give this also. High loads (AC, trailer, entertainment, lighting all at once). Poor connections. Low temperatures. Failing battery. Low idle speed. And so on.You can dismiss all of this as irrelevant to your problem, but anything that would cause you to be blamed for inappropriate load draw would be doubly true in these cases. The fundamental problem is that the alternator feeds a great many customers, all of which vary in quantity and condition a great deal from vehicle to vehicle and over time.Given that you don't feel that the ignition switch is adequate solution I can think of nothing that doesn't involve direct sensing of engine rotation that can work reliably. There are many many ways to do that. Place a small generator with friction wheel rubbing one of the pulleys or belts. Put a mark on one of the pulleys and sense it optically. Tap into the magnetic signal used in the ignition of most modern cars. Tap into the OBDII system on modern cars and read the engine RMP. And actually a non-rotation sensing method did occur to me. Put a pressure sensor in the exhaust and look for the exhaust pulses.

author: PoDuck
author_rank: Regular Contributor
timestamp: April 13, 2022, 09:20:59 pm
content: Quote from: bdunham7 on April 13, 2022, 08:54:32 pmThe range of vehicles can be anything from 1974 to present internal combustion engine vehicles that don't shut off the engine or the alternator while "running". And by "running", I mean that the engine is under its own power, after being started.

author: Peabody
author_rank: Super Contributor
timestamp: April 13, 2022, 09:25:35 pm
content: Honda uses a two-stage charging system that keeps the alternator at something like 12.4 volts under normal operation in the daytime. This saves on mileage, but is a bad system because the battery isn't kept fully charged, and sulfates up and dies about twice as fast as normal. You get high voltage only under high current - i.e. when the headlights are on. So a voltage of 12.4V would tell you nothing about whether the engine is running or not.

author: PoDuck
author_rank: Regular Contributor
timestamp: April 13, 2022, 09:34:02 pm
content: Quote from: inse on April 13, 2022, 09:09:39 pmYes, it needs to work in different cars. It has a remote that can turn it off, which can be used for vehicles that voltage detection wouldn't work on, as well as turn it off when it is undesirable for it to be on generally.Essentially, what I am working on is just a different type of catalytic converter alarm than exists at the moment. I have the rest of the stuff breadboarded and working, and it works fine, but that is working off my bench power supply. I would like to make it automatically arm when the vehicle is off though. It doesn't have to use this method, but I would like to do it by detecting voltage, as that is the easiest thing to detect. I even considered trying to detect ripples in the voltage, but I'm not sure how I could passively monitor that, and it would have similar voltage range issues.

author: Benta
author_rank: Super Contributor
timestamp: April 13, 2022, 09:38:10 pm
content: Quote from: CatalinaWOW on April 13, 2022, 09:16:15 pmThat's a nice one. I like it.Another option would be a temperature sensor on the exhaust manifold.

author: bdunham7
author_rank: Super Contributor
timestamp: April 13, 2022, 09:39:52 pm
content: Quote from: PoDuck on April 13, 2022, 09:20:59 pmOK, so no hybrids, no Hondas that disable alternator at times and probably some other oddballs. And I don't know if you'd include modern vehicles with that annoying 'stop-start' feature, but your description seems to exclude them. You can't use fuel pump power, which otherswise would have been ideal, because your description doesn't exclude old carbureted vehicles or diesels with mechanical pumps. You can't use ignition or sensor signals, because your range includes old cars and presumably diesels. Your voltage sensing idea will almost work, but there will be at least some cases where particular vehicles will be on the wrong side of your 13.7 volt threshold, and moving it won't help much.So its hard to come up with a single universal approach. Intake manifold barometric pressure variation is pretty reliable, but I don't think it would be hard to make a system that works properly will every possible engine--and you'd have to install a baro sensor in some applications. Alternator current might work, but again you need a sensor. Alternator field would work on a lot of cars, but not all. Oil pressure would probably be your best bet as long as a few seconds of delay in the response isn't a problem--but cars do have different circuits for oil pressure sensing so you'd need to accommodate that or add your own sensor.

author: PoDuck
author_rank: Regular Contributor
timestamp: April 13, 2022, 09:43:28 pm
content: Quote from: CatalinaWOW on April 13, 2022, 09:16:15 pmAn especially weak alternator and an exceptionally dead battery can do that, but I've tested the voltage of many vehicles to see if the alternator was performing properly, and I don't remember ever seeing voltage below 13 volts at idle, even with all the lights, A/C, etc. on, unless the alternator was bad.Given that the person that asked me to design this is planning on having any random person be able to install it, I would really like to stay away from adding more sensors, or tapping into wires that may cause damage to critical systems. It needs to have connection to the battery, and a connection to another sensor and a siren. No tapping into wires necessary.Ultimately, since it has to work on vehicles I can't sense this stuff for, it doesn't need to be 100% reliable on every vehicle. It can be turned off while the vehicle is running manually. It's just one of those things that would be nice if it worked without much thought for some number of people.

author: PoDuck
author_rank: Regular Contributor
timestamp: April 13, 2022, 09:46:37 pm
content: Quote from: bdunham7 on April 13, 2022, 09:39:52 pmAs I said, I know there will be edge cases that don't work, but for those they can turn it off manually. It will be useful on all those other vehicles, and can be used, but it just wouldn't be automatic.As for the voltage sensing, am I wrong in thinking that a ~10.7V zener would still have it in some state of turning off when the vehicle is off?

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: April 13, 2022, 11:12:29 pm
content: The signal from the oil pressure switch is the easiest way. Just a simple switch that gives you either battery voltage if the engine is running and 0v if it is stopped.

author: WatchfulEye
author_rank: Regular Contributor
timestamp: April 13, 2022, 11:27:28 pm
content: Why can't you just take power from a permanently powered circuit and take the activation signal from an ignition powered circuit.All cars have multiple circuits which are permanently powered and multiple circuits which are powered only when the ignition switch (or equivalent push-button system) is set to "run". These are easy to access from the fuse box with fuse taps - just have 2 fuse taps, one to an always on circuit (e.g. interior lights) and one to an ignition powered circuit (e.g. cigarette lighter, electric windows, ECU, etc.). Many in-car accessories, such as dashcams work this way.The problem with battery voltage monitoring is that many (most?) modern internal combustion engine cars have start-stop features or some type of alternator management (where battery charging is periodically stopped to save fuel).

author: james_s
author_rank: Super Contributor
timestamp: April 14, 2022, 12:20:58 am
content: Quote from: PoDuck on April 13, 2022, 09:34:02 pmWhat is the advantage of knowing whether the engine is actually running or not? Why not just go by whether the ignition switch is on? If the switch is on then the car is probably occupied, either by somebody authorized to use it, or it has been stolen in which case no alarm is going to stop a thief by that point.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: April 14, 2022, 01:30:28 am
content: One of the wires going to the radio is a signal wire that is high when the ignition is on.

author: inse
author_rank: Super Contributor
timestamp: April 14, 2022, 04:19:28 am
content: Not necessarily, the radio can also be turned on by CAN bus.The automotive electronics has changed so much between 1974 and today, that an universal solution may be hard to find.Simple switches have turned into sensors, a lot of stuff is connected via busses.Why can't you design your circuit to use so little power that can be left active all the time?By the way 78L05 is not suitable for automotive.Did you also consider all the required input protection against spikes, load dump, reverse polarity?What about temperature measurement on the exhaust maybe in combination with a motion sensor?I had been annoyed by an unreliable theft alarm on my last car so much that I removed it.

author: Circlotron
author_rank: Super Contributor
timestamp: April 14, 2022, 05:07:59 am
content: What about a contact microphone attached to a relatively noisy area of the engine, e.g. valve gear cover?

author: BrokenYugo
author_rank: Super Contributor
timestamp: April 14, 2022, 05:13:57 am
content: "Key on power" is the automotive term.

author: fordem
author_rank: Regular Contributor
timestamp: April 14, 2022, 12:18:18 pm
content: If you want to know when the engine is running, monitor the voltage at the oil pressure switch - if you have 0V or close to it, the engine is either not running or will be very soon.The oil pressure switch closes (short circuit to the engine block/chassis ground) when there is no oil pressure, and opens when the oil pressure is above approximately 3~4 psi, the circuit is usually pulled high by an incandescent lamp wired between the switch and ignition power. Depending on ambient temperature, oil viscosity and in some cases the oil filter in use, it is possible to have low oil pressure for the first few seconds after the engine has started, but generally speaking, most engines will have enough pressure to extinguish the light before the key leaves the start position.

author: PoDuck
author_rank: Regular Contributor
timestamp: April 14, 2022, 12:19:40 pm
content: Quote from: WatchfulEye on April 13, 2022, 11:27:28 pmThe start/stop feature seems to only be a feature of cars, so far. I haven't seen trucks, SUVs, or RVs that have this feature, and it isn't just modern vehicles that are having their catalytic converters stolen.The whole point is to make something that is somewhat idiot proof, in terms of installation, for the majority of situations. I would like your average moron to be able to install it without having to hire someone. Tapping into the CAN bus, oil pressure sensor, installing an additional knock sensor, etc. can be tricky, even for someone like me, who is extremely familiar with the systems. On the other hand, if it has to be connected to the battery anyway, we might as well use that, if it can be done. If it won't work for certain vehicles, they still have a key fob they can arm and disarm the system with.

author: PoDuck
author_rank: Regular Contributor
timestamp: April 14, 2022, 12:30:47 pm
content: Quote from: inse on April 14, 2022, 04:19:28 amI'm not looking for a universal solution. I already resigned myself to the fact that this might not work. It would be nice to find something that works in the vast majority of situations though.As for it being active all the time, it's a catalytic converter alarm. Other existing systems use vibration, sound, or PIR sensors to set off the alarm. These things would be triggered while driving the vehicle. My sensor, while not being based on vibration, sound, or motion, would still be triggered when the vehicle is running.Ultimately I could forego this whole line of thought, and just make everyone arm and disarm with a key fob, but I thought it might be a simple thing to implement something that made things easier for most users. I don't know about you, but fumbling around with my key fob would seem to be a bit more aggravating if I had to do it with two fobs.

author: PoDuck
author_rank: Regular Contributor
timestamp: April 14, 2022, 12:34:26 pm
content: Quote from: fordem on April 14, 2022, 12:18:18 pmThis would suffer from the same drawbacks as detecting voltage change. Not all vehicles run all the time. When they are off, they would not have any oil pressure. This would possibly work on more vehicles, as those that reduce charge to increase mpg would be covered, but not enough vehicles to make it worth causing additional installation challenges for the technically uninclined.

author: CaptDon
author_rank: Super Contributor
timestamp: April 14, 2022, 12:38:08 pm
content: What kind of Cat Converter alarm, the fact that it is missing, stolen or just not working up to par? Your zener driving the fet is bollocks. The fet gate has megaohms of high impedance and a zener has leakage and a somewhat soft knee. You could use A.C. coupling to the battery circuit and amplify the ripple caused by the charging circuit. The ripple will be there even when the battery is fully charged since all systems are actually powered by the alternator while the car is running. It seems you are creating a circuit with no real purpose or need. My ECU tells me the health of my converter and if you are trying to do a 'missing or stolen' circuit what are you going to attach to the converter that can stand the heat? What if your unprofessionally designed circuit catches fire and the car and/or garage/house the car is parked in is a total loss?? Got any good lawyers on your payroll?

author: fordem
author_rank: Regular Contributor
timestamp: April 14, 2022, 01:06:16 pm
content: Quote from: PoDuck on April 14, 2022, 12:34:26 pmI recognize that there is a difference between vehicle running and engine running - you may have noticed that I prefaced my suggestion with the phrase "if you want to know when the engine is running".Now that you have told us what you're trying to achieve, how about a simple relay with normally closed contacts, fed from the accessory (ACC) circuit - accessory power goes live, relay engages opening the circuit shutting down the alarm, switch off and the relay drops out closing the circuit and powering up the alarm.You want ease of installation - plug it into a USB port or power outlet, those go live when the ACC circuit powers up.

author: bdunham7
author_rank: Super Contributor
timestamp: April 14, 2022, 01:06:47 pm
content: Quote from: PoDuck on April 13, 2022, 08:08:22 pmI didn't really look at this diagram before. If you've decided to use a voltage threshold to activate your device, you need a different plan. Assuming V_OUT is the vehicles battery voltage, turning the MOSFET off will float up the ground of the 7805 regulator and increase it's output voltage to 12 volts or so. It's not clear what you are doing with those voltages, but it will probably toast everything that is expecting 5 volts. As for using zeners and VGSto determine a threshold, that won't work very well. The zener will have some leakage and the MOSFETs will vary a bit and the VGSthreshold isn't sharp and so on. A better way to to this that is easy to understand is with a voltage comparator circuit using an op-amp. If you have regulated voltages already at 3.3V, you just feed the + input of the op-amp the 3.3V and the - side gets the vehicle battery voltage through a voltage divider of ratio 13.7:3.3, which is 4.15:1, or as close to that as you can get with commonly available 1% resistors. Or you can use a separate reference voltage if your regulated supplies are too noisy or not accurate enough for the characteristics you want.

author: PoDuck
author_rank: Regular Contributor
timestamp: April 14, 2022, 06:30:11 pm
content: Quote from: CaptDon on April 14, 2022, 12:38:08 pmI am fine to not use the zener driving the fet. It was just an idea that I didn't have the parts to test yet. Ripple is a good idea, and I considered it, but thought it would be more complicated to implement than something that would detect the voltage.As for what I'm going to attach to the converter, I'm not going to attach anything to it, so heat is not an issue. The method I am using is unique as far as I can tell, at least for alarming cars, and took me a long time to work the bugs out, so I'm not wanting to share it online for someone to beat me to the punch. It isn't meant to detect if the cat is missing or stolen though. It is meant to alert if someone tries to steal it. It is pointless to alert someone if their cat is already stolen. They will find out as soon as they start their car.

author: PoDuck
author_rank: Regular Contributor
timestamp: April 14, 2022, 06:40:37 pm
content: Quote from: bdunham7 on April 14, 2022, 01:06:47 pmThanks for looking at it. V_OUT is 12V unregulated from the vehicle. It simply passes through reverse voltage protection prior to this. I have a couple linear regulators in there, which I will likely be changing out for buck converters. In this configuration, I figured I would just shut off the power to the regulators, so there would be no voltage available other than 12V. I guess that isn't critical though, and the op-amp idea sounds very good. It would certainly deal with all the issues.Thanks

author: james_s
author_rank: Super Contributor
timestamp: April 14, 2022, 10:03:43 pm
content: Quote from: PoDuck on April 14, 2022, 12:19:40 pmLots of trucks and SUVs have that idiotic "feature" too, I remember seeing a product specifically sold to disable it on Ford trucks. Start/Stop is a gimmick to game the way emissions are measured in the USA and possibly other places, nothing more. The amount of fuel saved is negligible and it greatly reduces the life of the battery and other components.

author: james_s
author_rank: Super Contributor
timestamp: April 14, 2022, 10:07:02 pm
content: Quote from: PoDuck on April 14, 2022, 06:30:11 pmCat thieves are in and out often in a minute or less. I don't see an alert doing much good, by the time you can throw your shoes on and run out there they'll be gone, and there have been an alarming number of cases of thieves shooting at car owners who confront them.IMHO the way to stop cat theft is by making it almost impossible to sell one for money unless you are a licensed dealer and have a paper trail. I would go so far as to make simple possession of more than a couple of them without paperwork a crime. Enforce severe penalties on any individual or business that buys cats without the required paperwork.

author: PoDuck
author_rank: Regular Contributor
timestamp: April 15, 2022, 01:15:28 pm
content: Quote from: james_s on April 14, 2022, 10:07:02 pmThat is true, and an alarm by itself isn't going to do much, other than annoy the thief, but the person asking me to do this insures storage areas, where lots of vehicles are stored. They had to deal with one lot where 17 vehicles had their cats stolen in one night. In a situation like that, alarms would certainly be helpful in mitigating the amount of damage that can be done at one time. His idea is that his company will charge more to insure vehicles that have no deterrent installed. The alarm would be the least intrusive means for that. They would get a further discount if they introduce some system for making stealing the cat take more time and effort.There is no solution that can totally prevent theft. Making it illegal to possess too many of something has never really served as a deterrent either. There are several ideas that have been floated, such as serializing the converters to link them to vehicles, but that does nothing for converters that are already on the market, unless the owner of the vehicle has an aftermarket serialization done. There are already systems, like "Leads online" where you can have companies that purchase things from the public list identifying information, along with serial numbers, on their database, where police can access it and sometimes catch the thief, and even less times recover the stolen property. That could go a long way, especially if the cat was stamped with the vin of the vehicle they were attached to. But, what happens to the aftermarket for vehicle parts? Could you no longer use a salvaged cat, since it will be serialized to a different vehicle?Beyond that, where there is money to be made, you will find people that evade measures to catch them. You can't sell a stolen vehicle, yet people do it anyway. They have VIN numbers that are unique, but vehicles are stolen every day. Often they end up in other countries. If you can't stop people from shipping entire vehicles out of the country, which are very difficult to hide, how are you going to prevent catalytic converters from being shipped out disguised in a load of scrap steel, for instance?Anyway, it's all well and good to talk about the best way to stop it, but those methods aren't in place yet. Until then, people have to do what they can to deter thieves themselves.

author: james_s
author_rank: Super Contributor
timestamp: April 15, 2022, 07:30:08 pm
content: People steal them because it is easy to sell them. Make it hard to sell them and fewer people will steal them. Engraving them with individual serial numbers seems like a really good idea and would aid in tracking them. I still think it would be worthwhile to make possession a crime, if someone has a pile of them in the back of their truck it's no longer necessary to prove they are stolen in order to put the person in jail. On top of that it would help a great deal if we would stop coddling criminals and get rid of the revolving door. I don't know if it's true everywhere but around here crooks are back out on the street before the police officer has finished the paperwork.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 15, 2022, 07:48:06 pm
content: Quote from: james_s on April 15, 2022, 07:30:08 pmA law passed here to make individual sales of catalytic converters to recyclers illegal. You have to be a licensed auto recycler or repairer. While this may reduce the theft of converters, the other effect it had was to make it difficult or impossible to recycle mine when I replaced the failed units on my vehicle.Just another installment in the diary of why we can't have nice things.

author: themadhippy
author_rank: Super Contributor
timestamp: April 15, 2022, 07:49:40 pm
content: QuoteAnd what about the legit trader transporting them being pulled over by a copper who only half understands the law.A colleague of mine spent several hours in custody for having a drum of red high voltage cable on the back of his truck,because according to the police only the electrical suppliers can obtain this cable so he must of nicked it.

author: Gyro
author_rank: Super Contributor
timestamp: April 15, 2022, 08:13:33 pm
content: You could always try the ebay passive protection approach.

author: james_s
author_rank: Super Contributor
timestamp: April 15, 2022, 09:15:16 pm
content: Quote from: CatalinaWOW on April 15, 2022, 07:48:06 pmThat's just a case of a poorly written law. It should either allow an individual to sell one to a recycler with paperwork showing the vehicle it came from, or allow an individual to recycle it for free without getting money for it.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: April 15, 2022, 10:55:05 pm
content: Quote from: james_s on April 15, 2022, 09:15:16 pmYou are right. But your fixes still have flaws. You can only reduce the drag on law abiding people, not eliminate it. A perfect law is kind of like an ideal diode. Easy to describe, sometimes not to hard to approximate, but always flawed.

author: james_s
author_rank: Super Contributor
timestamp: April 15, 2022, 11:10:34 pm
content: Quote from: CatalinaWOW on April 15, 2022, 10:55:05 pmYou're right of course, but converter theft has reached epidemic proportions, it's happening even in nice low crime areas. There is a balance point and IMO we are not there yet. I suspect they are being bought by a limited selection of unscrupulous scrappers, a few sting operations might put a big dent in it. They could also do bait stings and park a truck somewhere with a nice big juicy catalytic converter easily accessible and wait.

author: DavidAlfa
author_rank: Super Contributor
timestamp: April 15, 2022, 11:41:56 pm
content: You know the battery light indicates wether the alternator is working or not, right?If the alternator works, the engine is running, so the lamp goes off.Then, all you need is to check is contact state and battery light.Code:Contact Battery lightOFF OFF Everything offOFF ON Wtf? Run!ON ON Only contact (Engine stopped)ON OFF Engine runningR1/R2 and R3/R4 avoids that any weird voltage turns the transistors on.With 100K/10K you need at least ~6Volts.But beware, in old cars the battery light is connected between 12V and the alternator winding, the lamp will turn off because the alternator self-feeds, thus the signal will be reversed (Active low)That's why there're two circuit versions!

author: vu2nan
author_rank: Contributor
timestamp: April 16, 2022, 03:24:57 am
content: In older vehicles the D+ terminal on the alternator would serve the purpose.With the engine running, +12V available on the D+ terminal could energise a 12V automotive relay to turn off the device.Nandu