lock doors when vehicle starts moving

Hi to all the smart people here that make me look stoopid! :)

I hope this is simple, and should be universal to a point for most of us.

I would like to be able to have the doors in my vehicle lock when it starts moving - most factory systems I have seen lock when the car gets to about 5MPH - I'd like to memic this, but as long as I can get them to lock when the car moves that will be fine.

My wife likes to lock the doors in her 2002 Saturn and I think that this will be a big convenience for her. I'd also like to do this in my 1997 Rodeo - I have an aftermarket alarm that locks the doors, but have no door switches for the doorlocks, so if I reach over to unlock a door for a passenger, I'd like for them to lock again when I start moving, without having to turn the truck off and back on to cycle the locks in the alarm.

I'd like to avoid trying to read what gear the vehicle is placed in (for locking say when it is put into drive) for the main reason that my truck is a manual shift and you would have to take it out of gear and put it back in for either auto or manual.

I figured I can use a switch of some type in the door to determine if the doors are actually locked or not - that's the easy part.

Any and all help is appreciated.

Well -- this will be an elaborate installation -- b/c from what I am gathering, you do not have power doorlocks in your Rodeo.

So you'll have to install door lock actuators on all four doors ---> technically fairly challenging (this requires dismantling the door liners, installing aftermarket hardware and wiring, etc)

Once you install your doorlock actuators (and door lock switches as well) you can wiring up an ignition auto-lock -- it'll lock the doors as soon as the car is started.  you don't have to tie the locking to the actual movement of the vehicle.

With the 2002 Saturn, this will be easier b/c the car already has power door locks..

peterubers wrote:

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Well -- this will be an elaborate installation -- b/c from what I am gathering, you do not have power doorlocks in your Rodeo.

Once you install your doorlock actuators (and door lock switches as well) you can wiring up an ignition auto-lock -- it'll lock the doors as soon as the car is started.  you don't have to tie the locking to the actual movement of the vehicle.

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I already have that covered - when I got the Rodeo last August, the first thing I did was install an alarm and doorlocks. I used to work at an install shop so that part was easy - and it does lock when I start the vehicle. However, until I install power windows (probably wont be for another year though) I wont have door lock switches installed.

While it does lock the doors when I start the vehicle, I do pick up my wife or friends from time to time and would like to have the doors lock automatically when I drive off instead of turning the truck off and back on to trigger the doorlocks.

I guess what I am really wanting is a way to trigger a relay when the vehicle starts moving - prefferably at a certain speed, but any movement will do if a certain speed is not possible.

There is a company that sells a programmable speed switch - its basically a programmable freq switch.

You can tie your door pins to a relay that will 'break' the ignition signal to your alarm.  This will make your alarm 'think' that the ignition is turned off each time the door is opened, causing it to relock the doors when the doors are closed.  Careful here though, as this is a recipe for locking your keys in your car!

It'd be easy enough to set up a circuit to trigger when you go past a set speed. 

The hard part is, you have to have a signal to work with though; do you have an electronic speedo or abs sensor you were planning to use?  You really need to know what you're doing if you're planning to tap into those signals, because you could easily blow things out.  Or you could just use a motion sensor to trigger it when the car starts moving. 

It seems to me it'd be far easier to stick a push button on the dash and run a wire to your DL actuators-  is this more for convenience or the geewhiz factor ?

KPierson wrote:

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There is a company that sells a programmable speed switch - its basically a programmable freq switch.

You can tie your door pins to a relay that will 'break' the ignition signal to your alarm.  This will make your alarm 'think' that the ignition is turned off each time the door is opened, causing it to relock the doors when the doors are closed.  Careful here though, as this is a recipe for locking your keys in your car!

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This sounds like what I'm looking for - as for locking the keys in the car, I can just use the +12v ACC to disable the feature so that it wiont try to relock the doors if the ignition is off.  Do you know who would sell this product or what I would search for?

dualsport wrote:

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It'd be easy enough to set up a circuit to trigger when you go past a set speed. 

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I figured it would but that's beyond my expertise to design - I can impliment it, but I have no idea where to start for the design.

dualsport wrote:

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The hard part is, you have to have a signal to work with though; do you have an electronic speedo or abs sensor you were planning to use?  You really need to know what you're doing if you're planning to tap into those signals, because you could easily blow things out.  Or you could just use a motion sensor to trigger it when the car starts moving.

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I have rear ABS on the Rodeo and full ABS on the Saturn, and I do have cruise control on both so I do have some type of speed sense wire to tap into if only I knew what I was looking for.

dualsport wrote:

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It seems to me it'd be far easier to stick a push button on the dash and run a wire to your DL actuators-  is this more for convenience or the geewhiz factor ?

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About 35% convenience and 65% geewhiz - in other words, as I tell all my friends when I make things work that they'd never imagine -- "because I can" :)

I would think you would want to limit the amount of time the relay is energized to prevent the solenoids from being extended for a long period of time (say you are backing down a lond winding road.  It probably won't hurt the solenoid, but it won't impress your friends either!

You could modify your idea with the 'steady to pulse' relay from the relay section.

OK, missed that part.

You're output time is going to be a fraction of the total switching time of the relay, which will be measured in mS.

It would probably have a better chance of working if you tied:

Reverse Input -> 87A
+ Door lock output -> 30
Then, wire 30 to 86, so that the relay energizes AFTER the signal has already passed through the relay
Pin 85 to ground

I still think that the output here will be way too short to fire the actuators.

Another option would be to use pin 87 instead of 87A and use the diagram to convert a steady signal to a pulsed signal.

KPierson wrote:

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OK, missed that part.

You're output time is going to be a fraction of the total switching time of the relay, which will be measured in mS.

It would probably have a better chance of working if you tied:

Reverse Input -> 87A
+ Door lock output -> 30
Then, wire 30 to 86, so that the relay energizes AFTER the signal has already passed through the relay
Pin 85 to ground

I still think that the output here will be way too short to fire the actuators.

Another option would be to use pin 87 instead of 87A and use the diagram to convert a steady signal to a pulsed signal.

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Yeah, I had it a little backwards - I had a decent thought in my head but not thoroughly thought out.  You can make it work, but you'll need to add an isolation diode.  You should get a pulse, slightly longer then the other way, but still not long enough to work.

This will effectively switch the switching contacts from a 'break before make' to a 'make before break' setup by allowing voltage to flow through the NC contacts BEFORE energizing the coil.  I am fairly certain this setup will still yield a total pulse output of less then 10mS (0.010S), WAY too short to lock the doors (0.3 seconds is the minimum I would shoot for, with 0.5-6 being optimal, and 0.7-0.8 being conservative).