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toggle earth supply

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wacurrie

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I need to supply the door locking system on my car with an earth signal for approx 2 seconds when the brake pedal switch is operated but when the pedal switch is released i need it to supply an earth signal again for 2 seconds. I can use a timer circuit and relay to supply the earth when the switch is activated but cant work out how to supply the circuit again when the switch is released
 
What should happen if the brake pedal is pressed for less than 2 sec?
 
I say 2 seconds but the exact time delay is not really important, it could be as little as 0.5 seconds. The brake switch supplies battery voltage when pressed. I need to convert this to an earth supply momenteraly to operate the child locking sytem on the car. When the brake pedal is released it has to again supply an earth momentarily to unlock the system.
 
I say 2 seconds but the exact time delay is not really important, it could be as little as 0.5 seconds. The brake switch supplies battery voltage when pressed. I need to convert this to an earth supply momenteraly to operate the child locking sytem on the car. When the brake pedal is released it has to again supply an earth momentarily to unlock the system.

hi wa,
I would suggest you 'tap' into the brake light circuit for your locking signal, do not use a simple toggle action as this could get out of sync with the pedal action.

ie: when brake light ON, child door lock ON, release child lock when brake light is OFF.

E
 
In normal driving conditions you will apply/release the brake many times. Surely you want the child lock engaged all the time you are driving? Why would you want it constantly locking and unlocking? That's going to leave the lock in the unlocked state for much of a journey. IMO that's not safe. It would also wear out the lock in no time. Wouldn't it be better simply to engage the lock whenever the ignition switch is 'on' then disengage it when the ignition switch is 'off'?
 
the child locks on this car already lock when in motion and disengage when stopped.I need them to also operate when the footbrake is applied and disengage when the footbrake is released. On this vehicle there is a momentary switch on the dash that, when pressed supplies an earth to the body computer to lock the child locks. to release them the switch has to pressed a second time.
 
to release them the switch has to pressed a second time.
Presumably this switch is disabled when the car is in motion?
If you've already got a momentary switch to do the job why do you want to use the brake pedal for the same function? I'm concerned about the safety aspect. How are you planning to incorporate this added circuit so that it doesn't conflict with the existing switching arrangement and over-ride the car's computer control of the locks?

Edit: In the UK a mod of this sort, which has safety implications, is likely to invalidate your insurance. Have you checked it out with your insurer?
 
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Hi alec_t
The dash switch is disabled when the car is in motion.the reason that the door must lock and unlock when activated with the brake pedal on this car is that it is going to be used as a taxi and it is a council requirement.
 
hi w,

It would be possible as I suggested earlier to use the brake light line voltage to trigger the door lock when when pressed.

What level of electronics experience do you have?

Door you have a wiring diagram for you car electrics?
E
 
Hi e
my electrical experience is ok but i,m very limited with electronics and I have the wiring diagrams for the car.
 
the reason that the door must lock and unlock when activated with the brake pedal on this car is that it is going to be used as a taxi and it is a council requirement.
I'm surprised any council requirement goes into the detail of locks being activated by the brake pedal. Can you post the text of that requirement, or a link to the relevant Regulation?

Edit: I found online a manual relating to London taxis and their automatic door locking system (ADLS) requirements.
This is page 43:
TaxiDoorLocking.gif
Are these the same requirements as yours? If so, how will you implement this bit:-
"With the ignition switched on the ADLS should engage when the vehicle has been moved forward more than 31cms and before a distance of 46cms has been covered. "

A further point. If the locks operate on a toggling earth connection how do you (as distinct from the computer) know when they are in the locked/unlocked state? If you added the proposed brake-activated circuit then pressing the brake when the locks were already locked would have the undesired effect of unlocking them.
 
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All councils have different regulations for the licensing of taxis. This council requires that the rear doors of the vehicle lock automatically when driven and on stopping they automatically unlock. This vehicle (a standard fiat scudo)already locks and unlocks the childlocks when driven/stopped. However they also require that when stopped the doors are kept locked by the application of the brake pedal. The London Taxi, converted merc vito and the CONVERTED fiat scudo all comply with this but only with the addition of a very complex ecu unit and wiring harness. It is complex because the ecu also carries out other functions, i.e. intercom system, electric steps,door open signs,taximeter,interior lights,etc
 
....and therein lies a problem; how to add the brake circuit without compromising the functions performed by whatever presently controls the locks in your standard Fiat Scudo :(
 
On this vehicle there is a momentary switch on the dash that, when pressed supplies an earth to the body computer to lock the child locks. to release them the switch has to pressed a second time.
Can you confirm whether this is a latching switch or not? If latching, it would presumably be maintaining an earth connection for a prolonged period rather than just momentarily.
Does this switch carry the full lock-motor current, or is it merely providing a logic 'low' signal to an IC which controls the motor?
Do you have access also to a LED/lamp voltage which indicates the lock/unlock state?

I have designed a circuit which provides a ~1sec pulse at pedal-down and another ~1sec pulse at pedal-up (the times are easily changed), which possibly could be wired in parallel with your dash manual switch, but I'm not convinced that without incorporating a lock state signal it could reliably provide the 'brake on = lock on' function.
What are the chances of getting a home-built circuit officially approved by your Council and insurer?
 
Hi alec_t
I managed to get an ecu that is used on the converted vehicles and connected the 10 wires that were needed to work the motion lock side and all is working fine. The connections needed were as follows:

12v constant battery supply
12v ingition supply
Earth
Wire from n/s/r courtesy switch(12 v when door closed)
Wire from o/s/r courtesy switch(12v when door closed)
Speed signal wire
Wire from brake switch(12v when pedal pressed)
Earth output to vehicle body computer to engage child lock
Wire from body computer informing state of child lock(12v when locked,earth when unlocked)
Wire to LED(12v when child locks on)

I noted that if the lock state wire is not connected ,then when the brake was pressed there was an earth switched 4 times at 1 second intervals on the output wire and the locks ratcheted on and off 4 times.
I will post a schematic in a couple of days
Thanks for your advice and help
 
I noted that if the lock state wire is not connected ,then when the brake was pressed there was an earth switched 4 times at 1 second intervals on the output wire and the locks ratcheted on and off 4 times.
With the lock state wire connected are the locks now controllable from the brake pedal as required?
I'd be interested to see the schematic.
 
Everything working as it should. I was trying to design something that would stop me having to fit the conversion ecu because it is a very large unit containing many circuits that wont be used on this car. I will post the schematic in a couple of days. Unfortunatley it isnt a full schematic,only the pin numbers that the wires go to and a description of their function.
Thanks again
 
However they also require that when stopped the doors are kept locked by the application of the brake pedal.

That could be interpreted as disable the electric locks when the brake is pressed. That's how I'd interpret that initially.

However, in general, you can't disable the manual locking mechanism. Is that what they want?

Is it all but the driver's door? That, might make more sense. You don't want the passenger fleeing a vehicle at any stop. You want the passenger to be LET OUT.

The brake method looks like a way to do this automagicly with little inconvience.

Now, when you include the driver's door, you also might prevent carjacking. Some guy reaching in an opened window, open the lock and pull the driver out, carjacking the car.

SO, I see two functions:

1. Disable electric unlock while the brake is pressed and car isn't moving.

2. Engage a solenoid that physically prevents the doors from unlocking when the brake is pressed and the car isn't moving. This includes manually unlocking too.

Child safety usually prevents the rear doors from opening from the inside, correct?

Am I missing something?
 
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