Door switch alternatives

[Bitsyncmaster]

I guess this would be a good place to post your experiments for replacing the door switch. Also could be used for the engine cover, hood and glove box.

My idea is to use a mercury tilt switch mounted in the moving door. These switches are not as common anymore. I bought 40 of them on EBay from China for 5 or 10 bucks.

Here is my mounting of the glass switch. The case is just a 1/2" high piece of vinyl porch rail. It's the 1.25" square uprights. I mounted two 1/4" flat tabs for connections and after soldering the switch, filled it with epoxy.

[dvonk]

nice, i like mercury switches. i have a vintage mercury light switch in one of the rooms of my house. id have to say that mercury is my favorite element, despite its toxicity... although you wont have to worry this switch breaking when its surrounded by all that epoxy. :smile:

do you know at approximately what angle the switch activates?

[Bitsyncmaster]

nice, i like mercury switches. i have a vintage mercury light switch in one of the rooms of my house. id have to say that mercury is my favorite element, despite its toxicity... although you wont have to worry this switch breaking when its surrounded by all that epoxy. :smile:

do you know at approximately what angle the switch activates?

It's pretty much an on or off any angle off of level. The glass tube is straight and the ball of mercury fills one end, the two pins (wires) are in the other end.

[Farrar]

8599

[TTait]

(all below is meant in the spirit of good fun and debate)

The door switches are not just to turn the lights on or off, they are also meant to alert you when the door is open, or more correctly - not quite closed.

The mercury switch isn't going to do that... If you adjust it to within a gnats ass, the lights will flash whenever you accelerate, turn, or even pass gas.

The only way to get both doors to work accurately would be to only park on a perfectly level surface every time. Even a less accurate compromise that gave up on the door ajar function but would turn the door lights on and off, may well flicker when you go around a good turn.

Two options to consider for a more accurate switch with no moving parts or brushes to wear and oxidize would be:

Proximity sensor - while you can adjust it a lot tighter than a mercury switch, and it would be unaffected by g forces, it would still be tough to get the accuracy to get the door open idiot light to work properly. Its a little pricey too.

An Optical sensor - Laser based perhaps? With this option you would drill two perfectly aligned pinholes - one in the door and one in the jamb, and put an emitter behind one and a sensor behind the other. With a little effort you could set it to be accurate - but you're drilling precision holes into your car...

Now that I've been just plain annoying, I should continue by being obvious and annoying.

You should also keep in mind that the switch has mercury inside a glass tube inside a door that probably has 5g's plus of deceleration when the door closes. When it breaks, it will drip. Into your eye (perhaps with a little ground glass washed in with it!) as you get out.

Unless you frequently have syphilis you probably don't want that mercury floating around in your body (the stainless one, or your own body).

[Bitsyncmaster]

I agree that the "door ajar" function will be lost with the mercury switch but I'm willing to bet 50% or more cars will not indicate both door latches are not latched with the OEM switch. I know a few times I have had to pull off the road to fully close my door. The door will rattle if both latches are not engaged.

The problem with a more elaborate "door switch" is you must keep it powered all the time. So power draw on the battery has to be considered.

If you adjust your door switch to only work with a latched door then you risk draining your battery when you park your car.

[Ron]

Wouldn't using accessory (instead of battery) power solve both parking problems???

[Bitsyncmaster]

Wouldn't using accessory (instead of battery) power solve both parking problems???

Then you would not get dome and door lights when you go to open the car.

[Ron]

Then you would not get dome and door lights when you go to open the car.

Hehe...both of us should of looked at the schematic first...It is already running off of accessory!:bang:

[TTait]

Dash indicator runs off accessory, while dome and door lights are always on.

The question is which of those sources would you use to power the new switch if you used an active switching technology... back to above if you run it off the constant power then your switches will draw power and run down the battery, regardless of whether or not the doors are open or closed. Run it off accessory, and the dome lights won't come on - even though the dome lights have power available, the switch would not be active.

[Bitsyncmaster]

I pulled the upper door panel off and was looking for a place to mount my mercury switch. There is one flat panel that looks like the correct angle but I have to make a new switch with the switch mounted so the terminals are not on the tilting end.

My drivers door latches real easy on the front latch but not the rear latch. So even if I took off the rubber cap so it would indicate the front latch is not closed, you would still need a rear door switch to sense that latch.

[Ron]

I'd personally leave it all as is OR make the dome lights come on when the door was, say 1/2 way or more open and forget battery drainage (Merc switch would be great). Then monitor the four door lock positions right at the latch arms with accessory powered IR sensors (cheep, simple, and power usage is not a problem even if hot all times, but no need to be anyway).

[Bitsyncmaster]

I'd personally leave it all as is OR make the dome lights come on when the door was, say 1/2 way or more open and forget battery drainage (Merc switch would be great). Then monitor the four door lock positions right at the latch arms with accessory powered IR sensors (cheep, simple, and power usage is not a problem even if hot all times, but no need to be anyway).

That would be the best solution but it would require some wires to separate the lights and the dash indicator.

Here is my next switch. The black tape is just for potting the unit.

[Farrar]

I got tired of fooling with that circuit and just put it on a toggle switch. Although I like this functionality, I am also adding a remote control to it. Should make it easier to find my car in a lot full of DeLoreans. :)

[Bitsyncmaster]

Here is the installed mercury door switch. Just held on with double sided carpet tape but I have some double sided "servo" foam tape on order for the permanent install.

[Bitsyncmaster]

Well I'm still learning things as I make modifications to my car. It turns out that mercury switches have a very large switch bounce when used on our slow opening door. I can see the door lights flash on and off when the door is passing through the half open position where the mercury switch transitions. I had to make a software change in my dome light unit which was using a deglitching routine for the normal door switches. Normal mechanical switches also bounce but the timing is way shorter for those. The mercury switch timing will sometimes exceed 400 ms.

I guess the ball of mercury hits the end of the glass tube and bounces like a steel ball would bounce if dropped on a hard surface. Probably longer contacts in the switch design would reduce or eliminate this problem.

[tommyrich]

I really like my Magnetic switch setup. It uses a threaded barrel reed switch that allows the switch distance to be precisely adjusted (to activate the dash light on the first latch position for example). And, since it does not make contact with the door itself, it will never wear out or go out of adjustment.
The downside is the switch cannot handle a lot of current, so I designed a small relay box that is activated by the switches. The relays take no power when the doors are closed, and there are separate circuits for the drivers light and buzzer circuit, using a double pole relay. The red/green leds are used when adjusting the distance to the small magnet that is glued to the door plate where the plunger usually contacts. I added a "cutoff" switch in the (now) spare hole in the drives side to turn off the lights when I have to doors open for a long time.
I have used this circuit for over 4 years and have never had a problem.
Tom -

892089218922

[Bitsyncmaster]

I finally got my order for the "servo tape'. Good thing I bought this because the carpet tape did not hold on the stainless (held great on the epoxy switch). Anyway, went for a drive around the neighborhood and never saw any dome light flash. So it looks like the mercury switch will work. Guess I will do the passenger door the same way.

[Bitsyncmaster]

I had to make some software changes to my dome light unit for it to work with mercury switches on the doors. The problem is long switch bounce when the doors are open and closed. The first problem was I treated a door switch action of less than 400 ms. as a glitch and turned the unit off. So I could get a few times when the door was open but the unit would not power up. The second problem was after the door was left open and battery saver mode was timed out. Then when I slowly shut the door I could get it into program mode. Standard door switches will not have these problems.

So if you want to use mercury switches on the doors, you will need to send me your older unit for a software update. New builds will have the new software.

[Bitsyncmaster]

I finally got my order for the "servo tape'. Good thing I bought this because the carpet tape did not hold on the stainless (held great on the epoxy switch). Anyway, went for a drive around the neighborhood and never saw any dome light flash. So it looks like the mercury switch will work. Guess I will do the passenger door the same way.

That "servo tape" has been holding fine for 5 years.