Are you sure you are giving the lock and unlock signals the same amount of time from the signal source, ie. holding the lock and unlock buttons down the same amount of time?

 

Yes,

At the moment the circuit is set up on breadboard and I'm using a spare battery to power it. Just a brief touch to the terminal on both occasions.

 

Any ideas?

 

If the amount of time that the relay needs to be active is in the least bit critical, you really need to drive it with a one-shot. A NE555 circuit would meet the need. There is a section available on this site that has all kinds of 555 projects. Using only a cap as a timing element when the energizing pulse time is an unknown and probably not consistent gives very inconsistent results. Also, the tolerance of caps is usually not very precise. With the 555 circuit, by changing resistor values, the time can be controlled very well.

 

The thing that made me veer away from the 555 is the fact they can only handle 200mA. The fact the mirror circuit is 10A fused and the central locking circuit 20A fused seems to suggest I'd blow a 555 quite quickly.

Maybe I'm mistaken?

 

The 555 circuit (one for each direction) would be used to drive the relay coils, not the mirror motor. Don't forget the protection diode across each relay coil, and be sure to observe proper polarity!

 

I see, basically my locking signal would be the trigger and I would supply the 555 with 12v from elsewhere.

The diodes are there to prevent back EMF? When you say proper polarity are you referring to making sure the diodes are the right way round?

Would it be possible to use a 556?

I've been reading up on 555 monostable circuits and it seems it might be the better way to go.

 

Yes, yes, yes, yes, and research is the key! Good luck. I would suggest using a pot in the timing circuit for the 555. Minor adjustments would be a lot easier. One other thing. The speed at which the mirror moves will depend upon battery voltage. Engine running vs engine stopped will make a difference.

 

I've been reading about 555s and have come up with a circuit. I'm still reading so it may not be correct but could somebody cast an eye over it? I would be very grateful. Whilst the diagram shows two 555s I will probably use one 556 instead.

 

Have you measured the voltages on the Lock/Unlock lines when NOT active? If zero volts, is it open or ground?

 

I haven't yet as it means dismantling the door trim. Looking at the circuit diagram though, it looks as if it would be ground.

 

Ground when Not Active?

 

Yes

Its all controlled with internal relays in the central locking ECU. When not active, both relays are tied to ground.

 

CitrPug,

I apologize for putting my 2 cents in so late in your thread but I just came across your posts.

From my point of view all that I see that is required for the desired operation is two Limit or Proximity Switches and one Relay per mirror.

The Normally Closed contacts on the Limit/Proximity switches are the only contacts (of the limit switches) used, one for fully extended and one for fully retracted.

In the de-energized state (as shown) the normally closed contact of the fully retracted limit is "held open" by the physical position of the mirror and the normally closed contact of the fully extended limit is in it's normal state (closed).

Operation is as follows;

1, Ignition is switched on and relay coil is energized (relay contacts change state), current flows through L/S 2, through the first set of relay contacts, through mirror motor, and then through the second set of relay contacts to negative. Mirror motor operates until limit switch fully extended is made and limit switch contact 2 is held open and motor stops.

Everything remains in this state until ignition is switched off.

2, Ignition is switched of and relay coil is de-energized (relay contacts revert to their original de-energized state), current flows through L/S 1 (normally closed (no longer held open)), through second set of relay contacts, through mirror motor, and then through the first set of relay contacts to negative. Mirror motor operates until limit switch fully retracted is made and limit switch contact 1 is held open and motor stops.

Normally motor current is not directed through limit switches or other "control" devices but in this instance I believe the current draw of your mirror motor can easily be handled by the devices now available.

Hope this is of help,
williamj

 

When I first read your post, I didn't think you had realized the fact that the two lines switched polarities depending upon Lock/Unlock commands. After looking further at your diagram, you are using the ignition On/Off state to control the mirrors with the aid of prox switches. Good idea and it may be a lot simpler to implement. We'll see what CitrPug thinks. You may have saved him a lot of work.

 

Willamj, thanks for your post. No apology needed, any input is appreciated.

Whilst using the ignition to control the mirrors would be easier, it's not what I'm after. It has to tie in with the central locking system as part of what is called 'remote total closure'. My windows will close if they are open and the vehicle is deadlocked, I'd like the mirrors to fold under the same circumstances. The mirrors must then unfold again on unlocking the vehicle.

I fear using the ignition would increase the wear rate on the motor simply due to the number of times it would be active.

 

CitrPug,

Locate whatever pins or connection points trigger the "Remote Total Closure" and tie that into a relay that replaces the "Ignition supplied Vs". Additional circuitry maybe required to control the additional relay but it should work okay.

williamj

 

CitrPug,

Locate whatever pins or connection points trigger the "Remote Total Closure" and tie that into a relay that replaces the "Ignition supplied Vs". Additional circuitry maybe required to control the additional relay but it should work okay.

williamj

That was my very first thought. The issue is mirrors need to unfold again when unlocking the car.

I'm now thinking the 555 circuit may be an option. Its basically just an add on to what was designed with the relays. I'm just wondering if there is a problem with it due to Bill asking if the circuit is open or ground when not active.

 

The reason I asked the open/ground question is that in your 555 diagram, you show a pull up resistor to the trigger line. Upon reflection, it really doesn't matter if they are open or ground when not active. Of course, when active they must be either +12 or ground, depending upon Lock/Unlock. You may want to add a capacitor to the trigger circuit (between our Lock/Unlock line and the 555) to give a short trigger pulse. That would insure that the 555 controlled the time rather than it adding to the Lock/Unlock pulse time.

 

I see. What value of capacitor would you suggest?