- I've been taking things to bits, and making things ever since I can remember, starting with dismantling knackered alarm clocks and watches and helping my dad fix the car. Now I have a well-equipped workshop and have aquired lots of new skills, so I can make better stuff. When they first appeared, I became involved with personal computers, and these and developments in electronics have increased the scope of the things that I can do. Just recently retired, so O yes, now I can make all sorts of stuff.....
Thursday, 8 December 2011
Saturday, 26 November 2011
Friday, 25 November 2011
Friday, 11 November 2011
Friday, 28 October 2011
At the moment, all it does is monitor the door status LEDs and the internal and external temperatures - this information is collected by the PC that it is connected to and displayed on a simple pop-up window on the PC. I also have some water leak sensors with solenoid water valves partly built that will be powered from this box, and a bloody great siren to go off if a leak is detected. The longer term plan is to put this information into a web page that can be accessed from any PC in the house, including an old touch screen Ameo. So far, so good, but now its time for some more adventurous stuff.
Friday, 21 October 2011
The circuit comes from an old issue of Elektor magazine, shown below:-
The LED leads are left long and the LED itself is glued into an alloy plate that is recessed into the edge of the door so that the circuit board just hangs off the LED leads. A space chiseled out of the door behind the plate houses the circuit and battery, there is just enough room to fit a standard C type torch battery.
The unit works by charging a capacitor very slowly, then releasing the charge momentarily to light a LED. Since the LED is only ’on’ for a small fraction of the time, the power consumption is minimal and the unit will comfortably run on a single 1.5 volt torch battery for a long period of time.
The original unit that I built used a single C type Duracell battery and did not have a switch – its been flashing 24/7 for over 5 years at the time of writing this, and shows no sign of slowing down yet. When the battery starts to die, the LED shines less brightly apparently.
The power consumption can be reduced even more if the circuit is switched on and off by means of a pin switch (like the ones used on car bonnet to trigger the alarm) embedded in the hinge edge of the door so that when the door is closed the flasher is turned off and uses no juice at all. Sounds easy, but most internal doors are reinforced internally with strips of card or similar, so you will need to find a long enough implement to poke or drill a hole across through all of these, and then use a long piece of wire to fish the wires through the hole.
The first one has worked so well, and for so long, that I am building two more for the other two doors.
Tuesday, 18 October 2011
My house is mostly open plan, so the lounge, dining room, hallway and the first floor landing/study areas are all open to each other. This is fine most of the time, but music played in one room is heard all over the house whether you like it or not, and it can get chilly on a winter’s night so I needed to be able to close off part of the space.
I built a partition across the end of the dining room, with a sliding door to cover the last metre or so. To allow plenty of light into the hall, the partition was built with a wooden frame and large glass panels – great, except that the sliding door weighed a ton and was hard to both move and stop as a result, and I was concerned that my small grandchildren might squash fingers and/or other body parts in it. I decided to motorise it, and this is a description of how I did this. I havn’t included any details of the construction of the partition itself, if you are interested in knowing how this was done, let me know
I started with hanging the door on a standard sliding door gear, a simple track at the top with trolley wheels attached to the door, and a plastic block screwed into the floor to guide it. The bottom of the door had a slot machined with a router, and a length of aluminium channel screwed in it to allow the plastic block to slide smoothly. This picture shows the door initially hung on the door gear and before the glass went in - it would have been too heavy to move around if the glass had been installed first:-
First, the drive motor. This needs to be fairly powerful to shift the weight, with a high starting torque, but it doesn’t need to run fast. A rummage in my junk box produced a 12 volt electric car window winder motor which is ideal, and a bit more digging produced a set of electric window switches out of a Renault 25. The motor runs in either direction simply by reversing the power, and the switches are designed to do the reversing of the power connections. I obviously needed a switch on either side of the door, and I also used the ‘window lock’ switch mounted high up so that I could turn the whole gubbins off to stop the children (and some of the grown-ups) playing with it.
Connecting the motor to drive the door was achieved by means of a length of thin steel cable which runs in a loop along the top of the door – I used a gearchange cable from a mountain bike, but you can buy cable like this by the metre from a DIY store. To drive the cable, the motor was fitted with a drum (mine came from a long forgotten photocopier, but it would be easy to make one on a small lathe) which the cable was wound round several times. The same copier produced a set of small guide pulleys to steer the cable.
Both of the cable ends are clamped to a plate screwed to the door using the ‘bolts-with-holes-in’ used on the brakes on bikes, these allow a neat fixing and also allow you to pull all the slack out of the cable so that it remains tight at all times – if there’s any slack in it, the drive pulley will slip and the door won’t move.
The initial trial run proved that this system worked, but the motor ran much too fast and the big heavy door took off like a tank with a baboon at the wheel, a bit unnerving to say the least. I bought a cheap motor speed controller kit from Jaycar and used this with trial and error to get the speed to a point where the door moved at a sensible speed and the weight was properly controlled, with major benefits to both my blood pressure and the structural safety of the house.
The last thing was a fail-safe method of stopping the door at both ends of its travel, even if the operator keeps their finger on the button. A simple micro switch is mounted at each end of the sliding door track, with an adjustable plate screwed to the ends of the door, so that the power to the relays is shut off when either of the switches operates - see picture at left.
To solve the power failure problem, I opted for driving the system with a small sealed lead acid battery of the type used in burglar alarms. This drives the motor, speed controller, and LEDs using 12 volts DC without the need for a mains transformer, and it keeps the door working for days without any mains power. To keep the battery topped up at all times, I installed a battery charger which is permanently connected to a power socket installed in the space above the door.
Other occupants of the house were understandably nervous that not just the power but the whole contraption might fail, leaving them trapped for ever behind the door – a valid point, as we’ve had one such failure when a poorly attached battery terminal came unhitched. The metal plate that clamps the ends of the cables is attached to the door with a pair of 10 mm diameter threaded rods that extend right through the door, with a slot cut in both ends so that they can be removed from either side of the door. When the screwed rods are removed, the plate is left hanging loose on the cables and the door is free to slide on the track. In the room 'inside' the partition, the space above the door has a couple of lift up flaps supported on short gas struts and contains a panic box containing a screwdriver for removing these screws as probably not many people watch TV with a toolkit in their pocket.
The panic box also contains a spare motor and a set of spare switches as insurance in case any of the parts fails and I can't remember where I put the spare bits, as I rather doubt that you can still buy window switches from a 1991 Renault 25. As a last resort there is also a spare door key so that if everything jams up and none of the emergency systems work you can always bale out of a window and get back in the house by more traditional means.
There is a small control panel above the door with LEDs to show that power is present, and although this was not its original purpose this has the massive advantage of shining a dim light down on the face of the door at night to save you the inevitable broken nose caused by walking into the closed door in the dark.
I originally thought it would be neat to shine LEDs into the edge of the glass panels to give them a greenish glow and spent an awful lot of time drilling holes and running wires to achieve this, but the end result is that the glow is very dim and only visible when all the lights are off, so I never switch them on. Brighter LEDs would work better, but if I was doing it all again I wouldn’t bother. These LEDs are operated by a switch on the panel above the door, with another small LED to show when they are on or off.
The door mechanism works really well, in spite of being made almost entirely from junk. Anyone can operate it, even when carrying an armful of stuff as the switches can be operated with an elbow, a nose, or any other sticky-out bit. It keeps working during the regular power failures that we get, and so far we havn’t managed to squash anybody, small or otherwise.
Friday, 14 October 2011
The first project to be described here is my door lock indicators. I have the euro style door locks rather than the more standard Yale type, and these require you to either turn a key (from the outside) or a knob (inside) to lock the door. They don't slam lock like a Yale and can't lock you out if the door blows shut while you are outside. They work great, but its impossible to tell if the door is locked or not without trying the knob. When locking the house it is therefore necessary to physically check each door, a bit of a pain especially when all the lights are out. The garage is attached to the house and has a remote-controlled door, and again the only way to check if the door is closed is to go and look. I needed a way to easily check the status of the doors, so I ended up fitting a set of LED lights to each door, operated by a micro-switch hidden in the lock plate.
The switch is a standard micro switch, mounted on to an aluminium plate which is screwed to the inside of the opening in the door frame where the lock tongue goes in. The plate has slots to allow the switch to be adjusted back and forth so that it engages properly with the lock tongue - too close and the tongue fouls on the switch and the door won't lock - too far away and the switch fails to operate. The wooden doors and frame expand and contract with the weather, and the lock mechanism is not very precise, so trial and error is the only way to get the adjustment right. I fitted a small piece of thin rubber over the switch operating button with super glue to cushion the switch a bit.
The lights are fed from CAT5 which carries power from a central 12v power supply located in the central 'engine room' in the house where the server and network stuff lives. Although CAT5 has 8 wires, I only used 4 of them and stripped away the spares to save space. I wanted to be able to mimic the lights to some central point, so the connections that operate the LEDs at the door are also carried back to the engine room.
The CAT5 terminates on a wall plate close to the door, then the cable is run behind the skirting to the base of the door frame. I routed a slot in the frame of the door and fed the wires up through that, then glued a strip of wood back into the slot to conceal them. The LEDs are mounted to a small piece of aluminium angle, recessed into the door frame, this also conceals the screws that hold the switch and the hole that the wires come through. The LEDs are standard 5mm types, so I drilled 5 mm holes in the plate and super-glued the LEDs
into the holes, then fixed the plate into the frame using a couple of dabs of 'No More Nails'. There's very little space in the hole, so it was necessary to chisel out a bit of the frame to fit the switch and make room for the wires.
The switches and LEDs are wired as follows:-
· +12v connects to 'COM' on the switch
· Oone leg of the red LED connects to NC
· Oone leg of the green LED connects to NO
· Tthe remaining legs of both LEDs are connected together, then to a 150 ohm resistor, and then to the 0v wire
· TTo be able to mimic the lights elsewhere in the house, I also connected wires to the NO and NC connections
The garage door has a similar arrangement, but because there's no need to conceal the switch its just mounted on an aluminium bracket screwed to the door frame. The door itself carries another bracket with a rod which engages with the switch, the rod is threaded to allow for adjustment
Conclusion - This is one of the most useful and least expensive features in the house. When going to bed, just walking through the house I can see instantly if the doors are locked and with all the house lights off the LEDs provide just enough light to navigate around without tripping over things. It was easy to do, cost nothing (already had the parts in my junk box) and works exceptionally well.
The next step is to connect the outputs from the door switches into my server where a small application will monitor them and display their status on a web page. The same web page will also display the image from the camera that covers the front door. A spare pocket PC mounted centrally in the house will view the web page over wi-fi. Watch this space for details