Detecting old and infirm getting out of bed.

The first system used an under mattress sensor, but the mattress was changed for a firmer one so it stopped working.

It was replaced with a floor level PIR, I questioned this from start as Mother has bad circulation in one leg, the other one is false, and she moves very slowly.

This has now been replaced with a PIR around 1 foot high. It did not even go off with me moving never mind my mother.

Although I know there are loads of units which may work, the second problem is turning them on and off as required. When the alarm goes off it needs some one on the first floor to cancel it, but the even is on the ground floor so step one is see what is wrong, then step two is correct, step three is cancel the alarm which may have been going for 1/2 an hour before we are in a position to cancel it.

For the door sensors we use a simple time switch, they are only active 9:15 p.m. to 7:45 a.m. that's OK, but bed sensor is together with wrist pendent so can't switch it off, OK when sensed the bed, but putting cloths away in the room sets off the alarm.

At the moment I put a oven glove over the PIR in the day, but problem is too easy to forget to remove it at night. What I really need is a local reset switch. I tried using a plug in remote switch, but again problem is when it is not reactivated. So what is really needed is a timed switch which can be pushed to cancel and inhibit for 15 minutes so when it goes off I can cancel and inhibit local to sensor.

Hard wired I could do it, I have a couple of spare PLC's I could easy write a program, but it's not hard wired it's all RF linked. Still have not tried using other RF equipment not sure if that would set off the devices.

Since mother is in a wheel chair any reset switch at 6 foot is out of her reach.

In the main when the alarm goes off, all I do is monitor, I watch to see all is OK, only if some thing goes wrong do I jump in and rescue.

So it's now at a stage where if I can fit an alarm myself then to heck with cost, at least I get a good nights sleep, but although an intruder alarm will likely work, they are not designed to be local reset or auto reset.

If the alarm auto reset after 5 minutes that would be OK, but better if local reset.

So open for ideas, does not need to be secure, but not really looking forward to hard wired system, RF does seem easy option.

Are you using existing alarm system fitted in house which you have modified?
What control panel are you using?
Various options

If control panel has programmable bell time change to 1min and change rearm function to 3 times.
That will make sounder ring for 1 minute and if your mother keeps moving around it will make sounder ring for up to 3 times before the system will need resetting.
You could change control panel for texecom elite range
Fully programmable bell time and rearm function.

You could fit pressure mats either side of the bed .These could be fitted under the carpet or place rugs on top of mat.
Pressure mats are open circuit so alarm panel will have to be programmed for open cicuit on that zone or wire between alarm zone and tamper circiut to work on older control panel
Make sure your mother will not tip on the rugs
You could also program onto chime zone to make internal sounder chime when pressure mat stud on
Need to no control panel for more options

Pressure mats are commonly used in care homes for this purpose.

A load cell under each of the bed legs might be the answer. Not an expensive packaged load cell but a force sensing resistor ( http://uk.rs-online.com/web/p/strain-gauges/1895590/ ) and a bit of DIY mechanics would produce a suitably (in) accurate measurement of total weight on the bed.

With four A to D channels and a bit of digital processing the change in total weight when the person got out of bed would be easy to detect.

It sounds as though your mother needs more care than you can provide.

The PIR is read by a "tynetec" Altec Response Portable Alarm Unit. It may be battery backed and portable but too big to fit in ones pocket and there are two of us so in real terms it hangs on a bit of wire on a hook in the wall, when I goes off we are more interested in mothers safety than cancelling the alarm specially since to cancel would likely be pointless as it will likely be re-triggered.

Once down stairs we are not anywhere near the unit to be able to cancel, so it continues to announce "Intruder Alarm, 01, flat" until we return upstairs. During the day I put an oven glove draped over the PIR to stop it working, I can't turn it off as it also works the wrist pendent and is battery backed.

The doors use a Chubb career alert unit no battery back-up and I use a simple time switch so only active 9:15 pm to 7:45 am so that is OK of sorts although there is a chance mother escapes during the day, so local isolation would be better, this could be done easy enough as the reed switch is separate to the RF unit.

Carers arrive at around 8 am and if we have had a bad night it would be nice to be able to catch up on sleep, but the PIR stops that as it goes off as the carers approach the bed.

The systems are clearly designed for a care home rather than family members living with the person in need of help. I am not permitted to alter the units, they belong to the local authority, so it would mean likely replacing the lot. However it is not something which one can go into B&Q and see a demo unit and select one which can be easy modified.

Hanse the question. It may be there is a system ready built that I can use direct or modify. If the RF bit and the sensor bit are independent then it should be easy to have local disable and cancel. Clearly for an intruder alarm local cancel and disable is not a good idea, but in this case mother is in a wheel chair so any switch over 5 foot is out of her control.