Hi all,
I'm designing the electronics for a flatscreen TV lift system, for tucking away a flatscreen TV inside a low design-furniture cabinet (see
As safety is an essential requirement for this type of machinery (the lift system is easily capable of squashing or even severing fingers), I'm looking for a reliable PIR detector module. The idea is to have it "look down" from the back of the TV into the machinery, so that the system will stop immediately if a body part or (warm-blooded) household pet is detected. The PIR detector should run off something between 6 and 12 volts (with a preference for 12V), consume no more than 10 mA, and provide a momentary low or high level signal upon triggering. A sensitivity setting is paramount.
I tried several cheap PIR detectors which are used for automatic door bells or proximity warning, but these have a tendency to trigger too readily; maybe they react to the changing heat pattern at the moment the lift starts moving (the TV is warm after use, and the movement probably makes the detector see quick changes in received heat), or maybe the PWM signal (though within permissible EMC levels) makes it go haywire.
And oh, the cost may not exceed some 20 dollars for a complete module. Schematics for PIR detectors are also welcome, but no doubt, existing mass-produced modules are cheaper than anything I can make.
And yes, I know that this will /not/ secure the whole thing against crushed fingers when the lid closes; we're contemplating several other measures for this. Also, the remote control is IR, with mandatory "button-hold" action, so that the operator must always be in sight of the system, and nothing happens automatically.
Thanks in advance,
Richard Rasker