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False Alarm From Wired Pir


EdGasket

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Standard industry knowledge really, still taught to students so I assume still valid. Google for semiconductor bathtub or follow links from wiki :

http://en.wikipedia.org/wiki/Bathtub_curve

 

Failures drop drastically in the first few months due to defects then rise fairly quickly around the 30 year mark due to diffusion and other wear out processes, leaving probability of failure looking like a section through a bath tub. Higher temperatures lead to earlier failures. Some components like DRAM have very much lower life span, and things like IGBT power devices are expected to live longer.

 

bee

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Standard industry knowledge really, still taught to students so I assume still valid. Google for semiconductor bathtub or follow links from wiki :

http://en.wikipedia.org/wiki/Bathtub_curve

 

Failures drop drastically in the first few months due to defects then rise fairly quickly around the 30 year mark due to diffusion and other wear out processes, leaving probability of failure looking like a section through a bath tub. Higher temperatures lead to earlier failures. Some components like DRAM have very much lower life span, and things like IGBT power devices are expected to live longer.

 

bee

Can tell you're not an installer

www.securitywarehouse.co.uk/catalog/

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just wanted a nice simple link....Very old alarms are quite common, very old company cars or computers ain't...

i have 2 Sinclair C5's - 30 years old and still going strong lol!

If you think education is difficult, try being stupid!!!!

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as it happens Mr H, also have a 40 year old Broom Speedboat, fitted with a 'massive' 5hp Tohatsu O/B engine :).

As one C5 is stock 12 volts, the other is a 24 volt conversion, i'm not sure which of the three is actually fastest - or for that matter which one floats the best either! ;)

If you think education is difficult, try being stupid!!!!

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true but great fun.

bought last year before hose pipe ban - then weather was kack, took the boat out first time a few weeks back over at shepearton mallet canal, surprised how many other boaters were interested in and knew of the boats make. I bought on price simply as a restoration project for me and gkids to work/play on, only paid £450.00 for the whole lot,

it looks ruff, due to me wanting to be sure it floats first before putting any money into it. seems at some stage many boaters have owned a Broom', bit like having a 'right of passage', got stacks if advice on original fitting etc.

maker is no longer trading, but has its own very busy enthusiasts forum.

If you think education is difficult, try being stupid!!!!

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  • 2 weeks later...

Finally found time to investigate:

1) The panel battery volts drop to 9.8v with the mains disconnected; should be 12v so I need to repalce that.

2) Measured faulty PIR circuit resistance at panel > 1Kohm whereas other PIR circuits less than 5 ohm at panel. Measured PIR at the PIR, 0.2 ohms. Cleaned up faulty PIR contacts and wire ends and reconnected; resistance at panel now 7 ohms.

 

Conclusion: Oxidised trigger connections to PIR causing high resistance and false alarm. New Yuasa NP2.8 - 12 battery ordered for £

 

Note: Regarding electrolytic capacitors ageing/bulging - this only affected a batch of Chinese capacitors over a few years around around the late 1990's and early 2000's where they had got the electrolyte formula wrong (stolen I think). Capacitors pre and post that era should not suffer from the problems described earlier in the thread. Being an earlier panel, my caps still look like new; no bulging or leaking.

 

Ed

 

NO PRICES IN THE PUBLIC AREA 

If you are unsure of the rules of this forum please familiarise yourself with them here

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Glad you got it fixed, but your spreading misinformation about caps not going high esr with age. Chinese capacitor syndrome caused caps to fail as early as 3 years old. Even perfect caps dry out with age and by the time they are 15 or so they increase their equivelant series resistance to the point where they are less effective at smoothing out ripple and transients. Testing with a capacitance meter doesn't always reveal the problem you need to use an esr tester. The first thing you do when restoring old electronics is replace the electrolytics, then look for open resistors and shorted semiconductors. I have spent years refurbising CRT monitors and power suppy units and done a stint in a lab testing new designs and doing failure analysis.

But whatever, you don't live next to me so I couldn't give a **** if your alarm goes off frequently.

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Ed, I need to agree with these guys. I'm not an alarm installer. I do have a degree in EE and spent a summer doing MTBF calcs for telecoms equipment. It is always the electrolytics that go first. At rated temp (85degC), they degrade significantly in just a year of operation. At 60degC (common inside an unvented box in the PSU), you might get 50,000 hours before degradation. 

 

It's not just cheap caps - these figures are for good Panasonic caps. The bad caps of the early 2000s got overstated, but now it seems like the opposite happens.

 

Speak to someone who repairs TVs - at least 50% of the time it will be a cap.

I have a blog, some of which is about alarm security and reverse engineering:
http://cybergibbons.com/

 

 

 

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Never had a disputed best answer before. Need a process for hoe to deal. Ill have a chat with the mods.

 

Norman? Surely he's got enough to do.

Originally said by Charles Babbage
On two occasions I have been asked [by members of Parliament], 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.

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Re. Best Answer - I have no idea why it is flagged as best answer, I was just reporting what I found and clicked the button that said 'Mark Solved' as i had found the problem. Apologies if that has upset some people; wasn't my intention. Ed

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I come from a TV repair background, albeit 20 years ago and would confirm the issues with caps, heightened more when subject to extreme temperature.

Norman? Surely he's got enough to do.

kiss my fat hairy what?

Nothing is foolproof to a sufficiently talented fool.


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