Life of 24x365

[Electroenthusiast]

How can i determine the life of my 24x365 Electronic Circuit?
Can i use it continuously, will it work well. I dont want to use a Heat sink here, because of space constraint; Moreover i'm thinking it to wrap it into a box and enclose it in a wall.

I can use the system for a limited period of time.
The system consists of Wall-wart, a 78XX, TTL IC'S, Relays, PCB, Switches, Resistors, capacitors and other basic components.

 

[Electroenthusiast]

hi anyone,
can i get this thread going?

 

[3v0]

There is not enough information to provide a firm answer.

Worst case. Due to a lack of ventilation the cirucit will die withing in the first few hours or days.

The answer is to provide enough cooling to let it last.

 

[arunb]

Operate the system under operating voltages, high voltage, low voltage and the nominal operating voltage.

Under these conditions check if the current ratings do not exceed the maximum specified values for each component.

The quality of the PCBs and the soldering can be checked by 'soaking' them in a high temperature environment (usually 40 degC), of course this will depend on the kind of component you are using.

After this the system may be run continuously for 72 hours (called burn test).

You can again check the system (after the burn test) and compare the results with the previous values for any deviations.

The testing procedure depends entirely on the kind of system being tested.

Apart from this you must also check for faulty soldering techniques (if soldered by hand), sometimes in elevated temperatures solders can give way this could cause loose connections.

It is difficult to provide an exact solution without knowing the exact end use of the product, and also whether it is a consumer or an industrial equipment.

 

[Electroenthusiast]

it's an hobby project...

Under these conditions check if the current ratings do not exceed the maximum specified values for each component.

I didnt get this one. If nominal Voltage is maintained, then how can the current rating exceed?

....(after the burn test) and compare the results with the previous values for any deviations.

Should i use multimeter to examine the differences? Current, Voltage?

will die withing in the first few hours or days.

Ok, i feel there's no other go..., but to keep the circuit outside(not enclosed in wall)....even if i use Heat sinkers

 

[Reloadron]

To reduce some of this to simplest terms. You are getting into life cycle testing or what would be accelerated life cycle testing.

Among the parts you mention are relays and switches both of which can be mechanical devices. Depending on the number of cycles of operation these devices should have an average failure rate based on cycles of operation. That information should be contained in the manufactures data sheets.

For example attached are some switch images. Note the image of the lever actuated micro-switch. Read this data sheet on a basic micro-switch. Suddenly a simple switch becomes a complex affair doesn't it?

Check the data sheets on the capacitors and see how they are derated at higher temperatures and voltages. The list goes on and on. Then once I have my parts and build the product I need to test it as was well covered to make sure it meets or exceeds what I say it will do.

Ron

 

[ronv]

Reliability

In one of my past lives I did failure analysis for a disk drive company. We built about 25 - 30 million of them a year. An ordinary failure rate was about 500 defects per million at installation with roughly 50% being customer caused (handling damage etc.) We could affect this number slightly with burn in. After that the failure rate was about .3 % per year with about 50% of that being in the head disk interface. If we had a big problem it was almost always either a design flaw or a component with a basic flaw. So I think your concern about component reliability is probably misplaced. Worry about the design and try to use tried and true parts. I've had good luck finding timing problems with voltage and frequency bias along with temperature. Mechanical (If you must) with shock and vibration.

 

[Electroenthusiast]

To reduce some of this to..........it will do.
Ron

But, i dont have any datasheet for a capacitor... i jus go to the shop, ask for a capacitor( something like 50Micro. Farad/ 20V); Buy it n use it... will i get datasheets for those?
I havent inspected datasheets for components like Heatsink, Capacitors, Switches, LEDs, Relays, Connectors
Shopkeeper jus provides me 1

At least, what would be the life of Wall-wart?

 

[schmitt trigger]

At least, what would be the life of Wall-wart?

Wall-warts of the simple iron-core transformer plus diodes and a capacitor are completely passive and "should" last a lifetime.

I put "should" under quotes since the most likely problem you will find here is that, in an effort to reduce cost, the transformer will be designed to operate at its maximum flux density. This will cause the transformer to run hot normally, but during input overvoltage conditions (i.e. at night or weekends), the overheating may be substantial.
Either of two things will happen next: the safety-agency mandated thermal cutoff will open; or if this is an ultra cheap wall-wart without any safety agency certifications, the magnet wire insulation will short.

So it boils down to a couple of things:
What is the maximum expected voltage (% above nominal)
And, what is the best quality wall-wart you can get.

 

[Electroenthusiast]

the safety-agency mandated thermal cutoff will open; or if this is an ultra cheap wall-wart without any safety agency certifications, the magnet wire insulation will short.

So it boils down to a couple of things:
What is the maximum expected voltage (% above nominal)
And, what is the best quality wall-wart you can get.

I have a 9V wallwart, i just wanted to use it in some my application...
Best Quality> I can buy as costlier one that i can get!

EDIT: Thermal MicroSwitch, mentioned above suites for this... Moreover i guess 78XX, has internal temp sensor; that would also do it.

But, i dont have any datasheet for a capacitor... i jus go to the shop, ask for a capacitor( something like 50Micro. Farad/ 20V); Buy it n use it... will i get datasheets for those?
I havent inspected datasheets for components like Heatsink, Capacitors, Switches, LEDs, Relays, Connectors
Shopkeeper jus provides me 1
At least, what would be the life of Wall-wart?

 

[Reloadron]

r.vittalkiran, I think what you need to understand here is that there is a considerable difference between you building something for home use in your home and designing and building a product to take to market.

If for example I decide to build something for use in my home I can stroll to my local shop like a Radio Shack and buy a few capacitors and transistors and whatever parts. These are just everyday parts. They are not going into the build of a product that involves for example safety of flight, safety of life or something really critical. If, however, I decide to design a product that will involve safety of flight, life or something along those lines it's a whole new game.

Ron

 

[tcmtech]

Without knowing what it is you are building and where it going to be used its impossible to say how long it will last. I have built many devices and circuit systems that are in 24 -365 usage applications and some even live in more extreme working environments such as the extremes of our local weather which can be from -35 F to 105+F with enclosure temps in direct sunlight over 150+ F along with humidity and moisture levels from near zero to soaking wet.

Designing for that environment is not hard if you use one of the many on line electronics data websites to find the upper and lower working limits of the components and their realistic life expectancies as published by their manufactures.

For added protection in the high moisture applications I coat the whole circuit in clear coat enamel paint to seal everything. Its a common thing that is done to commercial grade circuit boards that have to work in harsh environments.

For the actual burn in testing I try to push the circuit to its absolute maximum load limit then run it at its highest likely ambient temperature it should encounter. To do so that can be done just by using a cardboard box and simple thermometer to read the working temp of the circuit in use. If it can survive for a 24 hour burn in test running at its top limits without component failures its likely it will last for a long time under far lesser working conditions and temperature extremes.

 

[schmitt trigger]

What tmtech describes is called "stress testing" and is a very effective way to test for survivability.

To his recommendations I would only add an input overvoltage. With a Variac adjust the input voltage to be at least 10% above nominal during the test.

 

[Electroenthusiast]

r.vittalkiran, I think ....a whole new game.

Ron

Hi Ron,
that was pretty useful...
later, when i'm gonna design something that needs accuracy/precision;
i'll definitely be using datasheets for those...

For the actual burn in testing I ......lesser working conditions and temperature extremes.

Since the operating current is less, normally few milliamps(idle) & at max it would reach 100mA(ON). I assume it would have a better life... the only thing i need to test is wall-wart, that gets heated up soon...
I may need a replacement of it, as mentioned earlier.

 

[Reloadron]

Oh, I like this part:

For the actual burn in testing I try to push the circuit to its absolute maximum load limit then run it at its highest likely ambient temperature it should encounter. To do so that can be done just by using a cardboard box and simple thermometer to read the working temp of the circuit in use. If it can survive for a 24 hour burn in test running at its top limits without component failures its likely it will last for a long time under far lesser working conditions and temperature extremes.

I like this too:

To his recommendations I would only add an input overvoltage. With a Variac adjust the input voltage to be at least 10% above nominal during the test.

I think we need to just run with a full Shake N' Bake but also toss in some thermal shock. We put it in a box and fill the box with liquid nitrogen after we bake it awhile. Then we need to bounce it around a little. I will guarantee when we get done there will be nothing left or.. you will have a hell of a great product!

You really have to love this testing stuff. If we don't kill it, then it can ship.

Ron

 

[tcmtech]

I think we need to just run with a full Shake N' Bake but also toss in some thermal shock. We put it in a box and fill the box with liquid nitrogen after we bake it awhile. Then we need to bounce it around a little. I will guarantee when we get done there will be nothing left or.. you will have a hell of a great product!

You really have to love this testing stuff. If we don't kill it, then it can ship.

Ron

Don't try that with the family pets though. Kitty doesn't take the liquid nitrogen bath followed by a good shake so well.

Kitty bits anyone?