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Defective Solderless Breadboard Causes Confusion

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tekochip
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Platinum
Mine Was Green
tekochip   9/3/2014 1:50:24 PM
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I had a similar issue with those sockets many years ago.  When I peeled off the backing to inspect the contacts I could see that they had event turned green.  Now I'm in the habit of replacing the sockets every few years.

I also remember trying to keep CMOS op-amps from oscillating when using breadboard sockets.

Nancy Golden
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Platinum
Excellent Advice
Nancy Golden   9/3/2014 4:38:53 PM
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Moral of the story: When a circuit does not perform as expected, consider every part defective until it proves itself to be good!


Some of my most time-consumimg troubleshooting ventures was when I made assumptions about some of the parts I was working with. This includes assuming that test equipment is operating correctly as well as commercial lab equipment such as power supplies were operating to spec.

HarryB
User Rank
Gold
Best idea: don't use solderless breadboards
HarryB   9/4/2014 9:36:36 AM
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Many years ago a friend of mine in college designed a voltage controlled light dimmer for theatrical applications, this at a time when lamps were often controlled by rheostats or autotransformers.  He attracted the interst of some manufacturers, who came to see the prototype in action.  Of course it was built on a solderless breadboard... and he spent an embasarring two hours in front of the customers... saying "but it works, it works just give me one more minute I'll show you." Needless to say the ship sailed long before he had the chance to get on board.

There are so many other ways to prototype that are robust and repeatable.  I use vector board and what used to be called 'flea clips' (Vector T42A) but now I often use board with copper patterns on them, such a "schmartboards" or those from www.beldynsys.com.  Solder is the programming language,  and nothing changes without my permission.

Avoid the "solderless-slab o'trouble". If its worth building its worth building WELL !

 

Bill G
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Silver
A compromise
Bill G   9/4/2014 10:11:43 AM
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There is an in-between position.  Solder-less breadboards are great for fast setups and rearrangements.  When ready to "carve-in-stone", there are (were) circuit board versions of the solderless breadboards, allowing you to transfer the components and wires, keeping the same layout, but solder "permanently".

Of course, even solder isn't permanent and can have corrosion issues.  Those who work on older cars know to never trust any connection.  My 80's M-B are notorious for bad solder joints - cold, cracked, or corroded, in many electrical boxes, plus tantalum capacitors that have passed their life expectancy (cruise controls don't work).

Radwan
User Rank
Iron
Re: Excellent Advice
Radwan   9/4/2014 2:56:28 PM
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Defect New Ics

Some time you may use a new brand ICs ,With evevn soldering board its will not

work, It will distabe you from where the circuit may have gone wrong But i would

like to tell you that IC it self is defective with it first time installation ,Even replacement of some ICs will give you same result.

So be careful from where to buy your ICs it should be original and from well

knowing company to save time and energy in this matter.

Tom M.
User Rank
Silver
You can't use a 555 for 1 hour delays
Tom M.   9/4/2014 5:03:38 PM
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At least not with any kind of repeatability.  The R-C product is so big you either need a huge C or a huge R, probably both.  Then the charging current through the resistor is so small it's down in the cap's leakage current.
Or in this case the leakage current of the solderless breadboard?
Tom M.

Wayne Eleazer
User Rank
Iron
Invisible Coatings?
Wayne Eleazer   9/5/2014 10:56:20 AM
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Some years ago I was working on a riding lawnmower.  The engine had only a weak spark.  I bought a new set of points for the magneto and installed them but then it had no spark at all.

Examination of the magneto revealed no problems.  The new contacts looked beautiful, clean and shiny - and the instructions that came with the points said "Do not sand these points!  They are fine as is and sanding will only damage them!"

But finally, desperate, I lightly sanded the points.  They were no longer quite as shiny - but then I got a nice spark.

The points had been in a sealed package and looked very nice, but I can only assume that at some point, perhaps in the packaging process, some kind of invisible coating had been applied that acted as an insulator.  And the instructions had specifically said not to sand the points!

I wonder how often this occurs, the packaging people perhaps doing something that makes perfect sense to them but proves to be disasterous to the component's use? 

William K.
User Rank
Platinum
Re: Excellent Advice
William K.   9/6/2014 4:52:41 PM
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Among the engineerrs and techs that I have worked with the solderless prototype blocks have a universal reputation for providing poor connectivity. So if a circuit did not function as expected the breadboard was always the FIRST suspect. This saved lots of time.

William K.
User Rank
Platinum
Re: You can't use a 555 for 1 hour delays
William K.   9/6/2014 5:01:17 PM
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TOM is correct, the 555 chip can be made to provide longer time delays, but if you use the very best low leakage parts you still won't get better than within 5% of the target time repeatability. I had to fix some assemblies that used them for longer delays and the first step, after veriying that the board functioned, was to do a complete cleaning with a moisture displacing flux remover. Next came an application of acrylic "ignition system waterproofing" spray. That would usually bring the assembly within the 5% tolerance band, at least enough to be acceptable for the application. A far better system is a cheap crystal oscillator/divider chip such as the CD4060, followed by a CD4040 if a longer delay was needed. The reason for selecting those chips instead of a more exotic one is that they are still multiply sourced and available from many suppliers. And they were cheaper than the high value low leakage capacitor needed to use the 555 circuit for a similar delay.

BobKoblish
User Rank
Iron
Re: You can't use a 555 for 1 hour delays
BobKoblish   9/8/2014 12:27:51 AM
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When long time intervals are required from a 555 timer, the resistor and capacitor values are high. High capacitance values typically require the use of electrolytic capacitors. When electrolytics sit uncharged for a long time, the oxide layer can tend to un-form, causing the capacitor's DC leakage current to increase. This can happen if the capacitor has sat for a long time, either in a warehouse prior to assembly, if the equipment is rarely used, or if the timing function is infrequently used. The capacitor's increased leakage current can change the timeout of the 555 circuit, or in extreme cases cause the timer not to trip at all. Been there, seen that.

When the capacitor is connected in the usual way with its negative terminal grounded and its positive terminal to the timer's Discharge and Threshold pins, it stays discharged until the timer is triggered. It can be useful instead to connect the positive side of the capacitor to the positive supply rail, and the negative side of the capacitor to the 555 chip's Threshold and Discharge pins. This way, the capacitor is sitting fully charged (and fully formed) until the timer is triggered.

But other commenters are right; there are better ways to generate long time intervals these days, either with a shorter RC time constant and an external counter, one of the new 555 variants with an internal counter, or an output from the microcontroller that seems to be at the heart of most products anymore.

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