Tricks of the Trade - knowledge for every day life

[Kasper]

Hi Everyone, thought it'd be fun to share some tricks of the trade.  What random things have you learned about electronics that help in every day life?

I'll get it started with one about batteries.  I've only tested this with LTC (lithium thionyl chloride) and alkaline: if you agitate dead ones, you can get a bit more life out of them.  Found this by investigating funny results caused by moving batteries during a battery drain test on a home automation product. 

In every day life, I use this to test the TV remote when it stops working.  If tapping it 'fixes it' then it is time to change the batteries.  I also use this trick to delay changing the batteries.  If it stops working while eating dinner or being lazy then a few taps 'fixes it'.  I wonder how often this is the cause of electronics being 'fixed' (and eventually broken) by physical abuse.

[fcb]

I heard that the BBC repair department had a category for repairs called CBI - stood for Cured By Impact.

[Cerebus]

On the subject of batteries - temperature. Batteries hate the cold.

Some primary cells will seem to have run out completely in the cold even though they are relatively new, let them warm up and they still have all their life remaining. Although I knew this in theory I first discovered it in practice years ago trying to take astrophotographs on a cold, clear winters night. I left camera and lens to cool down to ambient to avoid heat haze appearing in the photographs from warm air coming off the lens. My [film] camera died completely despite having a set of batteries in it that were probably good for another year of almost daily use, just because the silver oxide battery got freezing cold.

Secondary cells - don't try to charge them when they are cold. They will accept much less charge when cold than when at room temperature. If you're using a cordless drill or similar out in the cold and the battery dies don't take it indoors and immediately charge it. Let it get up to room temperature first, then charge it. Especially applies to battery packs with a permanent low capacity lockout - like Makita ones, where if the battery fails to accept 'sufficient' charge three times the battery management chip permanently marks the battery 'bad' and disables it.

[Kasper]

I heard that the BBC repair department had a category for repairs called CBI - stood for Cured By Impact.

'cured' seems like an exaggeration.  Maybe TIBI would be better: temporarily improved by impact. 

[Kasper]

On the subject of batteries - temperature. Batteries hate the cold.

Some primary cells will seem to have run out completely in the cold even though they are relatively new, let them warm up and they still have all their life remaining. Although I knew this in theory I first discovered it in practice years ago trying to take astrophotographs on a cold, clear winters night. I left camera and lens to cool down to ambient to avoid heat haze appearing in the photographs from warm air coming off the lens. My [film] camera died completely despite having a set of batteries in it that were probably good for another year of almost daily use, just because the silver oxide battery got freezing cold.

Secondary cells - don't try to charge them when they are cold. They will accept much less charge when cold than when at room temperature. If you're using a cordless drill or similar out in the cold and the battery dies don't take it indoors and immediately charge it. Let it get up to room temperature first, then charge it. Especially applies to battery packs with a permanent low capacity lockout - like Makita ones, where if the battery fails to accept 'sufficient' charge three times the battery management chip permanently marks the battery 'bad' and disables it.

Nice tip about charging, I wonder if any of them consider the temperature before applying the lockout.

My last star-gazing attempt was for Perseid meteor shower this August.  First year in a while it wasn't smokey in August so we actually had a chance to see them.  Forecast said clear skies so we went camping.  It got cloudy at dusk and rained on us.

[nightfire]

Alkaline AA cells: Determine the charge by dropping them on the minus side on a hard table- when full, they will simply fall to the table- empty cells bounce back due to the changes in the chemistry.

[tooki]

I heard that the BBC repair department had a category for repairs called CBI - stood for Cured By Impact.

The technical term is “percussive maintenance”! 

[cgroen]

Alkaline AA cells: Determine the charge by dropping them on the minus side on a hard table- when full, they will simply fall to the table- empty cells bounce back due to the changes in the chemistry.

The first time two of my colleagues told me that trick, I was like "are you serious", I thought they were trying to pull my legs.
But sure enough, it works every time! Now I have in turn won a couple of free beers on that account 

[Cerebus]

I heard that the BBC repair department had a category for repairs called CBI - stood for Cured By Impact.

The technical term is “percussive maintenance”! 

Or Correction By Clobbering <- this is more inclusive, as it also applies to fixing PEBKACs as well as equipment failures.

[richard.cs]

Alkaline AA cells: Determine the charge by dropping them on the minus side on a hard table- when full, they will simply fall to the table- empty cells bounce back due to the changes in the chemistry.

Gas pressure bowing out the bottom and making them bouncy?

[nightfire]

No, bottom is still flat. The internal structure is a bit more fluffy and therefore a bit elastic.

[Berni]

Here is one:
PCB Cleaner spray (the usual isopropyl and ethanol mix) used to clean flux off your boards is excellent at removing hot glue from pretty much any surface.

Just soak the blob of hot glue in the stuff, leave it sit for a few seconds than pry at it a bit while its still wet, the hot glue suddenly looses all adhesion and just falls off, but it doesn't seam to dissolve the hot glue at all so it does not make any mess.

[Cerebus]

Oh, glue makes me think of another.

You can remove dried PVA glues by soaking them in an alkaline solution. Water alone just very slowly wets them, an alkaline environment degrades them. A bit of washing soda (sodium carbonate) in water does the trick. The usual caveats about not doing this if water or alkali are going to damage the glued items applies, obviously. Taught to me by a guitar maker/repairer.

[exe]

When I was student, I used to recharge alkaline batteries. Still do this sometimes, though the capacity is poor.

[Syntax Error]

If you're long sighted, the watch makers trick of wearing two pairs of reading glasses, one in front of the other, means you can solder PTH and SMD parts, without the need of a stereo microscope.

Depreciated mouse mats are an excellent source of neoprene sheeting for all kinds of DIY packing and mounting tasks.

[andy3055]

When the sticky residue from scotch tape remain on plastic surfaces (old tape tend to this), stick a new piece of scotch tape and pull it off rapidly like removing hair by waxing.
To preserve AA, AAA and even button cells, keep them in a cool place like in the refrigerator. They will last much longer than leaving them in a drawer.

[Bud]

Alkaline AA cells: Determine the charge by dropping them on the minus side on a hard table- when full, they will simply fall to the table- empty cells bounce back due to the changes in the chemistry.

The first time two of my colleagues told me that trick, I was like "are you serious", I thought they were trying to pull my legs.
But sure enough, it works every time! Now I have in turn won a couple of free beers on that account 

I recall there is a EEVBlog video on this one.

Edit: Or it was a Big Clive's video

[jmelson]

To preserve AA, AAA and even button cells, keep them in a cool place like in the refrigerator. They will last much longer than leaving them in a drawer.

Do NOT, however, store wrapped in aluminum foil!  My wife's grandma did this and couldn't understand why all the batteries were dead.
I had to tell them why.

Jon

[andy3055]

Of course! I bet he did not know that Al foil is a conductor.

[Kasper]

Alkaline AA cells: Determine the charge by dropping them on the minus side on a hard table- when full, they will simply fall to the table- empty cells bounce back due to the changes in the chemistry.

The first time two of my colleagues told me that trick, I was like "are you serious", I thought they were trying to pull my legs.
But sure enough, it works every time! Now I have in turn won a couple of free beers on that account 

I recall there is a EEVBlog video on this one.

Edit: Or it was a Big Clive's video

EEVblog #508 - Can You Test Battery Charge By Dropping It?

[Halcyon]

Not so much electronics, but Fran's little trick for re-seating self-tapping screws by starting in reverse first until it finds the groove. So simple, yet effective.

[andy3055]

Not so much electronics, but Fran's little trick for re-seating self-tapping screws by starting in reverse first until it finds the groove. So simple, yet effective.

Good point.

Actually, it works for all thread types.

[RoGeorge]

Best trick ever, everybody can try it today if you don't believe me: 

Shout trick or treat to get candies. 

[Cerebus]

Best trick ever, everybody can try it today if you don't believe me: 

Shout trick or treat to get candies. 

Or a free bucket of disinfectant! 

[greenpossum]

Used lithium button cells make quick THT LED testers. No current limiting resistor required.