Very cheap molded enclosures?

[Rich Grise, but drunk]

Our approach many years ago was simply to glue fake naugehyde onto plain
old aluminum.

"Fake" "naug[a]hyde?" I thought naugahyde was already fake! ;-P

Cheers!
Rich

 

[Rich Grise, but drunk]

Hello Don,

It depends. The ads look nice but upon further inquiry things can get
out of hand quickly when mods are required.


I always wondered where the naugas are grazing ;-)

They've taken up residence with families:
http://www.naugahyde.com/promoitems_nauga.html

so they probably eat pizza or something. ;-)

Cheers!
Rich

 

[Joerg]

Hello Rich,

They've taken up residence with families:
http://www.naugahyde.com/promoitems_nauga.html

Ah, I still learn something every day. So they are from Wisconsin....

Regards, Joerg

 

[Carl Ijames]

That's along the lines I was thinking but I didn't look hard enough
I guess I should pause before typing, sigh . Of course, I meant "use
a bridge rectifier" on the input so the device works no matter which way
it's plugged in, when you have the supply voltage to spare.

No, you can't, not even a Schottky. That would require dropping the uC
clock too much to allow for a deep enough battery depletion. The usual
tricks are to split up VCC and run 'naturally protected stuff' such as
LED directly so the heavy current hitters are taken care of. The
(hopefully low current) remainder gets the resistor and diode to GND
treatment. This will deplete a battery when it's left in the wrong way
but that's a small price compared to a fried unit. As long as nothing
gets hot and the electronics can stomach the reverse that the diode
allows. Fuses are usually a no-go because that's nowadays considered a
field failure by the discerning consumer.

Interesting. I'd pretty much guessed about the LED's, but I wasn't sure
what you did for a uC or other ic's.

 

[Joerg]

Hello Carl,

I guess I should pause before typing, sigh . Of course, I meant "use
a bridge rectifier" on the input so the device works no matter which way
it's plugged in, when you have the supply voltage to spare.

That would be even worse, causing two diode drops.

Interesting. I'd pretty much guessed about the LED's, but I wasn't sure
what you did for a uC or other ic's.

It boils down to a detailed study of all the data sheets. With discretes
you can sometimes get enough safety for the highest possible battery
voltage and some of the chips might be for automotive and, to some
extent, tolerant enough. In a car a battery reversal can easily happen
although I doubt that the very 'modern' vehicles with all their
processors would survive. Worst case you'd be wielding the fire
extinguisher.

For many newer parts the data sheets have become skimpy and one may not
be able to find out how much of a polarity reversed current will have
damaging effects. That leaves only external protection.

One fact that is often overlooked is the temptation of consumers to plop
NiMH or NiCd in there instead of alkaline AA cells. Those can pack an
incredible punch and some are able to sink well over an amp into
anything that gets in the way, causing undesired pyrotechnical effects.

Regards, Joerg

 

[[email protected]]

Hello NT,


Square ones are usually a little more in cost. But not a lot so this is
certainly an option.

For this app it would be better if they are spread apart a bit so that
the lettering next to them could be large font, for people with not so
good vision. It will be used by people with and without their reading
glasses on but the unit will be close by. A short row of adjacent LED
can be a challenge for folks that need reading glasses and I am pretty
much on the way to become one of those myself ;-)

Regards, Joerg

I think you want the world, and you want it cheap!


NT

 

[[email protected]]

One fact that is often overlooked is the temptation of consumers to plop
NiMH or NiCd in there instead of alkaline AA cells. Those can pack an
incredible punch and some are able to sink well over an amp into
anything that gets in the way, causing undesired pyrotechnical effects.

Regards, Joerg

1A? NiCds can kick out 60A for short periods.

NT

 

[[email protected]]

One fact that is often overlooked is the temptation of consumers to plop
NiMH or NiCd in there instead of alkaline AA cells. Those can pack an
incredible punch and some are able to sink well over an amp into
anything that gets in the way, causing undesired pyrotechnical effects.

Regards, Joerg

1A? NiCds can kick out 60A for short periods. Ask the r/c modellers.

NT

 

[John Devereux]

1A? NiCds can kick out 60A for short periods. Ask the r/c modellers.

Yes! I once had a flatmate that thought it would be funny to discharge
one of my AA NiCds with a paperclip. Turned red hot and caused deep
skin burn.

 

[Joerg]

Hello NT,

I think you want the world, and you want it cheap!

In this case it's not just me that wants the world. It's like "Can we
pour this $500 machine into something that costs a pittance?". But guess
what, sometimes we got it!

The rather pathetic thing is that most of those projects succeeded by
reducing integration, replacing chips with discretes and so on.

Regards, Joerg

 

[Joerg]

Hello NT,

1A? NiCds can kick out 60A for short periods.

Yes, especially D cells. With some of them you could start a car. Cheap
NiMH AA cells are a bit more wimpy but can still do quite a few amps.

Regards, Joerg

 

[Hubert Ball]

Dear Roger,

In the UK at least, there is an intermediate 'form' of injection moulding
available. With this, the dies are made of much lower quality material,
with a life expectancy of only about 2K+ pieces. They are made using a
fairly simple CNC process, and the tooling costs are perhaps 1/100th that
of a normal injection moulding process.

How are these production-way's are called in the UK?

Can you link some companies who do that way of business?

THX in advance
Hubert