Homebrew PCBs

sailingto wrote:
> You are correct - I should watch my typing better.  My mind gets
> faster than my fingers sometimes.

Too true -- and the risks of a mistyped URL are all the higher these 
days... (I remember the days where mistyping a URL got you an error 
message :-/ )

> Those are neat boxes - I saw those on ebay and almost ordered some,
> but DealExtreme is less expensive - that the price they have some
> some of the DVMs with 2.7" digits -
> http://www.dealextreme.com/details.dx/sku.29234 for only $14 shipped?
> May not be expensive, but I'll bet it works just fine.

To be honest, I wouldn't trust a cheap DMM -- I've had really bad luck 
with the "pound shop special" (= dollar store special) DMMs; they tend 
not to be particularly accurate.

Then there was the memorable occasion when one of mine lost the ability 
to detect voltage -- continuity beeper worked fine, so I thought the 
meter was fine. Taking 240V from the side of your hand to your 
wristwatch really does tend to wake you up quite quickly...

You can get used Fluke meters for pennies on the dollar these days; a 
Fluke 25 or 27 in reasonably good nick should only set you back £50 at 
the absolute most, plus maybe £10 for a set of Pomona DMM probes (which, 
curiously enough, are compatible with most of the Fluke accessories). A 
meter like that will last you the rest of your life, unless you do 
something stupid with it. My 25 is about the size of a housebrick and 
weighs about the same too...

If you want a nice, low cost bench DMM though, the Solartron 7150 and 
7150plus are quite nice (as long as you replace the mains filter 
assembly before powering on -- the X-Class capacitors tend to fail 
spectacularly after a few years). Expect to pay about £40 for one that 
needs a new PFM, or £80 for one that's been properly refurbished and 
includes the leather case and a good set of probes. Stewart of Reading 
have a couple of new/unused 7150Plus-es for £150...

Last but not least are the HP bench DMMs -- 3478As (5.5-digit) are going 
for about £100 these days; its big brother the 34401A (6.5-digit) tends 
to sell for about £300-400 used or ~£700 used.

"Verily, thou hath but little value, but the loss of a fine test meter 
causeth much woe and despair back at the shop" :)

> Those boxes would be good for projects - sort all the SMD parts of
> each size to each box....  Yes, I think that would be good.  I spend
> a good bit of time trying to sort those tiny SMD parts especially
> when it gets to the 0805 and 0604 parts.  I remember when the 1206
> parts were small!

I usually don't go below 0805, but I've got some 0604 parts for a few 
LVDS experiments. I want to get my grubby mitts on some RGB LED arrays 
and make a nice, big "any colour you like" display panel. Unfortunately 
the student budget says "no", so it'll be a nice, big "any colour you 
like as long as it's a shade of red, green or amber" panel (for the 
price of one 64-LED 8x8 RGB panel, you can get ten 64-LED 8x8 Red/Green 
panels -- and that's buying at the 1-off price for both).

It'll also be interesting to see what LVDS looks like on my 200MHz 
digital storage scope. I'm guessing "pretty poor at anything above 
40Mbit/sec".

-- 
Phil.
ygroups@...
http://www.philpem.me.uk/