Alt-BEAM Archive
Message #11517
To: "'beam@sgiblab.sgi.com'" beam@sgiblab.sgi.com
From: Wilf Rigter Wilf.Rigter@powertech.bc.ca
Date: Wed, 8 Mar 2000 07:32:36 -0800
Subject: [alt-beam] Re: Recycling PCB parts - was Quick-Change components
A word of caution and advise.
Applying uncontrolled heat from a torch, heatgun, BBQ etc to remove
components from surplus pcb's will almost always result in evil smelling
toxic fumes and smoke that can make indoor and even outdoor areas
uninhabitable for days. While for safety reasons I strongly caution against
using this recycling method I would share the following tips:
Do this work outside in an open, well ventilated area, away from other
lifeforms.
Wear gloves, safety glasses/goggles and preferably a properly fitted
respirator mask with an organic vapor cartridge and use a small fan to
direct smoke away from you.
With the pcb suspended component side down between two sawhorses or equal,
the part to be removed is "firmly" gripped (not crushed) with some surgical
clamps, a small vise grip or a chip puller. Heat the top solder side of pcb
while gently pulling on the part to remove it when the solder melts. Work
systematically from one end of the board to the other taking advantage of
the preheated components, adjacent to the area of the pcb your working on.
While heating, the pcb will occasionally delaminate and "spit" globules of
molten solder for several feet so wear those goggles or else! Parts
connected to large ground planes or chips with bent-over leads are often the
most difficult to remove and the most likely to generate smoke.
To clean up excess solder on component leads use solder wick, however with
the right temperature, heating time and experience, the parts should come
off the board ready to be used.
Good luck and be safe.
wilf
> -----Original Message-----
> From: Feser, Jason [SMTP:jfeser@ea.com]
> Sent: Tuesday, March 07, 2000 11:01 AM
> To: 'beam@sgiblab.sgi.com'
> Subject: RE: Quick-Change components
>
If you use the torch on a severe angle (10 degrees) to the pcb, the
solder
runs off quickly and the components stay fairly cool. I only use it
when a
soldersucker won't do the job well enough (like a strip of 168
pins...). I
have yet to destroy a component. Just use common sense and pull the
torch
away if your pcb starts to smoke ;P
nock on wood ;)
:j'
11518 Wed, 08 Mar 2000 10:44:04 -0500 [alt-beam] Re: Silicon Diodes beam@sgiblab.sgi.com "Sathe Dilip"
Daniel Grace wrote:
>
> Silicon Diodes produce an electrical current when
> exposed to sunlight, am I right in that? How much
> current/voltage? Does it depend on the manufacturer? I
> can find silicon diodes just fine, but none specify
> the current or voltage developed in sunlight.
It is true that if you expose any PN junction to light, it will show
some photovoltaic characteristics. Most devices are manufactured to
minimize this effect because it is an undesirable characteristic for
most applications (exception is opto devices where you want to use these
characteristics). e.g., If you are talking about general purpose
rectifying diodes, most of them come packaged in opaque plastic or
metal. ( How do you plan to expose the junction to light?). Now this
being an unwanted characteristic, they do not list it in the
specifications.
Even in glass packaged diodes, where you may think that the junction is
exposed, the manufacturer has more than likely applied an oxide layer on
top of the silicon to make it 1) inert to gases during processing or 2)
to reduce this photovoltaic effect. In solar cells they specially
process the PN junction to keep it translucent so that light can reach
it all over the surface & not only edge wise as it would in a normal
diode.
Two things you can try are:
Try LEDs. They will show a measurable (though feeble) Voltage & current
(if you have a sensitive multimeter.
If you have in your junk some old TO-3 packaged power transistors, open
the little tin can by cutting it carefully at the top. This exposes a
substantial sized silicon die. If the device is a working one, you can
get a few tens of micro amps at about 0.5 volts in bright sunlight. I
have tried this with some 2N3055 transistors.
Dilip
----------------------------------------------------------------------
The early bird may get the worm, but the second mouse gets the cheese.
----------------------------------------------------------------------
11519 Wed, 8 Mar 2000 08:02:46 -0500 Re: Tower hobbies servo Richard Piotter
> How are Futaba brand servo motors??? Had one, but it was destroyed due
> to mistakes by me! :)
>
> The other Futaba I had was easily modified for continuous rotation.
>
> I'm looking for a combo of durability, strenth (even if slow), and
> efficiency. I want to make sure these things are worth the cost.
>
>
> Dave Hrynkiw wrote:
> >
> > At 12:06 AM 3/8/00 , Timothy Flytch wrote:
> > >Be vary careful with Tower... they are a lot like Rat Shak... They will
> > >put their name on anything!!! They always use the lowest bidder... and
are
> > >very inconsistent... I would say stick to the name brands...
> > >
> > >>i really want to start on a second walker and was thinking of using
the
> > >>servos from solarbotics (the tower hobby ones). Are they decent to use
for
> > >>the cost?
> >
> > We've never had any problems with these TS-53's - solid units, although
a
> > bit noisy. But they're easier to modify than the HITEC units, which is a
plus!
> >
> > Regards,
> > Dave
> > ---------------------------------------------------------------
> > "Um, no - that's H,R,Y,N,K,I,W. No, not K,I,U,U, K,I,_W_. Yes,
> > that's right. Yes, I know it looks like "HOCKYRINK." Yup, only
> > 2 vowels. Pronounciation? _SMITH_".
> > http://www.solarbotics.com
>
> --
>
>
> Richard Piotter The Richfiles Robotics & TI web page:
> richfile@rconnect.com http://richfiles.calc.org
>
> -- Make Money by Simply Surfing the Net or responding to E-Mail!!!
> -- Click below!!!
>
> http://www.alladvantage.com/go.asp?refid=ATL147
> http://www.spedia.net/cgi-bin/dir/tz.cgi?run=show_svc&fl=8&vid=329630
>
Home