I've been looking at these machines in jewelry supply catalogs.
They're expensive. And too much money for just my hobby budget.
Anybody know how these work? I'm checking on Google today but any help
is sure appreciated.
Thanks,
Eric R Snow

On Mon, 13 Jun 2005 09:41:29 -0700, Eric R Snow
wrote:

I've been looking at these machines in jewelry supply catalogs.
They're expensive. And too much money for just my hobby budget.
Anybody know how these work? I'm checking on Google today but any help
is sure appreciated.
Thanks,
Eric R Snow

Based on zero firsthand knowledge about CD welding, I'd say you could
probably build one fairly inexpensively. I did recently build a
transient generator that produces 150-amp pulses for EMI testing.

One model, http://www.powerstream.com/spot-welder.htm, claims 680,000
uF of capacitance and 110 joule output with voltage up to 18 volts.
That's about $100 worth of caps if bought new from Digi-Key, but you
might do much better at a surplus outlet. A supply to charge the
caps would be dirt simple if you don't need high rep rate.

Switching could be done with MOSFET's or a big SCR. I'd use
MOSFETs. IRF1404Z from Int'l Rectifier can handle 100-amp pulses
with no problem; they're $1.64 each in lots of 10, and I'd use 10 of
'em in parallel for 1000-amp pulses.

I think lead resistance would provide some current limiting, but I'd
still use a series inductance of about 220 uH to limit peak current to
1000 amps or less. That'd probably be an air-core inductor to
avoid saturating core material.

"Don Foreman" wrote in message
...

Switching could be done with MOSFET's or a big SCR. I'd use
MOSFETs. IRF1404Z from Int'l Rectifier can handle 100-amp pulses
with no problem; they're $1.64 each in lots of 10, and I'd use 10 of
'em in parallel for 1000-amp pulses.

I think it would be easier with fat Smart-FETS than with an SCR. Unless
you're very lucky, you'll not find a gate turn-off SCR in that kind of
capacity you can afford.

And unless you can gate the thing off, you'll have a tricky system to adjust
the energy delivered to the work. With gating, you could just vary the
pulse width, and keep the peak voltage constant. The IR smart-FETS are
nearly indestructible, so the output stage would be easy.

A farad of capacitance at the 18v working voltage wouldn't cost much, for
ordinary filter caps, but you'll need units specified for CD duty, or you'll
fry the welds (or crimps) to the plates inside the caps at the currents
you're asking them to deliver.

LLoyd

Lloyd E. Sponenburgh wrote:

"Don Foreman" wrote in message
.. .



Switching could be done with MOSFET's or a big SCR. I'd use
MOSFETs. IRF1404Z from Int'l Rectifier can handle 100-amp pulses
with no problem; they're $1.64 each in lots of 10, and I'd use 10 of
'em in parallel for 1000-amp pulses.



I think it would be easier with fat Smart-FETS than with an SCR. Unless
you're very lucky, you'll not find a gate turn-off SCR in that kind of
capacity you can afford.

A big SCR works fine, unless you need +/- 1% control of energy due to some
standards organization. I build one of these things years ago. You
adjust energy with
a variable voltage power supply. I used a 100 A SCR, and applied a
strong trigger
pulse with a switch and R-C network to get the SCR saturated quickly.
I used ordinary computer-grade caps, and it worked until the equipment
was no
longer needed.

Jon

It is not quite as simple as just discharging some capacitors. The
capacitors should have a low ESR [effective series resistance] or they
might blow. That is why "photo flash" caps are made. Older small
welders used oil filled caps at higher voltage and discharged them
through a pulse transformer. If you ave access to used machinery stores
look for Sippican [sp] or Hughes. They were used in the vacuum tube
industry and we used them in the "old" days to make modules with
discreet semiconductors.

Chuck P.

MOP CAP wrote:

It is not quite as simple as just discharging some capacitors. The
capacitors should have a low ESR [effective series resistance] or they
might blow. That is why "photo flash" caps are made. Older small
welders used oil filled caps at higher voltage and discharged them
through a pulse transformer. If you ave access to used machinery stores
look for Sippican [sp] or Hughes. They were used in the vacuum tube
industry and we used them in the "old" days to make modules with
discreet semiconductors.

Chuck P.

Wouldn't an old CD welder with oil filled caps also likely be loaded
with PCBs?

Pete C.

In article , Pete C.
wrote:

MOP CAP wrote:

It is not quite as simple as just discharging some capacitors. The
capacitors should have a low ESR [effective series resistance] or they
might blow. That is why "photo flash" caps are made. Older small
welders used oil filled caps at higher voltage and discharged them
through a pulse transformer. If you ave access to used machinery stores
look for Sippican [sp] or Hughes. They were used in the vacuum tube
industry and we used them in the "old" days to make modules with
discreet semiconductors.

Chuck P.

Wouldn't an old CD welder with oil filled caps also likely be loaded
with PCBs?

Pete C.


Probably. There are still a lot of them around.

Chuck P.

In article ,
"Pete C." wrote:

MOP CAP wrote:

It is not quite as simple as just discharging some capacitors. The
capacitors should have a low ESR [effective series resistance] or they
might blow. That is why "photo flash" caps are made. Older small
welders used oil filled caps at higher voltage and discharged them
through a pulse transformer. If you ave access to used machinery stores
look for Sippican [sp] or Hughes. They were used in the vacuum tube
industry and we used them in the "old" days to make modules with
discreet semiconductors.

Chuck P.

Wouldn't an old CD welder with oil filled caps also likely be loaded
with PCBs?

If you aren't stupid enough to open them, I can't see any reason to care
that isn't 100% pure paranoia.

Same applies to asbestos... "Abating" the so-called threat creates more
threat than existed if it had just been left alone... (No, I'm not
saying that asbestos is harmless - Just that it's harmless *WHEN LEFT
ALONE*)

--
Don Bruder - - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See http://www.sonic.net/~dakidd/main/contact.html for full details.

Basically spot welding with a large cap as the power supply to limit the on
time.

--
Why isn't there an Ozone Hole at the NORTH Pole?

Here are a couple of links to sites that have schematics that you can view

http://www.imageindustries.com/products/cd_110.asp
See link at right side of page for Exploded Diagram and Schematic
Shows power section only, but it gives an idea of the parts count for the
output section.

http://roborific.com/node/19
Shows actual parts that can be used to build the welder

Sites with various types of units, and some descriptions, specifications
etc.
http://www.unitekequipment.com/Produ...w.asp?id=40096

http://www.iaid.com/acatalog/The_Man...Welding_Units_
69.html

http://www.caswellplating.com/kits/sput_weld.html

http://religion.p5.org.uk/cdwelder.htm

http://www.midwestfasteners.com/capacitor-discharge.htm

WB
.................

"Eric R Snow" wrote in message
...
I've been looking at these machines in jewelry supply catalogs.
They're expensive. And too much money for just my hobby budget.
Anybody know how these work? I'm checking on Google today but any help
is sure appreciated.
Thanks,
Eric R Snow




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On Tue, 14 Jun 2005 08:30:34 -0400, "Wild Bill"

Greetings Bill,
Thanks for all the links. I had found the roborific and caswell ones
but not the others.
ERS

wrote:

Here are a couple of links to sites that have schematics that you can view

http://www.imageindustries.com/products/cd_110.asp
See link at right side of page for Exploded Diagram and Schematic
Shows power section only, but it gives an idea of the parts count for the
output section.

http://roborific.com/node/19
Shows actual parts that can be used to build the welder

Sites with various types of units, and some descriptions, specifications
etc.
http://www.unitekequipment.com/Produ...w.asp?id=40096

http://www.iaid.com/acatalog/The_Man...Welding_Units_
69.html

http://www.caswellplating.com/kits/sput_weld.html

http://religion.p5.org.uk/cdwelder.htm

http://www.midwestfasteners.com/capacitor-discharge.htm

WB
................

"Eric R Snow" wrote in message
.. .
I've been looking at these machines in jewelry supply catalogs.
They're expensive. And too much money for just my hobby budget.
Anybody know how these work? I'm checking on Google today but any help
is sure appreciated.
Thanks,
Eric R Snow




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http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

Wild Bill wrote:
Here are a couple of links to sites that have schematics that you can view

http://www.imageindustries.com/products/cd_110.asp
Yup, a bank of caps, an SCR and a couple more caps that can be switched
in for more energy. All the rest is bells and whistles, mostly.

Jon