[Dennis 9412]

Hi Marc

I have one of the HobbyCNC systems I bought a couple years ago and I am using a 10 amp Transformer for bow power, as recommended by Dave Rigotti.

2 amps is barely enough. The more amperage you use the more heat you get. On the HobbyCNC site there is a link to a bow power supply. Just use that and you'll be fine.

I was able to put the board and the power supply into a "1411X" enclosure available from Hammond Manufacturing, the same people I bought the transformer from. I use the GMFC software and it works great.

Regards,

Dennis

[747drvr]

Hi Dennis,

Thanks for your input ! I was reading about power supplies and it looks like the 24VAC 10A is the ticket . After rectifying , it will output around 33 VDC unloaded . If that isn't enough for the wire I guess a regulated power supply would be required to get the voltage up to but not exceeding 35v .

What flavour of GMFC are you using ? Light , PE or Pro ?

Marc

[kcaldwel]

Dennis,

Do you have the link or parts list for the Hammond transformer and rectifier? I can't find it on the HobbyCNC site.

I'm not sure I can build a PS for less than this 36V switcher from MPJA:

http://www.mpja.com/prodinfo.asp?number=16034+PS

I was told last night you can hook switchers up in series. I have two 24V, 6A switching supplies. If I can turn the voltage (they are somewhat adjustable) down to 18V, I may try hooking them in series.

Some people on the Yahoo group were talking 45V to drive the small wires, but of course you can't go through the FoamPro board at that voltage - I don't think... Anything past 42V is considered dangerous voltage, and should be treated like it will kill you.

Kevin

[Vulcan1]

I have the Pro board from Dave (Hobbycnc) which is not the foam package but I added the wire heat and timing board to make it work with Gilles software. I dont think Dave sells the separate board at the moment. He Reccomends the 10 amp transformer but we are also using the pc supplies in series for the 24 volts. If you go that way there are some good spots on the net about making them. Just remember one supply has to be insulated from the other or the smoke flies. The Stepper chips will take up to 42 volts and it depends what specs you are reading. Dave sells with his package a 57,000 uf capacitor and on my system it ends up 39 volts which is very close to the max. You want to leave some leeway on it also. As mentioned his wire heat uses the pc supply and if you put a big cap with it you also get the power you need. So far I have made 3 power supplies for working with the systems I have been playing with. At the moment I have at home a pic controlled wire working but have to make the pcb and then put the big juice to it. I am also using a 47,000uf cap with it. There are quite a few with there own systems and some are more high tech than others but they all work along the same lines.
I am in Hanna for the weekend baby sitting my 2 grandaughters and there keyboard comes up with some funny characters when typing. I get an è for an asterick for one part so will wait to get home before reccomending some places to look.
John

[kcaldwel]

Well, my 24V switchers only turn down to 20V, so two in series would be 40V. I'm not sure I want to try that with the FoamPro board.

After a bit of research, it seems it is not an issue to hook up switchers in series. PC supplies are a bit different, and you should separate the common from the ground internally on the downstream supply, so you don't have to isolate the cases:

http://www.antennex.com/preview/archive3/powers.htm

I think this means I could even run a 24V supply, with a 12V one in series to get 36V. or adjust the 24V supply to 22V so I get 34V for the FoamPro board. I'm no electronics expert though so I'll have to check on that.

Kevin

[Dennis 9412]

Originally Posted by 747drvr

Hi Dennis,

Thanks for your input ! I was reading about power supplies and it looks like the 24VAC 10A is the ticket . After rectifying , it will output around 33 VDC unloaded . If that isn't enough for the wire I guess a regulated power supply would be required to get the voltage up to but not exceeding 35v .

What flavour of GMFC are you using ? Light , PE or Pro ?

Marc

Hi Marc:

I am using the PE version. It does everything I want to do, all in one neat little package.

Regards,

Dennis

[Dennis 9412]

Originally Posted by kcaldwel

Dennis,

Do you have the link or parts list for the Hammond transformer and rectifier? I can't find it on the HobbyCNC site.

I'm not sure I can build a PS for less than this 36V switcher from MPJA:

http://www.mpja.com/prodinfo.asp?number=16034+PS

I was told last night you can hook switchers up in series. I have two 24V, 6A switching supplies. If I can turn the voltage (they are somewhat adjustable) down to 18V, I may try hooking them in series.

Some people on the Yahoo group were talking 45V to drive the small wires, but of course you can't go through the FoamPro board at that voltage - I don't think... Anything past 42V is considered dangerous voltage, and should be treated like it will kill you.

Kevin

Hi Kevin:

I have the diagram here somewhere. I'll find it and make a pdf file from it and e-mail it to you. Probably won't be able to do it until next weekend though, as I will be away from home until Friday night. PM me with your e-mail address and I'll get it to you.


Regards,

Dennis

[kcaldwel]

My cutter is up and running, and working very well. I am interested in cutting cores for others as well. My table is expandable with table slides and leaves (leafs?). I can cut up to 48" panels, but I need to upgrade my powers supply to get past 36" right now.

I have a vacuum foam hold down system that prevents deformation of the core during cutting from weights on the foam.

I am on Vancouver Island.

Kevin
www.sealbayaero.com

[747drvr]

Very nice . Mine's much smaller and simpler . I finally got it back and set up to do a few small cores . I'll be modernizing the board , steppers and software in the near future.

Marc

[Vulcan1]

I was doing some browsing around looking for a few electronic items when I came across this wire from Active Electronics. I think this may be good especially for cutting long panels. The part number I am going to try is (24 BNC) which is a 24 guage nickel chromium bare resistance wire. It is rated for temp up to 1680 deg C. It comes in a 1/4 lb. spool and the cost is $16.63 by there website. I am not sure what the stretch would be but I don't think the heat will bother it.
John