Search found 124 matches

by AllenWallace
Sun May 19, 2013 5:56 pm
Forum: High Voltage - Fusor Input Power (& FAQs)
Topic: Need help to review the circuit schematics
Replies: 9
Views: 3317

Re: Need help to review the circuit schematics

For safety, please place back to back diodes across the meters. The meters work with voltages below the diode drop, and in case of a fault, the diodes prevent high voltage from arching through the meter face plate to the operator.
by AllenWallace
Wed Nov 21, 2012 4:31 am
Forum: High Voltage - Fusor Input Power (& FAQs)
Topic: Can I turn a postive power supply into a negative one ?
Replies: 9
Views: 2888

Re: Can I turn a postive power supply into a negative one ?

You need to make a simple marx generator, which will turn your positive HV into a pulsing negative HV.
by AllenWallace
Fri Sep 07, 2012 4:24 am
Forum: High Voltage - Fusor Input Power (& FAQs)
Topic: What is the minimum power input needed for a demo fusor?
Replies: 7
Views: 3103

Re: What is the minimum power input needed for a demo fusor?

<t>I've seen star mode using a flyback transformer from a old CRT monitor. it was driven using the traditional two 2N3055 transistors and since the flyback output is positive, and the fusor needs negative, I grounded the red wire and connected the fusor to the return pin on the bottom of the flyback...
by AllenWallace
Tue May 01, 2012 1:46 am
Forum: Fusor Construction & Operation (& FAQs)
Topic: Help with Arduino DAQ
Replies: 6
Views: 3076

Re: Help with Arduino DAQ

I rather like the TI launchpad. For under $5 you get a USB emulated COM port serial interface with a handful of i/o including 10 bit A/D. You have to be willing to program in C.
by AllenWallace
Sun Mar 18, 2012 8:59 pm
Forum: Vacuum Technology (& FAQs)
Topic: Cold Cathode Ion Gauge controller
Replies: 2
Views: 1287

Re: Cold Cathode Ion Gauge controller

My do-to list for the next few months include building a micro-processor controlled cold cathode gauge. I'd love to discuss the theory and practical considerations.
by AllenWallace
Wed Mar 14, 2012 8:25 am
Forum: Vacuum Technology (& FAQs)
Topic: Vacuum Pumps, can it be good AND cheap?
Replies: 14
Views: 5691

Re: Vacuum Pumps, can it be good AND cheap?

<t>Call or visit every neon sign shop and also every testing lab that does helium leak detection.<br/> Explain that you are doing a high school science fair project and can you have a old pump ?<br/> <br/> I got my most excellent welch 1397 pump from a discarded helium leak detector. It pulled the f...
by AllenWallace
Sat Feb 11, 2012 3:57 pm
Forum: Fusor Construction & Operation (& FAQs)
Topic: Getting surplus parts from colleges.
Replies: 10
Views: 3305

Re: Getting surplus parts from colleges.

<t>All universities have policies that require items to be submitted to a surplus redistribution/sales/disposal program. However if the item is 'scrap', then it is thrown out. If it's large or heavy or mazmat, it costs them $$ to get rid of it. They will be happy to let you 'dispose' of it as long a...
by AllenWallace
Mon Dec 12, 2011 5:02 am
Forum: Fusor Construction & Operation (& FAQs)
Topic: Star Mode at last
Replies: 10
Views: 4457

Re: Star Mode at last

<r>> ...15,000 (+7,500/-7,500 volts AC at 30 mA...<br/> <br/> Are you sure? I could be mistaken, but from your description it sounds like you are using a NST (Neon SIgn Transformer). If this is the case, you are running about a few hundred volts at best. Read the FAQs regarding NSTs and current limi...
by AllenWallace
Mon Oct 31, 2011 2:05 pm
Forum: Vacuum Technology (& FAQs)
Topic: Cheap Ebay Turbo Pump with controller
Replies: 6
Views: 2524

Re: Cheap Ebay Turbo Pump with controller

Post Mortum: The bidding ended at $879.
by AllenWallace
Fri Sep 16, 2011 4:03 am
Forum: Vacuum Technology (& FAQs)
Topic: Pump connections
Replies: 5
Views: 2329

Re: Pump connections

The difference is that with the extra valves you can open the vacuum chamber without slowly cooling down the diffusion pump.

The simple valving requires that the pump be cool before venting. Also, if you vent too quickly, you will blow the diffusion pump oil into the vacuum chamber.