Search found 59 matches

by dtief
Fri Jan 30, 2009 7:53 pm
Forum: General Discussion
Topic: New Board Look?
Replies: 29
Views: 4423

Re: New Board Look?

I prefer the "old" layout also. I'm on a lot of forums, and they all have the poster's info to the left. Also, too much wasted blank space on the new style. Actually, it's not the blank space, it's the too much info with the topic that's bugging me. It's all vertical, instead of efficiently using th...
by dtief
Tue Jan 27, 2009 6:58 pm
Forum: General Discussion
Topic: Analog TV Switch Off postponed ('til June 09)
Replies: 12
Views: 2397

I got my 2 converters - just in time, unless they print more coupons. The way my CATV company has been slowly moving the channels we watch to their ridiculously expensive digital tier, we will be back to over the air (exclusively) for TV.
by dtief
Mon Jan 26, 2009 6:44 pm
Forum: General Discussion
Topic: Neodymium Magnets
Replies: 21
Views: 6877

This place has VERY big and dangerous magents. I bought 2 of their 1" cube neodymium magnets. Truly impressive.

http://www.unitednuclear.com/supplies.htm
by dtief
Sun Jan 25, 2009 6:40 pm
Forum: General Discussion
Topic: Appliance Repair
Replies: 23
Views: 4137

I repair just about any / everything I own. Usually try to get better stuff, so it's less likely to need repair, and more likely to be worth bothering with if it does. I won't spend hours on a $25.00 item. As far as washing machines go, this one is hard to beat for reliability & easy self repair & s...
by dtief
Fri Jan 23, 2009 1:39 pm
Forum: General Discussion
Topic: Is RadioShack that confused?
Replies: 73
Views: 14988

I gave up on RS about 30 years ago. That was when I discovered industrial electronics suppliers that sold good quality parts.
by dtief
Tue Jan 20, 2009 4:52 pm
Forum: General Discussion
Topic: Sealed Lead Acid Battery
Replies: 6
Views: 1451

If the battery is more than a few years old, or has been sitting discharged, buy a new one, it's dead.
by dtief
Tue Jan 20, 2009 4:46 pm
Forum: General Discussion
Topic: Circuit city drops the big one...
Replies: 15
Views: 3249

In a while, some other store will develop into a chain, and the cycle will continue. I've seen so many stores come & go, some new one comes along, then goes downhill (whether due to not adapting with the market, or new owners screw up what made the store/s successful), then out of business, some new...
by dtief
Mon Jan 19, 2009 6:01 pm
Forum: General Discussion
Topic: Why Don't HEPA & Electrostatic Dust Trappers Work?
Replies: 7
Views: 1600

Here's some of what I have done along these lines. In my early 20s I started to be allergic to dust / pollen. I bought a real electronic air cleaner. Something like Grainger 5C417. It was almost 30 years ago, so it wasn't this exact unit. It has a stack of aluminum plates, set up with opposite charg...
by dtief
Sun Jan 18, 2009 5:44 pm
Forum: General Discussion
Topic: High current voltage doubler - considerations ?
Replies: 31
Views: 6198

The 99% efficiancy @ full load sounds a little optimistic to me. I have com across voltage doublers (by switching capacitors around) for low power - IC's even. But they are only good for low power. You want 20A output. That requires a minimum of 40 Amps input. Thje charging peaks would be substantia...
by dtief
Wed Jan 14, 2009 7:14 pm
Forum: General Discussion
Topic: Startup Delay Box Needed
Replies: 3
Views: 1401

I ordered PC boards for a "powerstrip" project that might do this. What my design does: Current sensor IC to detect a load on one outlet. delay turn on & off of 2 other outlets. The delay of turn on & off are seperatly adjustable, and the 2 on/off times can be different. Also, one of the delay outpu...
by dtief
Sat Jan 03, 2009 7:41 pm
Forum: General Discussion
Topic: MOSFET heat
Replies: 18
Views: 4468

The gate has significant capacitance, especcially with the bigger (current) FETs. Since we are talking about a switch mode power control, the FET has to be turned on & off very fast. Charging & discharging a capacitor very fast requires current to flow.

Dave
by dtief
Fri Jan 02, 2009 7:44 pm
Forum: General Discussion
Topic: Keypad Behind Glass
Replies: 27
Views: 4792

psycho wrote: Not sure if it will go through glass, though.
If it works by RF like the QTxxx it should. Glass doesn't block RF.
by dtief
Fri Jan 02, 2009 7:40 pm
Forum: General Discussion
Topic: MOSFET heat
Replies: 18
Views: 4468

Another alternative: Use a bigger FET like HUF75344G3. RDs On .008Ohms. That would dissipate almost 10 times less power. Near 3W at 20 Amps. They are only $2.27 @Digi-Key.

The gate drive current would be higher.
by dtief
Fri Jan 02, 2009 7:25 pm
Forum: General Discussion
Topic: Keypad Behind Glass
Replies: 27
Views: 4792

I used a bunch of QT240s in this project: http://home.comcast.net/~davidtief/projects/BigPiano/BigPiano.html They would work through glass easily. The QTxxx series has a range of chips, from 1 input to many. I used the QT240s because they are 4 sensors to 4 bits, no encoding, so they could replace m...
by dtief
Sat Dec 27, 2008 5:43 pm
Forum: General Discussion
Topic: LED light experimentation
Replies: 22
Views: 7294

Re: LED

My other concern on fiber optics was the necessity for a powerful light source [snip] on-off cycling device where the light is on for example 1sec and off 2 sec and repeated. I suppose this cycling might get around the temperature buildup? The K2 Luxeons at 4-5 Watts are very bright. The highest po...