Search found 98 matches

by gadgeteer
Mon Mar 17, 2003 10:36 pm
Forum: General Discussion
Topic: Panic Switch
Replies: 7
Views: 1598

Re: Panic Switch

An SCR is a good choice. I gutted the power supply for my Bachman "N" guage 4-4-0 "General", Central Pacific model train. Idgets had used a multi-tap transformer, so the train speed varied by jerky levels (and nowhere in between). A simple linear regulator, with a zener reference driving a darlingto...
by gadgeteer
Mon Mar 17, 2003 10:05 pm
Forum: General Discussion
Topic: telephone busy light is not right.....
Replies: 17
Views: 3278

Re: telephone busy light is not right.....

There's no reason why the zener current can't be significantly reduced; of course, too low and you get into the diode's "knee". But I don't see why it can't work reliably with zener currents of a few tenths of a milliamp. The other transistors can easily compensate for the low zener current. <p>Then...
by gadgeteer
Wed Mar 12, 2003 11:47 pm
Forum: General Discussion
Topic: telephone busy light is not right.....
Replies: 17
Views: 3278

Re: telephone busy light is not right.....

I would absolutely go the route of "BRIGHTER LED" rather than lower resistor. No one is s'posed to connect anything to the phone lines anyway; so the lower the drain, the better. If you get a nice 3000-10,000mcd LED, you can reduce the LED power.<p>Less is better...<p>You should also be able to use ...
by gadgeteer
Wed Mar 12, 2003 11:35 pm
Forum: General Discussion
Topic: Getting more current from power supply
Replies: 24
Views: 5677

Re: Getting more current from power supply

Hmmm---Russ may be right. <p>Also---do you have an oscilloscope? It's nice to view the output---sometimes it is discovered that instead of a supply, we've built an OSCILLATOR...<p>I've never trusted the designed "current limit" in the IC. I once bought a high-power regulator (was it an LM339?); it l...
by gadgeteer
Wed Mar 12, 2003 2:16 pm
Forum: General Discussion
Topic: Are most people here Electrical/Electronics engineers?
Replies: 36
Views: 5979

Re: Are most people here Electrical/Electronics engineers?

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by no_vice: Professional: smart enough to teach it, but smart enough to get paid instead ? Hey! If those inverters are that efficient, AND can handle CURRENT, they should be used in a 120V (170V p-p ?...
by gadgeteer
Wed Mar 12, 2003 2:00 pm
Forum: General Discussion
Topic: Getting more current from power supply
Replies: 24
Views: 5677

Re: Getting more current from power supply

Page 13 might be a better circuit. REMEMBER---you can't just PARALLEL transistors---you hafta put a couple tenths of an ohm in EACH emitter lead, to prevent "current hogging".<p>I built a power supply based on a zener reference---simple zener diode and resistor---which is amplified, and sent to a po...
by gadgeteer
Tue Mar 11, 2003 11:14 pm
Forum: General Discussion
Topic: Age?
Replies: 24
Views: 3647

Re: Age?

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>And fighting over whichever shards of shrapnel we could find<hr></blockquote>What a memory! I bet you've heard a BUZZ-BOMB, too! <blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>good dr...
by gadgeteer
Tue Mar 11, 2003 10:51 pm
Forum: General Discussion
Topic: 50A or greater
Replies: 19
Views: 4242

Re: 50A or greater

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Russ Kincaid: How this works (most likely) is that the switcher converts 12 VDC to 170 VDC at 2.5 amps. The switching frequency may be as high as 500 kHz or 1 mHz. A full bridge output converts to ...
by gadgeteer
Tue Mar 11, 2003 2:10 pm
Forum: General Discussion
Topic: Age?
Replies: 24
Views: 3647

Re: Age?

How does a 15-year-old have enough money to buy a '97 camaro? I could use that kind of money about now...<p>And 15-year-olds do not make good drivers. I fully support movements to raise the driving age to 21. Remember, I was 15 once.<p>If you will take a little advice, Chessman, it's given in a spir...
by gadgeteer
Tue Mar 11, 2003 1:37 am
Forum: General Discussion
Topic: low voltage LED
Replies: 9
Views: 1473

Re: low voltage LED

I had a "Dicken's Christmas Village Santa"---open frame plastic display, 71 LEDs, with all its LEDs tied in parallel (very poor "design"; all reds hog the current)---once I separated the colors and added proper ballast resistors, the current consumption dropped from 1.5 amps to less than ½ amp. And ...
by gadgeteer
Tue Mar 11, 2003 1:07 am
Forum: General Discussion
Topic: inexpensive TO-220 mounting hardware?
Replies: 11
Views: 1672

Re: inexpensive TO-220 mounting hardware?

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>while you have a heatsink glued to your right thumb.<hr></blockquote>Ha ha ha! :D <p>I have a colleague who is older---and worked with probably that exact stuff. He was talking to an insufferable co-worker, who refused...
by gadgeteer
Tue Mar 11, 2003 12:46 am
Forum: General Discussion
Topic: 50A or greater
Replies: 19
Views: 4242

Re: 50A or greater

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Switching power supplies like the ones in most pc's supply large currents right off the line in a very small package. <hr></blockquote>They still have transformers---but because of the much higher oscillator frequency,...
by gadgeteer
Tue Mar 11, 2003 12:28 am
Forum: General Discussion
Topic: Video Camera Detector Schematic?
Replies: 27
Views: 4289

Re: Video Camera Detector Schematic?

BTW, if anyone's interested---I just built the 8-inch loop made from three layers of ribbon cable, with a variable cap paralleled; it works great. Place it next to an AM radio, and it really jacks up the weak stations...<p>(RS sells one of those antennas, works very well...)
by gadgeteer
Tue Mar 11, 2003 12:20 am
Forum: General Discussion
Topic: Video Camera Detector Schematic?
Replies: 27
Views: 4289

Re: Video Camera Detector Schematic?

I'm a little slow on "RF" stuff. Still kinda regard it as "black magic". (Forgotten the Smith chart stuff, modes, etc.)<p>Why would I need to change the coil? Why couldn't I just use F(0) = 1 / 2·¶·(LC)½ , and leave L alone but change C? <p>And how do you "heterodyne" a 15khz signal with...
by gadgeteer
Mon Mar 10, 2003 1:05 pm
Forum: General Discussion
Topic: Video Camera Detector Schematic?
Replies: 27
Views: 4289

Re: Video Camera Detector Schematic?

Thank you, sir! I did the search, and found some pre-made-products (like the VCD-42 and VCD-43). Fine if you have $145 (for the 42) and $279 (for the 43).<p>Why can't I just use an AM radio, and change the tank circuit to be reasonant at 15,735 hz rather than 550,000 hz? Can't I just slap a capacito...