Search found 134 matches

by Chris Foley
Wed Jul 30, 2003 9:32 am
Forum: General Discussion
Topic: stepper motor problems
Replies: 6
Views: 1197

Re: stepper motor problems

You might want to look at one of the better stepper motor tutorials available on the web...<p>http://www.cs.uiowa.edu/~jones/step/<p>This will answer most of your questions.
by Chris Foley
Mon Jul 28, 2003 10:13 pm
Forum: General Discussion
Topic: Optoisolators
Replies: 9
Views: 2106

Re: Optoisolators

If you're a "newbie", and want a "KISS" circuit to optoisolate logic 1s and 0s, try the H11L1. It has everything built in except the current-limiting resistors for the LED at the input and the pullup for the open collector logic gate at the output. Also, it's made with hysteresis (no in-between volt...
by Chris Foley
Sun Jul 20, 2003 9:20 pm
Forum: General Discussion
Topic: 2 questions
Replies: 4
Views: 840

Re: 2 questions

Check your assumption that it's a ground loop by unplugging the CD and shorting the input. If you've still got buzz, you might have a problem in the tube preamp/amp. Check the caps first -- if it works otherwise, hum on well-designed tube amps can be a result of dried out/hi-Z electrolytics.
by Chris Foley
Mon Jul 14, 2003 10:16 am
Forum: General Discussion
Topic: solar powered fan
Replies: 2
Views: 785

Re: solar powered fan

P = V * I 3.9W = 12V * Fan Current Fan Current = .325A Your fan requires 325mA current.<p>8Ah = .325A * h hours of fan operation h = 24.6, meaning a fully charged battery will power your fan for 24 hours.<p>8Ah = .12A * h charging hours 66.6 charging hours to acieve full charge.<p>There are a couple...
by Chris Foley
Sat Jul 12, 2003 6:09 pm
Forum: General Discussion
Topic: Optocouplers @ Audio Freqs ?
Replies: 13
Views: 3346

Re: Optocouplers @ Audio Freqs ?

Less expensive audio isolation transformers (such as the one from RS) do have the tendency to drop off at the high and low ends. You know, one of the things you might want to try is to build a preamp/buffer (as simple as using a dual audio quality op amp to create two voltage followers for impedance...
by Chris Foley
Fri Jul 11, 2003 8:23 pm
Forum: General Discussion
Topic: Which Micro Controller to Choose?
Replies: 9
Views: 2516

Re: Which Micro Controller to Choose?

The latest issue (July 7) of Design News (one of the best free-distribution engineering trade magazines) has an article talking about your question -- "Hands-On Review of Microcontroller Development Kits". Without giving things away, I can say that they have a lot of good things to say about both th...
by Chris Foley
Fri Jul 11, 2003 8:00 pm
Forum: General Discussion
Topic: Optocouplers @ Audio Freqs ?
Replies: 13
Views: 3346

Re: Optocouplers @ Audio Freqs ?

To paraphrase the Oracle,<p>"What's really gonna cook your noodle is when you ask yourself why people answer them..."<p>By the way, when you use a "Y" from the line out (nominal 1K ohm) to two line loads, you have in effect a 500 ohm load. The impedance mismatch will mean that you will lose 33% of y...
by Chris Foley
Fri Jul 11, 2003 3:29 pm
Forum: General Discussion
Topic: Optocouplers @ Audio Freqs ?
Replies: 13
Views: 3346

Re: Optocouplers @ Audio Freqs ?

I believe you generally use a ground loop isolator audio transformer for this problem. I think Radio Shack sells one for $14.99 (270-054). You just plug the line out RCA plug in on one side, and plug the line in RCA plug on the other. Self-powered, simple, and you'll probably get real good results. ...
by Chris Foley
Fri Jul 11, 2003 3:01 pm
Forum: General Discussion
Topic: Optocouplers @ Audio Freqs ?
Replies: 13
Views: 3346

Re: Optocouplers @ Audio Freqs ?

The Analog Devices AD210 is a potted epoxy package 2.1" X 1.0" X 0.35". If you've got one, save it -- you never know when you'll need it!<p>Russ is right. The least expensive method of analog optocoupling is simply to mix a bias current for the LED of a 4N28 or other optotransistor, say 12 to 16mA, ...
by Chris Foley
Fri Jul 11, 2003 1:47 pm
Forum: General Discussion
Topic: Optocouplers @ Audio Freqs ?
Replies: 13
Views: 3346

Re: Optocouplers @ Audio Freqs ?

By the way, Chessman's idea is not insanely complicated -- it's been done and it's on the shelf, except that instead of an optocoupler, it uses modulated/demodulated transformer isolation (which also, incidentally, provides an isolated +/-15VDC supply along with the signal). It's called the Analog D...
by Chris Foley
Fri Jul 11, 2003 1:36 pm
Forum: General Discussion
Topic: Optocouplers @ Audio Freqs ?
Replies: 13
Views: 3346

Re: Optocouplers @ Audio Freqs ?

You're talking about optocoupling an audio signal (line level), right? A couple of questions:<p>1) How much do you want to spend?<p>2) How much distortion are you willing to live with? Is DC voltage important, or only the AC signal?<p>3) What's your upper and lower cutoff frequencies?<p>There are a ...
by Chris Foley
Thu Jul 10, 2003 12:28 pm
Forum: General Discussion
Topic: Here's How to Solve Our money Problems!
Replies: 21
Views: 5390

Re: Here's How to Solve Our money Problems!

I'll second Will's opinion on this post, especially the part about being off-topic. This is not a newsgroup, and we don't need or want filters.<p>The author of the post should go to<p> Google alt.politics.economics newsgroup <p>where his opinions will be right at home.<p>[ July 10, 2003: Message edi...
by Chris Foley
Tue Jul 08, 2003 4:46 pm
Forum: General Discussion
Topic: varible power supply for a pm dc motor
Replies: 6
Views: 1508

Re: varible power supply for a pm dc motor

<Quote> "...with 90 volt l5 amp rating..."<p>By the way, is this an 0.5A, 1.5A, or 15A motor? I think you've got a typo -- "L5"?
by Chris Foley
Tue Jul 08, 2003 6:48 am
Forum: General Discussion
Topic: varible power supply for a pm dc motor
Replies: 6
Views: 1508

Re: varible power supply for a pm dc motor

Permanent magnet 90VDC motors are usually driven from DC motor drives, sometimes called SCR drives. These commercially available motor drives typically have speed control through a potentiometer which is either mounted on the enclosure or, for "open frame" drives, is connected at the terminal block....
by Chris Foley
Thu Jul 03, 2003 3:17 pm
Forum: General Discussion
Topic: One-shot design needed
Replies: 3
Views: 1083

Re: One-shot design needed

desterline has a good idea. You're already familiar with the 555; you might want to start with a standard 20 microsecond one-shot with a CMOS 555. Let's assume a regulated 5VDC supply. If you load the output pin with a 40K resistor in series with a 10K pot, you can adjust the wiper of the pot to giv...