Search found 12 matches

by larussell
Mon Aug 04, 2003 10:11 am
Forum: General Discussion
Topic: Buying a digital multimeter
Replies: 16
Views: 2818

Re: Buying a digital multimeter

If you want a good one (as opposed to a $5 one), definitely check out the resale market. Normally eBay is expensive, but there is so much surplus equipment out there (I think after all the .com failures) you can often be the only bidder on an item and get it really cheap). Also think about whether y...
by larussell
Mon Aug 04, 2003 8:23 am
Forum: General Discussion
Topic: Any hints on how to buld pedometer?
Replies: 13
Views: 2049

Re: Any hints on how to buld pedometer?

30 meters (100 ft) is about right as a worst case error for GPS. That is the size of a standard U.S. suburban 1/4 acre lot, which I would think is close enough for use as a pedometer. As you acquire more satellites the accuracy gets better, down to 15 feet in my experience.<p>Surveyors use something...
by larussell
Mon Jul 28, 2003 11:03 am
Forum: General Discussion
Topic: electric meter rotor rpm vs power
Replies: 5
Views: 911

Re: electric meter rotor rpm vs power

Thanks; I'll check it out and see if I get something reasonable on mine.
by larussell
Mon Jul 28, 2003 8:15 am
Forum: General Discussion
Topic: electric meter rotor rpm vs power
Replies: 5
Views: 911

electric meter rotor rpm vs power

Does anybody know how to take the rpm of the rotor on an electric meter and convert it to kilowatts? I have found general info on the net that says the meters are calibrated with a strobe, but nothing specific that says how you know many RPMs = 1kW (or how many rotations = 1 kWH).
by larussell
Fri Jul 25, 2003 7:45 am
Forum: General Discussion
Topic: Question about previous question
Replies: 6
Views: 1411

Re: Question about previous question

Your only other option to using a laser printer is to print and then copy with a copier where they will let you put in your own paper.
by larussell
Thu Jul 24, 2003 12:46 pm
Forum: General Discussion
Topic: Bike spedometer
Replies: 10
Views: 1536

Re: Bike spedometer

If your willing to spend $20 for a cheap digital voltmeter or surplus panel meter, then all you need is a way to generate an average voltage proportional to the rotation speed. For example, a magnet, coil, diode, and capacitor. The faster the wheel rotates, the higher the voltage and more frequent w...
by larussell
Thu Jul 17, 2003 2:12 pm
Forum: General Discussion
Topic: Project
Replies: 6
Views: 1815

Re: Project

I would do it with a Basic Stamp and a temperature sensor. You don't need a micro lab, just a PC and their cheapest getting started setup with the whole development environment right there on the chip/board that's going to be the final product.<p>You can do a discreet design with logic chips, etc, b...
by larussell
Thu Jun 26, 2003 1:46 pm
Forum: General Discussion
Topic: Timer Chip
Replies: 5
Views: 1327

Re: Timer Chip

a 556 timer chip will work, as long as it doesn't have to be too accurate
by larussell
Thu Jun 05, 2003 2:47 pm
Forum: General Discussion
Topic: Model Rocket Lauch Timer
Replies: 9
Views: 1356

Re: Model Rocket Lauch Timer

I don't have time to draw a schematic but I can tell you how to hook it up. If you know enough to know to use cascaded 555s then I think you can figure out the details.<p>Look at Figure 1 in http://www.national.com/ds/LM/LM555.pdf <p>Connect a normally open pushbutton switch to ground to the input (...
by larussell
Tue Jun 03, 2003 2:13 pm
Forum: General Discussion
Topic: Extermely High Speed Timer?
Replies: 3
Views: 718

Re: Extermely High Speed Timer?

Assuming for descriptive purposes that when your transmitted and received signals are active it represents a logic "1", if you transmit a pulse which is longer than the max round trip delay, and feed the transmitted and inverted received signal into an AND gate, than you will get a pulse out of the ...
by larussell
Tue Jan 14, 2003 1:59 pm
Forum: General Discussion
Topic: pic serial data
Replies: 4
Views: 1160

Re: pic serial data

How about a VCO (voltage controlled oscillator) set to go between the two frequencies based on high or low input? Or two 555s set to the two frequencies with gates to choose between them based on high or low input?<p>The modems are hard to find because no one uses them anymore; the hams use software...
by larussell
Mon Jun 17, 2002 2:02 pm
Forum: General Discussion
Topic: Cordless phone range
Replies: 16
Views: 2681

Re: Cordless phone range

10 blocks to the mile in some parts of the country, 12 in others. In NYC blocks are rectangular, so the direction matters.<p>How about GPRS radios?