Search found 71 matches
- Tue Jan 28, 2003 2:31 am
- Forum: General Discussion
- Topic: cheap (and maybe dirty) quadrature oscillator
- Replies: 1
- Views: 1890
Re: cheap (and maybe dirty) quadrature oscillator
You need a clock, 3 inverters, and 2 d-latches.<p>` ` ` ` ` +----o<|---+ ` ` ` ` ` | +-----+ `| ` ` ` ` ` +-|D ` Q|--+---Q0 ` ` ` ` ` ` | ` ` | clock-+-|>o-|> `` | ` ` ` |` ` `+-----+ ` ` ` | ` ` ` | ` ` ` | ` +----o<|---+ ` ` ` | ` | +-----+ `| ` ` ` | ` +-|D ` Q|--+---Q1 ` ` ` | ` ` | ` ` | ` ` ` ...
- Tue Jan 28, 2003 2:10 am
- Forum: General Discussion
- Topic: Hello! Newbie to electronics
- Replies: 8
- Views: 4896
Re: Hello! Newbie to electronics
"The Art of Electronics" is likely the best book on my shelf for discrete circuits, though it's probably not the quick intro you're looking for. Are you looking to get into embedded systems or analog stuff or ???
- Tue Nov 12, 2002 11:26 am
- Forum: General Discussion
- Topic: JFET vs BJT
- Replies: 4
- Views: 3083
Re: JFET vs BJT
Also... here's a fun one...<p>Look up the data-sheet for a JFET and look at the data sheet for a typical N-ch JFET the MPF102 (I've got a link below). Look for Idss and look at the min and max values. You'll notice that the min is 2mA and the max is 20mA. This means that some large percentage of the...
- Tue Nov 12, 2002 11:10 am
- Forum: General Discussion
- Topic: JFET vs BJT
- Replies: 4
- Views: 3083
Re: JFET vs BJT
Another really important design consideration is the tolerance of the manufacturing process. FETS and JFets in particular have very poor manufacturing tolerances, on the order of 10 times worse than BJTs. FETs also have poorer noise characteristics.<p>To get an idea, browse through the data sheets f...
- Tue Nov 12, 2002 10:52 am
- Forum: General Discussion
- Topic: Microphones
- Replies: 9
- Views: 9280
Re: Microphones
Generally, you'll want to use a JFet pre-amp stage to accomodate the very high output impedance of the piezo crystals. There are numerous examples across the web.
- Tue Nov 12, 2002 10:46 am
- Forum: General Discussion
- Topic: Microphones
- Replies: 9
- Views: 9280
Re: Microphones
Piezo-electric mics convert the mechanical energy carred by the sound waves into an electrical energy. Therefore, a volage is generated by the microphone, but the impedance is high (10ish of Meg-ohms I believe). Piezo crystals are used to generate power for roadway flashers in Japan (the yellow ligh...
- Tue Oct 29, 2002 10:30 pm
- Forum: General Discussion
- Topic: antenna length
- Replies: 5
- Views: 4656
Re: antenna length
c = 3x10^8 m/s (300,000,000 m/s)<p>1/4 wave whip antenna<p>length = c/(4*f) meters<p>example:<p>2.4 GHz - (3x10^8)/(4*(2.4x10^9)) = 3.125 cm<p>900 MHz - (3x10^8)/(4*(9x10^8)) = 8.333 cm<p>27 MHz - (3x10^8)/(4*(2.7x10^7)) = 2.778 m
- Fri Oct 11, 2002 7:02 pm
- Forum: General Discussion
- Topic: capacitor types
- Replies: 19
- Views: 12844
Re: capacitor types
I'm from an entirely different school of though. I'm a much newer member of the electronics community than many of our valve-lovers, and therefore I am focused on modular and digital techniques.<p>The most appealing approach to me is a clean amp (having characteristics approaching ideal) and adding ...
- Thu Oct 10, 2002 10:00 am
- Forum: General Discussion
- Topic: PIC/Stamp Microcontroler Where to Start
- Replies: 9
- Views: 5933
Re: PIC/Stamp Microcontroler Where to Start
I started out with Microchip's PicStart programmer, and it works rather well for assembly projects. I've done a fair amount of programming (20 or 30 projects each) in c and assembly on the PIC, and have found that Microchip's dev tools are somewhat unstable at times and that the chips aren't as powe...
- Thu Oct 10, 2002 9:37 am
- Forum: General Discussion
- Topic: Relay for water cool system
- Replies: 4
- Views: 3147
Re: Relay for water cool system
You could build a board with a microController to PWM some SCRs. This would allow the board to vary the power without dissipating a plethora of heat.
- Thu Oct 10, 2002 9:25 am
- Forum: General Discussion
- Topic: Voice Recognition
- Replies: 8
- Views: 4619
Re: Voice Recognition
I'm believe that most of the successful voice recognition software uses a time-domain analysis.<p>For an example of a cheap boars that recognizes a few commands, goto...<p>SensoryInc.com
- Sat Oct 05, 2002 10:51 pm
- Forum: General Discussion
- Topic: diode
- Replies: 19
- Views: 8674
Re: diode
Tunnel diodes have a operating region in which the device exhibits a negative resistance.<p>The first radio transmitters were operated without the use of a three terminal device. The US military even used 1 MegaWatt transmitters before the invention of the vacuum tube. This was made possible by the ...
- Tue Sep 24, 2002 7:37 pm
- Forum: General Discussion
- Topic: New style 3rd brake light
- Replies: 4
- Views: 2836
Re: New style 3rd brake light
Just to throw it in there... MOSFET switches are cheaper and more effective than big BJTs for simple on-off, low-speed switching.<p>As an example, for $2.52 in quantities of (1), the IRF1404 from International Rectifier has an on resistance of 0.007 Ohms max at 160dC. Therefore, at 100A, there is a ...
- Sun Sep 08, 2002 11:15 pm
- Forum: General Discussion
- Topic: Defining a cathode
- Replies: 7
- Views: 4360
Re: Defining a cathode
Jeeves told me:<p> cathode 1 : the electrode of an electrochemical cell at which reduction occurs: a : the negative terminal of an electrolytic cell b : the positive terminal of a galvanic cell<p> IversonSoftware.com told me:<p> Electrolytic cell , an apparatus in which chemical change is caused to ...
- Sun Aug 25, 2002 11:03 am
- Forum: General Discussion
- Topic: Switch debouncing
- Replies: 9
- Views: 4663
Re: Switch debouncing
the lowpass filter is proned to making the problem worse... The lowpass makes the signal rise and fall more slowly, keeping the signal around the switching point for a longer period. any spike or noise that occurs around this region can cause another trigger.<p>The simplest scheme is a pair of inver...