audioguru

Fudy, You want to make a TV transmitter? It is very complicated (vestigual sideband, video and audio carriers with colour and stereo sidebands, sync, etc.) and is probably illegal without having a broadcaster's license. The Guru has spoken.

Fahad, Don't wind the transformer windings with your hand, or the wire will get twisted. Just spin the ferrite like a winch, and let the roll of wire also spin.

InFLak, Do you want to fix the broken mister by making your own circuit to replace its "cement thing"? The piezo certainly doesn't work at 1.7MHz, so the cement probably has a digital frequency divider inside. The little piezo will have a very low efficiency at only 340Hz, and its buzz would be annoying, so please check again its frequency on your working unit. The frequency is probably 25KHz to 45KHz. The BU406 is just a high-voltage output amplifier.

Stuee, Two LM3886 amp chips can be bridged to drive an 8 ohm load. It will current and SOA limit if it was bridge-driving a 4 ohm load. Most car speakers are 4 ohms, so this application is not suitable for a car amp. Besides, a car amp is lucky to provide at most 20W of real RMS, low distortion and wideband power when bridged into a 4 ohm load, without using a step-up supply voltage converter that all the big car amps use. When bridged and driving 136W into an 8 ohm load, the LM3886s use a supply voltage of 56V, but when bridged can use a single-ended supply without using output capacitors. Hotwaterwizard, Bridged amps produce only slightly more distortion. The only difference is that the amp's output current is doubled, since an 8 ohm load "appears" to be 4 ohms to each amp in the bridge. See on the data sheet where typically 0.002 percent distortion at 8 ohms rises to only about 0.004 percent at 4 ohms, at 1KHz when using +, - 28V supply. Sure, the distortion doubles, but look how low those numbers are.

Yes, Ante. This is my 1st and only computer, and it is a 486DX/100. I upgraded to the last 486 chip that Intel made, with Pentium features such as bigger L1 cache memory. The CPU chip and its 5V to 3.3V regulator are fitted to a daughter board that is the same size as an older 486 DIL chip. My computer doesn't even have any L2 cache memory. My Compaq computer is all-in-one, like a Mac, so I couldn't upgrade the motherboard. My cable ISP has announced "Extreme Hi-speed" at 5MB/sec., but I'm happy (except for jerky video) with my 486 and its 1MB/sec download speed.

MP, I have heard that Win98, 2nd edition, would eat my 2G hard-drive (with many files) for lunch and again for dinner.

To All, Didn't anyone notice? The oscillator's frequency CANNOT increase when the soil's resistance also increases, as my idea requires: So I'll try the original circuit with an added delay capacitor and a new 74HC132 to replace the old 4093. I'll report my findings.

Greenpogo, Doesn't a leyden jar and any other capacitor charge with Direct Current? Your neon transformer produces Alternating Current. To convert the AC to DC use the high-voltage rectifier from a colour TV. Your film container may not have enough insulation to hold a charge. The film manufacturer may use an anti-static ingredient (conductive agent) in the plastic, in order to avoid static sparks (from the film sliding around) from ruining the film. A plasic container company once demonstrated the difference of their anti-static containers to the ordinary containers from their competitors. After only 1 week sitting on a shelf, the anti-static ones were much cleaner. The ordinary containers attracted dust like a magnet to iron. The ordinary ones would make a good leyden jar.

Ante, A triangle wave can be extremely linear if you use an integrator that is made from an opamp that has a voltage-gain of 100,000 or more, and use a low frequency. Of course the linearity drops at higher frequencies. Gross linearity error can be seen as a departure from a straight line on a scope.

ZomBiE, The LM3886 can be bridged to give typically 136W of low-distortion wide-band power into 8 ohms. You should build it, layout a PCB and post it in our projects section. Do you have access to a low-distortion generator and distortion analyser? It will be important for you to analyse the amplifier's results since its PCB layout is an art at keeping the high currents from interfering with its inputs.

Hi Zia, welcome to our forum. About this power supply: 1) We have already determined that the transformer's 3A rating is too low because the output of the power supply is 90VA (30V X 3A). If you use a much higher current rated transformer, then its voltage won't sag as much during rectifier conduction, and its voltage won't rise as much with no load. Maybe a 5A rating is good. 2) I don't remember if the heatsink problem with the little 2N2219 was discussed, but I agree with you that a T0-220 would be much better. 3) We also determined that using a higher current bridge rectifier instead of those little diodes will reduce losses and allow for a heatsink. 4) We have had many suggestions for the size of the filter capacitor. In order to reduce loss due to ripple voltage, make it really large, such as 10,000uF. 5) As you have read here, the minimum and maximum voltages at the filter capacitor are crutial: a) A minimum voltage of at least 33.9V when the project has a 30V, 3A load. b) A maximum voltage of less than 36.4V when the project has no load, when using the 44V replacement opamp. If you include a 10% mains voltage variation then these voltages are impossible. Perhaps this project should be rated to only 25V output, and when using changes as above should perform very well with a 24V/4A or 5A transformer.

Thanks, MP. Microsoft won't let my old browser into there either, "Connection with server cannot be established". This minor problem is the only one that I have had. My wife says that an occasional contest URL won't let her in. I have heard that newer browsers are resource-hogs and eat hard-drive space. Therefore the browser on my 486 will remain as it is.

Ante, Ha, Ha, and S-O-S to you too.

Kevin, Thank-you for correcting me. I am sorry that I got the sequence wrong. A good description of RMS, simple meters and true-RMS meters is here: http://www.ee.unb.ca/tervo/ee2791/vrms.htm

Too many choices. MP, Which alphabet Font setting is your OE using on your Win98?

MP, Thanks for the suggestion but Microsoft won't let me in because their "update" URL responds only to browsers using IE5.5 and up, which I don't have. They want me to BUY an update. I think that I am on the right track: I just changed the alphabet in my OE font settings to "universal" from its previous "western", and now my e-mail notifies look the same but send me to the Community Index page instead of previously the Catagory Index page (which now is even worse). Now I have many more alphabet settings to try. Hey Mixos, One of those alphabet settings is GREEK! Should I try it first?

To All, How come, OOOps, why is it that Cdak's professional and even his own graphs show a heartbeat with a low frequency vibration? If a heart beated with those vibrations then I think that its owner wouldn't be alive for very long. Is it the skin under the stethoscope head that is vibrating? Is it the electret mic's diaphragm? I doubt it. Is it the preamp almost motorboating? Is it the low-pass filter ringing? Has anyone seen a live heartbeat scope? (Never mind those simulated ones on TV)

Thanks, Guys. Another improvement: A bi-colour LED that flashes Green when the soil is not too dry, and flashes quickly Red when the soil is very dry.

Cdak, The electret microphone preamp circuits that I build don't pick-up hum, so why does yours? No shielded cable?

To All, I was going to build a bunch of these cheap circuits (with my improvements), but now I realise that LED brightening (dimming in reverse) is a lousy way to indicate soil dryness, as i explained earlier (and now I have an even better idea): I am certainly not going to use a complicated display circuit for a dumb plant! My new idea is to have a flashing LED indicate soil dryness. When the soil is wet then the LED is off. As the soil dries, the LED begins flashing slowly. As the soil dries even more then the flashing-rate increases. When the soil is very dry then the flashing-rate will be so fast that the LED will appear to be on steadily. The circuit will be simple and cheap (1 CMOS IC, a couple of resistors and capacitors). The flashing will keep the average current drain low, for long battery (2-3V) life. The probes will have AC across them, preventing plating-action and corrosion. It will not cause arguments about how it works. The circuit WILL work. I could use a bunch of these. Any comments?

Mixos, Yes, I see that all other forum replies that work OK for me do not use a semi-colon (;) in their notify URL. Maybe my e-mail client does not know your font, I see that the "dot" of the semi-colon looks to be very high. If you can't fix it then maybe it is time for me to upgrade my Win98, but Microsoft won't let me in because my browser (IE 4.01) is too old. New computer? Yeah, maybe in 10 years when my new bios/clock battery dies (I haven't replaced its original 10-years-old one yet).

Mixos, I got this error about 1 minute ago: Warning: file(): php_network_getaddresses: getaddrinfo failed: Temporary failure in name resolution in /home/electronics-lab.com/www/footer/linkman_0.php on line 30 Warning: file(http://www.electronics-lab.com/footer/linkman_0.php?mode=links): failed to open stream: Resource temporarily unavailable in /home/electronics-lab.com/www/footer/linkman_0.php on line 30 Warning: join(): Bad arguments. in /home/electronics-lab.com/www/footer/linkman_0.php on line 30

Kevin, Are you talking about a True-RMS meter that uses a special chip to do the mathematical function, or a simple meter that average or peak rectifies the signal, and assumes that it is a pure sine wave during its adjustment calibration? The simple meter does not remove the DC, its input capacitor blocks any input DC. Its recifier converts the AC to its equivalent DC for it to measure. The True-RMS mathematical chip does not change the wave by converting it into a square wave. It mathematically multiplies the number by itself. This mathematical function does not occur first, but last. First, the average is mathematically square-rooted, then integrated, then squared.

Siddharth, A photo transistor, and even a photo-darlington transistor, do not have enough output current to power an incandescent light bulb. The regulator in your circuit does not boost the current. That is good that your emitter-follower/regulator circuit works well. If you provide an input voltage that is 0.7V more than is required by the light bulb, then you don't need the regulator. Just connect the light bulb to the emitter and to ground. A cold lightbulb draws up to 10 times the current than when it is lighted, so select a transistor that is rated for that much current.

Kurt, For what is it that you need to shift the phase, audio? or video? Over what frequency range, telephone quality? or CD quality? For video, VHS quality? or DVD quality? What are you making? A quadrature modulator? Please provide as much information as you can, so that we can help you better.