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# Fowkc

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1. ## RC Circuit (How?)

Clarify what's happening here... in the first diagram, pin 4 is normally closed. In the second, it's normally open... You'll have to experiment to see what voltage your relay turns off at. I'm not sure how your second circuit is meant to work, but I can see the principle (using a capacitor to keep the relay on). Assume the capacitor starts charged at 12V, work out how the voltage on the capacitor changes with time, then use that equation to get the capacitance you need for a 1s pulse.
2. ## Reading Pulse signal from a flow meter

There are a number of PCI and USB based dataloggers/oscilloscopes avaliable for the PC. Any number of these would work, but they're quite expensive and perhaps a bit over-the-top for pulse counting. Google "PC datalogger" or something like it.
3. ## Lets make our printer wireless !

I have considered this in the past. Using IR is interesting, but probably quite complicated. To get full functionality, you'll need to buffer whatever data the computer sends, send it one bit at a time via IR, plus any status bits. You'll then need to re-compile those bits into a parallel stream and send it to the printer, at the same time dealing with any stauts bits the printer can output. I'd say it's more than possible, but the IR bit is probably quite simple compared to getting the data conversions done.
4. ## Protecting the motor

The device you use will be put in series with the motor. When the motor is stopped/stalled, the current through it will increase. So your polyswitch or current limiting circuitry will trip the circuit if the currnet rises too high.
5. ## free energy motor

Anyone else reminded of "all your base are belong to us?" Sarcasm aside, I have not seen one overunity site that actually describes HOW the thing is meant to work. There are very vague allusions to bits of particle theory, mostly virtual particles that are somehow tapped by this carefully timed motor. Most of the sites do not have a single equation in their desciption that might shed some light on the mechanisms behind the operation of overunity devices. However, most sites DO say something like "overunity devices have been around for years!" Funny then, that not one single commercial product has been sold. Lots of patents issued, but no products sold. Could it be that on close inspection, they don't actually work? I know I'd like to buy a device that meant would never have to pay energy bills ever again...
6. ## free energy motor

So, if we accept the rather dubious premise of "phi-flux", how does the circuit harness this energy? You mention timing circuits, but it's all a bit vague. For instance, you say there is "no Lenz law". Normally all the components in the circuit you posted obey all Maxwells equations. What is special about the configuration here?
7. ## Numeric counter displayed in 7-segment LED

Those are the ICs you need, so it's just a matter of wiring them up correctly: http://www.aaroncake.net/circuits/counter.htm Make sure your seven segment display is a common anode type if you're using this circuit. If not, either find a common anode type, or swap the 7447 for a 4511
8. ## Help! Connecting power supply to small load/solenoid

A solenoid is not really a "short circuit" in the normal sense of the word. If you drew out the wires in a solenoid or inductor, the behaviour would be of a normal piece of wire. The coiling up of the wires means that the coil creates a magnetic field inside it. This magnetic field in turn sets up a voltage across the solenoid which will oppose the applied voltage. The measurement of the resistance of a solenoid (as far as I know), is not a very good indicator of the current it will draw, as the behavior is dependant on that current. Think about a transformer winding: low resistance, but the behaviour when a voltage is applied is very different from a resistor of the same value.
9. ## free energy motor

So what is the motor powered by? What are the physical principles behind the motor turning? I think we're all a bit confused.
10. ## PCB Etching Tank - Do it yourself

I already etch lots of one off boards, current process is printing onto tracing paper, UV exposure, develop and etch in a plastic tray. This would be fine if I didn't share a house with four other guys. If it could go a bit quicker and be a bit more "self-contained", I'd get in the way less. Thanks for all the help, sorry I was a bit insistent. I was sure it would work, I just like to understand why.
11. ## PCB Etching Tank - Do it yourself

I haven't actually bought anything yet, I'm collecting information. I'll only be etching one-off boards, so I won't have a lot of etchant to heat. I'm still not sure about this, you say: Well "top-of-the-scale" for the aquarium heaters I've seen is about 32C. Presumably you get your etchant hotter than that, so how do you do it? Do your heaters go higher than that temperature, or is it a result of heating much less liquid that they were actually designed to heat?
12. ## PCB Etching Tank - Do it yourself

OK, what sort of wattage heater should I be looking at then? It seems to be the case that a more powerful heater is meant to heat a larger volume of water (i.e. larger fish tank) to the same temperature (about 32C), rather than actually increase the temperature any further and kill your fish. I can see how a more powerful heater would pump out more heat initially and then pretty quickly turn itself off as the etchant reached temperature, but it would still try and keep the temperature at about 32C. Obviously I'm mistaken, since lots of people have done it and it works, but I'd like to understand why...
13. ## NEED HELP IN A BAD WAY.... LED PROJECT

Hmmm... can't remember how I got round that... perhaps it wasn't an issue, not sure - it was a good few years ago! But there must be a way around that problem. The last 4017 output could be used to turn on a PNP transistor to switch the SCR power on. When that output goes high, the transistors turn off and the SCRs reset. Again, it's not elegant (you only get 9 outputs), but it probably works.
14. ## PCB Etching Tank - Do it yourself

I keep meaning to build myself an etch tank, but one thing eludes me: People use aquarium heaters to heat the etchant, but all the aquarium heaters I've seen have a built-in thermostat that keeps the water at a maximum of about 32C, about 10-15 degrees too cool. How do you get around this, or is there something that I'm missing?
15. ## NEED HELP IN A BAD WAY.... LED PROJECT

Sounds similar to a project I did for GCSE. I had the 555 clock a 4017 decade counter. Each output was connected to a thyristor that turned an LED on. Thus after 10 pulses, all the LEDs were on. It's not the ideal solution, because it requires 10 discrete thyristors, but it worked.
16. ## Fiber Optics

What sort of project are you looking to do? Fibre optics is just a way of carrying information, so the possibilities are endless really. You could try and build something that transmits music from your stereo to another room in your house, for example. Or you could try and send information down a fibreoptic cable from your computer. Telephone signals are carried by fibreoptics over long distances, so a telephone that used a fibreoptic cable instead of a normal copper wire lead would be pretty cool. A bit pointless, but cool. Is the project for any particular purpose (school, college?) or are you just looking to have fun?
17. ## smps modification

You might want to look at the "5v to 3.3v" thread near this one. Basically deals with the same problem, but you'll need to account for the increased current your converter will be carrying.
18. ## 3 Legged 5600uf cap

Type "three terminal capacitor" into Google and a lot of pages come up. Looks like they're designed to conteract the inductance of the leads to lower the ESR. Or something like that, I'm no engineer. ::)
19. ## Mp3 Player

There are interfaces for microcontrollers (via SPI, I2C) that will allow communication to/from USB devices or memory cards, but I'm not sure if they'll cope with the data rate needed to play MP3s. For instance: http://www.silabs.com/tgwWebApp/public/web_content/products/Microcontrollers/USB/en/USB_MS_RD.htm
20. ## Microphone Switch

Most switches activated by sound that I've come across use a circuit similar to this one: http://www.fowkc.com/elec/clapper.shtml That's electrect mic --> amplifier --> input to logic / microcontroller. Mine works, but I'm sure it's not perfect.
21. ## Voice recognition system

Do you mean an ADC (analog-digital), not DAC (digital-analog)? That is, to take the analog waveform from the voice and convert it to a binary number, then send that to Simulink for analysis? I've never done voice recognition, but I imagine you'll need a high quality microphone, followed by a low noise amplifier, followed by a high speed ADC chip. From there, you'll need to get the digital data back to MATLAB. Does your PC have any kind of data capture card? I've used MATLAB extensively, but only with NiDAQ capture cards and a Textronix digital scope. I don't know about getting data to a PC without a capture card or other suitable interface. Of course, another options would be to plug a microphone into your sound card, capture .WAV files, and use MALTAB to analyse those!
22. ## Rocket Staging Circuit

Yep, that'll be your basic Estes igniter. I haven't done model rocketry for a number of years, but I recall that Estes igniters needed a lot more power to ignite compared to electric matches. That was probably intentional, as Estes stuff is used by people new to the hobby. If they're harder to ignite, less chance someone will launch a rocket up their nostrils (or something equally painful).
23. ## Rocket Staging Circuit

Not to start an argument, but I wouldn't attempt making my own igniters unless I knew exactly what I was doing. Anything you tried to bodge together by scraping, filing and gluing is liekly to be a)more dangerous and b)less reliable than anything you'll buy. Try getting some igniters that use less current. I'm guessing you're using Estes igniters? Switch to electric matches. At least one website I found claims to have some which will ignite consistently at 1.5v with 0.5A: http://www.firefox-fx.com/kits.htm
24. ## Rocket Staging Circuit

Or going the other way, you could use a couple of 1F 'supercaps', designed for memory retention. Let's assume you have three supercaps in series (assume each has a voltage rating of 5V), to give .333F. Charged to 12 volts, that's 4C of charge. Now take your igniter, which has a resistance of around 4ohms. Attaching the charged supercaps will produce a current of 3A initially, dropping exponentially to 1.5A after 1s. That would probably do it, but I'm not sure that the supercaps will like a 3A current draw!
25. ## Problems with my 555 circuit

If the capacitor is indeed the issue, agreed. Try changing the resistor values instead. In general in a 555 circuit, you should keep capacitor values small and resistor values high, within reason. Or that's what I've come to believe.
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