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EdwardM

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Everything posted by EdwardM

  1. Hi Ante the music was brilliant, why improve on perfection? ;D Great New Year to you too Ed
  2. Hi All a few days ago one of our contributors came up with this web site http://www.ebaumsworld.com/videos/xmaslights.html and my wife and I were blown away by the sound/light. I'm thinking of doing something similar/different during this year - does anyone have experience of this sort of thing, ie, is it likely to be something like DMX512 or a dedicated matrix or whatever? All contributions gratefully received Happy New Year Ed
  3. Hi Audioguru sorry, I just had to say it... You're the LEaDing LIGHT Happy New Year Ed
  4. Hi Bedri try a google search for TEMPEST. All electronic equipment radiates energy in some way and with a sufficiently sensitive receiver these signals can be picked up. For example, a computer monitor receives signals across a screened cable - the screening is not perfect and you can get radiation in the low short wave band. Internally, the monitor, if it's a CRT, generates a very high voltage which is modulated by the information displayed on the screen, so it's theoretically possible to snoop on what is being displayed. Whilst I don't have any hands-on knowledge of the equipment or techniques involved, I do know that in many government/military systems there are TEMPEST requirements which need to be satisfied. Apart from that, it's very unlikely that your neighbours would have the resources or equipment necessary to see what you have done with your computer. Ed
  5. Hi Logitec I don't know of a linear regulator chip (like the 7805) which will do as you require with an input which is only 0.4V above the required regulated voltage and that's why I gave the answer that I did, I know that manufacturers are continually improving their products and what you need may be available real soon - but I haven't seen it ??? Ed
  6. Hi Logitec 3.6V @ 10A IS 36W. If your converter is, say, 80% efficient, this means that the input power is 10/8*36 = 45W. Therefore the input current at 4V would be 11.25A, if this amount of current is available then you will need to design a DC-DC converter to do the task. This means learning about a number of things and experimenting as well. Learning about inductance, rate of rise of current in an inductance, properties of transistors used as a high current switch and a host of other things. However, the effort is worth it and one of the best introductions to the subject that I know of are the applications notes of the various manufacturers who produce DC-DC converters. Best of Luck Ed
  7. Hi Ben the fact that your circuit works happily with batteries means that there is nothing wrong with it. I suspect that the transformer/adaptor connected to the AC line is not capable of supplying the current needed to drive the speaker at a sensible volume. A couple of things to try... Use a (preferably analogue) multimeter in series with the batteries to measure current or - If you can borrow/obtain a power supply which has a current and voltage readout, you can verify how much current is needed at 12V, you will then be able to say if the adaptor is 'man-enough' to work. Hope that helps Ed
  8. Hi an even simpler way of doing it... It requires the student to start a stop-watch at the beginning of the test and at every 5 minutes to record current and voltage in her notebook - no hi tech required ;D Best of Luck Ed
  9. Hi Wesley seems to me that one solution is to buy or build a simple data logger, I've used PICOscope in the past which is essentially an analogue to digital converter(ADC) and will in conjuction with some PC software produce a graph of some quantity(current, voltage, pressure etc) against time. You could also design your own based on a PIC or other microcontroller which could use its own display of time or be connected to a PC. For myself, provided there are no constraints in using a PC for the project, I'd use a low cost PIC with built-in ADC and make an RS232 link to a PC - the PC can then provide, using Visual Basic or other programming language, real time displays of current and voltage as well as showing a graph of load current against time. Hope this helps (Bearing in mind that in the UK, we know not of these 7th grades or otherwise or the age of the student ;D) Ed
  10. Hi if your multimeter has typically a 100uA meter movement for full scale, this means that at each of the ranges you mention, 10V, 2.5V and 0.5V there will be a resistance in series with the meter of 100KOhms, 25KOhms and 5KOhms - representing a varying load on the AA battery that you are measuring. It's unlikely that three independent ranges would be faulty (the only realistic common factor being the meter movement) so, the most reasonable explanation to me would be that your are measuring a dead battery which has insufficient current capacity to move the meter. Try measuring a new battery, which should give a reading of about 1.5V~1.6V. You could also try measuring the voltage across a forward biased diode (0.6V~0.7V). Hope that helps Ed
  11. Whoa, I'm not given to sarcasm - honest! ??? What I meant was that no matter how much you pay for a system which produces code for you, unless you understand and can verify its operation you can never be sure that it truly 'works'. Also, I was being honest about aircraft software, that's what I currently do - verify software used on fighter aircraft, including PIC based and ST10. Have a Nice Day Ed
  12. Hi At $690US, I'd expect it to control every available PIC. As a lazy programmer, I'd like to find find a system which would allow me to control the world with a minimal number of keystrokes, however, I've haven't found one - so I'll have to go back to work next week and carry on preventing aircraft falling out of the sky because of a bug in the code Have Fun Ed
  13. Hi All relative to 7805's and such like - by the time a fresh 9v battery drops below the voltage necessary to sustain a 5v output, you will be long since bored by a single LED flashing around a loop and probably moved on to several (hundred?) in sequence. Belated Merry Christmas Ed
  14. Hi Joseph "Gray codes are named after the Frank Gray who patented their use for shaft encoders in 1953" "A Gray code represents each number in the sequence of integers {0...2^N-1} as a binary string of length N in an order such that adjacent integers have Gray code representations that differ in only one bit position. Marching through the integer sequence therefore requires flipping just one bit at a time. Some call this defining property of Gray codes the "adjacency property". The above I've taken from http://cafaq.com/extra/gray.html one of the many web sites which refer to Gray codes. The most important thing about Gray codes is the fact that each angular(or linear or whatever) transition causes a change in only one bit of output. To put this in context, imagine an angle encoder system which had 10 fingers making contact with concentric copper pads and was a binary representation of angle and further that it had been calibrated in the laboratory to be perfect at 20 degrees Centigrade. So, rotating from say an angle of 15 deg (1111) to 16 deg (10000) means 5 fingers (in this example) must transition perfectly at the same time and that there must be an infinitely small gap between tracks. Imagine what happens at other temperatures? What happens when the gap in a track is not infinitely small? There are a number of angular encoding systems used in radar, not all based on Gray code - could you give some more detail? Ed
  15. Hi Saadmir the 4009 allows you to do level shifting, for example driving TTL logic from a CMOS source. The supply voltage, Vdd has a range of +3 to +20v and Vcc, whilst the datasheet doesn't say, should have the same range. In a level shifting application, Vdd would be set for the input (source range)voltage. (If you were using 15v cmos, then Vdd would be set to 15v). If you want to then drive TTL from the 4009 then Vcc would be set to 5v. Hope that helps Ed Go to http://www.jaycar.com.au/semiconductor.asp for the data sheet
  16. Hi MikeB Take a 4.7Kohm resistor from +5v and connect it to the input. Connect a switch between input and ground. This circuit will count every time there is a transition from high to low voltage on the input pin. The first thing you may notice is that each time you hit the switch and expect an increase of 1 in the displayed count, you get several counts - this is switch bounce and can't be avoided unless you add a debounce circuit first. There are also many other kinds of input that you can use which don't suffer the bounce problem to the same extent, for example, optical or magnetic switches. Hope this helps Ed
  17. Hi reference the relay switching rates, I once designed a system to play a sound organ and it used relays to fire each note, as I remember the switching time was in the order of 10-20ms, you just need search almost any electronic suppliers parts pages to get the details Ed
  18. Thanks MP that's exactly what I was suggesting but in reading over what I've posted, it does need more detail. However I did take econs' question literally and pointed to one possible way to solve the problem. Ed
  19. Hi econ there is an excellent introduction to opamps, particularly chapter 4, which will help to solve your problem Best of Luck Ed http://homepage.mac.com/tbitson/weather/TI_OpAmp_Tutorial.pdf
  20. Hi Scott start small and build up to it... the previous post will get you initially 4 bits, building up from there (16 possibilities and beyond) There are things like the 8255 chip which will expand an 8 bit interface. Lots of PICs allow multiple I/O ports which can then be used to drive the outside world. There are many processors like the ST10 range which, if memory serves me correctly, will drive directly 114 I/O ports. There are also 8035/8041 derivatives with different ranges of I/O. I know it's not easy but you have to try to define your requirement and then work backwards to try to find a minimal/low cost solution whicih will satisfy the original problem Best of Luck Ed
  21. Hi jonny your requirement should be fairly easy to satisfy... It can be done in a number of ways, for example, a microprocessor (PIC or other) can with suitable circuitry, detect the presence of master power and illuminate a green LED, likewise it can detect the presence of current in the heating coils and light a red LED and when that current disappears, illuminate the yellow LED for any given time, it isn't difficult to do if you have the right equipment. I don't know where you are geographically but I would have thought that this is the kind of project that a local high school or college may find interesting for its students Best of luck Ed
  22. Hi Alun I almost feel a competition coming on, how few components are absolutely necessary for a VCD? Ed ;D
  23. Hi cyw1984 first thoughts: I presume you don't want to send all 3000 at once to the 8051 but just a current value? You could do something like... Public Sub Send5Chars(Value as string) 'The 5 characters have been previously made into a string which looks like "nnnn" MSComm1.Output = Left(Value,1) MSComm1.Output = Left(Value,2) MSComm1.Output = "." MSComm1.Output = Left(Value,3) MSComm1.Output = Left(Value,4) End Sub ...and would be invoked like this: Send5Chars "0123" Does that help? Best of Luck Ed
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