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  1. Bose: The buzz sound that you heard was caused from not using a large enough transformer. Freerider: There are much better inverter designs on the web, which will give you much better satisfaction. I would rate this project as a learning project for basic inverter design. Years ago, Delco introduced a very similar design to this one in the US which was mounted on the inner fender well of your car and gave you 120VAC to run appliances from your car. These were also very primitive and barely useful. However, they did sell a lot of them. MP
  2. Please do not post IC requests to the Projects Q/A forum. It is for discussion of projects found on our site. I have moved this topic to the correct forum. MP
  3. You won't get much resolution without specialized chips. Here is an article about a simple form of audio delay using 1 bit ADC. Perhaps this will help. http://www.elecdesign.com/Articles/Index.cfm?AD=1&ArticleID=8056 MP
  4. An LM7805 will work fine in your automotive application. You could also use a LM78L05 which has a smaller package. You will certainly need the capacitors on input and output. For the input, it depends on how clean the DC12 is. I have never seen a car generate a real clean DC voltage, so I would recommend that you go with a fairly large value on the input. On the output, you will want a 0.1 uf in parallel with a larger value such as 10 uf, both bypassed to ground. If you don't have a 10 uf, use anything from 4.7 to 100 uf. This is not a critical application and you have a lot of latitude to play with here. For your application, I doubt that you will see any difference. Also, I don't mean to change your thoughts on the design, but if you are only using the voltage as a trigger, you could also use a comparator chip to do this. MP
  5. TJ, Correct on both questions. I recommend that you stay under 5 mA. I normally use 5V through a 4K7 ohm resistor as a parallel port pin high. For best results you do not want to float the pin in any state. You should insure it always has a 0V or 5V level by tying the port pin high or low. Otherwise it might float into an unstable voltage and report incorrectly. Additonal note: The car battery is not a true 12 volt source. Rarely will you see a good automotive battery read 12 volts. It is usually closer to 14. You want to make sure you do not exceed the 5 volts to the parallel port. Add a zener diode for protection if needed or use a 5 volt regulator. An opto-coupler would also be an alternative. Exceeding 5 volts to the parallel port could damage it. MP
  6. When you use your resistive divider to drop the voltage down to 5 volts, you just need to select values of resistors to limit the current. This is basic ohm's law. V/R. Was this your question or did I misunderstand? I am not sure how you intend to monitor status by using one 5 volt pin. As an interface to the parallel port, you could use an LM3914. This would give you the resolution you need. There are also many other ways to proceed. You need to convert from analog to digital to read anything useful from the parallel port. MP
  7. Jack, Everyone gives away the assembly code programming compilers. There are also many free C compilers, but they are very specific to the brand of chip you use. For example, you would need a different compiler for PIC than you would need for AVR if you write in C. Actually, you would use different instructions in asm, too. The reason is that the different micros have different instruction sets and different hardware, etc. The micro manufacturers seem to cater to different parts of the world. AVR is easy to get samples in the US whereas it is hard to get free samples in some other Countries where PIC is easier to get for free. Just go their websites and ask. If you can get free samples, they will put a distributor in touch with you. MP
  8. Just use R2R ladder and an output buffer or op-amp. MP
  9. You don't need a programming board for Atmel AVR. Just make a programming cable and use one of the free C compilers found on the web. MP
  10. Topic moved. Posted in wrong forum. Projects Q/A is reserved for discussion of projects in this site's project section. MP
  11. Here is a digital volume control from our site: http://www.electronics-lab.com/projects/audio/010/index.html You can also see other projects from this site by pressing the blue link at the top of the page titled "Projects" MP
  12. Please post a drawing of your setup. Are you trying to power the motors directly from the output port? If so, you need to compare the current rating of the motor with what the PIC can provide. Did you mean you have an LED in series with the motor, drawing away some of the very little power provided by the output port? Try removing the LEDs. A transistor on the PIC output port pin is usually required, depending upon the motor. If removing the LEDs does not help, you need to add a transistor. Of course, this is all without seeing your schematic. There might be other reasons in play. MP
  13. Your LEDs are pulling too much curent for this little transistor. Since we do not know the built in resistor value and the specs on these LEDs it will require a little research and calculation of your own. If you do not have this information, you can remove the LEDs one at a time on your bench to see how many you can actually fuel from this circuit. As mentioned above, do not be surprised if you have burned out the transistor and need to replace it. I think your L272 op-amp combination is ok since you have tested it to work with only one LED. Basically, you are drawing too much current with the added load of more LEDs. Remember that even though they will all take the same voltage, you need to add up the current used in all the branches of your circuit. In this case, you have several branches where the original circuit had only one. You can either re-design this circuit or you can eliminate some LEDs and build more than one of these circuits to sit side by side when you determine how many of your LEDs it will actually power. MP
  14. For this distance I would recommend a power amp as audioguru has suggested and I recommend a horn instead of a speaker. MP
  15. How many stations or momentary push buttons are needed? How much voltage and current being switched? MP
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