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  1. KrisBlueNZ

    microprocessor types

    In addition to what Steve said: These forums are here so that people can get advice and guidance from others with more experience and more detailed knowledge on specific topics. We are all volunteers here, and we contribute because we like to use our experience to advise less-experienced...
  2. KrisBlueNZ

    Car sound system conversion to home use.

    You don't need any diodes - there is only one power supply (assuming you buy the eBay one you linked to - it looks pretty good). Just connect the power supply positive to a bank of fuses, one for each bit of equipment, and common the negatives together. Use HEAVY and short wires everywhere! It...
  3. KrisBlueNZ

    Multiplying Voltages?

    As usual, describe your application. As usual, Google is your friend.
  4. KrisBlueNZ

    TDA2030A Headphone Amp Gain too high

    You can just put a passive attenuator (two-resistor voltage divider) on the input. But I definitely would not drive headphones directly from a high-power amp. A fault could easily destroy them, and my headphones are not cheap. Also the background noise, which would be inaudible from a speaker...
  5. KrisBlueNZ

    30v DC to 27v DC

    You want to drop 30V DC down to 27V DC with a load of 6 amps? A few diodes in series are a simple option. Go to Digikey's parametric selection system: http://www.digikey.com/product-search/en/discrete-semiconductor-products/diodes-rectifiers-single Check the "In stock" box. In the "Current -...
  6. KrisBlueNZ

    dark activated circuit lamp

    I drew up a circuit for a dark-activated motor here: https://www.electronicspoint.com/question-mosfet-t258206.html#post1536817. The diode isn't needed because a light bulb is not an inductive load. You can replace the motor with a light bulb. As duke37 says, you need to keep the LDR away from...
  7. KrisBlueNZ

    Design question on microcontroller and TIP122

    I just noticed that you're using an 8051 to drive the MOSFET gate. The 8051 port architecture is unusual; it's called "quasi-bidirectional" and the pin pulls up only weakly. (It pulls down strongly.) This means there's no problem with clamping the gate voltage to one diode drop above 4V, so you...
  8. KrisBlueNZ

    Help to build a device to revolutionise an industry

    I've found that an inability to express oneself clearly and accurately is often, but not always, a sign of an inability (or sometimes a disinclination) to think clearly and accurately. Conversely, clear writing explicitly demonstrates this ability and inclination. An inability to think clearly...
  9. KrisBlueNZ

    Current limiter add on

    Hmmm. AA Portable Power Corporation of China. Well, the data sheet does clearly make that claim - for the first three charge/discharge cycles, at least. And it even mentions one international standard. And they're pretty cheap - USD 54 for eight! I guess it's possible...
  10. KrisBlueNZ

    bi directional communication to multiple nodes over 1 wire

    Well, you're the expert :-/ The TDA5051A doesn't limit itself to zero-crossings. That's why I expect it will have a much higher bit-error rate than the X10 method. I think you would need to use a protocol with strong error detection and retries, or forward error correction.
  11. KrisBlueNZ

    bi directional communication to multiple nodes over 1 wire

    I don't know. I don't have any experience with sending data over power lines. I found the TDA5051A with a parametric search on Digikey for power-line carrier modems - it's the only one they stock. The TDA5051A looks good, but any system that sends data over power lines needs a robust protocol...
  12. KrisBlueNZ

    Design question on microcontroller and TIP122

    Because a battery's terminal voltage drops as it discharges, and will also drop temporarily during times of heavy load because of the battery's internal resistance. Assuming you want the circuit to work up until the point where the battery is practically flat, you need to design it using the...
  13. KrisBlueNZ

    Programming cameras to detect patterns

    Well, if a team of experienced programmers at Apple can do it, someone with no prior exposure to image processing should be able to whip something up, no trouble, right? ;-)
  14. KrisBlueNZ

    Current limiter add on

    Really? What brand claims 10 Ah for a D cell? Do you have a link to a data sheet?
  15. KrisBlueNZ

    Design question on microcontroller and TIP122

    No, that's right. The issue is the amount of voltage it will drop. If your peak current is say 1.5A and Rds(on) is 0.070 ohms, the voltage drop (calculated using Ohm's Law: V = I R) is 0.135 volts. This probably isn't a problem, but you could definitely improve on that voltage drop. You will...
  16. KrisBlueNZ

    Design question on microcontroller and TIP122

    N and P polarities of MOSFETs, as well as for junction transistors, do cause confusion. Your second diagram shows the general connection for a P-channel MOSFET. The first diagram is wrong. The last six lines of your post are wrong. I'll try to explain from the beginning. First, remember that...
  17. KrisBlueNZ

    Need help to build police siren/LED flasher

    That's good news. That solder doesn't look very healthy to me. Is it lead-free solder? Are there any markings on the reel? A 30 watt soldering iron would be better, and a temperature-controlled iron is best, but 40 watts should be alright. Make sure you're not holding it on the joint for...
  18. KrisBlueNZ

    bi directional communication to multiple nodes over 1 wire

    That should be very obvious. The earth wire must be a direct and solid connection to earth. Anything you connect in series with the earth connection will compromise this essential function and will be illegal. But in any case it doesn't make sense to say that you would send data "through" the...
  19. KrisBlueNZ

    Help to build a device to revolutionise an industry

    You could use PLCs for prototyping until you get it working properly; you would then have working prototypes to present to a company or person to get a custom solution manufactured. This would put the onus on you, as it should be, to demonstrate that your idea is workable; doubt about this is...
  20. KrisBlueNZ

    RS485 signal transmission - LED panels

    Thanks for the diagram. That's very helpful. The grounding arrangement looks fine to me. I notice that on the MAX485 at the left side of the top breadboard, pin 3, the transmit enable input, is not connected to anything. This is a high-impedance input and it may pick up noise if it's not...
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