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  1. Hero999

    Power supply ignorance

    I've just Googled for Mastech 30V 6A power supply and I get lots of results. If the origional poster had given the model number, then I might've been able to find it and check that it says the maximum power rating in the specification.
  2. Hero999

    power supply protection for car projects

    Yes vintage cars can be especially bad at suppressing ignition noise. How much current are you drawing? What's the typical input voltage? I assume this is a 12V system and not a 6V system. Connect a 15R to 18R 0.5W resistor in series with the regulator. Connect an 18V 1W zener and 10μF...
  3. Hero999

    Looking for temperature sensor with +/- 0.5 degree accuracy at 25 degrees.

    The low voltage of 1.8V is going to be the problem. What about using a precision thermistor?
  4. Hero999

    Power on, LEDs on for 4 seconds?

    They're not LEDs, take a closer look at the schematic. The pinout for the 555 is on the datasheet which can be found using Google. If you can't find the relay datasheet, and the pinout isn't clearly marked on the relay, it's quite easy to determine it yourself. The coil will have a resistance...
  5. Hero999

    Power on, LEDs on for 4 seconds?

    Good, I'm glad you got there in the end.
  6. Hero999

    Optical Mark Scanner

    You don't need image recognition or anything like that. A standard computer scanner is the cheapest way of doing it. It is possible to use an IR beam break or reflective sensor but it won't detect red pen.
  7. Hero999

    Power on, LEDs on for 4 seconds?

    What part of the formula do you not understand? t = 1.1RC t is the time delay in seconds. R is the value of the resistor in Ohms. C is the value of the capacitor in Farads, 1
  8. Hero999

    Optical Mark Scanner

    Why not use a conventional scanner connected to  PC and do the optical mark recognition in software?
  9. Hero999

    Power on, LEDs on for 4 seconds?

    The formula for calculating the time is on the schematic. As a general rule R should be between1k to 1M. How accurate does it need to be? Beware that typical electrolytic capacitors have a tolerance of 20% so even if you use values that will theoretically give exactly 4 seconds, the actual...
  10. Hero999

    Power on, LEDs on for 4 seconds?

    Use a 555 timer.
  11. Hero999

    0-30V Stabilized Power Supply

    What do you think? The circuit will obviously work as long as you're aware that the supplies on the right will not be isolated from each other and if you don't know what that means then I suggest you do some more research before building it.
  12. Hero999

    0-30V Stabilized Power Supply

    How can it possibly be shorted when it's clearly open circuit? If you need to ask such questions then you obviously don't have enough experience to build it. I suggest you read more about basic circuit theory and Ohm's law and basic before building this project..
  13. Hero999

    Guitar Aplifier

    As Q5 and Q6 carry a considerable current, the PCB traces need to be thick enough to carry the current, otherwise it'll behave like a fuse. Of course the transistors need to be on a good heat sink. If the amplifier is driving a 4Ω load, the heatsink should be rated to at least 4
  14. Hero999

    0-30V Stabilized Power Supply

    What do you think?
  15. Hero999

    0-30V Stabilized Power Supply

    Connect the two power supplies in series and use the point where the two supplies are joined as the 0V point.
  16. Hero999

    0-30V Stabilized Power Supply

    You can't do that with a single supply. You need to build two supplies and put them in series to make a +/- 30V supply.
  17. Hero999

    Input and Output impedance

    I wouldn't advocate trying to help those with spam in their signatures.
  18. Hero999

    circuit distortion

    What do you mean? Operating an op-amp with too higher voltage swing at too higher frequency will result in slew rate distortion which is nothing to do with the noise or distortion specifications.
  19. Hero999

    circuit distortion

    For some reason my previous post was delete, maybe it was my mistake. I've retrieved it from the bin. The saturation voltage will always increase if the collector current is increased even if the base current is increased. A transistor is saturated when an increase in base current no longer...
  20. Hero999

    Guitar Aplifier

    The 0V supply rail should be connected to the case which should also be connected to safety earth/ground. The inputs should be connected to whatever you're connecting the amplifier to with screened cabe.
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