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  1. kellys_eye

    Wiring LEDs to Corresponding Switches?

    Regardless. You still need to know the total current requirement OR you get a power supply that you know will have sufficient current capacity based on the average requirement for ONE LED/switch combo multiplied by the max potentially in use. Using 'worst case' of 100mA per LED and 20mA per...
  2. kellys_eye

    300 V DC Power Supply

    You're not kidding - fatal voltages/currents. Only those familiar with working with such need apply! For most experimental purposes the currents required to drive a decent valve (tube) design would be fatal if inappropriately used so precautions are VERY necessary - I won't list them, it's...
  3. kellys_eye

    Brain storming layout for safety lighting circuit. Help.

    no you won't. Given that the input port of the micro has an almost negligible current requirement all you need concern yourself with is having sufficient current flowing in the zener to maintain regulation (5mA??) and changing the input from 20V to 30V means dropping 15-25V (for a 5V output) at...
  4. kellys_eye

    Resistance of wire seems to go down when part of a circuit?

    A decent clamp ammeter (DC) is essential for currents over 10 or 20A. Whilst these types of devices aren't as commonly used as ordinary multimeters they are now quite a lot more affordable than they were a few years ago. You can also purchase (or build) a milli-ohm meter designed, as the name...
  5. kellys_eye

    Resistance of wire seems to go down when part of a circuit?

    Fuses protect the CABLING, not the equipment, so for a fan requiring 450W (37.5A) you would need 8awg for the main feed to/from the relay/fan. The relay CONTROL wiring can, of course, be much smaller. a 40A fuse would be appropriate for 8awg.
  6. kellys_eye

    Bell Carrol Plasma Cutter - Cut 40

    The spark looks to be generated from the items shown here: The yellow transformer output feeds the multiplier/rectifier circuit comprising the diodes and 'blue blobs' (capacitors). It will be high voltage and high frequency (input) and the transformer itself is fed from an oscillator...
  7. kellys_eye

    Wiring LEDs to Corresponding Switches?

    You are adding complications at each and every post by not being fully advisory with your requirements. You now show LED-lit buttons along with LEDs you want to light........ I presume you want the buttons to light when the button is pressed AND the attached LED to light at the same time?
  8. kellys_eye

    Brain storming layout for safety lighting circuit. Help.

    Use a series resistor and a zener diode (rated at 3.3V or 5V depending on the logic level you need) at each input. The zener will clamp the input voltage to the chosen level regardless of the input voltage and be capable of handling anything up to 100's volts if that should occur.
  9. kellys_eye

    Need to reduce 5V 500ma to 3V 30ma

    A couple (or three) series wired silicon diodes will drop enough to make it work. I doubt the keyboard will worry too much about the voltage being 10-20% either side of the 'rated' voltage, them being batteries that can vary in full terminal voltage depending on the type fitted.
  10. kellys_eye

    Resistance of wire seems to go down when part of a circuit?

    When measuring such low resistances you have to be aware of the effects of poor contact resistance - even pressing the test meter probes 'harder' can make a difference to your readings. At high currents ALL connections need to be very clean and very secure. The fuse holder itself is often an...
  11. kellys_eye

    3 phase driver as generator system

    ...by using it to power a motor, yes. ...it can't.
  12. kellys_eye

    Can a Chopper Realistically Be Built

    It would be necessary to integrate any DIY chopper into the existing circuitry so do you have a system schematic that shows how the chopper is fitted as part of the whole? The 'chopping' part of the design is (seemingly) straightforward however the CC/CV modes and their adjustment takes...
  13. kellys_eye

    Comedy Thread

  14. kellys_eye

    Wiring LEDs to Corresponding Switches?

    confusion reigns!
  15. kellys_eye

    Can a Chopper Realistically Be Built

    That would result in a 170VDC or 340VDC output assuming a standard 120/240V alternator side. Accordingly they would require a power converter to get the 90V DC and a SMPS to get 90V DC @300A is no simple circuit! Does the set the OP has still have the inverter part fitted and does it work?
  16. kellys_eye

    Can a Chopper Realistically Be Built

    How do they derive the 90V input? I assume the generator side is a standard 120/240VAC output.
  17. kellys_eye

    LCD backlight control with M.NT68676.2A LED controller board

    Not really - they actually DO control the brightness of the backlight which you can clearly observe if your screen power saver is set and you observe the brilliance slowly decreasing to 'off'. That controller board shows CN5 pin 4 as labelled for backlight control - presumably requiring a PWM...
  18. kellys_eye

    Wiring LEDs to Corresponding Switches?

    The power supply in your example would be 12V - and you'd need a current capacity of 30 x 20mA which is 600mA so a 1A power pack would be fine. To drop the 12V to the LED voltage (which varies depending on the chosen colour - around 1.6V for red and up to 3.6V for white) you need to pick the...
  19. kellys_eye

    Can a Chopper Realistically Be Built

    Such welders will have a variable output voltage (around 10V to 80V). Currents of 300A are relatively easily handled with paralleled MOSFETS but finding the right ferrite core is probably the most difficult aspect of a design. Unless you get it completely right you risk blowing up a lot of...
  20. kellys_eye

    Multiple CCD signal to single, summed signal

    I would have thought NOT as you're conflating the principle of phase arrays for radio signals with DC levels as produced by a CCD element???? Would it not be a case of simply taking the raw CCD element signal(s) and summing them pre internal signal processing? You then take that resultant...
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