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  1. (*steve*)

    Acer X223W LCD Monitor

    @Angel Angelov , you reported a post rather than replying to it. Try again :-)
  2. (*steve*)

    Hour meter for laser cutter

    At the hackerspace I frequent we have a couple of laser cutters. We want to keep track of the laser time to track tube life. Someone got inside and found a signal that is about 4V when the laser is off, and 0V when it's on. Some more investigation revealed that it can't sink or source much...
  3. (*steve*)

    Determining LED values

    For a lot of LEDs I use, a couple of mA is plenty. Like you, I don't bother much with calculations most of the time because I'm not going for maximum brightness. A couple of days ago I wanted to have the same brightness for two LEDs, one powered from 24V, the other from 5V -- The rough...
  4. (*steve*)

    Determining LED values

    You can assume that a very small change in voltage across a LED will result in a very large (and not easily calculable) change in current. For example, if a string of LEDs has 20mA flowing through it, and the voltage across them is 10V, an increase in this voltage of 0.5V would increase the...
  5. (*steve*)

    Determining LED values

    Audioguru is right. If there is no series resistor then you shouldn't apply a voltage, no matter what the arrangement. However, if LEDs are in parallel strings, then each string should have a series resistor. With this it matters little whether you apply a voltage or a current, but in this...
  6. (*steve*)

    Determining LED values

    The simplest method is: get 4 AA batteries in a holder that has a 9V style battery clip Then get a 9V battery clip with leads and solder a 330 ohm resistor to one lead (apply some heatsink to insulate the join leaving a small party of the free end of the resistor exposed if you wish). Set...
  7. (*steve*)

    Voltage Controlled Voltage Source (VCVS) - Piezo Buzzer

    "RETARD RETARD". <-- Why is the aircraft calling me retard?
  8. (*steve*)

    Voltage Controlled Voltage Source (VCVS) - Piezo Buzzer

    From what I understood, the difference in behaviour desired is different from that obtained by asserting the different signals on the alarm itself.
  9. (*steve*)

    Voltage Controlled Voltage Source (VCVS) - Piezo Buzzer

    If you set up an adjustable 3 terminal regulator, you could use a couple of digital outputs to turn on or off a couple of MOSFETs which select the resistor between the adj pin and ground. This would allow you to digitally select the voltage passed to the buzzer.
  10. (*steve*)

    Piezo Control voltage source

    Umm, musician, not museum.
  11. (*steve*)

    Piezo Control voltage source

    That circuit is similar to what I've recommended a local musician use to interface a large number of these devices to an Arduino. You can get by with something significantly simpler than that if you only want to hold a peak voltage for a short amount of time before reading it. In my case, we...
  12. (*steve*)

    Voltage Controlled Voltage Source (VCVS) - Piezo Buzzer

    So, what signals do you have available? PWM will need to be filtered or it will modulate the sound from the buzzer.
  13. (*steve*)

    Voltage Controlled Voltage Source (VCVS) - Piezo Buzzer

    That datasheet doesn't indicate that a lower voltage will work, but I presume you've tried it yourself. What input signals will you use to set the voltage? Do you want to supply an equivalent voltage, or one of a couple of logic levels, or something else? A simple solution is to apply a...
  14. (*steve*)

    HP 400F AC voltmeter

    I recommend you check A2Q15, A2Q16, A2Q17, A2C38, A2C39, and A2C40. These are the components commonly associated with a meter deflection with no input. Edit: Edd has already suggested looking at those caps.
  15. (*steve*)

    4n25/35 optocoupler detect led on/off

    For the configuration as shown, you need a pulldown resistor.
  16. (*steve*)

    Vizio E470i-AO television has a black screen. Which part do I replace?

    First thing to do is to open it up to access the power supply and check for the obvious faults. Does it definitely have LED backlighting? If not, you may be looking at a high voltage power supply for CCFL's. In either case you'll be looking for the same stuff initially. Just remember that...
  17. (*steve*)

    Resistors, Capacitors, Zener diodes... Why the funny values?

    Well it's a geometric series. <-- edit, geometric sequence. There is a constant multiplier between each value. For the En series, the value is the nth root of 10.
  18. (*steve*)

    BNC connector

    Because it can. Seriously, that question is so unfocused as to have no real answer. What do you actually want to know?
  19. (*steve*)

    Homework help!

    Also, this sort of stuff sounds like it comes straight out of the recommended reading or from the lesson/lecture. If be asking if he hasn't skipped out of the required reading or zoned completely out in class. If it's the reading, then this is the simplest, just locate the text and make him...
  20. (*steve*)

    Resistors, Capacitors, Zener diodes... Why the funny values?

    I'm pretty sure you meant "Geometrically"
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