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  1. Hero999

    NEED BATTERY-POWERED PROGRAMMABLE TIMER

    You have contradictory requirements: programmable and plug and play. A simple PIC microcontroller would be a perfect programmable timer. The PIC12F508 could do what you want with the addition of a transistor, a resistor and a capacitor. It can be programmed with C, BASIC or assembly.
  2. Hero999

    What is a Reactor? (Context: Substations)

    A reactor is just a large inductor. It has many applications, one is to compensate for the capacitance of the cables to minimise losses.
  3. Hero999

    Need help updating a circuit

    The INA114 looks simialr to the AD521 http://focus.ti.com/lit/ds/symlink/ina114.pdf The OPA128 is recommended to replace the AD515 http://www-micrel.deis.unibo.it/DATA_SHEETS/OPA128.pdf You could also try contacting Analog Devices.
  4. Hero999

    130vdc 2a from 230vac

    You could try using a single diode half wave rectifier. Failing that, an autotransformer, which is half the sze and cost of a transformer with two windings and a bridge rectifier will do.
  5. Hero999

    Questions about infrared cordless headphones

    Here's an idea for an IR transmitter which uses PWM at 90kHz. The two LM393s should be replaced with a single LM339 to save cost. I just used the LM393 because there's a model for it in LTSpice. I've not tested it. If you want a receiver I'll have a go at designing one.
  6. Hero999

    Questions about infrared cordless headphones

    I was going to say how crappy this project is but decided to leave it to audioguru who I knew would enjoy it more and be more constructive than me. AM is also bad because the response of the photo-diode photo-transistor won't be matched so there will be non-linearities which will distort the...
  7. Hero999

    DC Potentiometer in AC circuit to control DC output.

    I doubt there's a problem with the meter. The voltages were unpredictable because they depended on the current drawn by the load which is unpredictable.
  8. Hero999

    How to open a 24VAC Water Solenoid

    You use 24VAC of course. To get 24VAC you need a transformer to reduce the mains voltage to 24VAC.
  9. Hero999

    Schematic advice for a noob

    I don't know and nor will anyone else because you haven't said what sort of servo mechanism you're using.
  10. Hero999

    DC circuit breakers rated >63A?

    http://www.lpa-group.com/pdf/downloads/HY-MAG.pdf
  11. Hero999

    failed RS-232 level converter :(

    You need a low value pull-down resistor on the input, otherwise when there's no signal Q1 and Q4 will turn on, allowing current through Q2 and Q5 which will cause Q3 and Q6 to turn on and short circuit the power supply. There will be switching waste because Q3 and Q6 will both turn on...
  12. Hero999

    failed RS-232 level converter :(

    Here are a couple ways to do it. V1 is more complicated and it has the disadvantage of both output transistors being on simultaneously for a point during switching but it'll have virtually no saturation loss i.e. you'll get +/-15V out. V2 is simpler and has the advantage of not having both...
  13. Hero999

    failed RS-232 level converter :(

    The transistors are biased so when there's no signal, they're all on. It looks like you've forgotten that a transistor's base is just a diode which will pass current. Look at the current flowing hrough the PNP transistor bases to the NPN transistors.
  14. Hero999

    Need solution to Complete this 240V AC Relay Driver circuit .

    That will do, there's no point in complicating things.
  15. Hero999

    Need solution to Complete this 240V AC Relay Driver circuit .

    The relay being powered continiously will not reduce its life. It's switching the relay on and off many times which reduces its life.
  16. Hero999

    DC Potentiometer in AC circuit to control DC output.

    The load can be connected in parallel with C1 which can be increased in size, if needs be. The circuit you posted is a bad idea because the potentiometer also increases the impedance of the power supply so the current and voltage to the load will also fall. The brightness of the LED will vary...
  17. Hero999

    Very Very Simple Thermal Fan Controller

    The switch does the reverse of what you want, it's off when the temperature exceeds 40oC and turns off when the temperature falls below 25oC.
  18. Hero999

    DC Potentiometer in AC circuit to control DC output.

    Here's another way to control the brightness of an LED. It's slightly more complicated but the current through the LED is regulated (it doesn't change much as the voltage varies) and the filter capacitor is much smaller.
  19. Hero999

    timer to trigger latch

    I know, I disagree, it's not small at all. The PIC12F508 comes in a large through hole DIP8 which can easily be soldered to strip-board. You can get it in smaller surface mount SOIC8 package which is still easy to solder, compared to the tiny DFN8 package which is only 3x2mm. Unlocked, you...
  20. Hero999

    timer to trigger latch

    What do you mean? It comes in a through hole DIP which is the same package as a 555 timer, uA741, LM393 etc. It's not hard to learn, especially if you program in BASIC. With an MCU that can be done in software without any need to change any comkponent values and the delay can be controlled...
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