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  1. AnalogKid

    Intruder Alarm Help

    1. Alarm disable switch inside the shed. 2. Alarm latch. Both of these are significant expansions of the original operational logic, but not a huge deal - IF (big if) you can run more wires out to the shed. the original circuit used one pair for both remote activation and remote display...
  2. AnalogKid

    Need help with a simple circuit

    There are many different technologies that can be used to do what you want: a relay, a logic gate chip, a pre-packaged flipflop logic chip, or two transistors plus some resistors. What parts do you have, and what parts are you comfortable using? Also, are AA batteries a requirement, or is a...
  3. AnalogKid

    Unknown components on this circuit board please help

    Could be a trimpot, or, for longer flash rates, an electrolytic capacitor. ak
  4. AnalogKid

    Intruder Alarm Help

    A pot in series with the beeper will let you adjust its volume, but the pot resistance value and wattage rating cannot be calculated without know the operating current at 12 V. ak
  5. AnalogKid

    Mind-boggling schematic of power supply.

    To start with, I don't understand why you think the +3.3 V output is connected to AC neutral. There is no connection between the AC neutral and any of the DC output voltages. You can draw a zig-zag vertical line starting above the center of C163, down through the middles of T1 and C16, over to...
  6. AnalogKid

    Intruder Alarm Help

    What is the siren manufacturer / part number / operating voltage / operating current - anything? Can you post a datasheet or link? ak
  7. AnalogKid

    Intruder Alarm Help

    Puttering around, first pass at a non-relay design. D4 and D5 protect the MOSFET input from noise and transients when the door is open. ak
  8. AnalogKid

    Intruder Alarm Help

    Here is a re-draw of your schematic to show what I described. Note that this will work only if the relay coil pull-in current spec is very low. ak
  9. AnalogKid

    Intruder Alarm Help

    Nothing wrong with your design so far in terms of the voltages and signals, but even with only 10 mA through the LED and relay coil in Part 1, battery life might be a problem. 1. If the sounder is a piezo beeper, it already is current limiting and does not need to be in series with a resistor...
  10. AnalogKid

    Op Amp 741

    Your schematic is fine as far as it goes. 1. It needs decoupling capacitors on both power pins. A minimum is a 0.1 uF ceramic capacitor from pin 4 and pin 7 to ground. Keep the leads as short as possible. Better is to add a 10 uF electrolytic cap in parallel with each 0.1 uF ceramic. 2...
  11. AnalogKid

    Would this simple circuit work?

    If the LED is built into the switch bezel, it usually has separate pins. Photo? ak
  12. AnalogKid

    Relay switching

    Depends on the relay coil resistance or nominal wattage rating. What is it? ak
  13. AnalogKid

    Electronic stimulator

    There is nothing on your schematic to indicate what are the inputs, where are the outputs, or shat the circuit is supposed to do. There is no "exit". To answer what I think is your question, LTS will not tel you the current into two unconnected points because *they are unconnected*. To see...
  14. AnalogKid

    Advice on splitting voices

    The RTS0072 datasheet *does* explain what the switches do. http://pdf1.alldatasheet.com/datasheet-pdf/view/103272/ETC/RTS0072B.html ak
  15. AnalogKid

    Need help understanding what this circuit does (urgent)

    Both the circuit and its software program are explained in detail in the picaxe PDF document you did *not* link to in your post. The schematic has several errors, but the operational descriptions are correct. http://www.picaxe.com/docs/chi008.pdf...
  16. AnalogKid

    Laser Emitter and Receiver

    What are you trying to do? What are you modifying? Why? Please post a schematic of your circuit. ak
  17. AnalogKid

    Relay switching

    The IRF840 is not a logic-level MOSFET, and needs a minimum of 4.0- Vdc from the gate to source to start conduction. The rule of thumb for these parts is a min of 10 V Vgs for "saturation." If your max drive voltage is only 3.2 V, search your vendor websites for "logic level MOSFET" and see...
  18. AnalogKid

    Score Counter PCB Help

    Both 4026 pins 2 must be grounded. Both 4026 pins 8 MUST BE GROUNDED. ak
  19. AnalogKid

    38Hz flash

    If the arduino is interfaced to both the transmitter and the receiver, then you can use it as both a modulator for the transmitter and frequency-detecting demodulator for the receiver, all in software. One way goes like this: Turn on the transmitter. Sample the receiver multiple times to see if...
  20. AnalogKid

    Current variations.

    Your understanding. There are several basic kinds of battery charger circuits, based on the battery type/chemistry being charged. The smart ones have several modes and adjust themselves automatically based on monitoring the battery terminal voltage. These can start out in a constant current...
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