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  1. hevans1944

    Looking for a data sheet on this transistor ? from a ultrasonic cleaner powersupply

    Well, at least the Base and Emitter connections are marked. Do you have any that more or less still work, i.e., the emitter-base and base-collector junctions measure okay? Maybe if you knew whether it was a PNP or NPN bi-polar junction power transistor you could try to find a substitute. Is...
  2. hevans1944

    Adjust the range of Transmitter

    The fruit can is just one way to easily adjust the radiated power to limit the effective range. Radio signals propagate.
  3. hevans1944

    Adjust the range of Transmitter

    There really is no way to control the range of a radio transmitter, except perhaps by changing the transmitter power. Even lowering the power is no guarantee that the range will be reduced. Range depends on a lot of factors and how you define "receive". Voice modulated FM (your circuit) will...
  4. hevans1944

    Save money?

    Yes, I am aware of the existence of cellular devices that attach to home security panels. These are usually installed by a third party as part of a monitoring service such as provided by Alarm Force, ADT, etc. I don't want to subscribe to a monitoring service. I haven't talked to my Sprint...
  5. hevans1944

    Save money?

    Oh, really? Mine is quite old, so whatever instructions came with it are long gone. What is so magical about 3 m height? Do you have a link to a reference? When I Googled "PIR mounting height" I got answers of considerable variance. One manufacturer, Genesis in the UK, recommends 2.5 to 4 meters...
  6. hevans1944

    Save money?

    I installed a pair of PIR-activated flood lamps above my two-car garage door a few years ago... maybe ten or fifteen years ago. Mine are not dim-able, and I see no reason to want them to be dim-able. I did hate the fact that they would come on whenever the wind blew and waving tree branches...
  7. hevans1944

    How can I measure Quiescent current of LDO's?

    For Kirchoff's Law, a node is any bounded region, not just a point where two or more conductors are connected. In this case the entire 3-terminal regulator with input, output, and ground is considered a node. The Law quite simply states that all the current entering a bounded region (a node)...
  8. hevans1944

    How can I measure Quiescent current of LDO's?

    Kirchoff's Law in action: What goes into a node must also go out of the node.
  9. hevans1944

    Where to start?

    Control systems is what I got hooked on while serving in the US Air Force. The defensive fire control system on B52-H heavy bombers that I was trained to maintain had hundreds of servos in it, ranging from tiny motors driving stacked potentiometers to compute the ballistic equation, to big...
  10. hevans1944

    Where to start?

    Welcome to Electronics Point Forums, Matt. I think the best way to learn electronics is to do electronics. I started out by messin' 'round with old radios and TVs back in the day, but there is an easier way today. Perhaps @KrisBlueNZ can point you at some breadboarding prototyping kits. I don't...
  11. hevans1944

    Summing amplifier

    In my current line of work there is a requirement to "count" the number of high-energy positive ions implanted onto (and into) a target material. The time the ion beam is on can range from a few seconds (at low doses) to several days (at high doses). The target is mounted to an insulated...
  12. hevans1944

    Summing amplifier

    Well, more or less. The output will drift up or down with zero input, depending on the bias current and voltage offset at the input of the amplifier A as well as leakage current across the capacitor terminals. It is really difficult to build a analog integrator that doesn't drift. Better to do...
  13. hevans1944

    Summing amplifier

    This is not "sort of like an integral function." It IS an integral function. Replace Rf with a low-leakage capacitor and the circuit will behave as you describe.
  14. hevans1944

    Summing amplifier

    Connecting Vout to V1 places R1 in parallel with Rin and shorts out V1 through the low (ideally zero) output impdance of A. The effect of that will depend on the source impedance of V1. In any case, V1 will then have little or no effect on the output. If the source impedance of V1 is very low...
  15. hevans1944

    Bending Radius of Lead when designing component footprint

    Since you apparently do have Internet access, and are designing a product, I suggest you Google "IPC standards" for the information you need. Most of us here like to help beginners, and I am definitely in that group because I still remember what it was like back in the day, but we can help...
  16. hevans1944

    Bending Radius of Lead when designing component footprint

    When you go to install the resistor, you will bend the leads perpendicular to the body of the resistor with a pair of long-nose or needle nose or round-nose pliers. In doing so, you will place a small radius in the bend that will extend the separation between the two leads just a little. It will...
  17. hevans1944

    Controlling Separate Source with Low Power Signal

    @Arouse1973: In post #8 @KrisBlueNZ proposed what is essentially "an emitter follower" with negative feedback to ensure unity gain. This circuit will provide unity gain and 8 A or more of load current. If it is necessary to translate 0 to 5 V input into 0 to 12 V output, more gain can be...
  18. hevans1944

    ATX PSU Power Toggle Circuit

    Good post, as usual, Kris. I didn't notice that -PS_ON was active-low. On schematic construction: wires that cross are assumed to not be connected, as you stated. Placing a dot where three wires connect is preferred practice. Avoid placing a dot where two wires cross and the intent is to...
  19. hevans1944

    General electronic questions

    I think @KrisBlueNZ answered your questions very well. I have some additional comments and the following observation: it appears as if you are trying to learn electrical circuit theory starting with a basis of house wiring and low-voltage battery operated equipment. That is an excellent...
  20. hevans1944

    Problem with 5v power supply

    Ho ho ho! Like the little Christmas tree lights? Must be a pretty good LED if it somehow goes into thermal shutdown at 300 mA and then lights up again after it cools off. Oh, wait, you were kidding us about the "blinking," riiiight? This must be the time of year to replace LEDs. Working late...
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