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  1. hevans1944

    Controller boards for multiple relays

    It is quite difficult to offer specific advice when the problem is ill-defined. It appears (1) you want to provide a multiplicity of +5 V output signals, presumably each with sufficient current to drive "shielded reed relays" on a separate external board, (2) that the number of outputs be...
  2. hevans1944

    SPTT reed relays

    Well, okay then. BTW, there is a special miniature toggle switch available that implements a SP3T switch action. No reed relays necessary if you operate this switch with your fingers, i.e., digitally.:D
  3. hevans1944

    Trying to find type/name/replacement cord

    That looks like a polarized connector. Does this have an external DC power connection, provided from an external AC-operated power supply? Many "coolers" that provide both heating and cooling do that by changing the polarity of the DC power input. Trace the wiring from the connector to see where...
  4. hevans1944

    Microcontroller for ECG (Holter monitor)

    I am currently experimenting with an Arduino Uno equipped with a Seeedstudio XBee shield with an XBee module plugged into the shield. Not exactly as small as possible, and it requires significant power, but this is a prototype. Eventually it will all get squeezed down to fit in a wristband. This...
  5. hevans1944

    Flash tube

    Have you had any success in identifying the energy storage capacitor that is discharged for each flash, and measuring its charged voltage state? These two pieces of information are essential to specifying a replacement flash lamp.
  6. hevans1944

    Microcontroller controlled by pushbutton for LED flashlight

    Since the back side of the target board is flat, the fixture could be just a hollow cylinder a few millimeters in length with a shelf and a single dowel pin (crown pin?) to index the target board position. The programming board of the same diameter as the target board but with pogo-pins attached...
  7. hevans1944

    Need help about RPM Sensor in automotive

    Do you suppose three successive posts will yield triple the number of responses? Just signal-condition the Hall effect RPM sensor to CMOS logic levels and feed it to a digital input bit on a CMOS microcontroller. Then roll a little code to measure the time between pulses and send it back out to...
  8. hevans1944

    SPTT reed relays

    It's been awhile since I have had teenagers in my house, but at one time four of them were practicing as a rock band in my garage. There were a lot of strange effects boxes out there, but I don't remember the details, just the fact that they were LOUD! I think some of the effects pedals were...
  9. hevans1944

    Microcontroller controlled by pushbutton for LED flashlight

    It is also important to machine a small fixture to hold both the target board and the pogo-pin board in alignment and in contact with each other. This is to allow rapid programing of several (100?) assembled boards in succession. The pogo-pin board should also have the connecting wires to the...
  10. hevans1944

    Capacitors dielectric

    Please sketch and upload to the forum a circuit diagram that shows what you are talking about. Your question doesn't make any sense to me. How can the bulb light up when the circuit is open? How is the capacitor discharging when the circuit is open? What is the capacitor discharging into? How...
  11. hevans1944

    Capacitors dielectric

    A DC current cannot flow through a capacitor's dielectric. By definition, a dielectric is an insulator for DC current. An AC current can flow in a capacitor, with some impedance to the flow, that is a function of the AC frequency and the capacitance. The higher the frequency, or the more the...
  12. hevans1944

    Hearing Aid Design

    You could possibly use the Telecoil to couple an audio signal from a "miniTek-like" clone into the hearing aid, but your device would be large, ungainly, and would have to be held against the hearing aid, like a telephone handset, to work. The range of the Telecoil pickup is quite small... a few...
  13. hevans1944

    Hearing Aid Design

    The miniTEk (and similar devices) uses Bluetooth technology to communicate with various third-party Bluetooth-equipped devices such as cell phones, MP3 players, TVs, etc. for the purpose of transmitting digital audio from these devices to Siemens binaural hearing aids via frequency-shift...
  14. hevans1944

    SPTT reed relays

    If you have to make sure there is only one path active at any given time, then a pair of SPDT reed relays will do that. The signal is applied to the common (movable) contact of relay 1 and from there is appears at its N.C. contact (Output A) when relay 1 is de-energized.. The signal appears at...
  15. hevans1944

    Hearing Aid Design

    Please tell us what hearing aid you intend to hack: manufacturer, model number, year of manufacture. Unless this is a "hearing aid" you wear in a box on your chest with speaker "button" ear pieces to convey sound to your ears, I doubt you will have the technical acumen to modify a commercial...
  16. hevans1944

    Electrons

    Some of it is correct. Anions and cations are normally associated with electro-chemistry. They have virtually nothing to do with how fluorescent lamps work. Read this Wikipedia article for an overview of how fluorescent lamps work. The "spectrum" of 2700K to 6400K refers to the apparent "color...
  17. hevans1944

    Microcontroller controlled by pushbutton for LED flashlight

    I am really enjoying this diversion too, Adam. It has offered me an opportunity to learn something new (PIC processors) and practice something I wasn't sure I was capable of doing without a lot of expensive equipment (SMD component placement and soldering). And it helps to have a community of...
  18. hevans1944

    Microcontroller controlled by pushbutton for LED flashlight

    Gee wizz, I am feeling so retarded lately... I FINALLY got a "program" to assemble without error. Not much of a program, just some PIC initialization, but now I can try playing with the I/O to try to find out who the current hog is. Next step is to put the PIC to sleep and see how much current...
  19. hevans1944

    Microcontroller controlled by pushbutton for LED flashlight

    We need to find a smaller SMD Schottly diode of modest forward current and reverse voltage rating... surely Digi-Key has something that will fit... perhaps the attached datasheet describes what we need.
  20. hevans1944

    Microcontroller controlled by pushbutton for LED flashlight

    So a person can hold the flashlight in their hand?:D
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