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  1. hevans1944

    8-Pin Development Board

    Nice work, John!
  2. hevans1944

    Digital calendar which flashes a LED when out of date range

    Okay, Canada has checked in with some good observations. Still looking for someone from South Africa. @Gryd3 it may indeed be possible to power the alarm box with on-board power, but that is probably not desirable. I would imagine it will be desirable to just do a "walk-by" to see if the...
  3. hevans1944

    8-Pin Development Board

    I am soooo envious!
  4. hevans1944

    Digital calendar which flashes a LED when out of date range

    Thank you. Much clearer. So you need a calendar reminder function that flashes an LED when the programmed date is reached, and continues to flash until the next programmed date is reached or a "reset" button is pressed. Do you want the reset function to act like a "snooze" function, so the LED...
  5. hevans1944

    Inverter 12V to 220V

    You could place the inverter in the same room you are heating with 220 V AC and improve the efficiency a little. Whatever "waste" heat the inverter produces because of its inefficiency will go toward heating the room. A one meter square solar panel collects about one kilowatt with maybe 15%...
  6. hevans1944

    8-Pin Development Board

    Received your three files and tried to open them in LTSpice. Got a message saying the "magic number" was wrong. Took me awhile to realize these were Eagle files, not LTSpice... a senior moment there. Took even longer to download the latest (7.6.0) 30-day trial version of Eagle, which was 56.3 MB...
  7. hevans1944

    Potentiometer Value and Rating?

    It also explains why I could never afford dance lessons, being handicapped with two left feet.
  8. hevans1944

    Question on KVL

    Yikes! So when they do finally arrive, are they "trade goods" to exchange with the natives, or are you going to etch some circuit traces on them? If traces there be, how do you plan to make that happen? Uh, this is very important to KVL analysis... probably.
  9. hevans1944

    Newbie needs help to power up a cable modem board

    Well, thanks for that. I didn't want to come right out and accuse the OP of trying to steal Internet service. Then I went back and read: So here is some enlightenment: Every Ethernet connection requires a MAC address. This is hard-coded into the cable modem and into every device that...
  10. hevans1944

    Question on KVL

    As for exposure... I don't think a UV LED is necessary. I use a box with a #2 (IIRC) photoflood lamp inside, positioned about ten inches or so above the PCB. There is a squirrel-cage fan that brings in cooling air and circulates it around the PCB and lamp. Exposure time for negative photo-resist...
  11. hevans1944

    Potentiometer Value and Rating?

    Hey! You gotta pay to play. And if you don't know what you are doing, you pay a lot more.
  12. hevans1944

    Newbie needs help to power up a cable modem board

    Does your cable TV service offer an internet connection? Mine does, but it is an extra-cost "feature" that is available with or without TV channels. I purchased a high-end cable modem after purchasing the cable internet service, saving the monthly rental fee charged by my cable service provider...
  13. hevans1944

    LED monitoring

    Why can't you just "monitor" the micro I/O pin that is driving the LED cathode? If it is "off" or high impedance, then you will "see" the 3.3 V supply at the cathode of the LED through the anode connection to the current-limiting resistor and the resistor connection to 3.3 V DC. When the LED is...
  14. hevans1944

    Potentiometer Value and Rating?

    Yeah, most of them were used as rheostats IIRC. Problem is the OP's load is only a half an ohm, so finding a pot with a low enough resistance, whether wired as a pot or wired as a rheostat is going to be difficult as well as inefficient. The solid-state semiconductor method is a better solution...
  15. hevans1944

    Question on KVL

    The boards you linked to are phenolic boards, which I would avoid because they absorb moisture. FR4 pre-sensitized boards here are more expensive but less problematical. Will continue looking for chemicals that I can use to coat my own boards. Mendelson's usually has a decent supply of...
  16. hevans1944

    8-Pin Development Board

    Man, that blue on black with the green and white overlays makes my head spin! Good thing you didn't throw some yellow in there or I would have gone blind! Maybe you should attach your Eagle file to an e-mail and I will try to fire up my copy of Eagle to look at it. That way I can toggle layers...
  17. hevans1944

    Winter down under time

    Just light some more candles for your "emergency light" and go read a book on thermionic energy conversion.
  18. hevans1944

    Question on KVL

    I did review it, and thought I had left a reply on this thread, but it's not there. Schematic looks good except some components are labeled twice (capacitors) and some are not labeled at all (resistors). Not sure why you would want to place capacitors across the resistors in series with the two...
  19. hevans1944

    Question on KVL

    I tried to download the Power Point Presentation, linked to in the YouTube site, and was informed that the website had been hacked and nastyware installed. So I abandoned that effort. Is there anything in particular about Ohm's Law, Kirchhoff's KCL and KVL Laws, Thevenin and Norton Equivalents...
  20. hevans1944

    Potentiometer Value and Rating?

    Well, actually "they" do (or did) make pots with this capability. They are quite large, several inches in diameter, and the "resistance element" looks like flat wire and it is wound on a ceramic substrate. The wiper arm is usually a carbon block, spring loaded against the resistance element...
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