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  1. hevans1944

    Hello everybody, thinking of buying this... What are your thoughts.

    Gee, for just a few dollars more you can get this 85 inch Sony.
  2. hevans1944

    Peltier

    Two grocery stores where I shop have a small cooler on a stand filled with circulating chilled water that you can drop a bottle into to chill the bottle while you shop. Takes about seven minutes or so to chill contents of bottle to same temperature as the water. The cooler top is open to air...
  3. hevans1944

    Peltier

    Peltier cooler: an inefficient solid-state heat pump invented by the French in retaliation for some perceived slight, probably by the Germans, who came up with the Thompson effect which is mostly identical to the Peltier effect. Doesn't hold a candle to mechanical refrigeration, but does have...
  4. hevans1944

    An IC for generating composite video signals

    It's a wunnerful question, not a silly question at all for those interested in vintage computers! You could start by trying to find this obsolete Analog Devices AD722 encoder. Good luck with that. I wasn't able to find any for sale anywhere, but I didn't try eBay. Caveat emptor there. You would...
  5. hevans1944

    Troubleshooting a diode voltage drop

    Well, in your case it was. And you still managed to hook up the external power wrong without realizing what the real problem was! BTW, you are very lucky. Most manufactures do not include a "reverse polarity protection" diode. Save a penny, earn a penny. I have a mixed bag of used wall-warts...
  6. hevans1944

    DC Motor drive

    Wow! That's some coil winder! If you can't get the carriage carrying the wire to run in both directions, you could still wind some boss Tesla coil secondaries. :D I saw on the North American Tools blurb page that they are supposed to sell buttress taps and dies, but I couldn't find any on their...
  7. hevans1944

    Converting LED to Street Light?

    The Boy Electrician by Alfred P Morgan has been out of print for many years, but there are decent photocopies available on the Internet. I had to look at several before I found the edition I read in my youth... the one that shows how to build your own x-ray machine and make radiographs of your...
  8. hevans1944

    DC Motor drive

    Well, maybe this company is on the other side of the pond from you has a hand-tap you could use. Lots of useful information on their website too. You could drill and tap a hunk of brass or bronze and then saw it in half to make a split-nut for your lead screw. Or get your tame model engineer to...
  9. hevans1944

    Understanding The Following Circuit

    That would allow pin 2 to be driven to the same negative potential (-0.5 V) applied to pin 3. But why not apply -0.5 V from the PSU directly to the 1 MΩ resistor in series with the CO sensor, with the other terminal of the CO sensor connected to 0V? Then you can just ditch that expensive...
  10. hevans1944

    Understanding The Following Circuit

    Raj, the only way that the MOSFET can provide a current through the resistor is if there is a negative voltage at the bottom of your diagram, said voltage applied to the other terminal of the CO sensor which then conducts the negative current provided by the resistor. Even then, unless the CO...
  11. hevans1944

    Converting LED to Street Light?

    A "Thank You" and maybe a "Like" are all that we ever expect here. Almost all who respond on EP with intelligent answers have many years experience in electronics, and I suspect many are also hobbyists. Electricity and, later, electronics has been my "hobby" since about age nine or so, when I...
  12. hevans1944

    How to control the speed of a 24vdc pump from circulating water temperature?

    Excellent idea! We plan to stay with my daughter and her husband in Sarasota when we visit Florida to inspect properties later this summer. Shouldn't be very many snowbirds cluttering up the state and jacking up prices in August or early September, so maybe we can find a boat rental at a...
  13. hevans1944

    RFID Multi Antenna

    Hmmm. I think the first step would be to "get smart" about RFID modules before worrying about antennas and range. Who makes the RFID module? Is it active or passive? Over what range of frequencies does it respond when queried? What is the output level of the device interrogating the RFID? What...
  14. hevans1944

    Air Compressor Controller

    This brings back some fond memories...
  15. hevans1944

    Understanding The Following Circuit

    What is this? Cobble up a circuit and see if it works? Where is the source that will drive pin 2 negative? Is the bottom end of O/P connected to anything?
  16. hevans1944

    24v stepper controlled by aruduino

    Where do the stepper motor wires go? Is there a schematic yet?
  17. hevans1944

    Running LED - all LED turn ON when reach the last LED?

    To get any of the sixteen LEDs to light you have to connect the LED cathode to common. However, the 74154 has sixteen totem-pole outputs, so you cannot just connect the LEDs to common through fifteen transistors when you get to the last state. That would short to logic common all fifteen of the...
  18. hevans1944

    How to control the speed of a 24vdc pump from circulating water temperature?

    <sigh> Well, it was just a thought... my wife and I sometimes travel to Cookeville TN from Dayton OH to visit her relatives there. On the way, we pass by a large fresh-water marina located below one of the TVA dams. We often see houseboats tied up there to a floating dock (which also contains a...
  19. hevans1944

    Converting LED to Street Light?

    It's all about how you bias the base of the transistor and its "current gain" versus how much current the LED needs to turn on and off, and how much current the relay coil needs to turn on and off. Ideally, you want the transistor to be fully "on" or saturated when the illumination on the LDR is...
  20. hevans1944

    help on a RF wireless LED project please

    This train may have already left the station. Check out this video and also this Google results page.
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