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  1. hevans1944

    Publishing my notes and potentially selling them

    Sure, the Internet is full of self-published notes, papers, opinions, diagrams, instructions, and (sometimes) even useful information. Yours would be a niche market of interest, perhaps, to anyone studying for the AM2 exam (whatever that is). There are several approaches to "selling" your...
  2. hevans1944

    Measurement -2.5 +2.5 with ADC

    I don't do schematics much. You should be able to draw one from my description and post it here. If you make mistakes, I will attempt to correct them. It's a very simple circuit: four resistors and one op-amp. Or maybe someone else here on EP can chime in with a schematic.
  3. hevans1944

    LED monitor using phototransistor

    I would try to use a short piece of transparent tubing (Tygon or similar) that will fit over the LED and contain on the other end the photo transistor, connected to your PCB with a length of twisted-pair wire. If you have a problem with stray light, paint the tubing black and depend on your...
  4. hevans1944

    Basic multisim - How do I know which pin number is what??? Help!

    I know nothing about Multisim, but did find this diagram (at this forum website) with pin numbers: I used this Google result page. Does that help any? I generally avoid simulation and prefer building circuits with real components. After reading the datasheets of course. :D
  5. hevans1944

    Motor Discussion

    Torque and speed are all over the map when it comes to DC motor drives. I have a pair of DC motors that came off a computer tape drive. These were used as servo motors to spin the reels very fast but stop on a dime when the desired area of the tape was found. I was going to use them with a...
  6. hevans1944

    Help with motion sensor and motor DC

    Well, it depends on how serious you are. I plan to replace my venerable B&K Model 2890A with the newer model 393, available for about $200 at various places on the Internet. The older model works just fine and it has never given me any trouble, but the newer version has more counts (60000), a...
  7. hevans1944

    LED monitor using phototransistor

    Do you wish to determine whether the LED is illuminated or not illuminated? In other words, whether the LED is defective? What is the color of the LED? How much current flows through it from the 3.3 V DC source when the microprocessor output is low? How do you plan to couple the LED light output...
  8. hevans1944

    Measurement -2.5 +2.5 with ADC

    The complexity of what you want to do depends a lot on the ADC resolution and accuracy. For an 8-bit ADC, it's not much of a problem. For a 23- or 24-bit ADC, it's a lot more complicated. Many microprocessors have uni-polar ADC built-in. The Arduino Uno, for example, has an ADC with a 0 to +5 V...
  9. hevans1944

    auto resetting timer 110v a/c

    Oh, I didn't notice the "off the shelf" requirement. Never mind the DIY approach I recommended. There are lots of commercial off-the-shelf (COTS) timed-delay-to-off products available. Some wiring required. And perhaps deep pockets. Good hunting!
  10. hevans1944

    auto resetting timer 110v a/c

    I purchased one of these to control a ceiling-mounted infrared heat lamp in my bathroom. Turn it to 60 minutes when I get in the shower and it shuts off automagically an hour later if I forget to turn it off after my shower. I don't think this is what the OP wants. Sounds like his well pump...
  11. hevans1944

    "Good" DMMs with bar-graphs - crippled by design?

    You make a lot of assumptions and generalizations about the way digital multimeter bar-graph displays work in conjunction with their 7-segment digital displays. I use a (now discontinued) B&K Precision Model 2890A digital multimeter with a 00000 to 51000 count 7-segment display, and below that a...
  12. hevans1944

    Help with motion sensor and motor DC

    Yeah, a multimeter is a very handy tool to have on hand when experimenting with electronics. Do you need any help in selecting a particular multimeter?
  13. hevans1944

    Converting LED to Street Light?

    It looks like you want a "street light" that turns on at dusk and turns off at dawn and operates from AC mains power. Plenty of these lights already exist on the commercial market. Some even have passive infrared (PIR) motion sensors to turn the light on during the dark time, thereby saving a...
  14. hevans1944

    vehicle external projection using laser beam on outside environment

    Aw, some nations don't concern themselves with patents. It is so much easier to rip off ideas from someone else than to come up with something original. This paradigm also saves a fortune in expenditures for original research and development. One of many reasons I think patents are generally...
  15. hevans1944

    Active and resistive load current

    The original poster, @kalpana, joined EP on June 17, 2016, and posted his question that same day. Since then, there has been no response from the OP. Nada. Nothing. Meantime, regular posters here have been playing "ring around the rosie" with the question. It's more than past time to stop...
  16. hevans1944

    Electronic System Design

    Oh, really? Did you not get anything from the links on this page? Everything I ever learned about television became instantly obsolete and irrelevant the day American broadcasting switched from analog NTSC standards to digital. Fortunately by then I was long out of the TV repair business and...
  17. hevans1944

    Power amplifier

    The application I cited was for intermittent remote monitoring of thousands of "smart" sensors scattered across a large area to which access could be denied for reasons of political boundaries, conflict, or other dangers to health, whether chemical, biological, or radio-logical. Continuous...
  18. hevans1944

    Power amplifier

    No it isn't. And the technology has been around for awhile. What is new is the ultra-low power requirements of modern electronic systems. Wireless power is commonly used to activate both active and passive RFID devices. Carrying this a bit further, one could scatter thousands of active "smart"...
  19. hevans1944

    Electronic System Design

    hnd = HND = Higher National Diploma. A British equivalent of a trade school, attempting to prepare people for a career as a technician. A goodly part of systems design is defining what is important and what is not so important and what doesn't even need to be considered. A powerful tool for...
  20. hevans1944

    Pushbutton circuit

    Here's my two cents: scan the array of switches however you choose that associates a number from 1 to 20 with each actuated switch. Let these numbers represent binary bit positions in three bytes of a four-byte word. The fourth byte is a CRC of the first three bytes. Now, either transmit the...
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