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  1. hevans1944

    Help amplifying a tiny current

    See post #36: LED OFF, RELAY ON. See my post #38. The opto-isolator in the SSR has a 440 Ω current-limiting resistor and the SSR needs about 4 V to light-up the opto-isolator LED and turn the SSR ON. So, the OP needs to place SSR control between the collector of an NPN transistor and Vcc, drive...
  2. hevans1944

    Help with invention

    Yeah! Being a somewhat elderly person myself, I always am on the look-out for "simpler and more user friendly," plus affordable is also nice. I miss my original flip-open cell phone... just touch-tone buttons and a really tiny screen... no texting IIRC. If I remembered to setup speed-dial, just...
  3. hevans1944

    It's 1890!

    Us time travelers gotta be creative and quick on our feet. Some martial arts and weapons training might be appropriate before departing on this adventure. Light weight, too!
  4. hevans1944

    It's 1890!

    I wanna be Daddy Warbucks when war breaks out! Sell arms and ammunition to BOTH sides! Maybe run a little rum on the side like Kennedy did. Buy me a whole bunch of honest politicians. (Honest politicians stay bought -- Robert Anson Heinlein) But most of all, I just wanna have FUN! I am already...
  5. hevans1944

    It's 1890!

    How about a sports almanac showing the outcome of all games from 1890 to, say, 1950? Worked for Back to the Future 2. This was the age of Tesla and Edison and rampant cut-throat capitalism, so money rules. Need to take something that will allow you make a fortune or two... and not lose it in...
  6. hevans1944

    Designing a Time Delayed Relay

    If you are dealing with high impedance, anything above about ten meg-ohms, cleanliness is the rule. Most flux residue is hygroscopic to some extent, even if the label says it isn't. If there is any moisture in the air then your flux residue becomes a problem in the making. I always drench...
  7. hevans1944

    Howdy do

    Steve Ciarcia has a website you should visit. You might want to subscribe to his Circuit Cellar magazine if you can't find it for sale in Scotland. I grew up admiring Steve and his work and today I still occasionally purchase a copy of his magazine. Not much rocket science there, but it is user...
  8. hevans1944

    Capacitor?

    Ooh! Letting the goo out is a precursor to letting the magic smoke out. Replace it quickly!
  9. hevans1944

    Designing a Time Delayed Relay

    Metastable (definition by Murphy): A system that is stable while you are looking at, but changes states when you look away. On testing the Allegro chips: You could use an AC load plugged into the convenience outlet and then use your spiffy DSO to see the waveform at the PIC socket coming from...
  10. hevans1944

    Charged or discharged

    I am sure (well, pretty sure...) that if you had just added some more LEDs your solar panel would be truly refreshed.:rolleyes:
  11. hevans1944

    Designing a Time Delayed Relay

    Could you post your entire source code file as an uploaded attachment instead of posting it inline inside brackets? I'll open the file and inspect the code in the latest version of MPLAB X and print it out if necessary. There is probably some sort of metastable state during power-up that is...
  12. hevans1944

    Charged or discharged

    I like your detailed explanation, @OBW0549. I think you nailed exactly what was going on in the video. Now, if we could only get a rational explanation why anyone would do this... investigations in free energy or perpetual motion perhaps? That's not allowed here. But curiosity is, so that's...
  13. hevans1944

    Designing a Time Delayed Relay

    The Allegro chips are Hall Effect current sensors. There should be virtually no voltage measured across the sensing inputs, pin pairs 1-2 and 3-4. And voltage measurement from those pins with respect to anything else is totally irrelevant! " I have voltage present between U2's sensing pins...
  14. hevans1944

    Help amplifying a tiny current

    Well, I am glad that is settled. So, IF we could find a SSR that didn't require a ton of current to turn on, then it could be connected between the output, DO, and common. The internal 10 kΩ pull-up resistor would supply current to the SSR when the output goes "high" and the open-collector...
  15. hevans1944

    electromagnetism

    Well, if so, Texas Instruments beat 'em to it with their DLP (digital light projector) product. I recently viewed a movie in a theater with 4K resolution that used the TI DLP to project color images on a huge theater screen. The resolution rivaled the images from a 70mm IMAX film projection...
  16. hevans1944

    Designing a Time Delayed Relay

    Twenty-one pages is a goodly and magic number for this thread.:cool: Will look at your code and try to find the answer to your Allegro problem. Yes, look for solder bridges and things like that. Sounds like one of the Allegro chips isn't working right, based on your description of the problem...
  17. hevans1944

    single mode for Hitachi Oscilloscope...

    It is a "single sweep" mode, useful for capturing (on film) a fast, isolated, trigger event. You set up the trigger threshold and wait for the event to occur with the camera shutter open. When the 'scope triggers a single horizontal sweep is produced and (usually) a "ready" light goes out to...
  18. hevans1944

    could someone please identify this component for me?

    Hundreds of picofarads for mica capacitors is common. A few microfarads is unheard of. I have a transmitter mica stashed away somewhere that is good for a few dozen amperes of RF current. It is mounted in a three or four inch diameter ceramic cylinder with heavy metal mounting plates/electrodes...
  19. hevans1944

    Help amplifying a tiny current

    The LED turns ON when the output, DO, is low... so that would work. No series resistor is necessary. However, it was my understanding that the the OP wanted the relay to turn on when the temperature was above the setting temperature and the LED was OFF. Whatever, I goofed on calculating the...
  20. hevans1944

    Help amplifying a tiny current

    Try using a little solder to hold the wires together.:p
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