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  1. hevans1944

    Solar panel help!!!!

    Wow! I wish every new poster here provided as much information as you did! Nice job on the coop door, but how does that chain-and-sprocket arrangement cause anything to move? Is it supposed to slide a door up and down? How does it do that? The electrical circuit appears to be incorrect. The...
  2. hevans1944

    How does this work?

    What is the purpose of the simulation? Is it to verify the posted example circuit works as advertised? Clearly that circuit will not produce a sustained output! Have you measured the inductance and resistance of the primary and secondary windings on the ferrite-core transformer? Have you...
  3. hevans1944

    How does this work?

    Do you actually have the pen shown in your image? Really? This image and the schematic were copied from this website, but without the explanation of the circuit operation which appeared below the schematic. In a nutshell: 22 μF capacitor is charged from battery through 5.6 kΩ resistor... time...
  4. hevans1944

    Solar panel help!!!!

    Work up a drawing of how you had everything connected together. Show ALL the wires and connections. Post it here for our inspection and comments. Doesn't have to be a "pretty print" CAD-type drawing. Just a legible sketch you make on paper and photograph with a cellphone or digital camera or...
  5. hevans1944

    Fuses, fuses...

    Three simple things you need to know about fuses: (1) Fuses DO NOT PROTECT EQUIPMENT. (2) Fuses PROTECT WIRES. (3) NEVER replace a fuse with GREATER CURRENT rating than the original fuse. It's okay to use a fuse with a lower current rating, but it may blow. Fuses blow to protect the wiring from...
  6. hevans1944

    Led's headlight issue

    Back in the day, my wife and I would do a walk-around inspection every month or so while one of us operated the controls inside the car: brake lights, tail lights, turn signal lights (front and rear), parking lights, courtesy lights, dome light, interior light(s), and head lights (upper and...
  7. hevans1944

    LED or CFL flickering with motion sensor in circuit

    This is just a guess... most solid-state switches (SCRs and TRIACs) require a minimum holding current that must be in phase with the zero-crossing of the AC line voltage before the semiconductor will latch on. Most CFL and LED line-operated lamps do not draw enough current, or the current is...
  8. hevans1944

    Ultra Bright LED Dimmer with a sliding potentiometer

    The sentence I have highlighted above in red is the only thing that makes any sense so far. To vary the intensity of your LEDs you need to vary the effective current your power source and resistor provides. The most simple and efficient way to do this is to turn the power off and on very...
  9. hevans1944

    Help finding a suitable transformer

    Where are you going to get the three-phase primary power from? Will a certified electrician install the transformer? Is this a wye connection or a delta connection? Is the secondary a wye or a delta? What are you trying to DO? A 40 kVA transformer, convection cooled, is a pretty good sized...
  10. hevans1944

    Designing a Time Delayed Relay

    :D:D:D:D Looks like you have nailed it! :D:D:D:D I trust this will transfer (minus the I/O statements) to the PIC. Should be easy to test if you have bread-boarded the Allegro simulator. Use your spiffy digital storage oscilloscope to monitor the simulation waveform as you crank it up and down...
  11. hevans1944

    RC Time Constant

    Well, pretty much. The capacitor charges exponentially through a series resistor toward the applied voltage, theoretically never actually reaching the applied voltage. The use of five time constants to represent "fully charged" is just for convenience. The difference in capacitor voltage after...
  12. hevans1944

    Can someone explain me how a BJT works?

    Your English is okay.:D Although this forum is based on English, it attracts worldwide participants. Some of us sometimes struggle to understand when people write, and English is not their mother-tongue, but everyone is welcome here. My southern neighbors speak Spanish fluently, but...
  13. hevans1944

    Can someone explain me how a BJT works?

    That depends on whether you care if your "understanding" is pretty much correct or just a poor approximation to reality. It could be argued that any understanding is just an approximation to reality, but some approximations are better than others. For example, in post #24, Colin disputes the...
  14. hevans1944

    need help with a relay

    You can always close a separate circuit with a logic-level signal by interposing a switching transistor and a relay. For most applications a 2N7000 MOSFET transistor is easy to hook up: connect logic-level signal to gate, connect a relay coil with a diode across its coil between a positive...
  15. hevans1944

    Working With 240v And Arduino

    Come summer, maybe you could add one or more Peltier coolers to the outside of the can, perhaps mounted between wraps of the heat cord? Not sure how you could control the humidity though. And you might have to add heat sinks to the Peltier coolers. Please post us some pictures when your first...
  16. hevans1944

    Designing a Time Delayed Relay

    It is the difference that is changing. Compute (max - min) and store that value, say as PK_PK, before entering the max/min loop. If you initialize max = min = 0x200 or 0x1FF (half of the full-scale ADC output range) before you enter the max/min loop, then the initial value of (max - min) will be...
  17. hevans1944

    Need help selecting a transistor for a large power load

    Is the intent to progressively turn on the four loads? Actuate SW1 and LOAD1 turns on; actuate SW2 and LOAD1 and LOAD2 turns on; actuate SW3 and LOAD1, LOAD2, and LOAD3 turns on; actuate SW4 and LOAD1, LOAD2, LOAD3, and LOAD4 all turn on? Is that what the three "steering" diodes are for? If so...
  18. hevans1944

    Working With 240v And Arduino

    You could add the little light in parallel with the heat cord so both come on at the same time. Maybe even use a higher wattage bulb. Maybe blow air across a large light bulb and use that instead of a heat cord. Lots of ways to make warm, dry, air. Back in the day you could buy nichrome heaters...
  19. hevans1944

    Designing a Time Delayed Relay

    Yikes! I almost missed that last post. Didn't show up in my alerts at first. Found it when I listed all the alerts to date. I think I got it wrong as to when to exit the loop. When temp_peak = max - min quits changing it is time to exit the loop. I'm a little busy right now, but I will try to...
  20. hevans1944

    Working With 240v And Arduino

    I think we should welcome you to the real world of interfacing to digital logic circuits. Strange and unexpected things can and do happen. I won't even attempt to explain what can go wrong, but will suggest that an oscilloscope is a very handy tool to chase the problem down and stomp on it. In...
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