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  1. hevans1944

    Selection of presence sensor

    A lot of public toilets in the USA have PIR sensors mounted in the wall behind the toilet. They "arm" themselves when someone approaches and then flush the toilet when you move away from the sensor. For a shower, you would want to increase the sensitivity, and perhaps fiddle with the IR Fresnel...
  2. hevans1944

    Detecting solenoid ON and OFF state

    Nah, it's all just "comic book" fiction... or graphic novels as they are called today for an illiterate generation of "readers". The "Loom of Fate" is not a movie, it was a loom featured in the movie. Movie and the loom have no resemblance to the real world. It's just escapist entertainment...
  3. hevans1944

    Selection of presence sensor

    A PIR sensor is insensitive to environmental temperature changes and should work well embedded in a shower wall. You should do some research on exactly how a PIR sensor works and why that previous statement is true. You are attending a university, are you not? They are supposed to teach you how...
  4. hevans1944

    Cheaper Source of Part#BT53

    Could you be looking to replace this Bluetooth transceiver with a cheaper Chinese counterfeit? Good luck with that. The Chinese are really good at reverse-engineering and duplicating successful commercial products, as well as developing some pretty nice technology on their own, now that they...
  5. hevans1944

    Mosfet IRF540 acting weirdly with Arduino

    Circuit looks okay. But the IRF540 can have anywhere from one to ten microamperes of leakage current (temperature dependent). So, if the resistance is large, the IRF540 will act as a voltage divider as result of the leakage current from drain to source. What is the value of the resistance?
  6. hevans1944

    Detecting solenoid ON and OFF state

    Thank you for the compliment, but I do not know all. I barely understand how a loom works, and have never actually seen or touched one, so my practical experience is non-existent with regard to looms. You are far more qualified to talk about this than I am. There is a 2008 movie, "Wanted"...
  7. hevans1944

    Detecting solenoid ON and OFF state

    I have been fascinated with weaving for a long time, but have never tried to build even a hand-loom. So, I Googled some information on dobby looms and their advanced enhancement, the Jacquard loom. A computer-controlled dobby loom is a common thing, but usually only a maximum of 24 harnesses or...
  8. hevans1944

    Detecting solenoid ON and OFF state

    The problem with simulation is accuracy. The real world exhibits skew when two or more digital variables, like PIC outputs, change "simultaneously". Even on your best day there can be enough propagation delay in logic elements and wiring to create "glitches" or momentary states that lead to...
  9. hevans1944

    Detecting solenoid ON and OFF state

    This appears to be very conservative design. I can't tell you whether all those pull-up resistors are necessary or not, but probably not. All the devices (including the PIC) have active totem-pole output capable of sinking or sourcing at least 4 mA of current with a 5 V supply, which means...
  10. hevans1944

    Electronic Equivalent of a 3P6T 'Rotary' 3-Deck Switch

    @Silver Hawk, I recommend that you use a Microchip PIC10F200 (or 202, 204, or 206) in an 8-pin PDIP package and build a prototype circuit while you learn to program the PIC. Unless you are skilled at using teeny, tiny, microscopic-sized parts, avoid the 6-pin SMD package for now. This particular...
  11. hevans1944

    Detecting solenoid ON and OFF state

    Sure. Same principle applies. Are you considering using CMOS logic? It should work the same way as TTL with somewhat better noise immunity. The important thing you need to remember is that time delay from when you actuate the coil of a solenoid to when the switch closes. During this short...
  12. hevans1944

    Looking for cheap ammeter that measure the smallest amp

    Yeah, if AC milliamperes instead of DC milliamperes are to be measured, that's a whole 'nother ball game.
  13. hevans1944

    Optical Encoder Issue

    This is clearly a shielding and power supply problem. The switch-mode power supply is probably responsible for the interference. Try wrapping the sensor ribbon cable in aluminum foil and, using a short jumper wire with alligator clips on each end, connect the end of the foil farthest from the...
  14. hevans1944

    Looking for cheap ammeter that measure the smallest amp

    Or how about this one. Just place a one-ohm resistor in series with your load and measure the voltage drop across it. Measures from 0 to 199.9 mA with a one ohm resistor in series with the load. Requires a 12 V DC wall-wart power supply.
  15. hevans1944

    Electronic Equivalent of a 3P6T 'Rotary' 3-Deck Switch

    For the diode and a rotary 1P6T switch solution, you simply apply power to the pole and attach forward biased diodes to the six throw positions, one diode for each LED that will be illuminated at a particular position. Therefore, at switch position 1 there are no diodes and no LEDs will...
  16. hevans1944

    Building a current source

    You are absolutely correct. But whether you need the I and D depends on what the load is and whether the control (command) input is varying. You do seldom see a constant current source with the derivative action: that tends to add unnecessary noise to the output. No response yet from the OP, so...
  17. hevans1944

    Detecting solenoid ON and OFF state

    You need to replace the exclusive-OR gate (XOR) with an open-collector NAND gate. If the solenoid command from the microprocessor is high, indicating the solenoid should operate, and the switch subsequently fails to close, then the NAND gate output will be low, indicating an error condition...
  18. hevans1944

    Detecting solenoid ON and OFF state

    Your "contact point switch" already provides an "active low" signal indicative of the solenoid state. The exclusive-OR gate does nothing except invert the switch signal, which an inverter would do with less complexity. What are you trying to DO with the other 127 solenoids? Do you want to...
  19. hevans1944

    Electronic Equivalent of a 3P6T 'Rotary' 3-Deck Switch

    So, if 0 represents off and 1 represents on, you want your three LEDs to sequence like this: 001, 010, 100, 110 or 011 or 101, 111 and 000? Does it make any difference, when two out of the three are on, which two those would be out of the three possibilities?
  20. hevans1944

    Building DIY Vacuum tubes

    I think you have succeeded. The low vapor-pressure epoxy sealing technique truly does bring this into reach of the rankest amateur who can get their hands on a decent vacuum pump. Hop
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