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  1. AnalogKid

    120v dc power supply

    It sounds like you are talking about an offline power supply making 160 Vpeak after the rectifiers. 1. The capacitor voltage must be greater than 160 V. 2x the peak voltage is recommended for long-term reliability. 2. Offline supplies are a banned topic. No gigantic power transformer, no...
  2. AnalogKid

    Need help on the evaluation board of a capacitive readout chip

    Or Field Ground. Frame, Field, or Chassis grounds usually are tied to earth ground. This can be at a different potential than the system or signal ground, and this can cause ground loops that inject noise into signal lines and cause other squirrely behavior. There is a jumper so the user has...
  3. AnalogKid

    I need a PCB designed

    The zener diode is reversed. And if the Signal Source has a bipolar output (that is, it can pull the Arduino input up to 5 V or pull it down to ground), then R2 is not needed unless you are counting on it to form a 94% voltage divider with R1. ak
  4. AnalogKid

    Power Supply...

    All secondary (rechargeable) batteries have a lower energy density (watt-hours per kilogram) than the equivalent primary (single-use/disposable) battery, so it might be possible to reduce the battery size/weight by going to disposables. But the size, weight, and connection complexity still will...
  5. AnalogKid

    Help with Class D amplifier

    That's 36 dB, not 63 dB. ak
  6. AnalogKid

    Power Supply...

    Amps (as opposed to milliamps) times days (as opposed to hours) = you better sit down for this. At 100% efficiency, 4 amps times 50 hours is a 200 Ah (amp-hour) requirement at 5V. For a 12 V SLA (sealed lead-acid) battery running at 13 V or greater that becomes 77 Ah. With a 90% efficient...
  7. AnalogKid

    I need a PCB designed

    The schematic in post #1 is incorrect. ak
  8. AnalogKid

    Help with Class D amplifier

    What are the peak to peak input audio voltage and the peak to peak audio voltage across the speaker? Voltmeters lie; trust a scope. ak
  9. AnalogKid

    Battery monitor indicator ??

    Maybe. It would take some tricky input scaling and using every other output to hit the step values, plus keeping the external transistor that bugs me. The apparent complexity of the post #1 schematic is deceptive because he is using a quad comparator, not four individual opamps as implied by...
  10. AnalogKid

    Power supply

    While neutral and earth ground are tied together in a breaker box in domestic US electric service, I'm not sure what the requirements are for 220 Vac when it comes from two 120 Vac phases 180 degrees apart. It might be that the third outlet contact is earth, not neutral, in which case it goes...
  11. AnalogKid

    Battery monitor indicator ??

    The voltage can be scaled to something withing the 3914 operating range. The problem is condition iv in post #1. Without several external components, the standard 3914 circuit will not toggle between acting as a bar graph for one range of input values, and acting as a single comparator for...
  12. AnalogKid

    Battery monitor indicator ??

    A 3914 can't display the status pattern he wants. ak
  13. AnalogKid

    Electronic Metronome

    Music synthesizers like them because they have the same harmonic field as square wave, but the spectral energy drops off more rapidly with frequency. This gives you some of the edginess of a squarewave tone without it hurting your teeth. ak
  14. AnalogKid

    Power supply

    The supply has a universal input, so either case you mention is ok in terms of powering the unit. The front end will work less hard with the 220 V version. However, the supply's power line EMI filter has caps from both the L and N inputs to FG (field ground, earth ground, chassis, whatever)...
  15. AnalogKid

    Battery monitor indicator ??

    1. What are the trip points now? 2. What is the part number or the opamp/comparator? 3. Any particular reason you didn't use a quad comparator like the LM339? 4. T1 can be eliminated and LED6 driven the same way as the other three LEDs by reversing the inputs to OP4. 5. None of the...
  16. AnalogKid

    Thermistor Temperature Sensor

    The wire is not the source of error for a 10K sensor. Even at high temperatures it is around 3K ohms, thousands of times larger than the wire resistance. OTOH, the unit is only +/- 1C accurate, so technically it is within spec. If you don't see a calibration trimpot peeking out anywhere, or...
  17. AnalogKid

    Recording the entire signal of an RJ11 line

    0 for 2. POTS (Plain Old Telephone Service) is essentially the same as in 1876, decades before the first electronic component (the vacuum tube) was invented. A telephone signal isn't just an analog signal, it is *the* analog signal. There is unidirectional power (-48 Vdc with a relatively...
  18. AnalogKid

    Electronic Metronome

    1. Yes, for many single-frequency R-C oscillators the output freq is dependent on one resistor, and that can be replaced with a group of resistors and a mechanical rotary switch, or a switching circuit controlled by a microcontroller. Also, each resistor probably will have to be a fixed...
  19. AnalogKid

    Electronic Metronome

    Yes, but as Bob said, a classic metronome has a very coarse indication of tempo. A metal bar with stamped notches and numbers for every 5 or 10 beats per minute is not at all precise, and a pot with a printed dial around it should be at least as good if there are a couple of hidden trim pots to...
  20. AnalogKid

    Polarity change for linear actuator logic question

    With all unipolar power supplies and relay control, there are two or three basic ways to do this and all of them take at least two relays. Performing two different tasks (power control and direction control) takes two switches of some kind. Separate from that - if S1 is built into the actuator...
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