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  1. AnalogKid

    555 circuit to hibernate computer

    What are the values of the two resistors you use to attenuate the battery voltage down to logic level? Based on those, you can calculate a noise filter capacitor that makes the circuit immune to short-term fluctuations. ak
  2. AnalogKid

    555 circuit to hibernate computer

    This is an electrical engineering forum. A schematic is a bit more than a suggestion. Separate from that, your circuit will not work because a 555 is not a true monostable. As you have discovered, once the trigger input falls below its threshold voltage the output will change state and stay...
  3. AnalogKid

    555 circuit to hibernate computer

    Please post your schematic. ak
  4. AnalogKid

    Found this circuit on youtube

    The 100K resistor is what turns on the MOSFET when it is dark. It forms a voltage divider with the photocell. When it is light, the cell resistance is so low that the voltage at the gate is too low to allow enhancement (conduction), and the LED is off. When it is dark, the cell resistance is...
  5. AnalogKid

    Durable flipflops and other counters?

    The manufacturer's datasheet for the exact part you have will have temperature ranges for both storage and operation. CMOS devices generate very little internal heat, so you cannot rely on insulation alone to protect it from extreme low temperatures. Beyond that, as above, most reliability...
  6. AnalogKid

    Push Button Sequencer Switch (No ICs)

    There are 2 4069's required for the schematic. One way to evaluate the relative "simpleness" of a circuit approach, especially for an amateur building a one-off home or school project, is to count the number of soldered pins. For digital logic, this includes all power and input pins, but not...
  7. AnalogKid

    Push Button Sequencer Switch (No ICs)

    In post #3, the first stage comes on when the switch is open. ak
  8. AnalogKid

    Pulse Width Modulation

    That is not how a monostable works. A monostable makes a constant-width (and constant-amplitude) output pulse whenever it is triggered. Based on your description, it sounds like PPM - pulse position modulation. The first 555 is variable frequency and the second one is constant-width. As the...
  9. AnalogKid

    Discrete 555 KISS Style (11 Transistors)

    While the operation might be identical, there are significant differences in performance between your circuit and the original. Are you aware of what they are? ak
  10. AnalogKid

    Discrete 555 KISS Style (11 Transistors)

    Reset input?
  11. AnalogKid

    Pic interface with sensor

    Your plan would work if the output were 5 V or more, but not with 0.65 V. IF I understand your description correctly, the gate-source voltage (Vgs) will be only 0.65 V when the FET is on. This is not enough to enhance the FET. You would have to pull the gate down to at least -2 V (depending...
  12. AnalogKid

    Push Button Switch Selector 'One hot' (No ICs)

    Your calculations are based on a series of assumptions that are not valid individually, let alone in combination. Since you are the one asking for free help, you could just supply the information. No, not ever. First, there is no "standard" battery with a 5 V output. Plus, I don't think...
  13. AnalogKid

    Push Button Switch Selector 'One hot' (No ICs)

    Reference Designators ! ! ! When a switch is closed, the collector of the bipolar transistor is a little below Vbat/2. Depending on the (secret) battery voltage, this might not be low enough to turn off any latched circuits. Also, the base current is (Vbat - 0.6) / 2 million. That might not...
  14. AnalogKid

    How to: power this old ringer?

    Traditionally, a phone bell needs around 70 to 90 Vac, at around 20 to 30 Hz. But to see if is even functional, use a transformer with a 24 to 48 Vac secondary. The armature won't be happy trying to move that fast, but you should get something out. ak
  15. AnalogKid

    Heathkit ET 3400

    So do I, with both of you. No, it isn't, for several reasons, not the least of which is that the majority of VME SBC's are Intel-based. Yes, VME grew out of the Motorola Exorcisor development system of the late 70's. But while it was away at finishing school in Europe, the control structure...
  16. AnalogKid

    DRC Error in PCB Design

    D1 and R1 are reference designators. An assembly number is a part number assigned to an assembled and test unit. This would be the number used if someone wanted to order a replacement device. In a manufacturing company, everything has to have a part number. This makes it possible to order...
  17. AnalogKid

    DRC Error in PCB Design

    To aid in orientation and troubleshooting, it is common practice to make the pin #1 pad a different shape from the other pads in a decal. Typically, most pads are round or oval, and the pin 1 pad is square or rectangular. This makes a big difference when you are poking around on the bottom...
  18. AnalogKid

    DRC Error in PCB Design

    An airwire is an unrouted trace. Your image shows three of them clearly (the very thin lines connecting pads). Once you route these, the error should go away. I'm not an Eagle expert, but there should be a way to turn off DRC until more of the board is routed. Then as a check of the final...
  19. AnalogKid

    1.5 volt bulb won't light in my circuit newbie

    Excellent ! ak
  20. AnalogKid

    1.5 volt bulb won't light in my circuit newbie

    Oh, BORSCHT ! algebra - noun: A system for computation using letters or other symbols to represent numbers, with rules for manipulating these symbols. https://en.wiktionary.org/wiki/algebra If that isn't Ohm's Law, then what is? ak
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