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  1. AnalogKid

    What the latch?

    Not all CMOS is created equal. The circuit in post #13 triggered a thought. The prime requirements for a latch are 100% positive feedback (that keeps the outputs stable when the input is removed) and a way for the input to override the latched state and force the circuit to the other state...
  2. AnalogKid

    What the latch?

    As noted above, a single SCR is the entire circuit if you have both normally open and normally closed switches. In this schematic, add a second reset switch in series with the one already there. http://www.zen22142.zen.co.uk/Circuits/Switching/latch2.htm Here are some other options. The left...
  3. AnalogKid

    What the latch?

    Notice that the first schematic does not have a resistor in series with the PNP base, but the second schematic does. This is a critical error, leading to premature death of the PNP. The second sch is correct. A consequence of both of those circuits is that the input should be floating when...
  4. AnalogKid

    4 channel optoisolator NC

    I don't know if you dropped a comma, but there is no such thing as a PNP MOSFET. ak
  5. AnalogKid

    4 channel optoisolator NC

    Note that in post #3, I said ***IF*** you want ground isolation, isolate the grounds (duh). Of course they can be connected, depending on the rest of the circuit requirements. Which are ... ? ak
  6. AnalogKid

    4 channel optoisolator NC

    If you want the isolation benefits of optical isolation, then keep all left side and right side signals completely separate. Do not combine the grounds. ak
  7. AnalogKid

    Electronic Gate Wiring

    Then two maglocks in parallel wired for 24 V operation look like they are at the save operating limit of the controller. With high res photos of the controller board and some probing around, we probably can figure out how to add an external power transistor driver with much higher ratings. ak
  8. AnalogKid

    Electronic Gate Wiring

    I have family in Warren, and I've driven through Lodi many times just to get off the freeways. And, traditionally, to buy Oreo's (long story). Looks like the mag lock has two coils for operating on 12 V when connected in parallel and 24 V when connected in series. And it has a SPDT (form C)...
  9. AnalogKid

    Electronic Gate Wiring

    Well, let's see....hmmm... I just don't know...maybe datasheets on the gate operator and the locks....?
  10. AnalogKid

    Electric curtain project: single Push button design

    My fantastic 2-relay solution ran into a glitch, in that the limit switches are not momentary. When the traveler hits one, it changes state and sits there. So it needs to be differentiated before it is combined with the pushbutton, and that is a biiiig cap for 533 mA, greater than 10,000 uF at...
  11. AnalogKid

    Electric curtain project: single Push button design

    I don't see the limit switches in there. ak
  12. AnalogKid

    What's wrong with circuit?

    I think it is a rectifier. Yes, I am aware that a zener diode acts as a rectifier when forward biased, That does not mean that a simple rectifier can act as a zener diode when reverse biased. And by "act as a zener", I mean with a defined, stable zener voltage. Please post a datasheet for a...
  13. AnalogKid

    struggling to learn basics - 555 timer led flasher

    1. In a series circuit, all of the current goes through all of the components. The current is determined by the voltage source and the sum of the impedances of the components in series. So if you have a 10 V battery connected to a 2 ohm and 8 ohm resistor in series, the total resistance is 10...
  14. AnalogKid

    Wiring up 2 or more 220V axial fans

    Definitely maybe. Photo of circuit board? ak
  15. AnalogKid

    Wiring up 2 or more 220V axial fans

    AC fans cannot be wired in series. Also, the fans are not polarity sensitive (there is no plus or minus input) so any straight parallel connection is safe. The fans won't care about 50 or 60 Hz, but might run faster on 60 Hz. ak
  16. AnalogKid

    struggling to learn basics - 555 timer led flasher

    Sorta kinda in the order of post #1.. 1. The primary function of a schematic is to show the signal flows and signal flow interactions, not to act as a physical wiring diagram. A schematic is a language unto itself. Generally speaking for both an overall schematic and the individual component...
  17. AnalogKid

    Help.. Modifying a circuit to eliminate 30 minute time out

    Working with nothing but your posts, we are literally blind here. Please post close-up photos of the guts, such as both sides of the printed circuit board (if there is one). My guess is that there is a small microprocessor doing the timing, as 30 minutes is a loooong time for a simple...
  18. AnalogKid

    Help me build a spaceship

    Start with a block diagram of the basic functional blocks, then block diagrams of those blocks' internal structures. ak
  19. AnalogKid

    Electric curtain project: single Push button design

    Is this the complete logic tree: 1st press: forward 2nd press or end of travel switch: stop 3rd press: reverse 4th press or end of travel switch: stop repeat If so, this can be done with two latching relays. Relay 1 is DPDT, forward/reverse. DC comes in, goes directly to the coil, and then...
  20. AnalogKid

    Timer What type is It? Please Help...

    ebay, a programmable timer is around $10. ak
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