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  1. AnalogKid

    Power failure alarm

    Your question is missing a *lot* of detail. What is the relationship between the timer and the alarm? Do you expect the battery to power the alarm for 2 hours? 2 hours is a loooong time for a 555 timer circuit; even the CMOS version would be iffy.. Rather than have us waste time trying to...
  2. AnalogKid

    want to tinker with my UPS.....

    I do. Can you post a sketch of the various components and how you have them connected now, and another with your proposed changes? Paraphrasing Rear Admiral Joshua Painter, "Engineers don't take a dump, son, without a schematic." ak
  3. AnalogKid

    want to tinker with my UPS.....

    Why? If the battery voltage and the battery chemistry are identical, the charger doesn't know or care about the capacity; all discharged batteries (of the *same chemistry*) look alike. The charger circuit will run longer before shifting down to trickle mode, but it already has a fan so that...
  4. AnalogKid

    want to tinker with my UPS.....

    OR, in American: Tang Yew Berry Mulch. ak
  5. AnalogKid

    I need a 350V, 1A PSU

    The LR8 has a max output current of 30 mA, and there is no application circuit in the datasheet to boost this. Also, its minimum input-to-output differential voltage is 12 V, while the LM317's is around 2 V at a 1 A output current.. ak
  6. AnalogKid

    I need a 350V, 1A PSU

    Based on that post, here's a plan. 1:1 or 1:2 isolation transformer plus a low voltage transformer gets you a peak voltage after rectification of 370 V. With lotsa filter capacitance, the ripple voltage minimums are around 355 V to 360 V. An LM317 regulates this to a flat 350 V. ak
  7. AnalogKid

    I need a 350V, 1A PSU

    Harris used to make something similar, in a TO-220 package for higher output current. I think they are all obsolete now. Note that the grand old LM317 will work in this application. It's 43 V rating is for the voltage from its input to its output, not from its input to GND.
  8. AnalogKid

    I need a 350V, 1A PSU

    A power Factor correcting (PFC) front end is a regulated boost converter. Usually these are non-isolated. One of these plus a 1:1 isolation transformer could do what you want. You might have to post-regulate it to reduce the high-frequency ripple. Is a 350 V output switcher a possibility, of...
  9. AnalogKid

    I need a 350V, 1A PSU

    Fixed 350 Vdc or adjustable over a range? What is the minimum output current expected? Some supplies have a minimum output current requirement; below that amount, the output regulation becomes unstable, the output impedance increases, etc. What does "smooth" mean? Filtered but with some...
  10. AnalogKid

    Mosfets as voltage dividers.

    That is an all linear supply, with the output current limited to around 2 to 2.5 A (not the 7 A stated on the drawing.) Also, D1 - D4 are rated for only 3 A. The circuit output voltage is adjustable from 10 V to 19 V -ish, it the power transformer can support it. You can replace the...
  11. AnalogKid

    Mosfets as voltage dividers.

    That is not much information to work with. Make and model of the bench power supply? Reason it needs to be rebuilt? In what way is it not working normally? Link to one of the videos you describe? Supply, its front panel, the board - anything? ak
  12. AnalogKid

    Mosfets as voltage dividers.

    What this?
  13. AnalogKid

    Help Repurposing an LED Sign Panel

    P.h.o.t.o.s.
  14. AnalogKid

    Simple Hall sensor alarm circuit?

    That is the safe way to start if you have no clues to the approximate current levels you are measuring. But in this case there are lotsa clues. Except for accidentally dead-shorting the batter, you are probably safe starting with the low range. But . . . At its heart, what you have is a volt...
  15. AnalogKid

    Simple Hall sensor alarm circuit?

    Yes. The 10 K resistor protects the reed switch contacts. When the switch is open, R1 charges up C1 to 9 V. This takes a several seconds because R1 is so large. When the switch closes, all of the charge in C1 is dumped through it in microseconds. Even though it is very brief, this can be a...
  16. AnalogKid

    Want to make a box that will open at a programmed time.

    https://www.ebay.com/itm/394863187122?itmmeta=01HTT4044SM5HQFJQK4A3TYZRM&hash=item5befae14b2:g:qWAAAOSwh4NlUxQr&itmprp=enc%3AAQAJAAAA4IuhgXTE4ijikRGNo9CkfL2SA1CKTFFwLB%2FUFi4%2FLDknK%2FppMMECrjJ%2FrsG1XDk4nE8Ax4ngkdAU0pPu1Kzgj8xlk3EwN8qSDICxJoh5%2F2sNISsGZ43lt53lfF6BOch46yJs2f7auQW236djxTt5O%2B%2...
  17. AnalogKid

    Want to make a box that will open at a programmed time.

    You said you like making things out of wood, so . . . ak
  18. AnalogKid

    Want to make a box that will open at a programmed time.

    Think about this. A spring-loaded lid that pops open when a latch is retracted. A small solenoid connected to the latch. A small wall-wart type power supply to power the solenoid. A lamp timer. A 3 am, the timer powers the wall-wart, which powers the solenoid, which retracts the latch. For a...
  19. AnalogKid

    circuit breaker alarm

    First, you have discovered a great truth - m-m-m-m-Many of the circuits on the innergoogle are intentional garbage. But there is an alternative. It is with great trepidation that I do this, because for an undisciplined soul this can be free crack cocaine...
  20. AnalogKid

    circuit breaker alarm

    A photodiode is not a fully integrated IR receiver; it's just a diode. It sees all ambient light of all frequencies from all sources. If any of it is in the right frequency range, it responds. It is common for a circuit like this to work in a dark room, but fail when the sun comes up because...
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