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  1. AnalogKid

    LED not working

    The original bulbs were incandescent. If the new ones are simple LEDs with no internal current limiting, they will burn up. Please post a link to the LEDs you are using. ak
  2. AnalogKid

    LED not working

    Shouldn't that be L-E-D - ? ak
  3. AnalogKid

    Relay LED Optocoupler Circuit

    Both sides of the opto couplers are referenced to the same GND. Because of this, the optos can be replaced with simple 2-resistor voltage dividers. ak
  4. AnalogKid

    LED 1 input 2 output

    After the second LED is on, what happens if the switch is toggled again in under 5 seconds? Does the circuit revert to LED #1, or does it stay on LED #2? ak
  5. AnalogKid

    Looking for an old Motorola IC OpAmp SC9533P (7308)

    Why? Those parts have absolutely nothing to do with this thread. am
  6. AnalogKid

    How to use low voltage switch for 110V circuit

    Too bad. The switch is rated for a max. of 30 V, so you will need a low voltage supply. Simple and cheap - an old USB wall wart / phone charger / camera charger / etc. That, plus a solid state relay rated for at least 50% more than your 110 V load current. Most SSR's have a current-limiting...
  7. AnalogKid

    RCA 45J Problem

    Any photos? Make and model number of the device? I know what you are talking about, but my guess is that half the people on this forum don't. ak
  8. AnalogKid

    Looking for an old Motorola IC OpAmp SC9533P (7308)

    That is an early audio power amplifier, probably rated for 2-5 W. GE made similar parts in the PA2xx series. In the 1970's, Sprague made the ULN2280 / 2281; they have the same package and probably the same pinout. Also, National made a variation of the LM380 in that package, plus the LM384...
  9. AnalogKid

    Adding an audio output to an old answering machine

    Yes. ak
  10. AnalogKid

    Using a DC voltage to drive a relay to interrupt a power supply

    You need a DPDT (Double Pole Double Throw) relay with a 24 Vdc coil. The relay contacts must be rated for more than 24 V, and the current rating for the contacts should be at least twice the power supply output current that is being interrupted. Connect the power supply output to the relay...
  11. AnalogKid

    Help To Determine Resistor To Dim Incandescent Light Bulbs

    Don't see why not. Two say LED because that's what most people are searching for. One says motor because that is another popular product. To be clear, I do not have any experience with any of these specific products. But a simple PWM circuit with a big enough power transistor should have no...
  12. AnalogKid

    Help To Determine Resistor To Dim Incandescent Light Bulbs

    If you want to buy rather than build, my first stop is ebay...
  13. AnalogKid

    circuit breaker alarm

    Here is a first pass at a schematic. The PIR signal at P1pin2 drives Q1 to control the beeper. When power is applied there is 0 V across C1, so the Q2 gate is at 9 V and it pulls the Q1 base to GND no matter the state of the PIR signal. After about 1 minute, C1 has charged up (down?) to...
  14. AnalogKid

    circuit breaker alarm

    How long a delay? The datasheet says the module can take up to 60 seconds after power-on to stabilize. The sensor output can drive a 2N2222 directly, so what is needed is a circuit to inhibit this for 1 minute, then get out of the way and let the PIR have direct control of the beeper. First...
  15. AnalogKid

    circuit breaker alarm

    Correct me if I'm wrong - the goal is to inhibit the sensor output at power-up, and prevent the beeper from beeping for a few seconds while you leave the room. After that, the sensor controls the beeper without delays - when the sensor "sees" something, the beeper goes off immediately. Yes /...
  16. AnalogKid

    circuit breaker alarm

    Again, need a lot more information. PIR device part number / model number / vendor / website - anything? Voltage and current ratings for the buzzer? What is the voltage for the circuit? What is the PIR device output signal when it senses someone - a high voltage level, a low voltage level...
  17. AnalogKid

    Power failure alarm

    Here is a first pass at a dual-555 solution. Of note is the very large timing capacitor for the 2-hour delay. Cleaned-up version to come. ak
  18. AnalogKid

    Power failure alarm

    That is a significant change from So now the beeper beeps for only one minute, but after a 2 hour delay? That would be a 2 x 555 circuit, one for the 2-hour delay and one for the 1-minute beeper time. But there is another approach. 2 hours is a loooooong time for a simple R-C timer circuit...
  19. AnalogKid

    Power failure alarm

    Nope. With the components shown, the 555 is pulsing power to a self-contained piezo beeper, the kind with a 1-transistor oscillator built-in. In very round numbers, the 555 oscillator is driving it at 1 second on and 1 second off, not at the 2 kHz to 4 kHz needed for direct drive to a bare...
  20. AnalogKid

    Power failure alarm

    That circuit has several problems. Why is there a 10 K resistor in series with the beeper. That will make for a very quiet "alarm", if the beeper sounds at all. Without connections dots, it is impossible to say if the circuit will even work. It shows the 555 powered by only the battery. The...
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