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  1. AnalogKid

    Converting LED output units

    With consistency better than accuracy, it sounds like they are relying on the LED beam focus to prevent the two receivers from seeing the wrong emitter. My guess is that there is no (or maybe only 1) calibration adjustment inside the box, and that moving the emitters close together will cause...
  2. AnalogKid

    Converting LED output units

    That was my first thought - this sounds lik a 99-cent problem. Or, just multiply by 3 in your head. The error is only 1.6%, and you will be surprised how quickly you will adapt to doing it quickly once you start doing it a lot. Every engineer who now bounces back a forth between metric and...
  3. AnalogKid

    Help with LED circuit

    What you show is a version of the second approach. I've seen this sch before and am not wild about it. The latches are set and reset by briefly overpowering an output with 100 ohms to the positive power supply. I'm working on a version of that that does not abuse the parts. I started this...
  4. AnalogKid

    3.5mm stereo audio jack

    NICE find. This site should be in a sticky. ak
  5. AnalogKid

    Help with LED circuit

    Background: All radio button circuits have two elements in common - a latch (1 bit for each switch input) and a signal based on all of the switch inputs OR-ed together - one signal that goes high whenever *any* switch is pressed. This can be done with resistors or diodes. One approach is to...
  6. AnalogKid

    Help with LED circuit

    A wall wart has a fully-isolated output, so that should eliminate grounding problems between the LED circuit and the amp circuits. But it doesn't eliminate all problems. Still need to know the open-circuit voltage across un-pressed switch contacts. For each switch, was either pin connected to...
  7. AnalogKid

    Help with LED circuit

    What you are after is called a "radio button" circuit. This is an electronic version of the "bail" function in a bank of ganged switches. Press one, anything else that was pressed is released. Named for the tuning system on a (old) car radio. Important details: 1. Power source(s) available...
  8. AnalogKid

    TH42PZ70B4Panasonic Flat Panel Television

    ... for an 8.5 year old thread. ak
  9. AnalogKid

    what type of switch and wiring arrangement would I need?

    Another option is p-channel power MOSFETs for the 5 V and 12 V, and an n-channel MOSFET for the 3.3 V (since you have 12 V available to drive its gate). A 30 A power MOSFET probably is chaper than a 20 A relay. For the relay, consider the T90 or T9x series from Tyco (used to be P&B)...
  10. AnalogKid

    555 astable timer to h-bridge for 2 channel christmas led lights

    To finish up, here is another (((concept))) schematic of a full H bridge driven by one clock source. For this one, a CMOS LMC555 is a much better choice because its output swings much closer to the rails, ensuring that the off transistors are really off without added base pull (up/down)...
  11. AnalogKid

    555 astable timer to h-bridge for 2 channel christmas led lights

    Here is the dual-555 version. I still show this as a 9 V design. By the bipolar LM555 datasheet, when running on 5 V, the minimum output voltage is about +1 V and the max. is about +3.3 V. That leaves about 2.3 V across the LEDs. That is enough for normal little discrete red or green parts...
  12. AnalogKid

    555 astable timer to h-bridge for 2 channel christmas led lights

    Yes, but it's not as much as you might think. Without the LEDs connected, the static current through R2 and R3 is 66 mA. But ... The 555 output is always either high or low, so one resistor always is "shorted out" by an LED. A typical red or green LED has a Vf of around 2 V. Without the...
  13. AnalogKid

    555 astable timer to h-bridge for 2 channel christmas led lights

    This is a first-pass (((concept))) schematic that shown a half-bridge drive for the LEDs. It is not as efficient as the dual-555 approach, but it is a minimum parts-count solution. Note that some of the components need adjusting; the ones shown are what is already in my design libraries. For...
  14. AnalogKid

    555 astable timer to h-bridge for 2 channel christmas led lights

    Getting there. You need only one current limiting resistor in series with the LEDs. Also, if you increase R2 and decrease C1 you will have an output closer to 50/50. As bertus pointed out, there is a circuit that gives almost exactly 50/50. It is the one I mentioned in post #2. I'll post it...
  15. AnalogKid

    555 astable timer to h-bridge for 2 channel christmas led lights

    Original 555: NE555 by Signetics. All bipolar circuit (35 NPN and PNP transistors). Many copies (it never was patented): MC555, LM555, etc. CMOS 555: lower power operation, lower output currents, higher top speed, etc. Overall, better operation if you don't need the super-fat bipolar...
  16. AnalogKid

    555 astable timer to h-bridge for 2 channel christmas led lights

    First, you can do this with nothing but a small wall-wart transformer with an AC output. You might have to add one series resistor depending on the transformer's output voltage. Second, R12 and R13 do not need to be such a low value. But ... What is the current value you want to push through...
  17. AnalogKid

    Hello and help!! (need circuit to see if a pump did run)

    Are you looking for an electronic circuit (IC or 2-transistor flipflop), or all AC wired products? If the latter ... Here is a dual-coil relay that acts like a set-reset flipflop. Wire one coil across the pump motor, and it sets the ff each time the motor runs. Connect the reset coil to 220...
  18. AnalogKid

    short circuit detector

    Only at the concept level. To us it isn't useful because of the strain it puts on the battery. ak
  19. AnalogKid

    short circuit detector

    It will do something, but not something useful. In this circuit, the beeper is on constantly until the probes are connected to a resistance of something less than 10,000 to 100,000 ohms. At that point the transistors attempt to place a dead short across the battery to turn *off* the beeper...
  20. AnalogKid

    short circuit detector

    Do you mean 'anathema"? ak
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