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  1. BobK

    two week lightbulb

    cm, m, in, ft, cubits? Bob
  2. BobK

    High-voltage failsafe?

    You stated that 15 Amps is safe. That is incorrect. Bob
  3. BobK

    Opamp current measurements

    Am I missing something? If the - input is connected to the negative rail, the feedback network is no longer setting the gain, no? You have open loop gain. Bob
  4. BobK

    Lm317 help?

    I doubt that the dimming control needs enough current to require an LM317. A simple potentiometer should do it. Unfortunately, the specifications do not mention an impedance or current requirement for the dimming control, so you would have to measure it to make sure. Bob
  5. BobK

    Help with simple project

    You don't need any diodes. You simply need two resistors. The high setting will put the two resistors in parallel. Bob
  6. BobK

    9-16vdc in 12vdc out, product substitute, DIY

    buck-boost converter. But one capable of 5A is not going to be cheap. Here is one that looks like it might work: http://www.ebay.com/itm/DC-Converter-6-32V-to-0-8-28V-Buck-Boost-Step-Up-Down-Car-Laptop-Power-Supply-/390583671479?pt=LH_DefaultDomain_0&hash=item5af099dab7 Bob
  7. BobK

    programming help!!!!

    Other than ALM[0] none of them can be 1. ALM[1] will be either 0 or 2 ALM[2] will be either 0 or 4 ALM[3] will be either 0 or 8 etc. If you want the ALM array to be 0s and 1s change the statements like this: ALM[p]=(hold_regs[r] & 0x0004) != 0; Bob
  8. BobK

    555 Timer & 4017 LED Circuit

    I can't read the schematic well enough to determine if the 4017 part is working. Bob
  9. BobK

    Solar is dirtier than coal....

    Isn't the sun already being nuked? Bob
  10. BobK

    555 Timer & 4017 LED Circuit

    Yes, like that. Define not working. Are you getting pulses out of the 555? Also, you have a switch for the power to the 555. When simulating is that switch on? bob
  11. BobK

    555 Timer & 4017 LED Circuit

    Yes, you are missing something. The threshold and trigger pins of the 555 must be connected to the top of C3. Bob
  12. BobK

    RF Project

    It would be far cheaper to find an existing product. There are plenty of remote control transmitter / receivers on EBay for on the order of $10-20. Bob
  13. BobK

    Microcontroller ADC reading?

    Yes, the capacitor is there to provide the burst of current needed when the ADC is sampling. This is standard practice with microcontroller ADCs. There is effecitively no current draw at other times. Bob
  14. BobK

    Two 12v inputs switching

    If they are both +12V I don't see how one is bright and the other dim. Bob
  15. BobK

    Battery Powered Power Supply

    A battery is a power supply. Your schematic is unreadable. How about telling us what you are trying to do? Bob
  16. BobK

    Microcontroller ADC reading?

    It should be in the spec sheet somewhere. But anyway, use a capacitor across the lower leg of the divider (about 100n) this will make the impedance very low. Bob
  17. BobK

    DAC output of microcontroller?

    It means your 1K and 100p is not going to make it. Use and opamp voltage follower as a buffer. Bob
  18. BobK

    PCB Etching with Hydrochloric Acid

    Well, I have never heard of using HCl for etching. Ferric Chloride is the normal etchant, and is not nearly as nasty. Bob
  19. BobK

    Multi-voltage step down

    You need to read the LED tutorial: https://www.electronicspoint.com/got-question-driving-leds-t256849.html Bob
  20. BobK

    Constant Current Source

    Perhaps now is the time for you to tell us what you are trying to do. You keep talking about a constant current source, but don't want it to change the output voltage, which is an oxymoron. Tell us what you want to accomplish, in terms of the voltage, current, and load. Perhaps this will...
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