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  1. KrisBlueNZ

    "Dimming" LED's with pot/rheostat by progressive shutoff

    Bob, he answered that in post #5. He wants the actual LEDs to have fixed brightness, and he wants the number of illuminated LEDs to change.
  2. KrisBlueNZ

    TDA1554

    A common cause of vocals being very quiet but having a "hall effect" is a broken ground on a stereo signal. Vocals are normally mixed dead centre of the stereo image, with reverb applied. This means that if you listen to the DIFFERENCE between the left and right signals, the main vocal cancels...
  3. KrisBlueNZ

    6 CELL LI-ION 22.2V BATTERY LEVEL MONITOR

    OK, the LM336Z-2.5 is a good choice. Your first diagram is right except that you need a resistor from the positive supply to the cathode of the LM336Z-2.5 to supply current to the LM336Z-2.5 so it can operate. This is the 5.6k resistor in the second diagram. It needs to supply at least 0.4 mA...
  4. KrisBlueNZ

    How to I half this output voltage!

    Yaser43082, your advice is bad. Please try to answer only questions that you are confident you fully understand. Harald has explained the problem. The resistors in your voltage divider are too low. They are dragging the LM335 output voltage down. You need to use higher resistor values, such as...
  5. KrisBlueNZ

    6 CELL LI-ION 22.2V BATTERY LEVEL MONITOR

    I wouldn't use a voltage regulator when you want a reference voltage. Regulators are not intended to be as accurate, even ones that claim to be "precision". That's because components aren't very fussy about their supply voltages - most ICs can tolerate supply voltage errors of at least +/- 5%...
  6. KrisBlueNZ

    "Dimming" LED's with pot/rheostat by progressive shutoff

    Yes, you can use an LM3914 to control multiple LEDs. In the standard LM3914 application, each of its outputs goes electrically low to turn on the LED connected to it. You need to replace each LED with a circuit that controls a number of LEDs. How many different steps do you want between "all...
  7. KrisBlueNZ

    6 CELL LI-ION 22.2V BATTERY LEVEL MONITOR

    A simple solution would be to replace the two trimpots with multi-turn ones, and remove all of the resistors connected to them. That's R1, R2, R3, R4 and R7. I would use something like this: http://www.digikey.com/product-detail/en/3296W-1-203LF/3296W-203LF-ND/1088051 This type of trimpot can...
  8. KrisBlueNZ

    Bad Capacitors?

    They probably aren't rubber. They're probably just round pieces of thin plastic. Pull them apart and see, but watch out for electrolyte leakage.
  9. KrisBlueNZ

    Onan 300-3056 control board repair

    The 1N5552 is available from Element 14. A 1N5406 would be a lot cheaper but its leads might be too thick to fit through the holes. Even though the generator's output voltage is only 120V there may be higher voltages at other parts of the circuit, so I would not use a 1N5404. The original was...
  10. KrisBlueNZ

    Need help with a PSU schematic

    Right Duke. I added a comment to my earlier post because I realised that the reverse voltage across C9 and C10 is limited to two diode drops by the combination of diodes in BR1 and BR2. I agree that separate diodes across C9 and C10 aren't needed.
  11. KrisBlueNZ

    Need help with a PSU schematic

    AFAIK, bipolar electrolytics won't tolerate ripple currents better than standard electrolytics. Also, lower value electrolytics have lower ripple current limits, so you may be chasing diminishing returns. I may have overestimated the importance of ripple current. Although the current...
  12. KrisBlueNZ

    Batteries - Switch between series and Parallel

    I think this is what they mean.
  13. KrisBlueNZ

    Need help with a PSU schematic

    I thought you were going to fix the old one, not buy a new one. We can help you fix the old one. Start by describing the symptoms. Are there any obviously damaged components? Have you checked the flyback clamp zener? Also, you could tell us where you're located. I assume you're in America...
  14. KrisBlueNZ

    Time Delay Relay for caralarm-->gpstracker

    Kind of. The resistor and capacitor together form a delay circuit. When the voltage from the alarm goes high (+24V), the capacitor starts to charge, through the resistor. The resistor limits the current. It's a bit like a rechargeable battery that charges up slowly because of the current flowing...
  15. KrisBlueNZ

    Need help with a PSU schematic

    OK that's good. I'll revise my load figure for the bootstrapped rail down to 40 mA. Some of that is for the regulator. I see from the comments on Keith's blog that several people have had problems with that power supply. But it's going to be easier and more convenient to fix it, rather than...
  16. KrisBlueNZ

    Need help with a PSU schematic

    Is that the problem with the original power supply? The STP7NB60FP is nothing special. It's an N-channel MOSFET, rated at 600V, 4.1A, 1.2 ohms Rds, in a TO-220 full plastic package. It's flagged as obsolete now, but there are many suitable replacements available from Digikey. Have a look at...
  17. KrisBlueNZ

    Need help with a PSU schematic

    Here's a simulation of the exact circuit you've drawn up, excluding the regulators. I'm describing the high-voltage rail as "bootstrapped" because BR1 uses the transformer secondary voltage directly, and BR2 uses the transformer's output voltage again, to add more voltage on top of that, which...
  18. KrisBlueNZ

    Help required with 555 timer project

    As KJ6EAD says, it's not just a case of electrons flowing through your wire, into the IC on one pin, and out on another. The 555 connects to both sides of the battery, and there are LOTS of current paths within the 555. It uses current from the battery for its own internal operation, and it can...
  19. KrisBlueNZ

    Improve battery life in LED Chaser

    CMOS devices, especially the old 4000 series, have relatively high output resistances (around 300 ohms, I think - somewhat dependent on the supply voltage). So there is normally no need for current limiting resistors. So the original design is acceptable. There is a problem using a resistor...
  20. KrisBlueNZ

    turn off circuit at low voltage

    Oh dear. I was too hasty in recommending that Seiko part. It DOESN'T have any time delay! (I didn't consider that would be possible, because every voltage monitor I've seen for microcontroller resetting DOES include a delay. But I was re-reading the data sheet and there is NO mention of any...
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