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  1. KrisBlueNZ

    LM2917 Speed Switch Help!!! PLEASE!!!

    Perhaps Mouser are having a 50 year retro clearout! That style of resistor was used in 1960s-era tube radios. A 10 Hz signal is 10 cycles per second. A cycle consists of an ON period plus an OFF period. So you need 50 ms ON, 50 ms OFF to get a cycle time of 100 ms which is 10 Hz.
  2. KrisBlueNZ

    Transistor Mosfet pairs to drive LED cube layers

    Yeah, the Si2333DDS-T1-GE3 is one of those. But it's a P-channel MOSFET running from 5V and the signal is 3.3V/0V.
  3. KrisBlueNZ

    Transistor Mosfet pairs to drive LED cube layers

    He's concerned about getting fast switch-off to avoid ghosting. Of course he could add a short delay between multiplex phases without losing significant brightness, then an NPN with a 1k collector resistor would be a good idea, and cheaper (if not smaller) than a quad driver in DIP-14.
  4. KrisBlueNZ

    SMPS Build...

    Linear Technology and National Semiconductor (now owned by Texas Instruments) both make a wide range of buck regulators. Many are self-contained in TO-220-style packages with five leads. In my experience LT devices are easier to use and operate more cleanly but are more expensive. Ratings up to...
  5. KrisBlueNZ

    LM2917 Speed Switch Help!!! PLEASE!!!

    How much current does that light bulb draw? I think the IC is only specified to sink up to 50 mA into pin 5. Edit: OMG, WHERE did you get those resistors? I haven't seen resistors like those in 30 years!
  6. KrisBlueNZ

    Transistor Mosfet pairs to drive LED cube layers

    I had a look at improving the driver, then I figured it would solve a lot of problems if you just used a driver IC. It's arguable that the main MOSFETs aren't really heavy enough to justify a full-fledged driver IC, but it's much more compact than a discrete solution, and not much extra cost...
  7. KrisBlueNZ

    Transistor Mosfet pairs to drive LED cube layers

    Yeah, SOT-23 is big enough to work with manually. Using transistors will slow things down a bit, but not significantly.
  8. KrisBlueNZ

    Transistor Mosfet pairs to drive LED cube layers

    There are a few problems with that design. I'll post an update when I've figured out the best way to solve them.
  9. KrisBlueNZ

    Transistor Mosfet pairs to drive LED cube layers

    None of those devices is very suitable. The drivers aren't specified to operate with 3.3V gate signals, and although the typical graph shows that a typical device would work, not every device they ship is "typical"! The main MOSFET you found has a very high ON resistance of 1.2 ohms, and...
  10. KrisBlueNZ

    Comparator inputs

    EinarA, thanks for your comments. The reason for biasing the inputs is that the offset adjustment may need to be quite large; it's not to compensate for error, it's because Viad wants to be able to favour one phase over the other. This requirement emerged somehow in the early part of the...
  11. KrisBlueNZ

    Matrix circuit for Keypads

    In the case of a 4-button keypad, arranged as 4x1, there's no need for an I/O pin to drive the "1". It can just be tied to ground, and only 4 inputs are needed. So it works out the same. But as Harald said, the principle applies to keypads with more buttons. A keypad with 6 buttons or more will...
  12. KrisBlueNZ

    Comparator inputs

    Thanks Duke. Yes that's true. The trouble with putting a potentiometer from the comparator's output to its non-inverting input is that the amount of hysteresis would not be directly proportional to the potentiometer position, and it would be impossible to remove the hysteresis completely. The...
  13. KrisBlueNZ

    Comparator inputs

    OK, I've taken duke37's suggestions and drawn up a new circuit. Even if Viad doesn't want to change his circuit, I'm interested in coming up with the best design possible. I've had no experience with current transformers so I'm just learning the techniques. I see this as a learning exercise...
  14. KrisBlueNZ

    How can the new Yamaha HH65 Hi-Hat Pedals be modified to work with the Yamaha DD-50?

    That's right. Mono cable: Tip --------------------------inner core---------------------- Tip Sleeve ---------------------shield---------------------------Sleeve Stereo cable: Tip --------------------------inner core---------------------- Tip Ring ------------------------inner...
  15. KrisBlueNZ

    JFET Voltage Controlled Switch

    I reckon you should make your own vactrols. Yeah the LM13700 seems like a pretty neat device!
  16. KrisBlueNZ

    Want to build a 2 event delay timer controller

    Hi Steve, Yes, CT is 0.1 uF the same as CN, CD and CF. The leftmost three are supposed to be covered by the "3X 0.1UF" marking and CD has its value marked separately, but CT is not listed in the "suggested components" section. You mentioned that there's no display on this project. Do you want...
  17. KrisBlueNZ

    Capacitor Multipliers in Pulse Generator circuit

    So the "trigger" is really an enable input? The 4051/4052/4053 are analogue switches. There are simpler ways to switch the power supply rails to an op-amp - transistors, for example. But it's easy to stop an astable multivibrator by just clamping the capacitor voltage, using a transistor or...
  18. KrisBlueNZ

    Comparator inputs

    Doh! Why didn't I think of that.
  19. KrisBlueNZ

    ad 620 instrumentation amplifier

    The 741's gain-bandwidth product (GBP) is 1.5 MHz so with a gain of 100 it's usable up to a maximum of 15 kHz. If the highest frequency in the signal from the vibration analyser is much less than 15 kHz, then you can use a 741, if they're still being manufactured!
  20. KrisBlueNZ

    Comparator inputs

    EinarA, Duke37 suggested that in post #5 on this thread. Actually his solution was slightly simpler - rectify the two CT outputs and simply connect them in series with opposing polarities. At least that's what I think he meant. The problem I have with that approach is the deadband near the...
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