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  1. KrisBlueNZ

    N channel high side switch

    Your first schematic is so incomplete I can't tell much about how, and whether, it would work. Regarding the second circuit, the isolated power supply is normally generated locally and it's probably a bad idea to use a separate mains-powered adapter for it; at the least, the adapter may not be...
  2. KrisBlueNZ

    Building prototype gadget - would appreciate advice :)

    Broadly, microcontrollers are single-chip devices (at least nowadays they are), with all or most resources in a single device. This means no expandability, limited RAM and ROM, a variety of peripherals built-in, and usually a user interface consisting of buttons and a small display or...
  3. KrisBlueNZ

    Battery Powered Power Supply

    I don't think that's a valid reason. Those values may work perfectly every time, but you never know how close that circuit is to not working. The proper engineering approach is to look at the specifications of all the components and choose values that will guarantee that it will always work...
  4. KrisBlueNZ

    Transistor Mosfet pairs to drive LED cube layers

    I think it's good that you're using a separate TLC5940 string for each colour. You'll probably find that you need to run the red, blue and green elements at different currents to get a neutral white.
  5. KrisBlueNZ

    N channel high side switch

    OK, so you understand why the MOSFET will not fully turn ON with your circuit? It's acting as a source follower; the source voltage follows the gate voltage with a few volts' drop (the Vgs voltage) and the MOSFET never saturates. You need two things to make your circuit work: a supply rail for...
  6. KrisBlueNZ

    Battery Powered Power Supply

    Greg, yes, I remember that design. As I remember, we had the problem in your constant-current load circuit where it oscillated because the kill signal disappeared as the switched voltage rail dropped. I don't think that will be a problem in this case, but it's worth prototyping it to make sure...
  7. KrisBlueNZ

    Battery Powered Power Supply

    Thanks Steve. We already knew about this design. I think Greg used it as the basis for his original on/off circuit for his constant current load circuit (in another thread). The discrete design in post #55 uses a similar idea (actually, closer to Greg's version of it). The main difference is...
  8. KrisBlueNZ

    Battery Powered Power Supply

    Here's an alternative. It draws ~0 current while OFF but about 3.5 mA while enabled. (For comparison, the 4013-based design uses ~0 mA in both states.) It might be physically smaller than an IC-based design, especially if you use the FDV30x MOSFETs, but it will probably cost more and take longer...
  9. KrisBlueNZ

    How to not hear Mylie Cyrus when I am playing guitar?

    Yes, you could build or buy a noise gate. I'd also suggest that you resolder all the soldered connections inside the guitar, and clean any switches (as well as the plugs and sockets). Only do the resoldering if you're confident you won't make a mess of the wires. It's easy to melt the insulation...
  10. KrisBlueNZ

    How to not hear Mylie Cyrus when I am playing guitar?

    I can't see any chart there... I think the line "EQ: 8 / 4 / 7 (Treb / Mid / Bass) means that you're supposed to set your equalisation controls (on the guitar or on the amp) to those positions. Treble control set to 8; Mid control set to 4; Bass control set to 7. I don't think those numbers...
  11. KrisBlueNZ

    Battery Powered Power Supply

    I can't find anything apart from CD4013 that will work over that supply range. So I checked out a few different manufacturers to see whether any of them put Schmitt triggers on their clock inputs. The NXP data sheet for their HEF4013B at http://www.nxp.com/documents/data_sheet/HEF4013B.pdf...
  12. KrisBlueNZ

    Battery Powered Power Supply

    Thanks for the feedback Steve. Using two flip-flops is no problem. The other one wasn't going to be used. The problem might be the SPCO momentary pushbutton. They're available but not common. http://www.digikey.com/product-detail/en/700SP7B10M2QEH/EG2594-ND/502058 simple SPDT (SPCO) pushbutton...
  13. KrisBlueNZ

    Battery Powered Power Supply

    OK, the layout in post #45 looks right. The decoupling looks OK. You could shorten the leads, but this is just 4000-series CMOS so it's not that critical. If that layout doesn't work, I don't understand why. I'll ask Steve to have a look at the design in case he can see something wrong with it.
  14. KrisBlueNZ

    Battery Powered Power Supply

    Are you sure? It looks pretty clear to me that the 10k resistor from 0V is connected to pin 5, not pin 3.
  15. KrisBlueNZ

    Battery Powered Power Supply

    I can't be sure, but it looks like your connections to pins 3 and 5 of the 4013 are wrong. Pin 3 should connect to the 10k resistor from 0V and the pushbutton from +V, and pin 5 should connect to the 330k resistor from pin 2 and the capacitor to 0V. You can add an LED with a 1k current limiting...
  16. KrisBlueNZ

    Woo-Woo Help building circuit

    The linked PDF is named "555TachometerCircuit". It does look like it could be a tachometer design. It won't work properly because the resistance of R7 in the supply circuit is far too high, and there is not enough information in that one schematic to tell how it is supposed to be installed and...
  17. KrisBlueNZ

    Help: Driving a 5 inches 7 segment display

    Another point I should mention is that TTL/LSTTL outputs do not pull strongly high and therefore do not have a good clean swing to drive a common-emitter stage. You might be better to use two cascaded NPN or N-channel stages for each output, because TTL/LSTTL outputs pull low much more strongly...
  18. KrisBlueNZ

    op amp and photo diode

    Microchip make a whole range of op-amps that are designed to run from 5V and have rail-to-rail outputs, and often, inputs as well. Look on microchip.com under op-amps.
  19. KrisBlueNZ

    Help: Driving a 5 inches 7 segment display

    I don't believe that the minor changes that I suggested in post #5 should make any significant difference to the operation of the firmware. A simple table lookup takes a matter of microseconds. Those suggestions were designed to make better use of the I/O lines and improve the versatility of...
  20. KrisBlueNZ

    Battery Powered Power Supply

    Make sure you have: CD4013 with V+ to pin 14 and 0V to pin 7, with a 0.1 uF decoupling capacitor across those pins All inputs on both sides grounded to 0V, except D and CLK on one side CLK connected through the pushbutton to V+ and through a 10k resistor to 0V Q-bar connected through a 330k...
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