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  1. KrisBlueNZ

    Split Rail Power Supply

    Yes, you can use a regulator to drop the output voltages, but the 78xx and 79xx devices aren't suitable - their dropout voltages are too high. The dropout voltage is the minimum input-to-output voltage difference, and the 78xx/79xx have dropout voltages of around 2~2.5V so you would need to feed...
  2. KrisBlueNZ

    Voltage controlled thru opamp playing up?

    Well, butter my buns! You're right! Figure 4-4 in the data sheet. I'm very surprised. The closed loop output impedance of the op-amp should be very low - under an ohm, I would expect. I would have thought that 47 ohms to a capacitor was by comparison a very weakly coupled load, and the op-amp...
  3. KrisBlueNZ

    pic16f88 not working properly

    If you use that code as written, neither of the pins will change state. Executing a bsf PORTB,3 will set PORTB bit 3 high each time round the loop and it will always be high; executing bcf PORTB,2 will set PORTB bit 2 low each time and it will always be low. You need to do this: lp: bsf...
  4. KrisBlueNZ

    pic16f88 not working properly

    Have you fixed the other problems? The bcf and bsf instructions operating on a different bit in PORTB, and the need for a delay subroutine?
  5. KrisBlueNZ

    Half Bridge Converter Question

    Yes Fish, I agree completely. I was assuming that the OP would read through our discussion, and if he had no idea what we were talking about, he would realise that he's bitten off more than he can chew. Re the sticky discussing the subject, I think the Microchip app note that Adam found is a...
  6. KrisBlueNZ

    Electric motor

    Hi Fish, good to see you again too! How are you going? The reason I suggested the stepper motor is that the OP says "it must not start with a jerk or stop suddenly." I believe you can get controllers that have configurable ramp-up and ramp-down times. It's a bit messy handling the ramp-down...
  7. KrisBlueNZ

    pic16f88 not working properly

    The first problem is that there is no instruction to loop back to the Led_flicker label. When the device gets past the last instruction, bcf portb,2, it will continue executing unprogrammed Flash ROM locations. These will normally contain values of 0x3FFF (all bits unprogrammed), which, as far...
  8. KrisBlueNZ

    Half Bridge Converter Question

    What are KTP and NPC? The best way to generate bootstrapped MOSFET drive for high-side N-channel MOSFETs uses a capacitor with one side connected to the half-bridge output point, that's charged up to a low-voltage supply rail (often 12V) through a diode when the bottom MOSFET is ON. Since...
  9. KrisBlueNZ

    No contact encoder

    An "optical coupler" _is_ a non-contact device. Have a look inside an old mouse - the type with a ball. The ball rubs against two axles, each of which has a slotted wheel, with LEDs shining through the slots and two offset phototransistors detecting the light. A simple microcontroller performs...
  10. KrisBlueNZ

    Inverse multiplexer

    Your question is very vague. A multiplexer combines multiple inputs onto a single output; a demultiplexer reverses this process. How many inputs and how many outputs do you have? Do you know how to control the mux/demux? Are the signals analogue or digital? What power supply voltage(s) do you...
  11. KrisBlueNZ

    Electric motor

    Another option would be a stepper motor driven by a controller that has configurable ramp-up and ramp-down. You can get exact control over the ramp-up and ramp-down times, and the running speed. I think you can get stepper motor drivers through eBay, but as Forrest Gump said, "eBay's like a bawx...
  12. KrisBlueNZ

    Voltage controlled thru opamp playing up?

    Ah, you mean C7. I was looking for a cap on an output. Yes, 100 nF directly on the output of a normal op-amp is guaranteed to cause problems! But as you say, the 47 ohm resistor in between is plenty high enough to prevent trouble.
  13. KrisBlueNZ

    Headlight Retrofit ProjectDR

    Hi Roman and welcome to the Electronics Point forums :-) I would like to try to help, but I don't have much experience with car electrics and the terminology you've used. There may be others on the forum who have more relevant experience. Also, there have been a number of threads on related...
  14. KrisBlueNZ

    VOX DA5 Amplifier repair help - no power when plugged in

    Well, thanks very much Tom :-) It's cool that you want to be cautious, but I think you'll do fine. If you do some major damage to the board, which I think is very unlikely, there are always other options. Wait for the soldering iron to get fully hot, and if it's a new bit, keep trying to push...
  15. KrisBlueNZ

    Voltage controlled thru opamp playing up?

    Which capacitor are you referring to, Adam?
  16. KrisBlueNZ

    Split Rail Power Supply

    Yes. No.
  17. KrisBlueNZ

    Blown resistor please help

    That style of inductor isn't used as the energy storage inductor in switching supplies - at least, I've never seen it. I think they're too lossy. All the SMPS inductors I've seen have complete magnetic loops - RM-series ferrite cores and similar, even ring cores, but not axial like that. As...
  18. KrisBlueNZ

    VOX DA5 Amplifier repair help - no power when plugged in

    Wow, thanks for the video. That really makes things clear. It looks like the copper track has actually lifted off the board, and broken off, on the pin furthest away from the board edge. This is what I suggest. Turn the board over so the tracks are underneath, and use the soldering iron on...
  19. KrisBlueNZ

    Half Bridge Converter Question

    Hi Adam, Re your first schematic, there's an asymmetry between the gate drive signals for Q1 and Q2. In both cases, the MOSFET responds to the gate-source voltage. Q2 has its source at the 0V rail potential, but Q1's source jumps around between 0V and +V. You have both drive signals...
  20. KrisBlueNZ

    Voltage controlled thru opamp playing up?

    I think you'll need to post all of the code here.
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