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  1. KrisBlueNZ

    Using Arduino to read bipolar signal (from plants)

    That's very good advice Harald. I have a couple of suggestions. You can combine the DC offset into the summing amplifier; just replacing the 10k resistor from the non-inverting input to ground with a 20k+20k voltage divider would do it I think. If the ADC is operating with a voltage reference...
  2. KrisBlueNZ

    Short burst voltage problem

    OK thanks. That's good information. Are there any possible current or future advantages to controlling the voltage on this pin from firmware? Would you want to override the trimpot value to any value other than 100%? Because if you don't, then Bob's suggestion is much simpler than digitising...
  3. KrisBlueNZ

    Hitachi tv convergence issues

    There is no convergence "chip". Modern CRTs are "preconverged"; the convergence is controlled by ring magnets around the neck of the tube which are set at the factory. If convergence, and especially colour purity, are badly out, I would suspect a loose shadowmask. Shake the tube and see...
  4. KrisBlueNZ

    Short burst voltage problem

    You haven't answered very many of my questions. Can you also post a schematic of what you have so far? I would like to see the voltage reference, the trimpot, and the driver IC. It would also be useful to us (as well as common courtesy) to tell us more about the overall project you are working on.
  5. KrisBlueNZ

    delay off timer for bathroom fan

    Hi Yossi. So the fan will connect to a connector that has three terminals: Phase (always present), Phase switched, and Neutral. So it can get its operating power between Phase and Neutral, and use the switched phase to tell whether the light is ON or OFF. This board with the CD4060 on it, is...
  6. KrisBlueNZ

    Short burst voltage problem

    Let's see if I can make sense out of your original post. You have a circuit that runs at 3.3V and includes a PIC. You need to generate a voltage signal with a range of 0~1.6V, to be used by a "drive chip". You have a trimpot and you want to set the normal (default) level of the 0~1.6V output...
  7. KrisBlueNZ

    Voltage switch

    Do you have just the MG811 sensor, or do you have some circuitry already connected to it? The sensor needs a 6V regulator to drive the hot wire, and an amplifier with a very high input impedance to detect the voltage and produce a voltage output that another circuit could monitor. Do you have...
  8. KrisBlueNZ

    Adapting old Apple RJ11 keyboard to USB

    You need to find out what type of keyboard that is. Four wires sounds like ADB (Apple Desktop Bus, see https://en.wikipedia.org/wiki/Apple_desktop_bus) but ADB uses Mini-DIN8 connectors, not RJ11, AFAIK. Whatever it is, to make an adapter yourself you would have to use some kind of programmable...
  9. KrisBlueNZ

    sigma delta ADC

    Neither of those documents is accessible without a membership to the web site.
  10. KrisBlueNZ

    Temporary on/off switch and second switch turns all off

    I like to exercise my design skills. Since I don't do it professionally at the moment, I take other opportunities :-)
  11. KrisBlueNZ

    Temporary on/off switch and second switch turns all off

    Because you gave such a clear functional description, I have designed a circuit that I think will do what you want This circuit operates from a 12V power source, and drives a 12V DC motor. It can supply up to 1A to the motor; if the motor draws more than that, you will need to use a larger...
  12. KrisBlueNZ

    How can I control a DC 12V motor

    I assume you are powering the pump from 12V? And the PIC is powered from a lower voltage? In that case there are two clear possibilities. 1. The PWM output from the PIC is not going up to 100% duty cycle. If you're only seeing 20% of the expected pump current, perhaps the PWM signal is only...
  13. KrisBlueNZ

    First time working with caps, is it ok to use bigger cap on lcd monitor?

    Low ESR electrolytics are not only - or even primarily - used for reasons of long term reliability. They are used to achieve specified ripple levels on the power supply outputs. Using a standard ESR component where a low-ESR component is required can cause problems with downstream circuitry...
  14. KrisBlueNZ

    First time working with caps, is it ok to use bigger cap on lcd monitor?

    Another two things techiesteve didn't mention are ESR (equivalent or effective series resistance) and ripple current rating. In power supply applications these are often important, and "standard" electrolytics like those sold by Radio Shack may not be suitable. If your replacement capacitors...
  15. KrisBlueNZ

    What value of resistors do I need and a sanity check

    You're welcome :-)
  16. KrisBlueNZ

    Apple Magsafe

    They really like to pack it in there, don't they. I was looking at a 90W supply for a friend. It's enclosed in a plastic case about 100 x 100 x 30 mm. There's a metal screen around the board, then some crusty stuff in there, presumably to improve heat conduction to the plastic case. He says it...
  17. KrisBlueNZ

    simple amplifier for LME49710

    You're asking strange questions. How about first answering some of the questions on this thread that are directed at you. Some of mine, perhaps. Maybe even ALL of them! Go on, make my day!
  18. KrisBlueNZ

    Lights activted by reed switch

    I usually give links to components on the Digikey web site, http://www.digikey.com, unless I know the person is in England, in which case Element 14 is the normal mail order supplier. There's also Mouser in the U.S.A. Digikey have a very wide selection, and their parametric seach is probably...
  19. KrisBlueNZ

    What value of resistors do I need and a sanity check

    You need to understand voltage, current, resistance, and current regulators. Read some Wikipedia articles and look for tutorials on those keywords. The TCDS circuit tries to make current flow in a load. In this application, this load is the subject's cranium, and salt water to ensure good...
  20. KrisBlueNZ

    HELP!!! Maytag Circuit Board

    I don't recognise the part number, but then I'm not very familiar with varistors. You said in post #3 that your 220V AC mains voltage doesn't go to the board with the varistor on it. That's a little confusing, as a "Bruce" would say. Are you sure about this? Where does the mains voltage go? How...
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