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  1. KrisBlueNZ

    Choosing an Opto Isolator

    Yes, cool.
  2. KrisBlueNZ

    Adding Aux input to older car stereo

    OK, IC201 is a YEAMSN761026. It's a four-input stereo input selector with volume, tone, and front/back fader. There's nothing special or important about it. CN401 on the back panel connects to the external CD or Minidisc changer. According to the interesting but incomplete information at...
  3. KrisBlueNZ

    Limit DC voltage draw

    There's no point trying this. The solenoid or motor is designed to run at a certain voltage. The power supply must provide that voltage, and must be able to provide the current that the solenoid or motor needs. Dropping the voltage, using a series resistor, will reduce the current drawn from the...
  4. KrisBlueNZ

    Communication Protocols (Which one to use)

    That's not a good idea. Don't you want to find out immediately if there's a failure? Perhaps if you describe the whole project we can be more specific. Also what are the power requirements for the slaves? If they're independently powered, RS-485 or RS-422 is probably a good option, although it...
  5. KrisBlueNZ

    PIC, 4digit 7seg display

    Convert your floating point number to a string, then convert that string to characters for your display working from left to right. When you hit the decimal point in the string, set the decimal point flag in the seven segment display data for the digit you just calculated. When you have...
  6. KrisBlueNZ

    hair straightener pcb repair

    A hair straightener with an LCD? That's a bit over the top! Why do you think the SN8P2722SG is faulty? Start by uploading some photos. Both sides of the board. And mark the place where you soldered the wire incorrectly. Why were you taking the hair straightener apart in the first place? Was...
  7. KrisBlueNZ

    Limit DC voltage draw

    Hi Sam and welcome to Electronics Point :-) "Draw voltage" isn't a meaningful thing to say. Voltage is a quantity that's provided; it is measured between two points. Current is drawn by the device that is being supplied (this device is called a load). A load is normally designed to operate...
  8. KrisBlueNZ

    Communication Protocols (Which one to use)

    20 feet is a problem for I2C. One-wire is supposed to be able to cover that sort of distance (it's designed for use in HVAC monitoring, among other applications). Input capture is helpful for receiving, and output compare could be useful for transmitting. Whatever method you use, you should use...
  9. KrisBlueNZ

    Circuit switching problem

    Can you post a schematic? The BT136 is a triac, not a transistor. Do they get hot? Do you have any kind of suppression across the solenoids? Usually a resistor and a capacitor in series are connected across inductive loads to suppress the back EMF. Google RC snubber.
  10. KrisBlueNZ

    PS-900 soldering iron heats, but not enough to melt solder

    When the tip reaches the Curie point, it becomes non-magnetised, and this is detected by a switch in the barrel that cuts off the power to the heater, right? So this switch enables the heater when it detects magnetism from the tip, right? So if the tip isn't seated properly, the heater won't...
  11. KrisBlueNZ

    help with AUTOMATIC WATER-LEVEL CONTROLLER project

    Right. When the light is blocked, the TSOP1738 output goes high. The trigger inputs on the 556 trigger when the pin is taken low. I believe that's an error in the design. But the 556 isn't needed at all. There's no need to set and reset the latch using pulses; it can be set and reset directly...
  12. KrisBlueNZ

    A few beginners questions

    Yes. That, and their age, and the probability that they're crap batteries - if the cordless screwdriver was very cheap, there's normally a reason for that.
  13. KrisBlueNZ

    Modifying Voltage Regulator Design !!!

    Yes. Use two of the same circuit; one set for 1.2V and the other set for 1V.
  14. KrisBlueNZ

    how convert squarewave to sawtooth wave

    Can you post a link to the article you showed in post #1? Tell us exactly what you want to do. Is your input frequency fixed or variable? What do you want to use the output sawtooth wave for? Give us an overview of your project. Then we may be able to suggest a better way to do it.
  15. KrisBlueNZ

    Boost converter 12V to 36V (25 mA load) using 555

    Here's a cheap, somewhat older device: LM3578AN: http://www.digikey.com/product-detail/en/LM3578AN%2FNOPB/LM3578AN%2FNOPB-ND/32487 There are other newer devices: LT1073; LT1082; LT1108; LT1111; LT1173; MAX630; MAX752. These devices are all available in 8-pin DIP.
  16. KrisBlueNZ

    Modifying Voltage Regulator Design !!!

    This is a straightforward linear regulator. The output voltage is determined by the ratio of R46 to R47. The reference voltage in the MAX8869 is 0.8V. This is the voltage that will appear at the SET pin (pin 11) when the output voltage is correct. With R47=30k, the R46 and R47 current will be...
  17. KrisBlueNZ

    Boost converter 12V to 36V (25 mA load) using 555

    R1 is much too high to keep Q1 saturated. You would be better to use a MOSFET. And there's no control loop for voltage regulation. Reduce the load current, and the output voltage will increase! D1's voltage rating is still too close - at least 30% safety margin is recommended (36 * 130% = 47V so...
  18. KrisBlueNZ

    Adding Aux input to older car stereo

    LOL :-) So you could switch her from the talkback station to the easy listening MP3 stream?
  19. KrisBlueNZ

    help with AUTOMATIC WATER-LEVEL CONTROLLER project

    Hi there and welcome to Electronics Point :-) Here's the schematic you're referring to. Both of your questions relate to detection of an interrupted infra-red light beam when the float in the capillary tube moves up or down far enough to block the relevant TSOP1738 infra-red...
  20. KrisBlueNZ

    Adding Aux input to older car stereo

    Good idea Gryd3. It would be great if he could hook into the CD changer audio and do it all properly, with proper protocol support as well. It sounds like quite a job though, which is why I suggested the crude mod. No he wouldn't need a buffer, especially if he's driving it from a headphone...
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