Search results

Search Forums New Posts
  1. KrisBlueNZ

    [HELP] Op-Amp used in resistance detection circuit.

    How much voltage is going to be applied to the heating coil to make it heat up? Will that be AC or DC voltage? Why do you want to measure its resistance? Are you trying to sense temperature? Is this a one-off project? Why don't you describe the whole project in detail. Otherwise we may spend...
  2. KrisBlueNZ

    Wireless trigger for LEDs and buzzers

    Yes you can use the interrupt signal to wake your microcontroller up. But do you intend to use any power-down features? Is it important? Because it makes your code design somewhat more complicated. An interrupt can wake the microcontroller, but in this setup, the interrupt handler should not do...
  3. KrisBlueNZ

    Need help hacking a respiratory monitor

    Right, if the signals have opposite polarity that doesn't really make any difference. But you should check that the data lines pull firmly high (> 3V) and low (< 0.8V) with no pullup or pulldown resistors connected to them, i.e. when the sensor has power but the data signals are only connected...
  4. KrisBlueNZ

    Power supply help

    You'd be surprised how many people ask vague questions, supply the absolute minimum of information, and simply ignore many of the questions we ask here. The HRD data sheet lists 50V as the absolute maximum input voltage, and 40V as the maximum recommended operating voltage. It is never wise to...
  5. KrisBlueNZ

    Simple power supply questions

    LOL :-) At least you have a good attitude! The whining noise MIGHT just occur at certain voltages; it may not be a problem at all. Try disconnecting the direct 5V supply, so there's only the regulator in circuit, and adjust the regulator output voltage steadily from 5.1V down to 4.9V or...
  6. KrisBlueNZ

    Car Battery Bounce Eliminator

    I thought so too, Bob. That's why I said I wasn't sure he had identified the problem. I guess it depends on what "loads of sparks" means. Everything is relative :-)
  7. KrisBlueNZ

    Power supply help

    You deserve a prize for answering all my questions! If the HRD has been damaged by the overvoltage then powering it from 24V will give you an unregulated, high output voltage, but if it wasn't permanently damaged, then it won't, so that's not conclusive. I don't have any suggestions for a...
  8. KrisBlueNZ

    [HELP] Op-Amp used in resistance detection circuit.

    The LM358's input offset voltage is typically around 3 mV, maximum around 10 mV. With a gain of 23 that translates into a DC error of up to around 200 mV which is 4% of full scale. The extra circuitry won't do what you want. What is its purpose? There are lots of designs around for...
  9. KrisBlueNZ

    Simple power supply questions

    Where did you measure that current? At the input, in series with the battery? You know that when you measure current, you have to interrupt a circuit and connect the multimeter across the gap? You don't connect the multimeter across the input of the power supply when you're measuring current...
  10. KrisBlueNZ

    Need help hacking a respiratory monitor

    You've figured out most of it already. The sensor contains two LEDs and two photodiodes (or phototransistors or similar). They are placed in such a way that the rotating vane interrupts the light and produces two signals that are "quadrature", or out of phase with each other. This allows the...
  11. KrisBlueNZ

    34063 voltage drop

    The MC34063 is an ancient device with poor performance. I don't understand why people are still using it. There are MUCH better alternatives available.
  12. KrisBlueNZ

    Power supply help

    What's the model number of the converter that you used to power the Arduino? Why did you use a 12V converter for the fans and a separate 11V converter for the Arduino? The Arduino should be able to run from 12V no problem...? The pins in the middle of your picture look OK. There's a bit of...
  13. KrisBlueNZ

    [HELP] Op-Amp used in resistance detection circuit.

    The LM358's output stage has a Darlington pull-up so it won't pull up closer than about 1.5V below the positive supply rail, which would limit the output voltage to about 3.5V. It also has an input offset voltage in the millivolt range so it would cause significant measurement error. As for...
  14. KrisBlueNZ

    Car Battery Bounce Eliminator

    I'm not sure that you've identified the problem, but if so, that's a good idea, and it's not hard to do what you want. The switching can be done easily by a large MOSFET like this one: http://www.digikey.com/product-detail/en/IXTQ200N10T/IXTQ200N10T-ND/1652581 You just need a drive circuit that...
  15. KrisBlueNZ

    Data sniffing from a RS232/485 network

    If your DOS machine has a 25-pin serial port, it transmits data on pin 2, and pin 7 is ground. If you have a second machine with a serial port, and you just want to capture the transmitted data from the DOS machine, you can link the grounds together and feed the data from pin 2 of the DOS...
  16. KrisBlueNZ

    Power Supply Help?

    From the schematics on the project page, I would say the load on the -15V rail will be less than 100 mA, probably less than 30 mA. The voltage won't be highly critical, as long as it's regulated, but it is used by the circuitry around R11 and R13, and R16, which relates to the trigger pulse...
  17. KrisBlueNZ

    Capacitor

    The Capxon LZ series electrolytics are very low-ESR (equivalent series resistance) components and shouldn't be replaced with "standard" electrolytics. You can get the data sheet from http://www.hestore.hu/files/LZ.pdf That version of the data sheet doesn't cover the 2200 µF 25V part but...
  18. KrisBlueNZ

    Fender 3 spring reverb tank

    Edit: Added NOT in the second paragraph (d'oh!)
  19. KrisBlueNZ

    Simple power supply questions

    Layout is important for switching regulators. That's why I was thinking that you might want to buy a fully assembled switching regulator on its own PCB from eBay. (I meant to suggest this in the Edit: paragraph in post #2, but I didn't explain that I meant a fully assembled regulator board...
  20. KrisBlueNZ

    Fender 3 spring reverb tank

    I suggest you try Googling driver amplifier for spring line reverb. I did, and one of the results is http://sound.westhost.com/articles/reverb.htm which has some useful information and a link to another site, http://www.accutronicsreverb.com/, which you should look at. Also check out other...
Top