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  1. Hero999

    Found good projects

    I admit, I was tempted to press the delete button when I saw this but I withheld fire. Which circuit do you have in mind?
  2. Hero999

    Switching power supplies and Earth

    It's probably more likely to be -24V 0 +24V. My guess is that the electric shock is caused by leakage from the mains to DC side via the RF suppression capacitors inside the SMPS. It should be a fialry low current and safe but when lots of appliances are connected together the currents add...
  3. Hero999

    Measure humidity

    Have you checked out the usual suppliers ie. RS Components, Farnell, Digikey, Newark and Jaycar? Yes, it's possible, there are many humidity sensors on the market. Normally they have a capacitance which varies depending on the humidity but it should be pretty easy to build an oscillator and...
  4. Hero999

    Motorcycle Universal Gear Indicator - Parts

    I've just read through this project. I think it's very clever how an old CMOS CD4026 is used in conjunction with an MCU so a 7 segment display can be controlled with only two pins. I have a couple of issues though: The documentation of how it actually works is lacking. Fortunately I soon...
  5. Hero999

    final year project: a blind stick that uses different sensors, help needed

    Yes but have you read the entire thread first? If not then it's the first thing you should do.
  6. Hero999

    How to generate negative voltage from PIC

    When I was talking about a buck-boost, I meant using the PIC as a controller not buying a pre-made controller-IC but if you already have a negative supply then you don't need a buck-boost converter. I think you're already going down the right path with op-amps but you're correct in that finding...
  7. Hero999

    0-30V Stabilized Power Supply

    The green coating is a solder resist layer which ensures the solder only sticks to the parts of the board that need to be soldered. I don't know if there's a way to do it yourself but you can get a green conformal coating which protects the copper track from corrosion and makes it look nice. I...
  8. Hero999

    5 x 555Timers

    I've never used a PICAXE before, from what I've read it's just a PIC with a built-in BASIC interpreter and is not the kind of thing I fancy using personally as it will cost more and requires less learning about PICs which is what I want to do but it might be your best bet. An industrial timers...
  9. Hero999

    5 x 555Timers

    You're in a better position than most to learn about MCUs. In this case, cost-wise both solutions will be similar as the price of the relays will dominate. I've had a quick look at the prices of components in my local suppler, the 555s will be slightly less expensive than the MCU plus the other...
  10. Hero999

    5 x 555Timers

    Other than a microcontroller, I was going to suggest the CD4069 which can be used to make three monostables per chip (two ICs) but then I realised that the output drive is pathetic so additional driver transistors would be required. I still recommend the microcontroller, buy a programmer...
  11. Hero999

    Rpm rev counter to high

    It's possible that passing the signal through a divide by two counter and setting the numbver of cylinders to 12 will work.
  12. Hero999

    5 x 555Timers

    I have a couple of suggestions: If you must use the old 555 timer, opt for the NE556, which has two in one package. I would suggest an alternative to the old 555 timer - sort of project can be simplified using a microcontroller making it possible to reduced the entire project to a single 8 pin...
  13. Hero999

    Confusion on type of capacitor to be used in SG3524.

    Please post a scematic.
  14. Hero999

    Electronic clock pulse generated from wrist- or pocket-watch

    Use an ultrasonic microphone with a suitable resonant frequency and a 32768Hz watch crystal as a filter. It should be pretty easy to square the signal with logic gates.
  15. Hero999

    Electronic clock pulse generated from wrist- or pocket-watch

    It's 32768Hz, not 33kHz and is a standard frequency which has been chosen because dividing it by 215 will give 1Hz and is easy to do with a simple binary counter.
  16. Hero999

    The correct place to insert a temperature sensor?

    Connect the power supply to the full load current at the lowest voltage and measure the temperatures of various components. Put the sensor near the warmest device. I wouldn't expect the transformer to get very hot, it'll be one of the voltage regulators. You shouldn't need any over temperature...
  17. Hero999

    Electronic clock pulse generated from wrist- or pocket-watch

    Or you could use a small ultrasonic microphone to listen to the 32768Hz signal produced by the crystal. But why bother? It's much easier to build an oscillator using a 32768Hz crystal.
  18. Hero999

    Program launch: "Get Paid to Publish your Project!"

    I agree, it seems like no one is checking the projects, a capacitor is also connected upside down, you don't have to be an expert to see that. There again, what do you expect when you're only paying someone $80 to design a project for you? You can't expect people to sell their best designs at...
  19. Hero999

    Program launch: "Get Paid to Publish your Project!"

    $80 dosen't sound much for a project, multiply it by ten and I might be interested. What about quality control? I notice that there are many projects on this site which contain errors. How are you going to ensure that this doesn't happen again?
  20. Hero999

    Idiot's guide to transformers ?

    If your meter is on the AC setting there shouldn't be too much fluctuation although there will be some because the mains voltage isn't perfectly stable. If the transformer is 12V, the LM7812 is unsuitable because there isn't enough headroom. The LM7812 requires at least 15V to regulate...
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