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  1. Hero999

    Led display digital Voltmeter not working

    How are we supposed to know what project you're building without the schematic?
  2. Hero999

    hello - I'm new and after a bit of advice.

    It depends on what you mean by test the circuit board? If you want to ensure that the PCB is as per the schematic then use CAD software which creates the PCB from the netlist and performs design rule checks for you e.g. Eagle or DXP. If you want to check circuit functionality you can get...
  3. Hero999

    0-30V Stabilized Power Supply

    You need a 30V transformer. C1 needs to be at least 6800μF, preferably 10,000μF for 30V@3A out.
  4. Hero999

    220VAC to 24VAc

    Yes, you can use a transformer, it just has to be decent. quality. I don't know whether your transformer has been manufactured to a high enough standard to be safe. Did you buy it from a reputable supply?
  5. Hero999

    Guitar Aplifier

    The resistor will cut the power delivered to the speaker and reduce the sound quality, you might as well build a small amplifier with a 0.5W speaker, four AA cells and an LM386 if you want it to sound like a clock radio. Changing R14 for an incorrect value will not help. There is an error...
  6. Hero999

    0-30V Stabilized Power Supply

    Assuming. a 30V transformer, a regulator drop out of 6.4V (going from what you said), a rectifier loss of 2V and an output voltage of 30V with a 3A load, I calculate the minimum filter capacitance to be 6521
  7. Hero999

    I don't know what I"m doing wrong.......about to give up....

    Have you heard the element turn off again? If so it means that the thermostat doesn't have a high enough heat setting.
  8. Hero999

    0-30V Stabilized Power Supply

  9. Hero999

    Guitar Aplifier

    The LED should not flash, it should be continuously lit but it's normal for it to remain lit for a couple of seconds after the power is removed, as the filter capacitor discharges. Where is the 470R resistor? What do you mean by in front of the speaker? Do you mean in series? If so, it's not...
  10. Hero999

    220VAC to 24VAc

    Just check the transformer is modern and has all the approvals required for your jurisdiction; in which case it will be isolated.
  11. Hero999

    220VAC to 24VAc

    Yes of course you can just a transformer with the appropriate power rating. If the transformer provides sufficient isolation, 24VAC is pretty safe.
  12. Hero999

    I don't know what I"m doing wrong.......about to give up....

    If that's as hot as your iron can get then you need to get a hotter iron. I was going to suggest that you check the voltage of the mains but the fact that the temperature is reaching 167
  13. Hero999

    Mimimize power consumption of circuit

    If you used the 74HC132 (note the different pin-out), as well as the OP290, the whole circuit will work down to 2V, enabling you to be able to run it from two AA cells.
  14. Hero999

    Mimimize power consumption of circuit

    Four rechargeable AA cells in series should last over 800 hours with the circuit as you've drawn it. If you want to reduce the power consumption further, then use a micropower op-amp such as the OP290.
  15. Hero999

    Guitar Aplifier

    If you've tested Q5 out of the circuit and the measurements are as above, then it's almost certainly bad. Don't worry too much about other components failing, just keep plenty of spares.
  16. Hero999

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

    It depends on they type of sensor you use. A cheap proximity switch will just output a high when the object gets within a certain distance of the sensor; most are adjustable but you need to use a small terminal screwdriver. A more expensive proximity switch will output a current, voltage or...
  17. Hero999

    I don't know what I"m doing wrong.......about to give up....

    I've never hard of foundation paper before. I've just Googled it and it came up with this which is very expensive, you can buy special proprietary toner transfer paper for less than that. http://www.creativegrids.com/acatalog/info_N0234.html
  18. Hero999

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

    It's up to you of course. If this is just an educational project then it probably doesn't matter how useful it really is. Have you considered the VCO idea I talked about in my first post?
  19. Hero999

    I don't know what I"m doing wrong.......about to give up....

    Tandy/Radio Shack have gone from the UK and Canada but still (as far as I'm aware) exist in the US. As you probably know inkjet won't work. A plastic rolling pin should be fine; it shouldn't melt as long as it doesn't come into direct contact with the iron for too long.
  20. Hero999

    Guitar Aplifier

    Yes, it might work now, as I said earlier, that doesn't mean its life hasn't been shortened. That means its broken, it shouldn't conduct between the collector and emitter without a base signal. Did you try to test the transistor whilst it's still in the circuit by any chance? it shouldn't...
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