Search results

Search Forums New Posts
  1. (*steve*)

    How can i add a trigger to this circuit to make it not electrocute the user?

    Do you mean your SCR is an ON703? I can't find an SCR with that part number, sorry. Can you post a picture of it? If you know anyone with a universal semiconductor analyzer you could hook it up and it would tell you. (something like this http://www.peakelec.co.uk/acatalog/jz_dca55.html)
  2. (*steve*)

    Proper procedure for reducing ripple on DC power rail? (e.g. oscilloscope reading -> filter design)

    Are you using you oscilloscope properly? What does the trace look like if you connect the ground clip to the probe tip? What if you connect it directly across a filter cap on your 7805? (you are using filter caps, right?)
  3. (*steve*)

    can't figure what the hell is wrong !

    The answer is that when you apply 5v to the base of a transistor that has 12v on the emitter via a switch you are effectively placing 12-5v, or 7V on the base (ok, that voltage is across the BE junction and the base resistor)* . Current flows from the 12v rail through the base resistor and the...
  4. (*steve*)

    How can i add a trigger to this circuit to make it not electrocute the user?

    703? I don't see a 703 in that circuit. The general answer is to look up the datasheet.
  5. (*steve*)

    Part required or is another suitable

    Should be fine. Do you know how to remove and replace those chips?
  6. (*steve*)

    Not getting oscillation as per circuit given

    That circuit uses a 74LVC1GU04. Why do you think you can replace that with a 74LS14? Those 2 chips have more differences than similarities. - TTL vs CMOS - 1 gate vs 6 - Schmitt trigger vs normal input - buffered vs unbuffered - significantly different input voltages and currents...
  7. (*steve*)

    OR-ing voltages together

    You can also use resistors connects to a virtual ground and measure the current which will be related to the sum of the voltages. Herald's solution with diodes will give you either the max or min voltage (depending on how you arrange the diodes).
  8. (*steve*)

    Sound Sensor

    You may need to reduce the gain of the amplifier so that it doesn't clip until the sound pressure is something over 140dB. At these sound pressures you might even have to attenuate the sound reaching the insert, and it is even possible that you don't need an amplifier!
  9. (*steve*)

    Sound Sensor

    Anything wrong with an electret?
  10. (*steve*)

    can't figure what the hell is wrong !

    Aaah, on the protoboard you are actually pulling the base low when you press the button and are disconnecting it with the button released. If your output from the microcontroller acts as open collector, it will work exactly the opposite. You're lucky it can turn them off at all. I would not...
  11. (*steve*)

    can't figure what the hell is wrong !

    Are you using the transistors on the protoboard? In any case, you have shown PNP transistors which turn off with a positive voltage.
  12. (*steve*)

    Proper procedure for reducing ripple on DC power rail? (e.g. oscilloscope reading -> filter design)

    No, you have half wave rectification. A link to the datasheet would be handy, but I'll go looking.
  13. (*steve*)

    can't figure what the hell is wrong !

    Change the logic of your program so that outputs are active low rather than active high. You've used PNP transistors. These are off when the bar is high and on when it's low.
  14. (*steve*)

    Sound Sensor

    A microphone should do the job
  15. (*steve*)

    Proper procedure for reducing ripple on DC power rail? (e.g. oscilloscope reading -> filter design)

    What is D4 there for? Ant reason not to use full wave rectification? I cannot recommend taking any measurements on this device using a mains powered oscilloscope. Are you using an isolating transformer?
  16. (*steve*)

    Proper procedure for reducing ripple on DC power rail? (e.g. oscilloscope reading -> filter design)

    Unfortunately I cant see the images on my phone, so things are not very clear to me. The problem could be nose from your adapter, your pre-regulator, or even your 3.3v reg. I recommend you look at the power supply rails (under load) from each. One possible problem is poor grounding in your...
  17. (*steve*)

    Getting into hot water

    Oh yeah. I see what you mean. The maintenance company isn't related to the manufacturer. It may be in the interests of the manufacturer to sell more of these boards with the potential fault. What I'm saying is that the maintenance company (who is losing the money) should be more interested...
  18. (*steve*)

    Resistors

    What formulae do you have for calculating power? Do you have one involving current and resistance?
  19. (*steve*)

    Proper procedure for reducing ripple on DC power rail? (e.g. oscilloscope reading -> filter design)

    I recommend you place a 10uF, a 1uF, and a 0.1uF capacitor near the power pins of the nrf24l01. This is in addition to the capacitor near the 3v3 regulator
  20. (*steve*)

    Proper procedure for reducing ripple on DC power rail? (e.g. oscilloscope reading -> filter design)

    Additionally, the current shouted may be higher than you expect if you are measuring them using a multimeter. Are you using a switch mode regulator or a linear regulator to supply the 3v3?
Top