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  1. KrisBlueNZ

    Dell Harmon Kardon Hk395 pc speakers

    LOL! A case in point is the data sheet for this very IC, the TDA7375A. In the characteristics table, the total power output at 14.4V supply in bridged mode is stated as 43W, which seems very good, but there is a little footnote that says "Saturated square wave output". In other words, "please...
  2. KrisBlueNZ

    Dell Harmon Kardon Hk395 pc speakers

    You're right, it's not the STA540. A tab is clearly visible in the photo, and the STA540 doesn't have a tab - it's in a "clipwatt15" package that is held to the heatsink with a clip. The TDA7375A seems to be indistinguishable electrically, and has the tab that you want. The data sheets are...
  3. KrisBlueNZ

    Interval Time Delay Relay

    Sorry, I didn't see your most recent post. So you have two dry contacts, one for UP and one for DOWN, that latch on permanently? And you need to provide two dry contact outputs to control the motor through the lift interface? I guess it's allowable for the motor to run on slightly once the lift...
  4. KrisBlueNZ

    Interval Time Delay Relay

    OK, you really need to describe the whole setup in a lot more detail. Otherwise we're just going back and forth suggesting things that aren't going to work. Can you describe the control signals please. I assume you have an UP signal and a DOWN signal, and these latch on permanently. What form...
  5. KrisBlueNZ

    Interval Time Delay Relay

    This is normally done with limit switches, that detect when the moving object has reached its upper and lower limit. In this case, the limit switches would be normally closed, and would open when the moving part reaches the limit position. You can use latching relays to control the motor. The UP...
  6. KrisBlueNZ

    Interval Time Delay Relay

    Another thing. What behaviour do you want when the circuit is not powered? Do you want your output contact to be open or closed? Also, do you want it closed during the delay, or closed after the delay? These factors affect which relay contact you use (normally closed or normally open) and...
  7. KrisBlueNZ

    Interval Time Delay Relay

    You're right, you want a relay. If you use one with SPDT contacts, your output will have a common contact, a normally open contact, and a normally closed contact, like in the diagram you linked to. One of these contacts will close DURING the delay, and one will close AFTER the delay, so you...
  8. KrisBlueNZ

    Blown capacitors in PC

    That's why we're suggesting that you replace ALL the caps of that brand. It's quite possible that the caps that are actually causing the problem are not showing any clear signs of failure. The fact that ANY of them are showing the tell-tale signs means that ALL of them are suspect.
  9. KrisBlueNZ

    cutting traces, lifting up IC pins, what tool to use?

    I see. So I guess to minimise the heating time, you need a quick way to remove all the solder, like a hollow tip iron with a strong suction pump. Once the solder is gone, you should be able to detach and lift the leg using a small blade like a scalpel. I googled "SMT removal" and most of the...
  10. KrisBlueNZ

    Dell Harmon Kardon Hk395 pc speakers

    From the track connections underneath, I think the output IC is an STA540. This is a rather nice quad audio amplifier. Two channels are being used in bridge configuration for the woofer, and the other two are used in single-ended configuration for the two satellite speakers. First check for the...
  11. KrisBlueNZ

    cutting traces, lifting up IC pins, what tool to use?

    If you're having problems with pads lifting off the board, here are a few suggestions from my limited rework experience. Use a smaller bit, a lower iron temperature, a temperature-controlled iron, solder wick instead of a solder sucker (these can jump around and bump the pad), or ideally a...
  12. KrisBlueNZ

    modified sinewave ups

    I hope it's not just me who thinks this is an extremely rude and inappropriate thing to say. You're asking someone here to "give you" the "solution" to your final year project. You have not provided any evidence that you've made ANY effort or progress yourself. You haven't shown us the part(s)...
  13. KrisBlueNZ

    Water tank refilling circut

    A latching relay might allow you to avoid the electronics. You would use the type that has two coils, one to latch the relay ON and one to latch it OFF. You'd use the latching relay to control the fill pump, and connect the OFF coil to the top float switch, so when the level reaches the top...
  14. KrisBlueNZ

    modified sinewave ups

    "I am new in electronics" "I'm trying to make a modified sinewave inverter" does not compute! No one here is going to design and simulate a modified sinewave inverter for you. I suggest you start with something simpler!
  15. KrisBlueNZ

    Blown capacitors in PC

    It's probably just a coincidence that it passed a POST after you cleaned the electrolyte off the caps. A few years back there were many cases of defective electrolytics on motherboards due to cheap components that used the wrong electrolyte formula. If this is another case of the same thing, I...
  16. KrisBlueNZ

    how can i find led specs

    How silly. They put a chip in there to flicker the LED and they don't even bother including a reverse-connected diode on it.
  17. KrisBlueNZ

    how can i find led specs

    As usual, Steve's advice is excellent. I would use three AA or AAA cells in series (4.5~5.0V brand new) and a resistor round 1K. The only thing I can add here is that the pretty drawing of the LED does not hold true for ALL LEDs. I have some low-current devices where the "cup" (the larger bit...
  18. KrisBlueNZ

    led coil generator problems

    The coil may be generating much more than a few millivolts but the multimeter may not be able to respond quickly enough, especially if it's digital (these have averaging circuitry). The obvious way to increase the output is to increase the number and lengthwise density of the turns, by using...
  19. KrisBlueNZ

    amplify ultrasound signal

    An H-bridge driver is a digital device and needs a square-wave input. If you feed a different waveshape into it, it will treat it as a squarewave anyway, so it makes no difference what waveshape you use. Only the duty cycle is significant, and you want that to be 50% so it would be best to use a...
  20. KrisBlueNZ

    Interval Time Delay Relay

    Yes, probably. You need to give a LOT more information. From the first link I can't even tell if you're switching low or high voltage, AC or DC, and whether you want to use an electromechanical relay or something else. You can probably make a fairly simple circuit using a 555 timer driving a...
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