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| putting a resistor in series with a speaker to increase the impedence |
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| Zero999:
The mute function can be used, as described in the TDA7492P data sheet. Failing that, use the timer relay circuit to bypass the current limiting resistor, once the surge has passed. 5 seconds is probably much longer than necessary. 1 second or less will do. |
| Adhith:
--- Quote from: Hero999 on July 26, 2018, 11:16:52 am ---The mute function can be used, as described in the TDA7492P data sheet. Failing that, use the timer relay circuit to bypass the current limiting resistor, once the surge has passed. 5 seconds is probably much longer than necessary. 1 second or less will do. --- End quote --- Ok got it. but one small thing what would be the wattage rating of the current limiting resistor?? Also would it be wrong to use a dpdt relay to cutoff both the left and right audio output to the drivers?? |
| Zero999:
--- Quote from: Adhith on July 26, 2018, 01:01:25 pm --- --- Quote from: Hero999 on July 26, 2018, 11:16:52 am ---The mute function can be used, as described in the TDA7492P data sheet. Failing that, use the timer relay circuit to bypass the current limiting resistor, once the surge has passed. 5 seconds is probably much longer than necessary. 1 second or less will do. --- End quote --- Ok got it. but one small thing what would be the wattage rating of the current limiting resistor?? Also would it be wrong to use a dpdt relay to cutoff both the left and right audio output to the drivers?? --- End quote --- The resistor is only used for a short period of time, so can be a fairly low power rating like 1W. You could add another relay to cut power to the speakers, but it shouldn't be necessary for this circuit, which should limit the inrush current to the amplifier, to a safe level. |
| janoc:
--- Quote from: Adhith on July 26, 2018, 08:45:23 am ---Another thing about the amp board is that, it plays a music at the startup of the amp and the BMS is shutting down just before that music is played. So does this means that the startup music is drawing all this current?? --- End quote --- That just means that your BMS/power supply is not suitable (is way too weak) for powering this amplifier. The amplifier has a low quiescent current (when not playing anything after the initial inrush) but then when you actually attempt to play sound on it, it needs to get the energy from somewhere. The same when there are any signal peaks (e.g. a big drum note). Then the current through the circuit will jump even an order of magnitude higher than the average current of the amplifier for a short moment. Your power supply must be able to handle this otherwise the amplifier will clip severely or you will burn something out. You must fix this before you try to do anything else because it is meaningless to troubleshoot issues with inrush current and what not when your power supply will not be able to handle the power requirements of your amplifier when actually in use anyway. BTW, I wouldn't trust what your meter shows you on the inrush current - multimeters are not great at measuring short transient events, especially if you have a cheap meter that makes only 2-3 measurements per second. There could well be a high current spike and you will miss it because it falls between two measurement cycles of your meter. A better way to measure things like this would be using an oscilloscope, e.g. by measuring the voltage drop across a small value shunt resistor. |
| johnkenyon:
--- Quote from: Hero999 on July 26, 2018, 11:16:52 am ---The mute function can be used, as described in the TDA7492P data sheet. Failing that, use the timer relay circuit to bypass the current limiting resistor, once the surge has passed. 5 seconds is probably much longer than necessary. 1 second or less will do. --- End quote --- Three ideas: 1) Use the suggested circuit, but bypass the current limiting resistor with a normally closed relay contact, and have a timer which energises it for 5 seconds. 2) Put a normally closed relay contact on the power rail between the reservoir capacitor and the load and drive the relay for 5 seconds at power up time. That way, you have 5 seconds of the battery feeding capacitor only, followed by the battery topping off the capacitor and powering the load. 3) Have the battery circuit permanently connected to the reservoir capacitor and switch the amp on afterwards. Same as 2 above, but the relay contacts are replaced by the on/off switch - no timer required. |
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