Hello, I'm fairly new to the Arduino game.. but so far so good!
I have an Arduino Leonardo that's wired into my OEM radio controls, and steering wheel controls. This is using a button matrix, and resistive ladder style design to convert button presses into a BlueSMIRF bluetooth modem that my Nexus 7 is paired to. Works great!
Anyway, I have a turnon thump issue because of the USB sound card initializing after the amps are running. It's very annoying and I figured the best way to fix this was to delay my amps from turning on.
So my idea was this:
To have 2 transistor based switches that would switch the car's 11-15v + current. I want to control these transistors via the digital 5v pins on the arduino. The problem I'm running into is most single transistor circuit designs use the 5v+ from the digital pin HIGH to trigger the transistor but the transistor is trigger the - side of the source current. I NEED to switch the + side of the source current as my amps use a + trigger for turn-on.
Anyone have any ideas how I can use the digital pins on the arduino to trigger the 11-15v + current of the car for my amps?
I'm looking to use this design with 2 digital pins so I can also control my DSP turn-on.
So you're thinking use P-channel MOSFET as high side switch, with pullup resistor on the gate (to +12V) to keep it turned off, and NPN transistor to pull the gate low controlled by the arduino, with pulldown resistor on its base to keep it turned off until Arduino finishes its reset and can drive the base high? (which turns on the NPN and brings the MOSFET gate low, turning it on).
How much current do the amplifiers draw at full power?
You say that the audible "thump" is because the sound cards power up after the amps are already powered, so why not approach the problem from another angle?
Instead of switching the amps on after a delay and have to worry about how to switch all that current, not being able to use relays and so on, why not mute the audio instead for the same amount of time that you would have delayed the turning on of the amps?
I'm assuming that the audio from the sound cards are line level, so a 4066B CMOS switch would work.
The amps will put about 1.5A of current total for remote-on switching.
I thought about switching the audio signal, but in all honestly the less devices between my source and the speakers the better. I'm running a digital coax cable between the soundcard and the DCX2496 DSP. Would the parts you have spec'd be digital friendly?
The other reason for controlling the devices separately over 2 channels was I reusing my power button on the OEM radio controls. I was thinking I could read the button and when pressed it would trigger my system on for a preset amount of time without needing the key. I give alot of demo's at shows, and it would be great to have my system active without leaving the person in the car with the keys (as they demo from the driver seat).
So I'd like to stick with controlling 2A of 12v+ current per digital pin if possible.. 8)
While that may do it, I definitely got confused reading that application note. LOL. Looks like that thing will perform many duties, but how I can implement it.. I don't have a clue.
I'm a bit confused.
You wrote that the sound cards (providing digital audio) on switch on cause a "thump" in the speakers which are driven by the amps.
Are you sure that it is the sound cards causing this?
Normally "thumps" and "pops" only occur with analogue audio due to the inline capacitors used to provide AC coupling.
I'm not 100%, but the thump actually registers on the level meters of the DSP on the input channels, and when I leave the USB sound card disconnected there is no thump. Maybe it's software telling the sound card to create that pop/thump noise? Not exactly sure what chain of events is leading to this, but I figured delaying the amplifier 5 seconds or so would eliminate any unwanted turn-on noises.
Along with the idea of a timed listening period w/out keys.
Have you tried disconnecting the digital audio feed to the amps as the sound cards are switched on?
Then a few seconds later connecting the audio feeds again.
No, but I guess I can try that easy enough. You thinking there is some kind of ground/dc interference that might be freaking out the DSP on first power?
Ya the amps have continuous power and ground. Then uses a 12v+ trigger to power them on. Each of my 3 Amps isabout 1/2a total draw from the 12v+ remote trigger.
