Powersuply in a car?

[Floriot]

Hello,

Can I run the Amp3 in a car without any modification. I thought it should work since it has a range of about 9 to 15 Volts, but a car battery can deliver quite some power. And would it be useful to connect it to a powercap?

Greetings
Florian

[Jan]

Hi,

Yes, you can connect AMP3 to a car 12V system. A power cap of about 10.000 or 20.000 uF is useful as batteries are not so fast responding to current changes, while current to the amplifier is changing fast. A cap helps stabilize voltage to the amp.

[Jan]

Hi,

Yes, you can connect AMP3 to a car 12V system. A power cap of about 10.000 or 20.000 uF is useful as batteries are not so fast responding to current changes, while current to the amplifier is changing fast. A cap helps stabilize voltage to the amp.

[samr7]

Any idea on the risk of the amp being abused or destroyed by voltage spikes in an automotive power system, like what might happen after cranking? Would some sort of a regulator actually help here?

I'm kind of a noob here and need some guidance.

Jan, nice job on the kit, it is VERY meticulously laid out. :D

Thanks..

[zapwizard]

I have two Amp3's installed in my car.
Running perfect for months now.
In fact they seem to handle power so well, they don't skip a beat even when the car is cranking.
Mine just keep on playing.

[zapwizard]

I have two Amp3's installed in my car.
Running perfect for months now.
In fact they seem to handle power so well, they don't skip a beat even when the car is cranking.
Mine just keep on playing.

[samr7]

Zapwizard, I felt very inspired by the pics you posted on flickr and some of your posts on the mp3car forum. Nice work! I wound up following your example.

Anyway, I spent far too many hours planning, screwing up, and eventually constructing this amplifier and a lot of money acquiring parts and new tools, and would not like to see it fail due to a hostile automotive electrical system. My car probably doesn't have any problems with this either, it's relatively new and it seems to disconnect its accessory power and head unit circuits on purpose while the engine is cranking. Regardless, there still aren't any guarantees and I would sleep a lot better given some protective measures.

This is what I'm thinking of doing:

Since the ideal 14.2V supply voltage of the AMP3 is higher than the nominal 13.8V of a car with the engine running, it doesn't seem to make much sense to use a voltage regulator device. Those only seem to be appropriate when the desired voltage is at least 1V-2V less than the input voltage. True? Such a device will also produce heat depending on the voltage difference and the current drawn by the load, and that can add up with one AMP3 drawing close to 5A at full load.

I took a crash course on zener diodes and it seems like a fuse and a zener diode should do the job here. Placing the diode in parallel with the amp and choosing a breakdown voltage as close as possible to 14.6V should short the circuit and blow the fuse in the uncommon case of the automotive voltage going too high for an extended period of time. As a bonus, it will also protect against connecting the supply with the wrong polarity. These diodes supposedly have reaction times on the order of milliseconds, and should hopefully protect the amp from steady-state overvoltage. Additionally, a transient voltage suppression diode also seems to make sense here, to deal with short high voltage spikes, as TVS diodes have reaction times on the order of nanoseconds.

This sort of arrangement is very primitive, and will render the amp useless in any car where the supply voltage occasionally or commonly exceeds the zener diode breakdown voltage, but that doesn't seem like a big issue. Another problem is that there aren't any 14.6V zener diodes and it seems like the best way to get close is to put some diodes in series where the combined breakdown voltage is close to 14.6V. This might be too sloppy for trying to create a reference voltage, but seems like it should work when the diodes' only purpose is to shunt enough current to blow a fuse. An 8.2V diode and a 6.2V diode in series seems like it would come close enough at 14.4V.

Have I made any glaring inaccuracies? Does this seem overparanoid?

[samr7]

Zapwizard, I felt very inspired by the pics you posted on flickr and some of your posts on the mp3car forum. Nice work! I wound up following your example.

Anyway, I spent far too many hours planning, screwing up, and eventually constructing this amplifier and a lot of money acquiring parts and new tools, and would not like to see it fail due to a hostile automotive electrical system. My car probably doesn't have any problems with this either, it's relatively new and it seems to disconnect its accessory power and head unit circuits on purpose while the engine is cranking. Regardless, there still aren't any guarantees and I would sleep a lot better given some protective measures.

This is what I'm thinking of doing:

Since the ideal 14.2V supply voltage of the AMP3 is higher than the nominal 13.8V of a car with the engine running, it doesn't seem to make much sense to use a voltage regulator device. Those only seem to be appropriate when the desired voltage is at least 1V-2V less than the input voltage. True? Such a device will also produce heat depending on the voltage difference and the current drawn by the load, and that can add up with one AMP3 drawing close to 5A at full load.

I took a crash course on zener diodes and it seems like a fuse and a zener diode should do the job here. Placing the diode in parallel with the amp and choosing a breakdown voltage as close as possible to 14.6V should short the circuit and blow the fuse in the uncommon case of the automotive voltage going too high for an extended period of time. As a bonus, it will also protect against connecting the supply with the wrong polarity. These diodes supposedly have reaction times on the order of milliseconds, and should hopefully protect the amp from steady-state overvoltage. Additionally, a transient voltage suppression diode also seems to make sense here, to deal with short high voltage spikes, as TVS diodes have reaction times on the order of nanoseconds.

This sort of arrangement is very primitive, and will render the amp useless in any car where the supply voltage occasionally or commonly exceeds the zener diode breakdown voltage, but that doesn't seem like a big issue. Another problem is that there aren't any 14.6V zener diodes and it seems like the best way to get close is to put some diodes in series where the combined breakdown voltage is close to 14.6V. This might be too sloppy for trying to create a reference voltage, but seems like it should work when the diodes' only purpose is to shunt enough current to blow a fuse. An 8.2V diode and a 6.2V diode in series seems like it would come close enough at 14.4V.

Have I made any glaring inaccuracies? Does this seem overparanoid?

[wiebel]

As far as I got it the ultimate maximum voltage of the chip itself is 16V so security measurements should probably take place at 15.5V or whatever.
I was thinking that zener aren't capable to take enough current to blow the fuse, I have seen a nicer circuit where a zener resistor serie triggers a triac which shorts the whole thing and blows the fuse, I think this "feels" a bit cleaner as zeners are more to reference things than to take real load. I'd be happy to hear that I'm wron as that would simplify the whole thing. But the idea to make something blow the fuse if anything goes wrong is definitely a good one, imho.

edit: After I did some research i found that the protection circuit I mentioned is called "crowbar". just for easyer googling.