Mukhalled Posted October 30, 2005 Report Share Posted October 30, 2005 Hi guysI've built an audio amp. to use in my car. The audio source is a (pc cd-rom) CD-player. They work pretty well together.I need a memory or something like that to keep what i'm listening to, for example:i'm listening to a song and the car is not started, when i get the car started, the current will be off for a second so i have to start the same song from the begining Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 30, 2005 Report Share Posted October 30, 2005 Hi Mukhalled,The CD/MP3 player in my car radio remembers what it was doing when the power was shut-off. It plays my wifey's Spanish music nearly every time I get in. My pc remembers where it (or my wifey) was surfing on the internet or anything else it was doing. My digital cable TV box remembers what it was doing, especially the loudness setting. They don't have a circuit to remember things, instead they use their brain with computer programs that control what they do (including my wifey?).If you are a computer-geek then you could write a program for the thing to save what it was doing when the power was cut, and another program to execute its return to that task when the power is restored. Those programs might have already been written and maybe posted on the internet. ;D Quote Link to comment Share on other sites More sharing options...
Mukhalled Posted October 30, 2005 Author Report Share Posted October 30, 2005 Hi Audioguru Thanx for your message. It's logical actually ;D , but in my project as you know ( audio amp + cd player ) there is no memory card or a chip which i can load a program in ??? , am i right? Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted October 30, 2005 Report Share Posted October 30, 2005 How about connecting both the car battery and an external battery to the CD with diodes so the power is never cut off to the CD player in the firstplace? Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 30, 2005 Report Share Posted October 30, 2005 You said you had a "(pc cd-rom) CD-player". A pc is a personal computer, isn't it?I suppose you could make an un-interruptable power supply for it, using a rechargable battery to keep it going as you start the engine.Alun had the same idea but he beat me to posting it! Quote Link to comment Share on other sites More sharing options...
Mukhalled Posted October 30, 2005 Author Report Share Posted October 30, 2005 Thanks Alun and Audioguru , it's really a good idea. i'll do it ;D Quote Link to comment Share on other sites More sharing options...
MP Posted October 30, 2005 Report Share Posted October 30, 2005 Mukhalled,If you are only concerned with momentary spans of time such as the switch moving from the accessory position to run, then you can add a large value Electrolytic capacitor between the positive power voltage and ground wires of your CD player. When your player goes off, it will take some time to drain the capacitor and it will still be powered up for a short period of time. When the key is only off for a short period of time such as in your example, the CD player functions will not be interrupted. You do not need a special dedicated circuit for such a feat.MP Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 30, 2005 Report Share Posted October 30, 2005 I don't think a cap would power a pc with a CD-Rom/player for long enough for the engine to start. Quote Link to comment Share on other sites More sharing options...
MP Posted October 30, 2005 Report Share Posted October 30, 2005 Who said anything about powering up a pc? He said he was powering the CD player from a PC. Not the PC. This would be powered from 12 volts and would be no different than any other peripheral in the car.However, if he DOES have a PC motherboard in the car powered from the 12 volt car supply, there would still be no difference in what I posted. A capacitor will cause a delay in the power down and might help him out. He just needs to select one which is large enough to compensate for the draw of what is powered. (CDROM does not draw much current).MP Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted October 30, 2005 Report Share Posted October 30, 2005 The problem is that the electrolytic capacitor would also discharge back into the car and attempt to power everythig else as well, a doide could be used to stop this. You could use a capacitor and very large capacitors are available, but whether this is a viable option depends on the nature of the load, f it contains a linear regulator and the load consumes 1A then it'll be a constant curent load so a 1F capacitor should last for one second if a voltage drop of 1V is acceptable however 1F capacitors are expensive. I think a battery is the best solution here it could even be rechargable and recharge of the car battery too. Quote Link to comment Share on other sites More sharing options...
MP Posted October 30, 2005 Report Share Posted October 30, 2005 Good point, Alun. He would certainly need to isolate the circuit with a diode. Not sure what is inside the equipment he is using, but, yes, if he has a regulator, he could get more efficiency by adding the cap after the regulator.Perhaps Mukhalled could give us more information about this circuit.MP Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted October 30, 2005 Report Share Posted October 30, 2005 You don't need a complex circuit for this.R should limit the current to a low level suitable for trickle charging, B is a Nicad or NiMH battery, here I've suggested a 9.6V racing pack, the diodes should have a sufficient current rating Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 30, 2005 Report Share Posted October 30, 2005 Do they make a CD-Rom/CD player with an audio output? The ones on my pc's don't. I have seen many people with a portable CD player but haven't seen anyone with a pc's external CD-Rom player connected to a battery pack. Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted October 31, 2005 Report Share Posted October 31, 2005 audioguru,I can see your point, I must admit the origional post was quite confusing but the following quote would imply this isn't a PC CD-ROM but a personal CD player.Hi Audioguru Thanx for your message. It's logical actually Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 31, 2005 Report Share Posted October 31, 2005 Hi Alun,In his 1st post, Mukhalled said he had a "(pc cd-rom) CD-player". If it is actually a portable CD player needing 3V at about 50mA from a car battery to 3V converter, and he needs backup time, then maybe he should just connect the voltage adapter to something that is continuously powered while cranking the engine.I suspect that it is a CD-Rom drive from a pc but it has an audio output. It is might be already continuously powered and needs 12V which drops too low during cranking.We don't know its minimum operating voltage to determine if a simple rechargable battery and diode will work. It might need a low-dropout regulator for its 12V. There might not be enough voltage from the car to charge an additional battery, since a 10-cell Ni-Cad or Ni-MH battery needs about 14V to 15V to fully charge. With such a high charging voltage then a diode won't work as a changeover device. Continuous overcharging must be avoided. Quote Link to comment Share on other sites More sharing options...
Mukhalled Posted November 2, 2005 Author Report Share Posted November 2, 2005 hi guyssorry to late. What i'm using is a CD-drive "reader" which we use in our PCs which needs +12v and +5v, and it has an audio output ... sorry about my eng it's a little bit hard to explain ... Quote Link to comment Share on other sites More sharing options...
audioguru Posted November 3, 2005 Report Share Posted November 3, 2005 Hi Mukhalled,I don't know how much current a CD-drive uses nor its minimum operating voltage but I think it needs a huge very expensive capacitor to power it while starting your engine. What powers your amp while starting? Connect them to the same connection. ;D Quote Link to comment Share on other sites More sharing options...
Mukhalled Posted November 3, 2005 Author Report Share Posted November 3, 2005 Hi Audioguru,they are in the same connection ;). It uses 1A at 5V and 1.5A at 12V. Quote Link to comment Share on other sites More sharing options...
audioguru Posted November 3, 2005 Report Share Posted November 3, 2005 I don't believe that a CD-drive uses a whopping 23W. A huge expensive 10F to 30F capacitor could power it for a second or two through a diode. Or it needs a rechargable battery.Is it connected to something that is powered all the time including during starting the engine? The car battery voltage drops to about 9V when cranking the engine, so maybe the CD-drive and its voltage regulators need more. Quote Link to comment Share on other sites More sharing options...
Mukhalled Posted November 3, 2005 Author Report Share Posted November 3, 2005 Is it connected to something that is powered all the time including during starting the engine? No, it's connencted together with the amplifier and they get the voltage from the (electric lighter, cigarette lighter) which is not always powered. I don't want to connect the audio system directly to the car battery because i might foreget to switch off it, then the battery may be "finito" ;D.so is there any hope ??? ;D Quote Link to comment Share on other sites More sharing options...
audioguru Posted November 3, 2005 Report Share Posted November 3, 2005 It's a can of worms. A huge cap is expensive. A rechargable battery might not fully charge but might work.My new car shuts-off the stereo if I open the door with the engine off. It shuts-off after about 10 minutes with the engine off but if I don't open a door (right in the middle of a breaking news report).My cheap portable CD player charges its two AA Ni-MH battery cells and would work for you.My portable Creative Nomad MP3 player holds thousands of songs on its 10GB hard drive and charges its four AA Ni-MH battery cells. It would work for you.I have 3 more of them to fix. Two of them are smashed so I use them for parts and one is nearly like new (about 2 years old) but its hard drive is broken, it needs a special USB cable (but I might have it in a huge box of cables) and it needs a battery.You wanna buy it after I fix it??? ;D Quote Link to comment Share on other sites More sharing options...
Mukhalled Posted November 3, 2005 Author Report Share Posted November 3, 2005 I can buy a new CD-player to my car but I think it's cool to build my own things ;D Quote Link to comment Share on other sites More sharing options...
Guest Alun Posted November 3, 2005 Report Share Posted November 3, 2005 I'm guessing a bit here, but thie 5V rail is probably a low current supply to power the microcontrolers and logic, if you keep it powered then it'll remember where it was even if the 12V rail goes down. You could test my theory by momentarally disconnecting the 12V, if I am right then you could use my circuit with a 7.2V battery and a low dropout 5V regulator for the 5V rail. Quote Link to comment Share on other sites More sharing options...
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