Electronic Memory!

[Mukhalled]

Hi guys
I'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

 

[audioguru2]

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

 

[Mukhalled]

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? 

 

[Alun]

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?

 

[audioguru2]

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!

 

[Mukhalled]

Thanks Alun and Audioguru , it's really a good idea. i'll do it  ;D

 

[MP1]

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

 

[audioguru2]

I don't think a cap would power a pc with a CD-Rom/player for long enough for the engine to start.

 

[MP1]

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

 

[Alun]

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.

 

[MP1]

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

 

[Alun]

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

 

[audioguru2]

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.

 

[Alun]

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

 

[audioguru2]

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.

 

[Mukhalled]

hi guys
sorry 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 ...

 

[audioguru2]

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

 

[Mukhalled]

Hi Audioguru,
they are in the same connection  . It uses 1A at 5V and 1.5A at 12V.

 

[audioguru2]

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.