Attn: anyone with a carputer.

[Digsy]

I need to know what you are using as a power supply. Not the actual caputer PSU, but any noise filters or voltage stabilisers you have between the battery and the carputer PSU.

I am trying to fit my Dension DMP3A hard disk based MP3 player and I am hitting a few problems. Namely, the unit seems to draw a massive current on startup (I had been warned about this and also read about it on some other forums). Apparently hard disk drives require a very large startign current when they first spin up. The way the Dension is wired, the power supply goes to the head unit and then the HDD module is powered off that. When you switch on the head unit it also "wakes up" the HDD. Problem is tha with the engine off, the current drain is sufficient that both parts of the system canot power up simultaneously so the hard disk just sits there until the head unit is switched off, then it boots up but because it realises that the head unit is not requesting any data from it, it goes right back into "sleep" mode! Daft eh?

You can also wire up the HDD unit directtly to the 12V feed, but even this isn't enough. I've tried different feeds and different earths with no joy. However, when the car is actually running everything powers up fine, so it must be a voltage issue.

I've already PMed Matty H about this but it just occured to me that anyone with a carputer might have experienced smiliar issues.

Any ideas?

[JustGav]

Well, I thought about this as well, since PC's require a 12v,5v and 3.3v feed and these usually need to be rock solid....

However to get them rock solid you would use a regulator, which have got voltage drops as a result...

My solution was fairly simple, in that I put an audio 1farad cap in front of the carpc stuff, that way it at least has some good filtering, and I used the travla case powersupply...not had a glitch yet..

Gav

[Digsy]

I was going to wire up a more "normal sized" cap to see if it helped (1000uF or something). I reckon that Dension would have mentioned it if anything bonkers like a 1F ultracap was required.

Seems like a logical solution though. Did you ever try it without the cap in place?

[JustGav]

Yeah I had it without the cap and it did work in all honesty, however it didn't withstand a crank, so I put the cap in for the entire system, which is isolated during cranking with a BIG fat solenoid.

Gav

[JustGav]

Also, I know a few people who run a small 12v battery with the system so that it survives cranking as well...

The other option is a power starter, which sits on the ignition and waits 5secs before activating the computer on igntion..

Gav

[Digsy]

Ok, cheers for the info.

I want to be able to use mine with the engine off, anyway. A dropout during cranking doesn't really matter as long as it doesn't physically damage the HDD.

I jus had a quick look on the Maplins website and you can buy anything up to 10000uF for a matter of pennies, so I'll get a range of caps and have a play this weekend.

Just for info, do you have a website where I can have a gander at those small 12V batteries and power starters?

[Chase]

I'm using an Opus 150W supply. Takes an ignition feed, and survives crank. No problems whatsoever with it.

[Digsy]

Just to clarify, this power supply is not actually for a carputer, so anythign designed to plug into motherboard won't do. I just need something that takes battery voltage + noise + cranking + other rubbish in and spits out a nice clean stable 12V.