Go Back   Team-BHP > Under the Hood > In-Car Entertainment


Reply
 
Thread Tools Search this Thread
Old 23rd March 2010, 18:47   #1
Senior - BHPian
 
greenhorn's Avatar
 
Join Date: Apr 2007
Location: TN-14
Posts: 6,838
Thanked: 1,318 Times
Default CarPC PSU doubts

I've still not figured out how the PSU in a CarpC handles the dip in voltage when you crank the engine.

Does it restart the PC , Does it maintain the voltage some other way ?

I was planning to run some thin client + a car laptop adapter, but then was wondering about how to handle restarts.

Does a carPC PSU handle it any better ?
greenhorn is online now   Reply With Quote
Old 23rd March 2010, 23:21   #2
Senior - BHPian
 
gigy's Avatar
 
Join Date: Jul 2006
Location: mumbai
Posts: 1,321
Thanked: 41 Times
Default

DC-DC PSU for automobiles maintain the power supply to PC even during cranks to ensure that it dose not shut down. i think they can hold on to almost 6volts (6 to 24v is typical range)
Additionally most of them have auto start and shut down feature built in to it to do the same automatically. the duration of shut down time can be varied with jumper settings on them as per requirement and make.
they also shut down the pc if the battery voltage goes low when the alternator is not running preventing dead battery.
hence many call them Intelligent DC-DC ATX PC power supplies.
This is the best way to power computer components in vehicles.

Last edited by gigy : 23rd March 2010 at 23:23.
gigy is offline   Reply With Quote
Old 24th March 2010, 16:09   #3
BHPian
 
techfreak's Avatar
 
Join Date: Aug 2009
Location: Leh
Posts: 287
Thanked: 157 Times
Post

Yes as Gigy says car dc-dc supplies are called Intelligent as they not only hold the voltage during crankings but also prevent from battery being deep discharged.

They do it with the inbuilt microcontrollers & the charge & current is most probably held by the capaciters.
techfreak is offline   Reply With Quote
Old 24th March 2010, 16:40   #4
Senior - BHPian
 
greenhorn's Avatar
 
Join Date: Apr 2007
Location: TN-14
Posts: 6,838
Thanked: 1,318 Times
Default

<a bit more technical> is the power held in a capacitor/inductor ( in which case how long can it hold)

or does the DC to DC converter just continue to draw current , even during cranking, and step up the voltage?
greenhorn is online now   Reply With Quote
Old 24th March 2010, 16:53   #5
sdh
BHPian
 
Join Date: Jun 2007
Location: Bangalore
Posts: 143
Thanked: 3 Times
Default

it is DC-DC convertors that do the job. No large capacitors on the PSU.
sdh is offline   Reply With Quote
Old 24th March 2010, 18:41   #6
Senior - BHPian
 
DerAlte's Avatar
 
Join Date: Mar 2007
Location: Bangalore
Posts: 8,076
Thanked: 2,876 Times
Default

Quote:
Originally Posted by techfreak View Post
... dc-dc supplies are called Intelligent as they not only hold the voltage during crankings ... current is most probably held by the capaciters.
Quote:
Originally Posted by greenhorn View Post
... the DC to DC converter just continue to draw current ...
Quote:
Originally Posted by sdh View Post
it is DC-DC convertors that do the job. No large capacitors on the PSU.
Correct - there are no large capacitors in the PSU. Nor can there be capacitors (like the ones used in ICE) that can hold enough charge to keep feeding current during the 1.5-3 seconds of crank.

The DC-DC converter, which monitors voltage on the incoming line, keeps doing it's job - producing regulated 3.3/5/12V - till the input voltage falls MORE THAN 20%. When that condition is reached, whether by a failing or low-charge battery or during cranking with a weak battery (no one tests THAT condition with a carputer, isn't it?), the DC-DC Converter fails the Power Good signal (PSU connector, pin 8), signalling to the motherboard not to do anything under those conditions. Motherboard keeps the CPU in a hold /reset state.

If during crank the voltage DOES NOT fall more than 20% (good battery), the Power Good signal stays high, and the carputer can work as usual.
DerAlte is offline   Reply With Quote
Old 24th March 2010, 18:46   #7
Senior - BHPian
 
greenhorn's Avatar
 
Join Date: Apr 2007
Location: TN-14
Posts: 6,838
Thanked: 1,318 Times
Default

Quote:
Originally Posted by DerAlte View Post
during cranking with a weak battery (no one tests THAT condition with a carputer, isn't it?), the DC-DC Converter fails the Power Good signal (PSU connector, pin 8), signalling to the motherboard not to do anything under those conditions. Motherboard keeps the CPU in a hold /reset state.
now THATS what i was worried about. So it helps to have a dedicated car SMPS after all. Thanks DerAlte
greenhorn is online now   Reply With Quote
Old 24th March 2010, 19:50   #8
Senior - BHPian
 
DerAlte's Avatar
 
Join Date: Mar 2007
Location: Bangalore
Posts: 8,076
Thanked: 2,876 Times
Default

Enh? The DC-DC converter IS the SMPS. Did you mean UPS, by any chance? I would think 2 small UPS batteries (to get 12V) connected to the main battery line through a forward-connected diode (current capacity suitable for the charging current), and feeding the SMPS - these batteries will always remain charged, but will never discharge to the main line, no chance of discharging their charge while cranking.
DerAlte is offline   Reply With Quote
Old 24th March 2010, 20:46   #9
Senior - BHPian
 
greenhorn's Avatar
 
Join Date: Apr 2007
Location: TN-14
Posts: 6,838
Thanked: 1,318 Times
Default

the other option was with a thin clientish PC off a 12-19V DC-DC converter. That converter can't do what I quoted from you in the earlier post. Maybe I should have said specialized carpc PSU
greenhorn is online now   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
PSU auto insurance lose out to pvt players mithun Indian Car Loans & Insurance 2 18th July 2009 09:47
Query: Will PSU banks like SBI be open on Election day tommorow in NCR? DCEite Shifting gears 6 29th November 2008 11:09


All times are GMT +5.5. The time now is 16:10.

Copyright ©2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks