Delay Tablet Startup till after crank

**dhantiflag** · 12-19-2011, 04:00 PM

Hello,

So i currently am using an android tablet as my carpc. I love it, its so much more stable, usable, and native that the carpc i had for 5 years... the ONLY issue i am currently running into is with power.

My 370z is push start, so when i get in the car and push the button, the radio comes on for a second then the car cranks, during that second the tablet gets power, (screen on), loses power( screen off), then after crank it should get power again but it all happens so fast that the tablet screen never turns back on. so what i am thinking is there a way to either Delay the power on to the tablet until after the crank or is there a way to keep the tablet enough power through the crank (cap maybe)?

**turbocad6** · 12-19-2011, 05:43 PM

well one thing is that you probably have it hooked up to accessory power which does drop out as the car is cranked, just like the radio does. one easy fix may be to power it from ignition rather than accessory. ign will not drop out on crank. the drawback then would be that the tablet will not be powered in the accessory position which is reached by just tapping the start button without your foot on the brake and not really starting the car. if you want it to be on accessory power but not loose power on crank you could power it with both ign & accessory by way of a relay or a few diodes... do NOT run both ign & accessory power to the tablet without a relay or diodes as this will cause all of the other accessories to be back fed from the ign feed.

I think either one of these options would be better than a timer. a cap might work too but I'd question how reliable it would be throughout the temperature extremes and possibly long cranks or restarts... feeding it ign or ign & accessory isolated from each other is probably your best bet & not so hard to do really...

**soundman98** · 12-19-2011, 09:04 PM

the other solution is a delay like this-- which could be programmed to wait until after the car is started:
http://www.newegg.com/Product/Produc...-pla-_-NA-_-NA

**OldSpark** · 12-20-2011, 09:04 AM

Or if you have a charge light, use its circuit to turn on the load once charging if worried about cranking sags.
(Yes, that's the UIBI without a battery. Connect relay output to relay coil to convert SPST to latching...)

But ACC or IGN or BOTH are easy.