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Premium Member
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293 Posts
Discussion Starter #1
Hi everyone,

Is it possible to set up the power supply to be stable when turning on the vehicle? What i need is when i plug a unit to a cigarette socket, and when i turn my key to Ignition I, the socket is getting 12V.But when i start the vehicle, the power cuts for a second and then gets back.

Is it possible to get stable 12V after i put the key to Ignition 1?
 

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Premium Member
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293 Posts
Discussion Starter #4
Okay,

well this is the situation, i got an vehicle camera... and i set it up this morning. It works great... The point is, i run the 12v cable into the underarm area socket. So when i turn the ignition from 0 to I and II i get 12 volts. then i wait about 3-5 sec, so the electronics in the vehicle sets up and then i start the engine.

So when i turn the ignition to II, the camera starts up and records. While i wait for those 3-5 sec the camera is rooling, but when i start the engine, the car dvr is loosing the power for a second, and thinks that its running on battery, and after 10 sec its shutting down. So i need to reconnect the 12v cable or press the power button, to get the camera recording again...
 

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1,777 Posts
He's saying that the 1 second starting time is putting the camera into battery mode due to confusion from the power shortage. A capacitor on it's own would work.
My mistake, I think you are correct after reading his post again.

His camera must work differently to mine, as if I remove the power, then plug it back in before the 10 seconds are up, the camera continues to record. That is why I assumed it must not of been getting any power for 10 seconds.

But yes, if only for ~1 second then a capacitor connected to the socket will solve the issue.
 

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The capacitor will have to have a minimum value. If you know the current draw for the load then the formulas Q=IT and Q=CV can be used as a ball-park guide...

e.g., if the load is 0.5A and the time delay is 5 seconds, then the required charge storage (Q) = 0.5A x 5secs, so 2.5 coulombs. Then, re-arranging Q=CV to become Q/V=C (and taking V as 12v), then 2.5c/12v = 0.21 Farads, or 210 mF. An electrolytic capacitor exceeding this value - and with a voltage rating of between 16v and 50v - can then be obtained and fitted across the wiring. You'll also need to fit a diode in the feed to prevent this capacitor discharging back into the car electrical system during starting.

Might be easier to buy one of these... http://www.ebay.co.uk/itm/Shark-1-Farad-Power-Capacitor-with-Display-/161127025282?pt=UK_In_Car_Technology&hash=item2583eb4a82#ht_196wt_958 but I've no idea how good they are.
 
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