Connecting a UPS to an ATX – PSU.
Before you all jump in and fry me because the cost of a UPS is far more expensive than buying a ready DC - DC PSU. I built this carputer with the exception of a touch screen, from hardware I had laying around.
I have been using an old APC UPS with a new battery to drive my ATX – PSU for close to a year now without any issues.
For anyone who is interested. This is the way I have set up my car PC.
DISCLAIMER:
If you do this you do it at your own risk. I will not be held responsible if you burn your computer your car or cause injury or death to yourself or others.
This diagram is a record of my own installation and a guide for others.
You have been warned.
A few people on this forum attempt to power their car PC using a DC – AC inverter via a UPS. As you may or may not know most UPS’s will not work with an inverter. Aside from converting DC to AC and then AC back to DC again, there is no need for the inverter.
I will explain how this works and I am sure there will be someone out there that will recommend changes and improvements. Please feel free to do so
(The circuit could use a few diodes.).
There are no fuses in this diagram however I do use fuses in my setup and recommend that you do so too.
First I will start with the UPS.
You need to turn off the alarm on the UPS otherwise it will annoy the hell out of you as there is no AC input.
The negative terminal ( - ) of the UPS battery is connected to the vehicles earth. RX5 and RX6 connect the UPS positive terminal ( + ) to the Vehicles positive battery terminal, only when the ignition is in the on position and the engine is not cranking.
NOTE Ignition is not the same as
Accessories. I do this so that I don’t flatten my car battery if I listen to music in the Acc mode. This way you will have only the UPS battery supply when the key is in the Acc position.
RX5 and RX6 are not 30amp SPDT relays. I use 60 amp SPDT relays for this purpose.
RX1 and
RX2 are switched when the key is in the
Acc position.
RX1 connects Pin 8 on com port 1 to the ATX 5v +. Used as a generic UPS in windows. When the Accessories are turned off windows will initialize a shutdown/Hibernate depending on your chosen setup. When the vehicle is cranked
RX6 will disconnect the UPS battery from the car battery and keep
RX1 energized to stop the PC going into Shutdown/hibernation.
RX2 switches
RX3 on
(I use one relay with multi poles to achieve the work of RX1 and RX2) when the key is in the Accessories position.
RX3 switched the UPS on. Once the UPS is on the PC should power up.
(You will need to set this option in the BIOS. Full on after power out or simular). Once the ATX PSU is powered it will energize
RX4 which will hold
RX3 on so that the UPS does not switch off when the accessories are turned off.
When the car key is turned to off
RX1 will disconnect the 5V + feed to Com port 1 pin 8 and start the shutdown process. If Windoze hangs, it will flatten the UPS battery only.
RX3 stay's energized because
RX4 is supplying power to it. Once Windows has shut down
RX4 will switch off and in the process
RX3 will switch the UPS to off.
If you’re UPS used a momentary switch to power the unit you will need to change the way
RX3 works. See
www.the12volt.com for more help.
Hope that this helps anyone who is interested in this type of power solution.
Cheers
Linear Mode
