Thread: PSU Recommendations for a picky engineer

Originally Posted by mpr90

Hi - I've been looking around for some time to find a good candidate for a power supply for my car PC, but haven't been able to find what I want. I am powering an IEI Wafer LX800 SBC (+5V only, supports AT or ATX power).

• +5V (3.5A) regulated outputs
• Ability to turn on either with the ignition or when I unlock the car remotely (i.e. sensing door unlock pulse)
• Auto shutdown after preset time if turned on with door unlock pulse (and ignition never turned on)
• Ability for the SBC to prolong shutdown time after ignition turned off (i.e. when I park in my garage, I want the PC to sync my music over WiFi, and it may need more time than the standard shutdown timeout allows)

The Carnetix P2140 box is close, as it has the unlock pulse input and the ability to prolong shutdown, but it doesn't have the required capacity on the +5V rail (although I could potentially use a DC-DC on the +12V output). Also, this thread puts me off.

I also looked at the M2-ATX, because I could then write custom firmware to support the behaviour I'm after (using, e.g. the jumper pins for the unlock pulse and prolong shutdown inputs). I presume that the firmware here is current - anyone know different? It looks like a chap called FMode has done something like this here.

The M4-ATX looks interesting with the USB interface, which might allow interaction between PC and PSU for my prolonged shutdown mode, but I didn't see anywhere how the interface works or whether you can have custom firmware (this thread may turn up something soon).

Does anyone have any other suggestions?

Thanks,
Matthew.

The CarNetix unit is as close as you're going to get for the requirements that you have. (maybe they'll custom build you one so you can get that extra 0.5 amp out of the secondary circuit)

Rest assured regarding that thread about their poor support ... the device speaks for itself ... I have had one for almost a year now, and no problems whatsoever. If you understand electricity, then you'll have no problems with the 2140, IMO.

Well nothing currently sold does what you want. So you are faced with 2 options: (a) code custom firmware, or (b) build custom hardware.

So you like soldering or flashing?!

I think coding would be the easiest and cheapest. Get the M2, and write your own firmware for it. With the M2 you have a ton of options for other hardware. With the carnetix and using all its juice, you are pretty much done for with peripheral devices.

Custom firmware/hardware all the way. I recommend the Texas Instruments ISRs for regulators. I run a PT6625 for a 5V supply (and PT5071 for 12v). They run nice and cool.