turning on rackmount 12V PSU

[horvat.kamca]

Hi,
a friend of mine got a few rackmount 12V SPAFFIV-03G  powersupplies and asked me for help how to turn them on. I've found description of PSU output connector in https://belfuse.com/resources/datasheets/powersolutions/ds-bps-fnd300-series.pdf .

Unfortunately, there is no PS_ON pin.

Do you know what standard this power supply is compliant with  and how to turn in on ?

PIN SIGNAL NAME DESCRIPTION
1-3, 13-15 V1 RTN V1 Output Return
4-6, 16-18 V1 V1 Output
7 - Not Used
8 - Not Used
9 PF Power Fail
10 I2C Voltage Input/Output
11 SDA Serial Data Line
12 SCL Serial Clock Line
19 - Not Used
20 - Not Used
21 LSB Address Input Line
22 RSD Power Supply Remote Shut Down
23 PS_PRSNT_L Power Supply Present signal
24 Fan Fail Fan Fail signal

[ledtester]

It looks like it is meant to be controlled via an I2C bus: https://www.i2c-bus.org/

This is a very common bus used with microcontrollers but you'll need more documentation on what I2C messages to send to the unit to control it.

I would contact Bel tech support to get the I2C protocol documentation for the device:

[NiHaoMike]

I would suggest starting with pins 22 and 23. Check what voltage they are to pin 1 (output ground) with input power applied. A pin that has about 3-5V open circuit probably needs to be pulled to ground and a pin with no voltage probably needs to be pulled up. (There's a reference to the enable signals being active when pulled to ground, try that first!) 100 ohm resistors are good for avoiding damage if those pins aren't what you were expecting. Also check the voltage of pin 10, that appears to be aux power and might be useful for pulling up signals.

[horvat.kamca]

NiHaoMike> Thanks, I've sent the suggestion to my friend.  Only instead of 100 ohm resistor, it's better to use 1k resistor. Another datasheet from BellFuse describes how Power Supply Present PIN should be treated in a little bit more detail

OUTPUT CONNECTOR DESCRIPTION:Power Supply Present
TYPE:Resistor (1 kΩ) connected to logic GND
LOW LEVEL/ HIGH LEVEL:Open/Pull up
V MAX/ I MAX: 10 V/10 mA

https://belfuse.com/resources/datasheets/powersolutions/ds-bps-fnp1500-1800-series.pdf

[TomS_]

Yeah, there will have to be some kind of standby power supply coming out of them, otherwise there would be no way to power the off-board control circuitry, and thus no way to ever turn them on fully.

Seems common to pull one of the signals down to get the main output to turn on. Fans may also spin up at that point if it has any. Ideally they will have an on-board fan controller to bring the speed of them back down to something less jet-enginey.