SGI Power Supply Tester (and other projects)

[Elf]

So, I am still working on the large stack of SGIs. I was warned that some of the power supplies might be in an unknown condition (e.g. worthy of starting up in series with a lightbulb), so the first thing I am doing is testing them. My main concern is not damaging any of the computer hardware due to a bad power supply.

Since there are a large quantity of them, the idea is to build a power supply tester to handle:

• At least Indigo, Indy, and O2 PSUs, in some sort of modular way
• Testing all possible voltage rails simultaneously under load. Somewhat arbitrarily: 3.3V @ ~11W, 3.3Vsb, 5V @ ~30W, 5Vsb, 12V @ ~20W, -12V @ ~2W. Not full load, but good enough to tell whether it would actually behave while powering a machine
• Providing visual indication of low voltage, high voltage, or OK status, per rail
• External outputs for measuring voltage and ripple per rail, with some amount of idiot proofing
• Repeatably surviving a short-through of the high-side switching voltages or mains to the PSU output
• To try and protect the PSU from itself, in terms of its AC input current
• Providing an excuse to start doing electronics again after a decade or so

Ideally I want it to be something nice that I can hold on to, rather than just hacked together.

Anyways I am at the step where I have designed the load boards and have just sent one off to OSH Park. The load boards are per rail, and:

• Provide input protection (somewhat excessively)
• Indicate the range of the voltage
• Connect it through to a resistive load bank

Once the load boards and main board are working in a satisfactory way, I will put them in a nice custom metal enclosure from Protocase.

I will try to post updates here occasionally so that it doesn't look like all those SGIs will just be gathering dust forever! Meanwhile, some of them are also getting cleaned off.




Load board: top / bottom. I think it turned out nicely.

[jan-jaap]

Interesting! So you've got external Rload resistors to dissipate the power, right? If so, the value here compared to, let's say, a load resistance and an oscilloscope is to protect the PSU in case of a mishap? How would this scale to bigger PSUs, which can put 1000VA into a single rail?

[Elf]

Interesting! So you've got external Rload resistors to dissipate the power, right? If so, the value here compared to, let's say, a load resistance and an oscilloscope is to protect the PSU in case of a mishap? How would this scale to bigger PSUs, which can put 1000VA into a single rail?

Ah, yes. For ones where the load is trivial (<5 W maximum before the crowbar kicks in) it is just a power resistor on the board, but past that, external power resistors connected via the P1/P2 spades. One or more 30W ceramic resistors per rail was what I had picked out.

I was trying to go for a few things with the input protection:

• Preventing the power resistors from overheating
• Protecting the power supply, connectors, etc. from excessive current draw if something has gone really wrong (e.g. transformer isolation broke down, some wire fell out and bridged through AC, dead bug dropped somewhere inappropriate, etc.)
• Protecting the comparator, etc. (for voltage status) against truly high overvoltages

For the rest, I wanted to have more of an "at a glance" status reading across all rails to go through testing more quickly, vs. having to move a resistor and meter or scope around. At most, to turn a knob to get more detailed access to different rails on an external meter/scope.

For bigger power supplies like the 1000VA number you mentioned, I think the design would have to be reworked entirely depending on whether that was voltage or current:

In the case of high current/low voltage (>100A), I'd probably abandon the crowbar/fuse approach and maybe try to shut down the PSU on the AC input side with triacs/SSRs. You could either leave a (huge, heater coil) resistive load bank hooked up to the output all the time or use more expensive parts like IGBTs to attach and detach it from the rails. You might protect the voltage sensing circuit but not the load bank, and protecting the connectors generally wouldn't be as much of an issue with huge bus bars.

For higher voltage/low current (>400V) you could still keep some input protection methods with fuses (ditching the crowbar and relying entirely on the GDT, etc.) but you'd have to be careful about the component ratings, creepage, etc. You'd probably want to optoisolate a lot of stuff before it got closer to the user.

[Elf]

I just received the first set of boards from OSH Park today and they look great!

Unfortunately... @Wolfcry just ran our van into a rock wall today and it is looking like it will cost a lot to repair. So I cancelled my outstanding Digikey orders and it looks like I will have to put this off for a while.

[Raion-Fox]

Ugh tough man. I would be happy to help repair if I wasn't across the country. I've been refurbing my Miata and I've helped with dozens of body damage repairs.

[Elf]

Thanks

[Elf]

Well, finally recovering (financially) from getting the van fixed, so I will be back to this soon.

Also a peek at another project I just started:

[johnnym]

Also a peek at another project I just started:

Interesting! Does this transform a USB keyboard to a PS/2, Sun, SGI style keyboard plus PS/2 mouse? Would be really useful. Will this also work with an Indigo (1)?

[Dodoid]

Cool! I designed a PS/2 to SGI adapter with all three connectors (Indigo+Onyx, 4D, Personal IRIS) based on the existing designs, but it looks like you're using far more modern components (mine was based on the schematic for the old mid-2000s all through-hole ones that seem to be floating around). I guess you are using newer code as well? All I had for mine was the .hex binaries that ran on the original, so I couldn't have made any code changes.

[Elf]

Interesting! Does this transform a USB keyboard to a PS/2, Sun, SGI style keyboard plus PS/2 mouse? Would be really useful. Will this also work with an Indigo (1)?

Yes, and yes
USB Keyboard & Mouse to PS/2, the old async serial SGI keyboard (Indigo, 4D, Crimson, Onyx), and Sun Type 5. Since the PS/2 interface is bidirectional I may also try to allow a mode for PS/2 to SGI/Sun or mix and match with USB input.

Cool! I designed a PS/2 to SGI adapter with all three connectors (Indigo+Onyx, 4D, Personal IRIS) based on the existing designs, but it looks like you're using far more modern components (mine was based on the schematic for the old mid-2000s all through-hole ones that seem to be floating around). I guess you are using newer code as well? All I had for mine was the .hex binaries that ran on the original, so I couldn't have made any code changes.

Yes, I am just making this one from scratch although seeing the mysteries around the old design was probably what motivated me to do it. This one is based around an STM32 ARM Cortex M4 microcontroller for the USB OTG support (to act as a USB host).

Sadly the ST USB library is not so great: only one device per USB interface. Currently the device has two USB ports (one for keyboard, one for mouse), meaning having both behind a USB hub will not work. But that is just a software problem that could be fixed. I may try to do that before I call it finished; depends how much of a mess the library code is.

[uunix]

This is great, and this is what I would want in THE ultimate adaptor.. Just my needs really and I do have many adaptors, but these have eluded me.

SUN (Type 6 below? None USB & Keyboard and Mouse in one) IN --TO-- PS/2 / USB OUT. The SUN keyboard 5/6 is a really neat keyboard, if a little soft and quiet. So meaning I want to plug in the SUN keyboard into any machine accepting PS/2 or USB as keyboard and mouse.

INDIGO IN (Keyboard and Mouse in one) --TO-- PS/2 / USB OUT , meaning I'd like to use the keyboard on a machine accepting PS/2/USB as keyboard and mouse again.

PS2 Mouse separate, PS/2 Keyboard separate IN --TO-- USB OUT (have a similar adaptor for my IBM Power InteliStation that you plug in a PS/2 keyboard in one cable, and a PS/2 mouse in the other that should come out as a USB.. but it doesn't work).

Just my wish list..

[miod]

SUN (Type 6 below? None USB & Keyboard and Mouse in one) IN --TO-- PS/2 / USB OUT. The SUN keyboard 5/6 is a really neat keyboard, if a little soft and quiet. So meaning I want to plug in the SUN keyboard into any machine accepting PS/2 or USB as keyboard and mouse.

Seconded. The comfort of type 3 and, to a lesser extent, type 5, is top-notch, and I really would like to be able to have an adapter allowing me to use them as USB keyboards, as long as the adapter sends the "keyclick off" command to the keyboard upon initialization.

[Elf]

This is great, and this is what I would want in THE ultimate adaptor.. Just my needs really and I do have many adaptors, but these have eluded me.

Thanks!

SUN (Type 6 below? None USB & Keyboard and Mouse in one) IN --TO-- PS/2 / USB OUT. The SUN keyboard 5/6 is a really neat keyboard, if a little soft and quiet. So meaning I want to plug in the SUN keyboard into any machine accepting PS/2 or USB as keyboard and mouse.

INDIGO IN (Keyboard and Mouse in one) --TO-- PS/2 / USB OUT , meaning I'd like to use the keyboard on a machine accepting PS/2/USB as keyboard and mouse again.

Unfortunately the asynchronous serial for Sun and SGI keyboards is directional on each pin and I didn't accommodate for switching the direction from host to device. Something to think about though!

I know there is another Sun keyboard to USB device adapter though: http://kentie.net/article/sunkbd/. Could be a candidate for making a separate, newer, smaller adapter.

PS2 Mouse separate, PS/2 Keyboard separate IN --TO-- USB OUT (have a similar adaptor for my IBM Power InteliStation that you plug in a PS/2 keyboard in one cable, and a PS/2 mouse in the other that should come out as a USB.. but it doesn't work).

PS/2 to USB I think is somewhat of a commodity; at least there are a few active converter implementations on Amazon, etc.

[jan-jaap]

I know there is another Sun keyboard to USB device adapter though: http://kentie.net/article/sunkbd/. Could be a candidate for making a separate, newer, smaller adapter.

Nice one, the PIC18F4550 comes with a USB 2.0 interface. Shouldn't be overly complicated to build something similar for the 4D/Indigo.

[uunix]

PS2 Mouse separate, PS/2 Keyboard separate IN --TO-- USB OUT (have a similar adaptor for my IBM Power InteliStation that you plug in a PS/2 keyboard in one cable, and a PS/2 mouse in the other that should come out as a USB.. but it doesn't work).

PS/2 to USB I think is somewhat of a commodity; at least there are a few active converter implementations on Amazon, etc.

I tried such thing, that I'm sure was from amazon, it consisted of just 2 cables with PS/2 connectors that joined into a USB plug.
I wanted such a thing for my IBM InteliStation which only has USB (no PS/2), anyway it never worked.

What did work was a USB KVM switch that I shared with my main PC, but the IBM had to have focus on start-up all the way through the boot process, else it never worked also.

Saying that, this was some time ago, and I have not tried it with my new KVM switch, which seems to be the Dogs Festivals for coping with all my older type machines.

Good luck anyway, looks like a super project.