Would you make a kit that provides 170VDC @ 600mA?

[robertbaruch]

That's 100W of possible death. But suppose you were trying to put together a (OSHW) kit that needed a ton of Nixie tubes that needed that supply. There's this seemingly legit power supply design from ON Semi that seems to do exactly what I need (I actually need only 22W max). Assuming I built it, tested it, and it seems to work, would you:

(a) Not sell the kit at all, that's too much power in the hands of the hoi-polloi,
(b) Sell the kit, but provide the power supply as a non-buildable unit (i.e. I'd have to put it together),
(c) Sell the kit, and let them build the power supply, too because knowledge is the best defense,
(d) Sell the kit, use a whole bunch of lower-power 170VDC power supplies for groups of Nixies,
(e) Sell the kit, but it doesn't need to be that well-regulated, use a 1:1 transformer for isolation, then rectify (170 VDC = 120 VAC),
(f) Some other suggestion?

Thanks!

--Rob

[Richard Crowley]

IMHO, the least offensive choice would be (c).  But I wouldn't do it if it were me.

1) It seems very risky to sell anything you expect to be connected to the utility power mains.
You could be at humongous risk if some idiot electrocuted themselves and/or burned down their house.
That is one major reason even large corporations with good insurance and good legal firms on retainer still use external power supplies (wall warts, et.al.)

2) Expecting amateurs with no significant previous knowledge/experience of SMPS to successfully construct one seems extraordinarily optimistic.
Having random customers build a low-voltage linear power supply seems pretty reasonable.
Even offering linear power supplies for high voltages doesn't seem unreasonable.
But SMPS, and especially with home-made transformers, seems quite risky.

Not to mention the significant power at a dangerous voltage which you already observed.

[Richard Crowley]

Now, using a beefy external AC wall-wart or line-lump and then a "backwards" power transformer internally for the 170V bus would be something I would consider.

[robertbaruch]

Ah, so there's a wall-wart which plugs into the kit, and the kit contains a transformer to get that up to 120 VAC -> rectify to 170 VDC. The wall-wart isolates the kit, so now there's only kit builder sticks hand in and dies from 22W of high voltage to the face. I suppose I can live with that. Can't make everything perfectly safe...

[3db]

I think it's a bad idea.
If somebody builds the kit and it doesn't work then they might try and fix it.
A lawyer would then have a few options to crucify you.
Build the kit yourself encapsulate it and sell it as a module.
If you must  https://www.eevblog.com/forum/Smileys/default/cheesy.gif

[mikeselectricstuff]

Use local, small DC-DC converters to power a few tubes each.

[T3sl4co1l]

FCC still matters if it's any kind of kit, because their definition of a kit requires that, following instructions, the typical build still meets limits.

Tim

[AF6LJ]

Seems to me the way around all this potentially costly liability
Is to publish the plans somewhere then sell the parts.
You are not providing instruction and it is up to the builder to make sure any FCC rules are adhered to. Responsibility is shifted to the builder.

[station240]

Having the PSU as a kit assumes the builder:
a) Has the correct test equipment.
b) Knows proper safe working techniques around HV supplies (eg strictly hands off).
c) Is aware of the disconnect between rectified AC and secondary DC output.
d) Can assemble it without any mistakes that could blow up (eg 400V cap backwards, rectifier installed wrong away around).

Yes you could document all this, doesn't mean people will read it. Instructional videos aren't that much of an improvement as it's easier to forget steps.
Oh the whole I'd preassemble the PSU, that way you only have to advise on how to safety relating to 170VDC into the Nixies.
 

[Alex Eisenhut]

(f) http://www.ebay.com/itm/DC12V-24-to-DC-200-450V-70W-high-voltage-converter-boost-step-up-power-supply-/121652391983?hash=item1c530c302f:g:wHAAAOSweW5VVfKP

?

[calexanian]

Does this really save any money or add a margin of safety over a small tube type transformer, diodes, and a filter cap? Especially in the sub 200 volt dc range.

[linker3000]

http://blog.xyzio.com/2011/09/05/a-low-cost-nixie-tube-power-supply/

Simple design based on a 555 timer. Eagle board and schematic provided.

[Richard Crowley]

http://blog.xyzio.com/2011/09/05/a-low-cost-nixie-tube-power-supply/

Simple design based on a 555 timer. Eagle board and schematic provided.

@robertbaruch says he needs 600mA
The xyzio web page cited claims the circuit is good for 1.75mA
That makes it unsuitable by a couple orders of magnitude.
600mA puts it likely beyond the range of inexpensive DIY switching supplies.

[calexanian]

http://www.antekinc.com/as-1t150-100va-150v-transformer/

I like the transformers from this company I have used several of them fr DIY projects.

[edavid]

Does this kit really include 300 Nixie tubes?

[starphot]

  Not for novices! You think that's a hokey circuit, try troubleshooting a Mil-spec 300v regulated power supply from a 3 phase, 240 VAC, 400 Hz input with cascading transistors in the output!  Late 1960's design in my test bench in my shop aboard my ship in 1975. It did go out once and that was enough. Avionics fire control system with peanut vacuum tubes, early silicon transistors with some germanium!

Joe

[acolomitchi]

@robertbaruch says he needs 600mA
The xyzio web page cited claims the circuit is good for 1.75mA
That makes it unsuitable by a couple orders of magnitude.

A single one, yes.
How about a "distributed PSU"?
As mikeselectricstuff put it above, "Use local, small DC-DC converters to power a few tubes each."

[robertbaruch]

BTW, if you want to see progress on this project:

https://hackaday.io/project/11095-rpn-nixie-calculator

For now, I've decided to get an off-the-shelf power supply. Not thinking of selling this at all, just making everything available for anyone to order their own PCBs and parts.

[edavid]

OK, you have 80 (!) IN-12 nixies, which have a maximum current of 3.5mA.  Even with a few commas lit, why would you need more than a 300mA power supply?

[robertbaruch]

Well, yeah, I've scaled the project down a bit I now only need 170 VDC at 150mA.

[b_force]

My guess is that if you write a proper and clear disclaimer in a way that the user HAS to read AND accept this disclaimer before even able to buy and open it, you will be all good.
If people than still hurt themselves by lack of skills, they had more than enough change to order a pre-build kit for example (or just cancel/not agree with the order). But in general how people interpret that, depends per country.
In EU if someone simply doesn't obey any precautions which he had to read AND accept mandatory before even starting with something, he doesn't have a change in court. Unless the whole disclaimer procedure is wonky of course.
I know that in USA it's a little different and people have a tendency to sue each other a little bit more easy.

In general, I think it won't be such a big deal.
You see these kinds of kits pretty much everywhere.

BTW, does a kit also need to follow any kind of standards, like creepage, PFC, EMI standards etc?
(despite the fact it's always wise to follow standards)