[time-nuts] Anybody want a Thunderbolt power supply?
nsayer at kfu.com
Wed Aug 31 19:42:19 EDT 2016
When I began the design process, I assumed - as would be reasonable - that ~30 mV P-P of noise and ripple were acceptable for input power supplies, and that before they were used for a precision purpose within the device that there would be further filtering if for no other reason that you’d think they’d want to limit coupled interference on the power lines. My assumption, given the extremely low draw on the -12 line was that they were using the -12 line just for the RS-232 level shifter (and that they were too lazy to use a MAX232 like everybody else).
Now that I’ve posted and had my assumptions disabused, I’ll need to go back to the drawing board for another attempt. The price point won’t likely be $25 anymore, but the question was whether anyone wanted a Tbolt power supply, and if I offer anything at all, I intend for it to be reasonably useful for its intended purpose. Like all the things I make for sale, it will be open hardware, which will afford everyone here more than enough opportunity for Monday morning quarterbacking. :)
> On Aug 31, 2016, at 4:02 PM, Charles Steinmetz <csteinmetz at yandex.com> wrote:
> Bob wrote:
>> I don't mean to cause offense, but is everything you don't like crap? The reality is that whatever the market will bear is what determines what comes to market. If you can find high quality goods on ebay that can be modified to fit your needs, then you win. There is a substantial market that either cannot do those mods or would rather spend their time elsewhere. So, what they're willing to pay is going to determine what's available for sale.
> No, but I often view things that don't do the job they need to do as crap, especially if they are offered in such a way as to suggest that they are, in fact, useful for the intended purpose. So, let's take the proposed power supply -- a switching regulator to develop +5v and -12v supplies from an existing +12v supply, with noise of 35mVp-p, offered specifically as a power supply solution for Tbolt GPSDOs. If the offering said explicitly that a Tbolt can't provide its best performance with the product because of its high noise level, then I might be on the fence about whether it was "crap." But if it were offered as a power supply for Tbolts with no mention of what I consider to be a large departure from acceptable performance for the intended use, then yes, I'd probably consider it "crap."
> The issue is that many users do not know what the relevant needs are. Rightly or wrongly, they are relying on suppliers to do that job for them. So, offering something for a particular use carries the implication that it is really useful for that purpose. If a seller tells a time-nut that a power supply is designed to run a Tbolt, an implicit representation has been made that it will work in that role as a time-nut would expect it to. But IMO, the proposed product would not do so because of the high noise level.
> So, what distinguishes this from packages that have been sold to time-nuts in the past that included power supplies that also did not work in that role as a time-nut would expect? In those cases, due largely to this list, there was widespread discussion of the issue and equally widespread knowledge that for time-nuts-quality results, the PS that came with the package needed to be replaced with something better. So at this point, if someone offers a PS to time nuts for use with Tbolts, it would be natural to assume that the seller was familiar with that history and was offering the "something better." So today, if that is *not* the case, it should be stated explicitly.
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