(from the designer) Obviously you didn't look carefully enough - it doesnt use any LS parts, but 4000 series CMOS, which unlike obsolete 74LS's show no sign of dying out after 25-odd years (probably never will), and I'd defy you to design a nixie clock with a cheaper or more widely available (worldwide) parts list.
As regards the timebase, why mess about hand-tweaking a watch crystal for accuracy when the power company gives you a very accurate, non temperature-dependent, non-aging timebase for free?
(from the designer)
The choice of power supply was carefully considered, and certainly not 'lazy'. The primary design goals were to produce something that could be built very small if required, and use only easily obtainable components.
This project started as something for myself, that I made available for others, not a magazine-style project for electronics newbies - the warnings on the page clearly indicate the potential dangers, which would not be significantly less with an isolated version.
I resent the comment questioning my competence from someone who doesn't appear to know what they are talking about. Transformerless PSUs are far from dead in real commercial products. when appropriately designed and packaged, they are no less inherently safe than transformer-based ones, and are commonly used where a small amount of low-voltage power is required. You will typically find them in rechargeable shavers, bathroom fan timers, Electric showers, electronic timeswitches, washing machines, power drill chargers amongst numerous other consumer and industrial products (some of which I design for a living, incidentally, with and without transformers). Transformerless PSUs are neither 'Bad' nor 'Wrong' - it's just that their appropriateness for any given application needs careful consideration.
If you want to get really picky, there are some aspects of this design that are actually safer than a 'conventional' design - the anode and other limiting resistors from the high voltage line limit the maximum amount of power that could be dissipated under fault conditions to below that which would be likely to present a fire hazard. The only component which could dissipate a significant fault energy is the bridge rectifier, which is protected by a fusible resistor. Also, the original 240v version has NO stored engergy at high voltage after power is disconnected.
By all means add an isolating transformer (as I have recommended on the page when faultfinding), but it will still bite you, badly, if you're not careful, and don't let isolation lull you into a false sense of security. If something looks dangerous, people will treat it with respect, if they think it is 'safe' that's where the accidents occur.
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(from the designer) Obviously you didn't look carefully enough - it doesnt use any LS parts, but 4000 series CMOS, which unlike obsolete 74LS's show no sign of dying out after 25-odd years (probably never will), and I'd defy you to design a nixie clock with a cheaper or more widely available (worldwide) parts list. As regards the timebase, why mess about hand-tweaking a watch crystal for accuracy when the power company gives you a very accurate, non temperature-dependent, non-aging timebase for free?
(from the designer) The choice of power supply was carefully considered, and certainly not 'lazy'. The primary design goals were to produce something that could be built very small if required, and use only easily obtainable components. This project started as something for myself, that I made available for others, not a magazine-style project for electronics newbies - the warnings on the page clearly indicate the potential dangers, which would not be significantly less with an isolated version. I resent the comment questioning my competence from someone who doesn't appear to know what they are talking about. Transformerless PSUs are far from dead in real commercial products. when appropriately designed and packaged, they are no less inherently safe than transformer-based ones, and are commonly used where a small amount of low-voltage power is required. You will typically find them in rechargeable shavers, bathroom fan timers, Electric showers, electronic timeswitches, washing machines, power drill chargers amongst numerous other consumer and industrial products (some of which I design for a living, incidentally, with and without transformers). Transformerless PSUs are neither 'Bad' nor 'Wrong' - it's just that their appropriateness for any given application needs careful consideration. If you want to get really picky, there are some aspects of this design that are actually safer than a 'conventional' design - the anode and other limiting resistors from the high voltage line limit the maximum amount of power that could be dissipated under fault conditions to below that which would be likely to present a fire hazard. The only component which could dissipate a significant fault energy is the bridge rectifier, which is protected by a fusible resistor. Also, the original 240v version has NO stored engergy at high voltage after power is disconnected. By all means add an isolating transformer (as I have recommended on the page when faultfinding), but it will still bite you, badly, if you're not careful, and don't let isolation lull you into a false sense of security. If something looks dangerous, people will treat it with respect, if they think it is 'safe' that's where the accidents occur.