Mulja tv repair portal
General => General Forum => Topic started by: Turnip on December 09, 2009,08:30:19
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Hi folks,
As I try mend most anything, have an old GPO pulse clock where customer needed a driver giving a single pulse 30 seconds apart and reset facility.
Initially used a modern clock movement with a modified minute hand and an opto interrupter, plus a multivibrator giving fast reset as pulse clock has no mechanical reset.
Works fine, but seems rather crude in this day and age - any thoughts on something more digital, or might be taken for one of those ancient valve chaps - whatever valves were (good PD500s for sale - an exceptional audio triode for currently trendy, low 3rd push-pull audio amps with a modest 25KV HT supply, have no suitable output transformers though) - Chris.
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Hi, Turnip. I have had a few slave clocks put aside for quite a few years. Operating a commercial repair shop, when I acquired them I had ideas of placing them around the building, operating from a master clock of some sort. I did some tests with the PC board from a cheap quartz clock driving a power transistor, and found that it would work for a maximum of about three slaves. The obvious solution (I thought) was an SCR or triac as the output element. But I had a few years previously started to build up a test instrument for producing a signal to simulate the ignition system of a motor car, to test engine analysers. I had experienced problems getting logic to drive SCRs in that project and it had been shelved for further information. I have since built some elaborate light dimmers for two triple auditorium picture theatres and gained a little more knowledge about driving triacs, so am now better equipped to revive the other two projects, WHEN I GET TIME ! I still feel that this would be the best solution. The devices used in the dimmers were MOC3021 as the optocoupling triac driver and BTB16-600B which would be suitable for my project but overkill for yours. But maybe you can develop that idea. From memory I left the coil of the clock motor connected and just tacked across it the extra circuitry. It saves a lot of work and should be real accurate. Maybe you can sub the coil of your slave for the quartz clock coil....if the impedance of the slave isn't too low, in which case you might try a little transformer, perhaps something like a horizontal driver transformer from a kinescope type TV ? If you damage a few quartz clocks along the way it's no great loss as they are so inexpensive these days. Cheers. :cheesy1:
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Thanks, Techno-,
Read your reply with much interest. My problem is a little different - only have one clock, so drive isn't an issue. A modern quartz movement does the biz, but it ain't exactly 'Millenium plus', and am somewhat embarrased as would prefer to count down from an Xtal, or even the mains supply, but haven't the faintest idea how to do it - Old analogue chap, me - valves, AC128's and relays R us, but trying to get with it - Chris.
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Hi, Chris. I built up a sporting events timer some years ago, with a crystal oscillator module (3 terminals, +, gnd and Output) and five decade counters as dividers. There were also start and stop buttons, a digital display and an amplifier fed with three different tones plucked from along the divider string to signify the end of the session, into a six-inch horn speaker. But the oscillator and decade counters portion was quite simple, the dearest part being the oscillator module operating at 1 MHz, I see Farnell still have them, looks like P/n 9712402, runs on 5V as do the 4017 decade counters. The output of MY string is one pulse every tenth of a second, so you would need one more counter. Modernising that a little, I'm using a chip CD4059A in a "power your car with hydrogen" project, which can divide by 1000, so it can probably be done with fewer parts if necessary. But 4017s are cheap and still available, although oldfashioned, and I'm still using them in projects. The output of the 4017s run on 5v may not be enough for the clock motor but a simple power transistor and base resistor should interface. If you need a different voltage for your motor you may need the power supply for the output stage at one voltage and then a three-terminal regulator to 5V for the other stuff. And you may need six dividers as five will give you pulses a tenth of a second apart, you will probably want half a second or a second between them. I have located the paperwork from my old project and can give you the PC board layout I used in an email, you can just add the extra stage, if you don't want to do a PC board, Veroboard should be possible if it's still available. If you want any of this info let's know.
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Many thanks Techno -
Still recovering from a good British Crimble - well it can take 'till April , Thanks for input, will study when eyes come together and focus, must admit that my crude solution seems to do the biz, but am not entirely happy - it's so mid 20th Century.
Thanks again - Chris.
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Thanks again Tech,
Crimble now passed, had time to check your last on that slave clock biz. Seems good, but as I have a ready 50hz available, would prefer to count down from there but have little idea as how to do it.
Analogue was us, digital or pulsy stuff is still black magic - Chris, the elder.
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Best one I've used is the AIM sports lap timer. large display which is easy to read when you're tucked behind the bubble. Just takes a few stripes on the bike. Just running the turbine without oil flow would be a very bad thing.
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Hi Rapid,
Wow, but can you do that again in English that Will Shakespear might comprehend.
Gotta do this as they all major in King Lear, but have troubles with those first two sisters - the third (Cordelia) found that porrage tasty and cool
Love 'em really - well, a little bit - Chris