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Low current crystal oscillator
Hello I have built 2 very simple 2-chip frequency counters with 8 LED binary readout see http://www.hanssummers.com/radio/sfreq/index.htm . My Mk2 counter is extremely small (just 25 x 16 x 16mm) and consumes a low current of 5mA max. The question relates to the 4.096MHz oscillator which uses the internal oscillator of the 74HC4060. Of the 5mA current consumption, 1.2mA is used by the LED's when max 7 are on at any one time. About 0.8mA by the diode-resistor gate logic, transistor switch, 74HC4040 and the voltage regulator. Fully 3mA is wasted on the 74HC4060 crystal oscillator + divider. It seems wrong to spend 60% of your current consumption on an oscillator, compared to less than 25% on the LED's. In the pursuit of excellence in this design, I would like to cut the current consumption of the oscillator section. Does anyone know of a better arrangement that will cut current consumption? Increasing the series resistor wasn't the solution. I put a 100K variable in here in place of the original 2K2. Initially as the resistor was increased the current consumption fell, but at higher resistances the current consumption increased quite dramatically. The optimum was at close to 4K7. 73 Hans G0UPL http://www.HansSummers.com |
regulator. Fully 3mA is wasted on the 74HC4060 crystal oscillator + divider.
It seems wrong to spend 60% of your current consumption on an oscillator, compared to less than 25% on the LED's. Try a plain 4060. |
Each sub-circuit in an equipment should be considered seperately, on its own merits, in respect of minimisation of power consumption. It is essential for the future of the human race that electronic design engineers are familiar with the basic principles involved. Energy consumption has to be paid for throughout life of the equipment. It's a part of the cost of ownwership. At present much of the world's energy requirements come from oil, gas and coal. Ordinary food is the principal source of energy of course and is always in short supply. Oil is also used to make plastics for the packaging industries, etc. World war has been in progress for many years about control of food supplies, the oil fields and pipelines. It is becoming daily more intense and building up towards Armageddon. Fundamentally it is a war involving the Multi-nationals, Wall Sreet Bankers and giant Insurance Companies, etc., completely beyond control of World Governments. Sooner or later the World MUST concentrate on atomic energy. The sensible French already have 90% of their energy requirements provided by atomic power stations. The remainder by hydro-electric and tidal power. The Japanese, having no natural biological energy resources, are also quietly well on their way. Iranians, oil producers themselves, are busy building there own atomic power stations in anticipation of a World oil shortage, but their efforts are sabotaged by multi-national legal and political warfare about who gets the development, investment and construction contracts. When the World is mainly on atomic energy, electronic circuit designers can feel free to enjoy themselves and exercise their unrestrained imaginations. ---- Optimistic Reg. |
Hans Summers wrote:
Hello I have built 2 very simple 2-chip frequency counters with 8 LED binary readout see http://www.hanssummers.com/radio/sfreq/index.htm . My Mk2 counter is extremely small (just 25 x 16 x 16mm) and consumes a low current of 5mA max. The question relates to the 4.096MHz oscillator which uses the internal oscillator of the 74HC4060. Of the 5mA current consumption, 1.2mA is used by the LED's when max 7 are on at any one time. About 0.8mA by the diode-resistor gate logic, transistor switch, 74HC4040 and the voltage regulator. Fully 3mA is wasted on the 74HC4060 crystal oscillator + divider. It seems wrong to spend 60% of your current consumption on an oscillator, compared to less than 25% on the LED's. In the pursuit of excellence in this design, I would like to cut the current consumption of the oscillator section. Does anyone know of a better arrangement that will cut current consumption? Increasing the series resistor wasn't the solution. I put a 100K variable in here in place of the original 2K2. Initially as the resistor was increased the current consumption fell, but at higher resistances the current consumption increased quite dramatically. The optimum was at close to 4K7. 73 Hans G0UPL http://www.HansSummers.com Not familiar with the chips you are using but you should use the lowest frequency oscillator possible. Maybe try the 32 + KHz crystal A lot of the current is used to charge and discharge internal capacity so doing that less often helps. Bill K7NOM |
On Mon, 21 Jun 2004 14:31:12 +0000 (UTC), "Reg Edwards"
wrote: Sooner or later the World MUST concentrate on atomic energy. Absolutely right, Reg. Even good old fission if necessary. Yeah, it's dirty but so what? Outer space has a limitless capacity for our radioactive garbage. Instead of encasing it in concrete and burying it, we should be just firing away in rockets. Way to go! -- "What is now proved was once only imagin'd." - William Blake, 1793. |
Hans Summers wrote:
Hello I have built 2 very simple 2-chip frequency counters with 8 LED binary readout see http://www.hanssummers.com/radio/sfreq/index.htm . My Mk2 counter is extremely small (just 25 x 16 x 16mm) and consumes a low current of 5mA max. The question relates to the 4.096MHz oscillator which uses the internal oscillator of the 74HC4060. Of the 5mA current consumption, 1.2mA is used by the LED's when max 7 are on at any one time. About 0.8mA by the diode-resistor gate logic, transistor switch, 74HC4040 and the voltage regulator. Fully 3mA is wasted on the 74HC4060 crystal oscillator + divider. It seems wrong to spend 60% of your current consumption on an oscillator, compared to less than 25% on the LED's. In the pursuit of excellence in this design, I would like to cut the current consumption of the oscillator section. Does anyone know of a better arrangement that will cut current consumption? Increasing the series resistor wasn't the solution. I put a 100K variable in here in place of the original 2K2. Initially as the resistor was increased the current consumption fell, but at higher resistances the current consumption increased quite dramatically. The optimum was at close to 4K7. 73 Hans G0UPL http://www.HansSummers.com On the other hand, you can always console yourself with the fact that 60% of your power budget is going toward making the thing accurate... -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
"Bill Janssen" wrote in message ... Hans Summers wrote: [snip] Not familiar with the chips you are using but you should use the lowest frequency oscillator possible. Maybe try the 32 + KHz crystal Bill, I am aware that CMOS current consumption is dependant on operating frequency. However the simplicity of the design demands a clock frequency which is a power-of-two multiple of 1KHz. Otherwise the counting range would have to be other than 0 to 99.5KHz. This counting range is perfect for amateur bands, the offset off the band edge or next multiples of 100KHz. In any case the counting frequency of the 74HC4040 in my tests was very similar to the 74HC4060 timebase since I was using an 80m VFO. But the current consumption of the 74HC4040 was negligble. Therefore there must be something about the oscillator configuration which is causing the high current consumption. That's why I'm wondering if there are other, more power-efficient ways of making an oscillator. Bear in mind that a 32768Hz watch crystal is only 125 times slower than my 4096KHz crystal. Assuming proportionality that's about 25uA. Isn't this rather large for a watch? What sort of capacity are we looking at in a watch battery... 25mAh or less? In this case a watch battery would only last 6 weeks, and that's just powering the oscillator on its own not even worrying about the watch hands. 73 Hans G0UPL http://www.HansSummers.com |
The problems of how to get rid of relatively minute quantities of mildly radioactive waste materials have been exaggerated by the oil conglomerates and the other multi-national companies in the control of world governments. They do it for obvious reasons via the international media which they also own and control. Whoever owns and controls the Internet will ruthlessly rule the Earth. Only the Chinese can prevent it. ---- Reg. ====================================== "Paul Burridge" wrote - Absolutely right, Reg. Even good old fission if necessary. Yeah, it's dirty but so what? Outer space has a limitless capacity for our radioactive garbage. Instead of encasing it in concrete and burying it, we should be just firing away in rockets. Way to go! |
Sooner or later the World MUST concentrate on atomic energy. The sensible French already have 90% of their energy requirements provided by atomic power stations. The remainder by hydro-electric and tidal power. The Japanese, having no natural biological energy resources, are also quietly well on their way. Iranians, oil producers themselves, are busy building there own atomic power stations in anticipation of a World oil shortage, but their efforts are sabotaged by multi-national legal and political warfare about who gets the development, investment and construction contracts. What about renewable sources providing all of it, and sensibly conserving energy with energy efficient appliances, homes, transport etc so that less of it is required in the first place? Nuclear fission of current fuels (Uranium) is in any case only a postponement of the problem since eventually Uranium supplies will be burnt up just the same as fossil fuels. The real costs of the nuclear alternatives have never been properly considered, since nuclear programs have always been subsidised by governments interested in the defence (or offence) applications of the technology and byproducts. Once the full lifecycle cost of the power stations is taken into account they become rather uneconomic in comparison to other forms of energy such as renewable sources. The latter would have become much much cheaper long ago had they received the same degree of subsidised research and development as nuclear. When the World is mainly on atomic energy, electronic circuit designers can feel free to enjoy themselves and exercise their unrestrained imaginations. At the moment my imagination concentrates itself on the unimaginably tiny and simple frequency counter with tiny current consumption. Forget nuclear, this thing could even run off solar power recharged batteries ;-) So please, indulge my fancy for an even lower current frequency counter containing just 2 IC's,, and tell me if there's a way! 73 Hans G0UPL http://www.HansSummers.com |
"Reg Edwards" wrote in message ... The problems of how to get rid of relatively minute quantities of mildly radioactive waste materials have been exaggerated by the oil conglomerates and the other multi-national companies in the control of world governments. They do it for obvious reasons via the international media which they also own and control. Whoever owns and controls the Internet will ruthlessly rule the Earth. Only the Chinese can prevent it. To get rid of even a relatively minute quantity of radioactive material into space requires the expenditure of rather huge amounts of fuels. Fossil fuels that is. Ooops |
Hans Summers wrote:
Hello I have built 2 very simple 2-chip frequency counters with 8 LED binary readout see http://www.hanssummers.com/radio/sfreq/index.htm . My Mk2 counter is extremely small (just 25 x 16 x 16mm) and consumes a low current of 5mA max. The question relates to the 4.096MHz oscillator which uses the internal oscillator of the 74HC4060. Of the 5mA current consumption, 1.2mA is used by the LED's when max 7 are on at any one time. About 0.8mA by the diode-resistor gate logic, transistor switch, 74HC4040 and the voltage regulator. Fully 3mA is wasted on the 74HC4060 crystal oscillator + divider. It seems wrong to spend 60% of your current consumption on an oscillator, compared to less than 25% on the LED's. In the pursuit of excellence in this design, I would like to cut the current consumption of the oscillator section. Does anyone know of a better arrangement that will cut current consumption? Increasing the series resistor wasn't the solution. I put a 100K variable in here in place of the original 2K2. Initially as the resistor was increased the current consumption fell, but at higher resistances the current consumption increased quite dramatically. The optimum was at close to 4K7. 73 Hans G0UPL http://www.HansSummers.com Here's a suggestion. I've never tried this, so YMMV. You're using a circuit that looks like: |\ ___ .---| O-----|___|--. | |/ R1 | | | | ___ | o------|___|--------o | R2 | | _ | | | | | o-------|| ||-------o | |_| | | 4.096MHz | --- C2 --- C1 --- --- | | | | === === GND GND created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de Yes? And you've maximized R2 and dinked with the value of R1, and the best you can get is R1 = 4.7kOhm? Probably what is happening is that you're fighting two contradictory effects in the circuit: Effect one is that the inverter wants to have a low-impedance output, so a low value of R1 will pull a lot of current from the inverter output. Effect two is that a CMOS inverter is designed assuming that it will be turned on hard; if it isn't then the complementary pair of FETs just conduct current from the VSS rail to VDD. I think that when you adjust R1 higher you're loading the output less, but you're also supplying less voltage to the input. Your 4.7kOhm value saves you output current, but drops the input voltage enough so that you start seeing more input current. Why don't you try playing with your feedback a little bit? I'm assuming that you have C1 = C2. If you decrease C2 while increasing C1 so that the series combination of C2 and C1 stays the same the voltage at the inverter input should be stepped up. Depending on about a gazillion factors this may reduce your current consumption. I would try the circuit below: |\ ___ .---| O-----|___|--. | |/ R1 | | | | ___ | o------|___|--------o | R2 | | _ | | | | | o-------|| ||-------o | |_| | | 4.096MHz | --- C2 --- C1 --- --- | | o--------o Vtest | | === --- C3 GND --- | | === GND created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de Make sure R2 is as large as you can get away with and make C3 about ten times bigger than the crystal's load capacitance, and leave C2 at about the crystal's load capacitance. Now measure the voltage at Vtest (please have an O-Scope!). Because you know C2 and C3 you can calculate the voltage at the inverter input and keep it to 5Vp-p as you play with C1 and R1. Now play with C1 and R1 and see if you can (a) reduce power even more, (b) keep a good strong signal at the inverter input and (c) keep your desired frequency stability. Increasing C1 should give you more voltage at C2, increasing R1 should give you less. There should be a point where you get good performance at less current than you're getting now. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
Tim Wescott wrote:
Hans Summers wrote: Hello I have built 2 very simple 2-chip frequency counters with 8 LED binary readout see http://www.hanssummers.com/radio/sfreq/index.htm . My Mk2 counter is extremely small (just 25 x 16 x 16mm) and consumes a low current of 5mA max. The question relates to the 4.096MHz oscillator which uses the internal oscillator of the 74HC4060. Of the 5mA current consumption, 1.2mA is used by the LED's when max 7 are on at any one time. About 0.8mA by the diode-resistor gate logic, transistor switch, 74HC4040 and the voltage regulator. Fully 3mA is wasted on the 74HC4060 crystal oscillator + divider. It seems wrong to spend 60% of your current consumption on an oscillator, compared to less than 25% on the LED's. In the pursuit of excellence in this design, I would like to cut the current consumption of the oscillator section. Does anyone know of a better arrangement that will cut current consumption? Increasing the series resistor wasn't the solution. I put a 100K variable in here in place of the original 2K2. Initially as the resistor was increased the current consumption fell, but at higher resistances the current consumption increased quite dramatically. The optimum was at close to 4K7. 73 Hans G0UPL http://www.HansSummers.com Here's a suggestion. I've never tried this, so YMMV. You're using a circuit that looks like: |\ ___ .---| O-----|___|--. | |/ R1 | | | | ___ | o------|___|--------o | R2 | | _ | | | | | o-------|| ||-------o | |_| | | 4.096MHz | --- C2 --- C1 --- --- | | | | === === GND GND created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de Yes? And you've maximized R2 and dinked with the value of R1, and the best you can get is R1 = 4.7kOhm? Probably what is happening is that you're fighting two contradictory effects in the circuit: Effect one is that the inverter wants to have a low-impedance output, so a low value of R1 will pull a lot of current from the inverter output. Effect two is that a CMOS inverter is designed assuming that it will be turned on hard; if it isn't then the complementary pair of FETs just conduct current from the VSS rail to VDD. I think that when you adjust R1 higher you're loading the output less, but you're also supplying less voltage to the input. Your 4.7kOhm value saves you output current, but drops the input voltage enough so that you start seeing more input current. Why don't you try playing with your feedback a little bit? I'm assuming that you have C1 = C2. If you decrease C2 while increasing C1 so that the series combination of C2 and C1 stays the same the voltage at the inverter input should be stepped up. Depending on about a gazillion factors this may reduce your current consumption. I would try the circuit below: |\ ___ .---| O-----|___|--. | |/ R1 | | | | ___ | o------|___|--------o | R2 | | _ | | | | | o-------|| ||-------o | |_| | | 4.096MHz | --- C2 --- C1 --- --- | | o--------o Vtest | | === --- C3 GND --- | | === GND created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de Make sure R2 is as large as you can get away with and make C3 about ten times bigger than the crystal's load capacitance, and leave C2 at about the crystal's load capacitance. Now measure the voltage at Vtest (please have an O-Scope!). Because you know C2 and C3 you can calculate the voltage at the inverter input and keep it to 5Vp-p as you play with C1 and R1. Now play with C1 and R1 and see if you can (a) reduce power even more, (b) keep a good strong signal at the inverter input and (c) keep your desired frequency stability. Increasing C1 should give you more voltage at C2, increasing R1 should give you less. There should be a point where you get good performance at less current than you're getting now. I just tried this with a 74HC04 (no HC4040s, no UHC04s more's the pity). Best current draw was 1.6mA at 4MHz was with 4.7kOhm and C1 = C2 = 47pF. Then I stuck in a 455kHz ceramic resonator that I have lying around and Bammo -- 750uA. So maybe adjusting the frequency lower would be a good thing? Digi-Key has 32kHz watch crystals. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
On Mon, 21 Jun 2004 16:31:08 +0000 (UTC), "Reg Edwards"
wrote: The problems of how to get rid of relatively minute quantities of mildly radioactive waste materials have been exaggerated by the oil conglomerates and the other multi-national companies in the control of world governments. They do it for obvious reasons via the international media which they also own and control. Whoever owns and controls the Internet will ruthlessly rule the Earth. Only the Chinese can prevent it. God help us if the Chinese take over in 20 years' time. But I was serious, Reg. There's nothing wrong with good ol' fashioned fission. Just blast the leftover crap into space and have done with it. It's lousy with radioactive debris anyway and the sun can swallow everything we throw at it. -- "What is now proved was once only imagin'd." - William Blake, 1793. |
Hans Summers wrote:
Hello I have built 2 very simple 2-chip frequency counters with 8 LED binary readout see http://www.hanssummers.com/radio/sfreq/index.htm . My Mk2 counter is extremely small (just 25 x 16 x 16mm) and consumes a low current of 5mA max. The question relates to the 4.096MHz oscillator which uses the internal oscillator of the 74HC4060. Of the 5mA current consumption, 1.2mA is used by the LED's when max 7 are on at any one time. About 0.8mA by the diode-resistor gate logic, transistor switch, 74HC4040 and the voltage regulator. Fully 3mA is wasted on the 74HC4060 crystal oscillator + divider. It seems wrong to spend 60% of your current consumption on an oscillator, compared to less than 25% on the LED's. In the pursuit of excellence in this design, I would like to cut the current consumption of the oscillator section. Does anyone know of a better arrangement that will cut current consumption? Increasing the series resistor wasn't the solution. I put a 100K variable in here in place of the original 2K2. Initially as the resistor was increased the current consumption fell, but at higher resistances the current consumption increased quite dramatically. The optimum was at close to 4K7. 73 Hans G0UPL http://www.HansSummers.com A 4060, using National's recommended circuit (from an '80 databook) and a 32768Hz watch crystal, pulls 32 microamp -- and like I said before, Digi-Key has 32000Hz crystals in stock, so there's your 1kHz reference. Now if someone would explain why I bothered to prototype this... -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
On Mon, 21 Jun 2004 23:13:36 +0100, Paul Burridge
wrote: God help us if the Chinese take over in 20 years' time. But I was serious, Reg. There's nothing wrong with good ol' fashioned fission. Just blast the leftover crap into space and have done with it. It's lousy with radioactive debris anyway and the sun can swallow everything we throw at it. There are only two small problems with this approach, since first you have to reach the 11.2 km/s escape velocity to escape the earth. The Saturn V moon rocket was capable of delivering about 40 tons to escape velocity. With this velocity, you just end up in an orbit similar to the Earth's orbit. In fact the Apollo 10 (or 12) third stage went into solar orbit, but a year or two ago, it was captured by the Moon and Earth and now it orbits the Earth for a year or two, before escaping back into the solar orbit. With some bad luck, this stage might have hit the Earth and imagine that it had contained 40 tons of highly radioactive waste, which would spread into the atmosphere... Thus, in order to avoid the risk of collisions with the earth in the future, an additional rocket burn is required in the solar orbit to prevent the orbit from intersecting with the orbit of the Earth. Thus reducing the available payload. If you want to drop something into the sun, you first must kill nearly all of the 30 km/s orbital motion of the Earth. This would require a huge amount of fuel and practically nothing would end up into the Sun. It is in fact much easier to escape the solar system, since only about 43 km/s is required or 13 km/s in addition to the Earth's orbital velocity. With Saturn V, maybe 500 kg would reach the solar escape velocity directly. Using Jupiter as a slingshot (as with Pioneer 11&12 and Voyager 1&2) maybe a few tons could reach the solar escape velocity. Unfortunately Saturn V does not exist any more and the Shuttle and the Proton are toys compared to Saturn V. Any launch failure would also be quite nasty with a lot of nuclear waste on board. Paul OH3LWR |
On Tue, 22 Jun 2004 10:19:41 +0300, Paul Keinanen
wrote: If you want to drop something into the sun, you first must kill nearly all of the 30 km/s orbital motion of the Earth. This would require a huge amount of fuel and practically nothing would end up into the Sun. Okay, well what about dumping it on the moon? Let's face it: there's not a lot of other suitable uses for this redundant body - other than providing tidal flows on Earth, of course. I guess you'd get some complaints from these idiots who've 'bought plots of land' on the moon, but they're never going to get to build on it in their lifetimes so WGAS? -- "What is now proved was once only imagin'd." - William Blake, 1793. |
"Tim Wescott" wrote in message ... Hans Summers wrote: A 4060, using National's recommended circuit (from an '80 databook) and a 32768Hz watch crystal, pulls 32 microamp -- and like I said before, Digi-Key has 32000Hz crystals in stock, so there's your 1kHz reference. Many thanks Tim. I didn't realise 32KHz crystals were available. The usual 32768 wouldn't give the right timing but 32KHz is perfect. You actually prototyped this and measured the current? Did this use an old 4060 or a 74HC4060? What's the difference betweem families in terms of current consumption? Also, how do these families compare to things like 74AC, 74ACT, 74HCT? I know the T means TTL-compatible levels rather than the old CMOS family compatible levels, but is the current consumption different too? What exact circuit is in your '80 databook? I just had a look at various datasheets from different manufacturers, and all seem to have the same configuration. The national datasheet for the 4060 shows values of 15M and 330K for the resistors to suit a watch crystal http://cache.national.com/ds/CD/CD4020BC.pdf . I also found this 74HC4060 datasheet for the ON Semiconductor version. It includes an interesting treatment of the calculation of the resistor values, see http://www.farnell.com/datasheets/42247.pdf . Loads of questions I know. But this is fantastic as it will enable me to reduce the current consumption of the thing to under 1.5mA. I hope I'm right in thinking that by replacing the LED switching transistor with a FET, I'll also save some current consumption because of eliminating the base-emitter current, but I'm not a FET expert. Another nice thing is the 32KHz crystals are physically tiny: 6mm long and 2mm diameter. This means if I use SMD IC's I can make a next generation counter a fraction the size of the current one which is already miniature. One problem remains, which is getting hold of a 32KHz crystal. I have never bought anything from Digikey. The part I need is XC972-ND and is priced (UK pounds) £0.47. However I notice that there is a £10 handling fee and £12 shipping! The total order cost would be £22.47, for one simple crystal. That's about US $41! Therefore does anyone in rec.radio.amateur.homebrew reside in the US, order frequently or in the near future from Digikey, and wouldn't mind adding one of those to their order and popping it in an envelope to me - I'll pay all costs of course as long as you don't charge me £10 handling ;-) 73 Hans G0UPL http://www.HansSummers.com |
Hans Summers wrote:
"Tim Wescott" wrote in message ... Hans Summers wrote: A 4060, using National's recommended circuit (from an '80 databook) and a 32768Hz watch crystal, pulls 32 microamp -- and like I said before, Digi-Key has 32000Hz crystals in stock, so there's your 1kHz reference. Many thanks Tim. I didn't realise 32KHz crystals were available. The usual 32768 wouldn't give the right timing but 32KHz is perfect. You actually prototyped this and measured the current? Did this use an old 4060 or a 74HC4060? What's the difference betweem families in terms of current consumption? Also, how do these families compare to things like 74AC, 74ACT, 74HCT? I know the T means TTL-compatible levels rather than the old CMOS family compatible levels, but is the current consumption different too? Normally I resist the urge to prototype things, but yesterday was slow and I could do this whole thing on a proto-board. I used a 4060, not a 74xCxxxx device. I have no idea how it'd play out on a xx4060, but with a 74HC04 and the watch crystal I was seeing 1.6mA, and with the 4060 I was seeing 32uA. This is an unfair test, because you're supposed to use the 74HCU04 for oscillators; I have no idea how much this affected things. I _did_ notice with the 74HC04 that running it at about 3V brought the current down to the 30-50uA region, however. What exact circuit is in your '80 databook? I just had a look at various datasheets from different manufacturers, and all seem to have the same configuration. The national datasheet for the 4060 shows values of 15M and 330K for the resistors to suit a watch crystal http://cache.national.com/ds/CD/CD4020BC.pdf . I also found this 74HC4060 datasheet for the ON Semiconductor version. It includes an interesting treatment of the calculation of the resistor values, see http://www.farnell.com/datasheets/42247.pdf . Your National datasheet matches the one in my databook. Loads of questions I know. But this is fantastic as it will enable me to reduce the current consumption of the thing to under 1.5mA. I hope I'm right in thinking that by replacing the LED switching transistor with a FET, I'll also save some current consumption because of eliminating the base-emitter current, but I'm not a FET expert. It should save a bit, but with a good junction transistor you should only have to apply about 2-5% of the collector current to the base to get saturation. If you're using one of the old standbys you should look at newer transistors -- Zetex is good for this. Another nice thing is the 32KHz crystals are physically tiny: 6mm long and 2mm diameter. This means if I use SMD IC's I can make a next generation counter a fraction the size of the current one which is already miniature. One problem remains, which is getting hold of a 32KHz crystal. I have never bought anything from Digikey. The part I need is XC972-ND and is priced (UK pounds) £0.47. However I notice that there is a £10 handling fee and £12 shipping! The total order cost would be £22.47, for one simple crystal. That's about US $41! Therefore does anyone in rec.radio.amateur.homebrew reside in the US, order frequently or in the near future from Digikey, and wouldn't mind adding one of those to their order and popping it in an envelope to me - I'll pay all costs of course as long as you don't charge me £10 handling ;-) The handling fee ($20 in the US) is only applied for small orders, so you can either get $1.00 worth of stuff for $21, or you can get $21 worth of stuff for $21 -- this still doesn't save you the shipping charges, though. 73 Hans G0UPL http://www.HansSummers.com -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
If this Mouser part will work, you won't have to deal with a minimum order.
http://www.mouser.com/index.cfm?hand..._pcodeid=69500 In case the link doesn't work, it's Mouser Part #: 695-CFV206-32K . 32 kHz, 12.5 pF. 73, "PM" |
Another nice thing is the 32KHz crystals are physically tiny: 6mm long and
2mm diameter. This means if I use SMD IC's I can make a next generation counter a fraction the size of the current one which is already miniature. One problem remains, which is getting hold of a 32KHz crystal. I have never bought anything from Digikey. The part I need is XC972-ND and is priced (UK pounds) £0.47. However I notice that there is a £10 handling fee and £12 shipping! The total order cost would be £22.47, for one simple crystal. That's about US $41! Therefore does anyone in rec.radio.amateur.homebrew reside in the US, order frequently or in the near future from Digikey, and wouldn't mind adding one of those to their order and popping it in an envelope to me - I'll pay all costs of course as long as you don't charge me £10 handling ;-) ======== Hans , May I suggest you check supply of above with Mode Components -Birmingham, small company (no VAT) www.modecomponents.co.uk Frank GM0CSZ / KN6WH |
On Tue, 22 Jun 2004 10:31:00 +0100 "Hans Summers"
wrote: One problem remains, which is getting hold of a 32KHz crystal. I have never bought anything from Digikey. The part I need is XC972-ND and is priced (UK pounds) £0.47. However I notice that there is a £10 handling fee and £12 shipping! The total order cost would be £22.47, for one simple crystal. That's about US $41! Therefore does anyone in rec.radio.amateur.homebrew reside in the US, order frequently or in the near future from Digikey, and wouldn't mind adding one of those to their order and popping it in an envelope to me - I'll pay all costs of course as long as you don't charge me £10 handling ;-) Over here you can sometimes buy those little stick-on digital clocks, made for sticking to your bathroom mirror. They cost about $3 and include a crystal, a display, and a battery, plus all the circuitry to make them work together. I think their exact frequency is 32,768 (= 2**15) Hz, so that dividing by 2, 15 times will count seconds. If this will work for you then buying one of them might be a very cost effective way to pick one up easily. If you can't find one there, I think I have one which I salvaged out of a dead watch. - ----------------------------------------------- Jim Adney Madison, WI 53711 USA ----------------------------------------------- |
Many thanks Tim. I didn't realise 32KHz crystals were available. The usual 32768 wouldn't give the right timing but 32KHz is perfect. You actually prototyped this and measured the current? Did this use an old 4060 or a 74HC4060? What's the difference betweem families in terms of current consumption? Also, how do these families compare to things like 74AC, 74ACT, 74HCT? I know the T means TTL-compatible levels rather than the old CMOS family compatible levels, but is the current consumption different too? Normally I resist the urge to prototype things, but yesterday was slow and I could do this whole thing on a proto-board. I used a 4060, not a 74xCxxxx device. I have no idea how it'd play out on a xx4060, but with a 74HC04 and the watch crystal I was seeing 1.6mA, and with the 4060 I was seeing 32uA. This is an unfair test, because you're supposed to use the 74HCU04 for oscillators; I have no idea how much this affected things. I _did_ notice with the 74HC04 that running it at about 3V brought the current down to the 30-50uA region, however. Ok thanks Tim, 32uA is great. I will stay with a 4060, I don't want to add an extra IC just for the oscillator (e.g. 74HCU04). Loads of questions I know. But this is fantastic as it will enable me to reduce the current consumption of the thing to under 1.5mA. I hope I'm right in thinking that by replacing the LED switching transistor with a FET, I'll also save some current consumption because of eliminating the base-emitter current, but I'm not a FET expert. It should save a bit, but with a good junction transistor you should only have to apply about 2-5% of the collector current to the base to get saturation. If you're using one of the old standbys you should look at newer transistors -- Zetex is good for this. I was using a BC547. I'll look into a better alternative. Thanks again 73 Hans G0UPL http://www.HansSummers.com |
"Paul_Morphy" wrote in message ... If this Mouser part will work, you won't have to deal with a minimum order. http://www.mouser.com/index.cfm?hand..._pcodeid=69500 In case the link doesn't work, it's Mouser Part #: 695-CFV206-32K . 32 kHz, 12.5 pF. Thanks Paul, I'm looking into this and a couple other alternatives. 73 Hans G0UPL http://www.HansSummers.com |
======== Hans , May I suggest you check supply of above with Mode Components -Birmingham, small company (no VAT) www.modecomponents.co.uk I checked Frank, they don't sell 32KHz. Only 32.768, and I have loads of those falling out of my junk box already! 73 Hans G0UPL http://www.HansSummers.com |
I think their exact frequency is 32,768 (= 2**15) Hz, so that dividing by 2, 15 times will count seconds. If this will work for you then buying one of them might be a very cost effective way to pick one up easily. If you can't find one there, I think I have one which I salvaged out of a dead watch. Thanks for the offer Jim, I have quite a few of those crystals already, but they aren't suitable for this application which requires 32KHz not 32.768. 73 Hans G0UPL http://www.HansSummers.com |
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