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Vibration monitor schematics posted
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I put schematics for both the remote sensor and base unit into the
Piezo Film directory. I'll start breadboarding this stuff this weekend (I work saturdays). No doubt I have errors in the schematics which I'll stumble across as I build the circuit. If anyone spots something wrong with the concepts - feel free to be brutally critical 8) |
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Stefan Trethan
You could of course add the 2,5V already with the first opamp, saving the second opamp...
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I don't think that adjusting this zenter value is strictly necessary (if you want no pot in the sensor box which i expect), it could be zeroed by the atmega software i expect. but the opamp will not cost much so... ST On Sat, 03 Apr 2004 16:05:14 -0000, ghidera2000 <ghidera2000@...> wrote:
I put schematics for both the remote sensor and base unit into the |
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--- In Electronics_101@..., Stefan Trethan
<stefan_trethan@g...> wrote: You could of course add the 2,5V already with the first opamp,saving the second opamp...necessary (if you want no potTrue, software zero would be easy to handle. How would I add the offset with only one op-amp stage free? I have no idea how to configure the other half of the sensor amp to provide the 1.25V offset. Actually... I have to go back and look at my 4-20ma stuff in the files section. I think the first stage op-amp did something similar. I almost had a brain hemmorage getting to understand how it works when I did that circuit. It was only extreme patience on the part of people like Mariss and Tracy Allen (stamp group) that I finally "got it". Oh well, time for work 8( |
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Stefan Trethan
simply look at basic opamp circuits, especially inverting and noninverting summing amps
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and diff. amps. you will figure it out.. ST On Sat, 03 Apr 2004 18:10:38 -0000, ghidera2000 <ghidera2000@...> wrote:
--- In Electronics_101@..., Stefan Trethan |
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Scott Thompson
¿ªÔÆÌåÓýJust got a chance to browse the schematic.
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Looks pretty comprehensive and will require further study, but your input power connector is wired so that it shorts out the battery.
?
Thanks for sharing,
Scotty
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--- In Electronics_101@..., "Scott Thompson"
<electronguy@e...> wrote: Just got a chance to browse the schematic.your input power connector is wired so that it shorts out the battery. Doh! I put the battery+ to ground instead of the supply... Good spotting ;) I've actually done a lot of thinking about this circuit and I've come to the conclusion that I have no idea how to effectively catch the average peak vibration and non-average peak spikes. I was thinking of putting a precision rectifier in the sensor box, adding gain in the monitor box then splitting the signal into two. Once would go straight to the ADC for measuring the highest spikes while the other would go to a capacitor for electrical averaging of the peaks. That way I can do the fast sampling for spikes without the overhead of peak value discovery and averaging (20 samples per wave thing) and just a single sample to find the average peak. Sounds good in theory out now I have to figure out how to do it 8). Probably use an OPA2340 to split the (rectified) signal into two and add gain, then experiment from there. Oh and, I did some experimenting with PWM signals through a long cable. Without a resistor added, the signal was distorted. I added a 1K resistor and the signal came out a lot cleaner. Think I'm getting a grasp of this cable capacitance problem. Its not so much added noise from the enviroment as it is the cable capacitance distorting the signal thats already there. Square waves turn into rounded corner waves and the amplitude bounces around. Less current means less capacitance effect, cleaner signal. |
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Scott Thompson
¿ªÔÆÌåÓý>I've actually done a lot of thinking about this circuit and I've
>come to the conclusion that I have no idea how to effectively catch >the average peak vibration and non-average peak spikes. ?
A Fluke 199 ScopeMeter in TrendPlot mode or a Fluke 189 Multimeter
with FlukeView Forms software could capture those +/- 70V spikes.
The 189 gives you the max/min/avg for all readings it logs.
>I was thinking of putting a precision rectifier in the sensor box, >adding gain in the monitor box then splitting the signal into two. >Once would go straight to the ADC for measuring the highest spikes >while the other would go to a capacitor for electrical averaging of >the peaks. That way I can do the fast sampling for spikes without >the overhead of peak value discovery and averaging (20 samples per >wave thing) and just a single sample to find the average peak. This sounds very reasonable to me.? My color organ was built on a
precision rectifier followed by six RC integrators.? These were fed
into a quad comparator.? Let me know if you need schematics for a
precision rectifier.
?
>Probably use an OPA2340 to split the (rectified) signal into two and
>add gain, then experiment from there. Yes, I was just going to suggest a buffer before the averaging circuit.
>Oh and, I did some experimenting with PWM signals through a long >cable. Without a resistor added, the signal was distorted. I added a >1K resistor and the signal came out a lot cleaner. Think I'm getting >a grasp of this cable capacitance problem. Its not so much added >noise from the enviroment as it is the cable capacitance distorting >the signal thats already there. Square waves turn into rounded >corner waves and the amplitude bounces around. Less current means >less capacitance effect, cleaner signal. ?
The resistor and the capacitance of the cable will form a low-pass filter.
This one's got me perplexed because your S/N ratio will be less.? Not sure
what you mean by amplitude bouncing around.? I would suspect that your
driver circuit is not capable of driving highly capacative loads.? It may
not be putting out enough current or has a lot of ringing, etc.? Place
a 50 ohm resistor between the output of the driver in the feedback loop and
see if it drives the capacitance with more stability.
This is interesting to me, so please keep me informed. ?
Good luck,
Scotty |
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