Recent content by rq3

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    Code structure - loop or goto

    Many thanks, Alan! You are a gentleman and a scholar.
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    Code structure - loop or goto

    Is there any particular benefit in terms of code size or execution speed between: Main: Do Stuff goto main and Main: do Do Stuff loop Just curious. I know goto's are anathema to some.
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    Constraints of Picaxe ICSP Programming?

    I went through this exercise a number of years ago. The 10k/22k input circuit was based upon the original RS-232 spec of +/-25 volts and the capabilities of the Microchip silicon (in particular the input protection diodes) at the time. The current Picaxe inputs are all CMOS with a very high...
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    power supply with large capacitance between regulator and 14M2

    Most linear regulator manufacturers strongly suggest a reverse diode across the regulator I/O if an output capacitor larger than 10-20 uF (regulator dependent) is used. The reason is that, should you short the regulator input, the large cap will discharge back through the regulator, and destroy...
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    More ADC questions and output questions

    Alan, I didn't state that well. The conversion is still 10 bits. Each bit holds 1 millivolt of resolution (1024 counts with a 1.024 volt reference). But the output is in two bytes. The lower byte, of two bits, holds the potentially worthless first two counts. The upper 8 bit byte holds the...
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    More ADC questions and output questions

    Well, a definitive answer that actually makes sense. Various Microchip products have different minimum ADC reference voltages because: 1) The FET switches that shunt the input signal to the sample and hold capacitor need a minimum internal supply to turn on fully. If they don't, then the...
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    More ADC questions and output questions

    The saga continues. The latest response from Microchip (which makes no sense to me), and my response to their response: Hi Ripley, We have heard from our internal team. The reason for this is a hardware limitation in the ADC internal circuitry. Those circuits are essentially biased by the ADC...
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    More ADC questions and output questions

    So after I got my circuit working to much more than my satisfaction, I did indeed open a ticket with Microchip (thanks for the kick, Goeytex; the last interaction I had with Microchip went no-where) several weeks ago. The initial response from them was to quote the datasheet, basically saying...
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    error with 50 Hz as a clock time base

    My first thought is that the poor op-amp is being driven into wicked saturation with an 8vac input while it is running on a 5vdc supply. It's a very old device, and may not have the latch-up protection that newer op-amps have. I think what you really want is a comparator with reasonable input...
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    Servo Control

    The "high end" download circuit in the Picaxe manuals includes a 180 ohm resistor on the SEROUT pin for the same reason. Most Picaxe pins are datasheet limited to about 25 mA, and that resistor keeps the pin intrinsic diodes from exceeding their ratings (which is larger than 25 mA). For the...
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    FVR 1.024 positive reference question

    I very recently went through this exercise, and as others have pointed out it is possible to use the 1.024 volt reference with no apparent problems. I never did get to the point of opening a ticket with Microchip to ask WHY they say not to use the 1.024 volt reference, especially since all of...
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    Fastest possible ADC response?

    @julianE, I used J-B Weld, which is a steel loaded epoxy with a very high temperature rating. It's common in the U.S., but for this application I think any decent epoxy would be fine.
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    Fastest possible ADC response?

    Well, that was interesting. Attached are photos of the resulting piezo sensor, which is almost immune to stepper motor movement and acoustic noise, but VERY sensitive to quick taps. The steel ball glued to the piezo is crucial and I have the entire sensor screwed to the interior of the...
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    Piezo Sensors

    premelec, that's fascinating. I know just about every modern car engine has a knock sensor based on a mass loaded piezo (which is where I got the idea). I'm just surprised that the 3D printer community hasn't stumbled across this in the past 10 years or so. It makes an astonishing difference in...
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    Piezo Sensors

    I've borrowed some technology from the auto industry, which uses piezoelectric sensors to determine if an engine is "knocking", or "pinging", so as to adjust the ignition timing to avoid this potentially damaging condition. My application was to use a common piezo disc to detect the contact of...
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