OK, 1v between 35 and 36 is good, but what does "it was extreamly high" mean?I did measure for 1v at 35 and 36 under the original build
(100K), but it was extremely high which is why I first attacked the
input portion.
Do you mean that you have removed the 10k resisitor which was connected between pins 30 and 31, and, the 1M resistor between the +ve input and pin 31 is now a 470k ??The 100K (for 20v range as link suggested) is now a 470K
(circuit indicates it as 1M). The nearby R-C is totally altered (the
10K is eliminated, I believe because I saw another circuit that did
not even have an R across the input, and the 10n is a 27n,
because that's also how that circuit had the sample input wired).
but what does "it was extreamly high" mean?
Do you mean that the displayed voltage was high?
Do you mean that you have removed the 10k resisitor which was connected between pins 30 and 31, and, the 1M resistor between the +ve input and pin 31 is now a 470k ??
If so, this could be the root of your problem.
I'm sorry about the confusion on pin 1 of the 7660. As I mentioned, my connecting it to 5V probably didn't change much. I used the Maxim MAX1044 which I thought had the exact same features as the 7660 but looking at the maxim datasheet again I see that the maxim chip has the "BOOST" feature and the normal 7660 does not. All it does is increase the clock speed and "enhance" the output.Where did you conjure "boosting" the CONVERTER's ouput?
Sorry, I'm a little unclear on which link you're referring to. I posted two links. The schematic from electronics-diy and the schematic from electronics lab. The electronics diy website is the one I pointed out the flaw in and I simply referenced the electronics lab website because I followed their instructions on setting up the divider at the voltmeter input.Your link is actually the circuit I posted above that didn't
list the parts values...
Your link does not specify grounding of 30/32/35,
but what you wrote makes it sound like you did ground them.
In short, yes. There is some error on the low end but insignificant in my opinion. It is nothing like the error I was experiencing before. I'm sure I could have gotten it even more accurate if I had trimpots to set the VRef and to set the divider.Lastly, before I try your suggestions, is the meter accurate
throughout the entire range of your variable supply ??
I have no idea why the connections between 32/30 and 30/GND are dotted but I indeed connected them.
I think I've demonstrated pretty well that it doesn't matter what values of resistors and pots you use in conjunction with 35 and 36 (to set VRef) as long as they enable you to get the reading into range and calibrate it.
The capacitor C2 which is connected between pins 33 and 34 of the IC has been selected to compensate for the error caused by the internal reference voltage and also keeps the display steady.
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