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maestrodamuz
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Posts posted by maestrodamuz
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This is about the power source using the 1K resistors, I used the LM 317T for positive voltage because I found out the 7805 refused to work with the 7905, this I have tested over and over again beforew comin to that conclusion. A positive voltage enters the 317T and is varied until +5V is at its output.
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Having gone through the circuits, datasheets, replacement guides (ECG master replacement guide from Philips) and after the alarm about the inconsistencies I came out with these corrections and I believe they are correct as far as am concerned. Also I have included a modified circuit diagram for the DVM which can measure both ac and dc voltages. The maximum ac voltage that can be measured depends on the type of rectifier used; I recommend an IC rectifier which has a peak reverse voltage of 1000V and maximum forward current greater than 3A.So as not blow up the rectifier leave a safe limit of about 100V i.e for a rectifier of PRV of 1000 V don
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I have done serious work on the volt meter, I have really had problems getting a -5v supply out of a 9v battery. I tried using the replacement for the cd4009 as indicated in the data sheet from intersil, cd 4049 all to no avail. I actually wanetd to run the unit from a 9v battery for portability sake, now i have had to revert to the good old transformer and using an LM 317T and LM 7905 in conjuction wit 2 polar capacitors of differnt capacitances I have been able to get the 2 voltages (-5v and +5v) now my problem is calibration, am using a 1k instead of a 1.2k to get the 0-2000v scale,(That is the only scale am using) I shall find out 2 nite if it will work. :'(
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I have checked out those inconsistensies and I have prepared the corrections, you guys will get them soon.
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You guys are leaving those of us in Africa out of this fun.
Led display Digital Voltmeter question
in Projects Q/A
Posted
I have done enuff research to confirm that it works the way it is in the schematic. I have carried it out and the DVM worked to an accuracy of 98%. Don't worry it will work. ;)