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    Led display Digital Voltmeter question

    I fixed it using this datasheet : http://www.datasheetcatalog.org/datasheet/TelComSemiconductor/mXrtrqt.pdf I used the top right schematic on page 19. The only thing i added was a trimmer over pin 30 and 31 so i could finetune the voltmeter. Now it works perfectly, it's on par with my DMM. I'll...
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    Led display Digital Voltmeter question

    I noticed that too, but on this site they say you can adjust the scale with a resistor between pin 30 and 31. That's why i used a 12k resistor for 0-200V. edit: so i took out the fixed resistor between pin 30 and 31 and switched it with a trimmer. Turns out it needed to be 31,5k. Strange but i...
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    Led display Digital Voltmeter question

    Did some new tests. I replaced the 12k resistor between pin 30 and 31 with a 10k resistor. Now i get weird results. So i leave the measuring points unconnected (floating). With the 12k resistor i had 00.0V but with the 10k resistor it rises to 38.xV. Then i measure the 1,58V battery and it...
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    Led display Digital Voltmeter question

    I'm going to put in the 1k trimmer this evening (if i have one). that is the only thing that still differs from the datasheet. This is how i use the voltmeter : In my 30V dc power supply i have a circuit with a 5V voltage regulator that is connected to a transformer. That transformer is...
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    Led display Digital Voltmeter question

    Yes i did. I'm going to look at the datasheet, see if i'm missing something, and also try out the 100k oscillator resistor. edit: 100k resistor didn't change anything. edit2 : The icl7660 ic is working normal. I did some new measurements : Battery is 1,58V, icl7660 shows 0,6V. It's a ratio of...
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    Led display Digital Voltmeter question

    I took out the damaged icl7107 and replaced it but for some reason everything i measure is more or less half of the actual value. My battery is 1,3V and my meter shows 0,6V. When i couple two battery's it shows 1,2V. So it's measuring now, but it measures half of the actual value. Playing with...
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    Led display Digital Voltmeter question

    Hello everyone, i've got a problem with my voltmeter. I just finished it and it shows 18.4V when i don't measure anything. It shows 1xxx when i measure a 1,5V battery and when i switch the wires it shows -1xxx. So it looks like it can detect when you switch + and -. When i hold the measuring...
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    Led display Digital Voltmeter question

    No, i think that is correct. I'm going to buy an ICL7660 ic soon and test it out. I've been searching on the internet and it turns out that the ICL7107 does need a negative supply.
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    0-30 Vdc Stabilized Power Supply

    I posted my pcb a few threads back, these are the pictures of the case i promised. The front, one digital voltmeter broke because i didn't have a galvanic isolated supply for it. I'm building my own now, pictures of it are below. There are 2 leds, one for the current limitter and one wich glows...
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    Led display Digital Voltmeter question

    I'm building this digital voltmeter with an ICL7107. http://electronics-diy.com/ICL7107_volt_meter.php I left away the negative voltage supply and just connected the ground to pin 26. I thought the negative voltage isn't needed when you only measure positive voltages. However, my display only...
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