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How would you monitor a bank of capacitor to tell if they are fully charged. I would like to display the precent of they're current charged state using an LED bar graph.

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    \$\begingroup\$ Do you have a separate voltage that you can use as a reference? \$\endgroup\$
    – Kellenjb
    Mar 16, 2011 at 15:51
  • \$\begingroup\$ This sounds VERY cool ill def be following this question. \$\endgroup\$
    – user3073
    Mar 16, 2011 at 16:19
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    \$\begingroup\$ Here's a start: national.com/mpf/LM/LM3916.html \$\endgroup\$
    – endolith
    Mar 16, 2011 at 16:36
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    \$\begingroup\$ Kellenjb, The reference voltage I was going to use would be the power supply voltage charging the capacitor. \$\endgroup\$
    – Talguy
    Mar 17, 2011 at 14:30

2 Answers 2

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Charge of a cap is CV = Q. Just measure V. This is quite different than a battery, much simpler

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  1. Build the LM3916 example circuit and connect the input to your capacitors.
  2. Adjust the LM3916 Vref so that the range matches the range you want to measure.

It already has a high-impedance buffer built-in, so it won't discharge the caps.

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  • \$\begingroup\$ During charging wouldn't the LM3916 show a 100% full \$\endgroup\$
    – Talguy
    Mar 17, 2011 at 14:30
  • \$\begingroup\$ No, capacitors don't charge like batteries. The voltage on the capacitor is proportional to the energy it is storing, so it will work for both charging and discharging. \$\endgroup\$
    – endolith
    Mar 17, 2011 at 18:11

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