I have also had the same results with a 470uF one. Charge and discharge voltage and current graphs for capacitors. What was interesting was that the original multimeter measured 0.46V, while the new one measures 0.51V, which seems to back up what you suggested since the new multimeter likely has a different internal impedance.Īs for the capacitor types: 1uF tantalum cap is charging to over 1.2V but gets discharged before quickly when I connect the multimeter so I assume this is going to 1.6V because the 100uF aluminum cap is charging to 1.6V (although it takes a long time to get to that, 1.4V is much faster). Capacitance and energy stored in a capacitor can be calculated or determined from a graph of charge against potential. I measured just about 50-60 nanoamps of current. What do you think ? I could be all wet, frequently am.Īfter making the original post I was able to get a much higher quality multimeter and test the device. This can be expressed as : so that (1) R dq dt q C dq dt 1 RC q which has the exponential solution where q qo e qo is the initial charge. The charging performance was found to be 6 times better than the one obtained from a low cost MPPT and the improvement was 5.7 when compared to a high performance. This has a direct impact on the overall charging efficiency of the SC. When you measure voltage across your capacitor with such a feeble light sourceĥ0 nanoamps will charge 1 microfarad at 50 milllivolts per second, initiallyĪs capacitor voltage increases, the DMM steals current via its 10 megohm input impedanceĪnd at 1/2 volt it's stealing it all so charging ceases.Īnd when you disconnect the meter charging re-commences a resistor, the charge flows out of the capacitor and the rate of loss of charge on the capacitor as the charge flows through the resistor is proportional to the voltage, and thus to the total charge present. The charging system, depending on how high the input voltage is, can have efficiencies ranging from 10 to 80. Here's what i think is the answer to your original question. You might need an electrometer to measure such feeble currentĪnd you didnt say how big is your capacitor I wager you get about 0.5 volts/10 megohm = 50 nanoamps. Try measuring the current your photocell makes by switching your DMM to lowest current range. Connect the DHT11 sensor to P0 For the OLED, connect GND to GND, 3V3 to VCC, SDA to SDA, SCL to SCK Code Connect your micro:bit to your computer and open MakeCode editor to start programming. Then you can't knock loos a whole lot of electrons, can you ? The light source is very very dim - I'm using a tritium phosphor vial as the source with a tube of reflective foil around it to redirect some of light back into the cell.
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