Questions about capacitors, and arduino

In summary, the conversation discussed different ways to get 5 volts using capacitors and a single AA battery. It was suggested to use a 4PDT relay switch or a solar powered garden light to achieve this voltage. The use of an arduino to control the charging and discharging of the capacitor was also mentioned, with the recommendation to use a resistor to prevent damage to the arduino. To measure the discharging, it was advised to connect the capacitor to an analog pin. The use of a relay was also discussed to isolate the capacitors from the arduino. It was noted that putting the capacitors in series will lower the capacitance but increase the voltage.
  • #1
jehan60188
203
1
hey all, I've been playing around with capacitors and have a few questions

Is it possible to get 5 volts over a capacitor using a AA batery? Or am I limited to 1.5 volts?
If I have more than 5 volts going into an arduino pin, that will cause damage. But I can use a voltage divider to drop that, right?

I want to use an arduino to control capacitor charging/discharging, but in order to avoid damaging the arduino, I want to use it only for controlling a relay that acts as a two position switch- one position for charging, another for discharging, and for measuring the current going into the arduino.

how can I do that second part? if I put a pin between the battery's positive terminal, and capacitor, can I have that go an analog pin for measuring?

thanks!
 
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  • #2
A simple way to get 5 volts using a single AA battery is to charge 4 identical capacitors to 1.5 volts, then use a 4-pole double throw (4PDT) relay switch to put them in series to get 6 volts. A diode drop will reduce this to about 5.3 volts.
 
  • #3
Another way is to use a solar powered garden light.

These are often discarded because the NiCd battery in them fails.

However, there is a circuit in them that converts the output of a NiCd battery (1.2 volts) to about 3.5 volts to run a white LED.

If you disconnect the solar cell, the circuit will work as if it was in darkness and give several volts out from a 1.5 volt dry cell.
 
  • #4
It seems the simplest to use the arduino itself to charge the capacitor to 5v, using a resistor if you are worried about damage to the arduino.
To measure the discharging of the capacitor, connect the negative lead of the capacitor to ground of the arduino and the other lead of the capacitor to an analog pin.
 
  • #5
thanks for the info everyone, i picked 5V arbitrarily, so using the arduino's output pin isn't possible (Since I may choose 10, or 25 or whatever volts)- hence the relay (to isolate the capacitors from the arduino)

iirc, putting them in series will lower the capacitance (since they sum in inverse)
v=q/c
c goes down, q stays constant, so v increases!
 

1. What is a capacitor and how does it work?

A capacitor is an electronic component that stores electrical energy in the form of an electrostatic field. It is made up of two conductive plates separated by an insulating material called a dielectric. When a voltage is applied to the capacitor, one plate becomes positively charged while the other becomes negatively charged. This separation of charges creates an electric field that stores energy. As the voltage across the capacitor increases, more charge is stored and the capacitor's capacitance increases.

2. How do capacitors affect an Arduino circuit?

Capacitors are often used in Arduino circuits to filter out noise and provide stable power to the microcontroller. They act as temporary energy storage, helping to smooth out any fluctuations in the power supply and prevent them from affecting the performance of the Arduino. Capacitors can also be used in timing circuits, for example in conjunction with a resistor to create a time delay.

3. What is the role of a capacitor in an AC circuit?

In an AC circuit, a capacitor acts as a resistor, allowing the flow of current through the circuit. However, as the polarity of the AC signal changes, the capacitor charges and discharges in a continuous cycle, resulting in a phase shift between the voltage and current. This phase shift can be used to control the amount of current flowing through the circuit, making capacitors useful in applications such as motor control and power factor correction.

4. How do you choose the right capacitor for an Arduino project?

The most important factors to consider when choosing a capacitor for an Arduino project are capacitance, voltage rating, and package size. The capacitance should be appropriate for the specific circuit and desired functionality, while the voltage rating should be at least 2-3 times higher than the maximum voltage expected in the circuit. Package size should also be considered to ensure the capacitor can physically fit on the Arduino board or in the project enclosure.

5. Can you use any type of capacitor with an Arduino?

While most types of capacitors can be used with an Arduino, the most commonly used types are ceramic and electrolytic capacitors. Ceramic capacitors are typically used for high-frequency applications, while electrolytic capacitors are better suited for higher voltage and energy storage applications. However, it is always important to check the specifications and suitability of a capacitor for a specific Arduino project before using it.

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