check to see if capacitor is full

? Draw a schematic and post a photo of it.

You probably want to measure the current into the capacitor at the low end, this will work whatever the cap voltage.

Use a shottky diode, then the voltage across this gives a logarithmic scale of current. The high current discharge path must not go through the diode (in fact it cannot, the diode is the wrong way round).

Here is the basic schematic.


Your rail gun operates on 5V ?

no this is an example. to make sure i get the reading of the capacitors when they are full.

/* ReadAnalogVoltage Reads an analog input on pin 0, converts it to voltage, and prints the result to the serial monitor. Attach the center pin of a potentiometer to pin A0, and the outside pins to +5V and ground.

This example code is in the public domain. */

// the setup routine runs once when you press reset: void setup() { // initialize serial communication at 9600 bits per second: Serial.begin(9600); }

// the loop routine runs over and over again forever: void loop() { // read the input on analog pin 0: int sensorValue = analogRead(A0); // Convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V): float voltage = sensorValue * (5.0 / 1023.0); // print out the value you read: Serial.println(voltage); }

this is my code to read the voltage meter.

plugged into 5v with 1k resister paralell with a0 picking up and nother resister 1k paralell going to ground. Serial si giving me 2.5. not sure if thats right.

That's all well and hood if you know how to calculate the resistor values for the rail gun circuit

Do you know the name of the rule that governs such calculations ? ( or it's namesake)

I. don't see anything that specifically pertains yo your application. All I see is sketches from tutorials. What is the posting voltage and current of your rail gun ?

i dont have anything to show for my rail gun but that is my project.

ambitious i know but i have the will and curiosity to do it.

so far i got a voltage reader now. so when i hook up the capacitors in parallel to add up massive voltage i can check when its charged by checking if any voltage is going through. if its going through near the full amoutn it means the capacitors are fully charged/saturated correct?

so i got my lcd to show me the voltage whatever the a0 pin touches.

now my next question is how can i confirm that the capacitor is infact fully charge ir even charging at all?

You don't get it do you ?

We can't answer your questions because you haven't answered ours . What is the operating voltage and current ?

operating voltage for what??

the capacitor? my rail gun isnt even made yet since i need to do a few things first…

Don't ask us how to measure the capacitor voltage until. you know what it is.

ok the capacitor is 100uF 25V.

Ofcourse i understand a rail gun requires much more then that.

the cap is just to get a basic foundation going.

Google voltage divider

Ok, lets keep it simple.

You are not asking about rail guns, or even capacitors really. What you are asking is: "How do I measure voltage?"

If you know how to measure voltage you can tell if a capacitor is charged. It's pretty simple, what is the supply voltage? (What is the voltage that you have connected to the Positive leg of the capacitor). That is what the capacitor should read for you to know it's charged. (remember, simple, we're not going into transformers or step ups).

You likely won't ever see a capacitor charging and discharging it happens so fast, you would need an oscilloscope to see it, a multimeter would not do it, you might see a slight fluctuation but that's it. Unless you have some MASSIVE capacitor banks..... And if that's the case, you really really really shouldn't be playing with them until you actually understand a bit more. If you are asking how to tell if a cap is charged it's unsafe for you to attempt to build something that requires extreme voltage levels or extreme amperage. Caution, Death or Serious Injury may occur from improper use of this equipment.

Here's an example:

You have a 12 volt supply. The positive leg is tied to the + on the capacitor (I'm assuming electrolytic? Looks kind of like a miniature soda can with two metal legs sticking out of the bottom?). The ground is tied to the negative leg of the capacitor (electrolytic's are polarity sensitive, you will blow them up if hooked up backwards, the negative leg usually has a stripe going down the side of the cap to denote it).

Put your volt meter across the positive and negative legs of the capacitor with the power supply hooked up, what do you read?

---It should be 12v, this means the capacitor is charged

Now unplug your power supply while keeping the meter across the legs, what happens to the voltage?

---The voltage slowly drops, it is dropping due to the very slight current that a meter requires to read the voltage. This is the capacitor discharging, once it reads 0 the capacitor no longer has a stored charge

If it's 12v and you want the arduino to read it you will need to hookup a voltage divider and send the output to an analog pin.


Using those resistor values you would end up with: Vout = Vin * (R2 / (R1 + R2)) or 1.2 at the analog pin with a 12v input.

But again, you really need to take the time to learn the basics before you get into anything dangerous.

where do you go to make purdy diagrams like that?

i never said i was asking for railguns, i was asking originally how to detect if capacitors are full then someone tried explaining to me voltage dividers.

im not quite sure how i would even know if a capacitor is charged because im not sure if my volt reader is working. REMEMEBER!!! i have nothing else other than what came with the starter kit.

question. for capacitors couldnt you just plug them on the power/ground strip on the breadboard?

Sure you can. But what's the point of doing that if you do not understand the component and its uses ?

Seems to me like you are trying to cut the corner and do some measurements to the capacitor, but you do not know what to expect. This is unnecessary for that component, because there's a world of information available on these components.

im a visual learner, i need to see how its done with the wires, schematics doesnt give me a complete picture. i need a visual representation.

Ok. What do you think you would accomplish by 'plugging them on the power/ground strip on the breadboard' ? Them is plural, so how many of them would you use at the same time ?

i was asking originally how to detect if capacitors are full then someone tried explaining to me voltage dividers.

Clearly you are not grasping anything you have been told since the beginning of this post. You do not seem to grasp that before you can use your starter kit and arduino to measure voltage, you need to be aware of the Maximum electrical ratings of the arduino (unless you want to fry it). Then you need to build an interface circuit CALLED A VOLTAGE DIVIDER (remember that part ?) to reduce the voltages greater than 5V down to 5V or less so that they can be connected to the analog input without blowing up the arduino. The equations and the schematic were given. You have been given all the necessary information to proceed with measuring the 100uF 25V capacitor (for which you have absolutely no means of charging beyond 5V at this time (based on the fact that you have not listed any other equipment at your disposal and have emphasized that all you have is the starter kit). You can practice making voltage dividers while you figure out how you are going to accomplish the rest of your project. Thus far, I have not seen any reply by you that indicates you have understood anything you have been told.

im not quite sure how i would even know if a capacitor is charged because im not sure if my volt reader is working. REMEMEBER!!!! i have nothing else other than what came with the starter kit.

I'm not so sure the problem is the meter , as it is the operator. If you have a problem with the meter, post a link and photo for the meter and state the problem.

because im not sure if my volt reader is working

This is a red flag. Your reference to a DMM as a "volt reader" instead of "multi-meter", indicates you probably don't know how to operate the meter to measure voltage. (it scares me to think that is even possible)

Why do I say that ? Do I think there is anything wrong with not knowing how to use a meter ? No, of course not. My point is that instead of posting on the forum about rail guns, you probably should have turned off your computer and sat down and read the Multi-meter User Manual from cover to cover.