How many resistors?

[LightBulb10]

Why do some circuits have so many resistors? I'm trying to create a circuit (nothing big) and according to my calculations I can get my desired current with one resistor. Do I need to have more than one or is it okay to only have one resistor in your entire circuit?

 

[Someone Somewhere]

Pull-up and pull down, often. Current limiting for LEDs sometimes, and timing circuits often use a resistor and capacitor if you don't need much accuracy.

What's the circuit?

 

[LightBulb10]

It's a portable charger circuit.

 

[Someone Somewhere]

OK. What type of battery are you charging, and from what source?

If you post a diagram of what you're thinking, I might be able to help.

 

[LightBulb10]

The charger has to charge a phone battery such as Li-Ion batteries. Basically any phone/iPad battery or small electronic battery. I also want it to be able to recharge itself so it can hold a charge. I would need capacitors for that right? How many? I'm new to designing boards so sorry if I come off as dumb.

 

[Someone Somewhere]

I'm getting lost as to where you're coming from. Are you trying to build your own version of e.g. this? If so, you'll need a large Li-ion or similar in there to store the energy in the first place.

You can't do that with only passive components (resistors, capacitors etc). You'll need some voltage regulation stuff; overcharging Lithium cells tends to end in flames.

 

[ex_bubblehead]

You have a whole lotta studying to do before you go trying to build a charger for Li-Ion. It's not as simple as you think. An improperly designed charger is downright dangerous.

 

[LightBulb10]

I'm getting lost as to where you're coming from. Are you trying to build your own version of e.g. this? If so, you'll need a large Li-ion or similar in there to store the energy in the first place.

You can't do that with only passive components (resistors, capacitors etc). You'll need some voltage regulation stuff; overcharging Lithium cells tends to end in flames.

Yeah... I'm essentially trying to make my own form of that charger. What exactly would i need in order to get an end result like that? Like I said... I'm new to this kind of stuff and really need help with all of this.

 

[LightBulb10]

You have a whole lotta studying to do before you go trying to build a charger for Li-Ion. It's not as simple as you think. An improperly designed charger is downright dangerous.

I know it's not simple but I want to know what exactly are the components that a circuit like that uses.

 

[ex_bubblehead]

You're approaching this from the wrong direction. You're trying to run long before you can even crawl. You don't yet have the foundational knowledge necessary and there's no way you will ever get that here. I suggest night classes in electronics from your local high school or community college where you will be schooled in basic theory, and get practical, hands on experience.

 

[Someone Somewhere]

You would need to make a DC>DC boost converter for at least one direction, if it's charging from 5V and outputting 5V.

If you were willing to charge from 12V, you could use a 2S battery pack and use a 7805 for output, and a combination of a fat resistor and adjustable regulator. Efficiency would go to hell though, and it would get hot. A purpose-built charger is the answer.

You'd also want these so that you don't accidentally set fire to your batteries: http://www.ebay.co.uk/itm/2-pcs-PCB-for-7-2V-18500-18650-Li-ion-Lipo-Battery-Pack-/400727478958

 

[LightBulb10]

You're approaching this from the wrong direction. You're trying to run long before you can even crawl. You don't yet have the foundational knowledge necessary and there's no way you will ever get that here. I suggest night classes in electronics from your local high school or community college where you will be schooled in basic theory, and get practical, hands on experience.

The question I'm asking isn't if i'm going to night school or not? I'm curious as to what the answer to this question is and that's why I'm asking it. I'm not asking it to get answers such as "Go to night school" or comments such as "You're trying to run long before you can even crawl". I find those comments to be offensive and to not have anything to do with the question that is being asked. So if you won't provide any knowledgeable insight on the question, I would appreciate it if you didn't answer at all. All I'm asking for is information, nothing else. Thank you.

 

[LightBulb10]

You would need to make a DC>DC boost converter for at least one direction, if it's charging from 5V and outputting 5V.

If you were willing to charge from 12V, you could use a 2S battery pack and use a 7805 for output, and a combination of a fat resistor and adjustable regulator. Efficiency would go to hell though, and it would get hot. A purpose-built charger is the answer.

You'd also want these so that you don't accidentally set fire to your batteries: http://www.ebay.co.uk/itm/2-pcs-PCB-for-7-2V-18500-18650-Li-ion-Lipo-Battery-Pack-/400727478958

So lets say I want to charge 5V and output 5V... i would need a DC>DC boost converter in one direction for it to charge the device and another in order for it to charge the battery?

 

[ex_bubblehead]

You're approaching this from the wrong direction. You're trying to run long before you can even crawl. You don't yet have the foundational knowledge necessary and there's no way you will ever get that here. I suggest night classes in electronics from your local high school or community college where you will be schooled in basic theory, and get practical, hands on experience.

The question I'm asking isn't if i'm going to night school or not? I'm curious as to what the answer to this question is and that's why I'm asking it. I'm not asking it to get answers such as "Go to night school" or comments such as "You're trying to run long before you can even crawl". I find those comments to be offensive and to not have anything to do with the question that is being asked. So if you won't provide any knowledgeable insight on the question, I would appreciate it if you didn't answer at all. All I'm asking for is information, nothing else. Thank you.

Without a basic understanding of electronic theory (can you explain Ohm's law for instance?) you can't possibly make use of any of the information we might give you.

 

[Someone Somewhere]

At this point, I would suggest focusing on an easier project first, or at least using pre-built circuits for charging it.

Playing with batteries can be seriously dangerous. Here's what can happen if you overcharge them: http://youtu.be/_d_nDH0Wpu4?t=2m50s

 

[LightBulb10]

You're approaching this from the wrong direction. You're trying to run long before you can even crawl. You don't yet have the foundational knowledge necessary and there's no way you will ever get that here. I suggest night classes in electronics from your local high school or community college where you will be schooled in basic theory, and get practical, hands on experience.

The question I'm asking isn't if i'm going to night school or not? I'm curious as to what the answer to this question is and that's why I'm asking it. I'm not asking it to get answers such as "Go to night school" or comments such as "You're trying to run long before you can even crawl". I find those comments to be offensive and to not have anything to do with the question that is being asked. So if you won't provide any knowledgeable insight on the question, I would appreciate it if you didn't answer at all. All I'm asking for is information, nothing else. Thank you.

Without a basic understanding of electronic theory (can you explain Ohm's law for instance?) you can't possibly make use of any of the information we might give you.

First of all, If I'm asking this it's because i will understand the information. If I didnt, I wouldn't be asking this information in the first place. Second of all, I don't need to prove to you if i understand ohm's law or not. But just to make sure that you understand it, Ohms law is a formula that can be used to find Voltage (V), Current (I), and Resistance (R). The formula is V=IR. If you have any basic understanding of math you will be able to notice that this equation can be rearranged to find out any of the three variables in the equation as long as you know at least two of the variables. So if you're searching for a resistor value, this equation will give you the answer. If your searching for the amount of current, this will give you the answer. If you're searching for voltage... THIS WILL GIVE YOU THE ANSWER. As you can see, I do not need anyone telling me if I will or will not understand the information that is being asked. If i'm asking it is because I have a use for it. Thank you.

P.S. Make sure that when you plug the current value into the formula (If you're trying to figure out something other than current) is in amperes. That should save you a lot of trouble. 😉

 

[LightBulb10]

At this point, I would suggest focusing on an easier project first, or at least using pre-built circuits for charging it.

Playing with batteries can be seriously dangerous. Here's what can happen if you overcharge them: http://youtu.be/_d_nDH0Wpu4?t=2m50s

I understand that it is dangerous but I'm not building the circuit yet. I'm just curious as to what would be needed to charge a battery so that I could design a circuit like this in the future. That's all.