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Electronics for Beginners Forum I am always trying to learn about electronics but two things always bog me down | | | Author | Message | | Anonymous
202 | Hi Orbilius,
I can see that you could have some difficulty with electronics if you struggle with math, as they are very closely tied together. Fortunatly, most of the math is not complex. It may seem complex, but it can usually be broken down to simple tasks of add, subtract, multiply, and divide. You computer should have a built in calculator program to help you with working out the answers. But you'll still have to understand the relationships.
We'll get to your fan questions in a minute, but before that, I would like to pass on a little bit of knowledge so that you'll understand my answers. There is a direct relationship between resistance (ohms), current (amps), voltages (volts), and power (watts). If you know any two, you can mathmatically calculate the others. There are basically two relationships and I'll show them with math, because that is the easiest way to say and understand them.
The first is the voltage relationship. In a circuit, no matter how simple or complex, the voltage (volts as V, but sometimes shown as E) will always equal the resistance (ohms as R, because I don't know how to put the upside down "U" on here for you) mulitplied the current (amps as A, but sometimes shown as I). Oh, yeah, when I said "always", that's pretty much what I mean. The math looks like:
V=RxA, but sometimes this is written as E=RxI
Using math skills, you can twist this around any way that you like, but it's still the same. Like these variations:
RxA=V
R=V/A
A=V/R
The second is the power relationship. In a circuit, no matter how simple or complex, the power (watts as W, and occasionally as P) will always equal the voltage (volts as V) mulitplied the current (amps as A). Again, when I said "always", that's pretty much what I mean. The math looks like:
W=VxA, but sometimes this is written as P=ExI
Using math skills, you can twist this around any way that you like, but it's still the same. Like these variations:
VxA=W
V=W/A
A=W/V
Now how can you remember this? Easy. Remember five things:
1. sometimes voltage is shown as E and sometimes as V.
2. sometimes current is shown as A and sometimes as I.
3. sometimes power is shown as W and sometimes as P.
4. when you need to calculate something about the power, remember to eat some PIE as in P=IxE.
5. when you are eating that PIE, please don't wipe it on your EAR, as in E=AxR.
So lets get all of the labels on your fans in the same format. Fan 2 and 3 are the same, so lets make fan 1 have the same information format. It has power and we need current. I think some PIE would be could. So, P=IxE, which is the same as W=VxA. So 12V multiplied by some amount of amps should work out to 1.4 watts, like 12Vx?A=1.4W. If we divide both sides by 12V, we get ?A=1.4W/12V, or simply A=1.4/12. If you run that through your calculator, you should find that the current on that fan should be at .11666 amps, or .12 amps.
If the fans each have a red wire and a black wire, you could connect all the red wires to the + connection of your power supply and all of the black wires to the - connection. This would be called "parallel". In parallel, each fan has the same 12 volts of pressure on it, but each fan will allow it's own amount of current at that voltage. So fan one will allow .12 amps through it, as we calculated. Likewise, fan 2 will allow .15 amps, and fan 3 will allow .32 amps. Since they are each allowing their own amount through, then the amount of current can be added together. So .12+.15+.32=.59 amps.
You say that your transformer, which is really a power supply since it's does more that just a transformer, can provide 12 volts, and supply current up to 1200Ma. In electronic, an upper case letter (M ro example)can mean something very different that a lower case letter (m). An M is usually understood to be Mega which means "x1000", while an m is understood to be milli which means "/1000". The different between M and m can be quite dramatic with electricity. If that power supply really does 1200 MegaAmps, then I expect that the wire (more like "cables") coming out of it are going to be as big around as you or me. I expect that they really mean milli. So probably they mean 1200mA, which is 1200/1000A, or 1.2 amps.
1.2 amps is almost twice the amount of current that all three of your fans would use all running at once.
So, for your fans, if you where to do the math:
Fan1 is 1.4W=12Vx.12A
Fan2 is 1.8W=12Vx.15A
Fan2 is 3.84W=12Vx.32A (This must be a bigger fan or something, because it going to be using about twice the current and power.)
All of you fans together use 7.04 watts of power (1.4+1.8+3.84). Will the math stay true to us? Lets see. 7.04W=12Vx.59A so it matches. (Okay, okay, it's actually, it's .5866666, but we rounded up before, remember?)
You power supply is rated at 12V and 1200mA, or 1.2A so:
PowerSupply is 14.4W=12Vx1.2A
For your slowly pulsing led light, there are a number of ways, but I would look at using a 555 timer IC chip, a 9v battery, and a few resisters and capacitors. Have a look in google.com for "astable 555 circuits" and I'm sure you'll find something.
Hope this helps.
Alan | Orbilius
1 | I am always trying to learn about electronics but two things always bog me down 1 the math im terrible at it, 2 i have dificulty understanding the relationship between amps and volts and watts.
So please bear with me and my possibly dumb questions.
I have several fans scavanged froman old pc they have different info on them as to their power characteristics which i will list below,
Fan 1 DC 12 V 1.4W
Fan 2 DC 12V 0.15 A
Fan 3 DC 12V 0.32 A This is just what is written on the fans Am i rightin thinking that i could work out the amp rating of the fan marked 1.4 w by testing its resistance and then doing V/R = I
Now my problem is i now have a laptop and wish to use the fans to make a laptop cooler, i have a spare mains transformer which can out put from 1.5 V to 12 V at 1200Ma (max). What i need to know is this, can this transformer be used to run one or more of these fans. i have a hunch that i can if i wire the fans in either series or paralel (to divide the amperage?) but im not sure, one problem is im not sure of the units involved I.E is 0.15 A the same as 1500Ma.
I do have some experiance making circuits but mostly from just following circuit diagrams, and i have read a number of books on electronics forrest m mims etc. but ive never been able to really discuss what ive read with anybody to see if ive understood it correctly.
If a device (in the above case a fan), says 12v 0.15A dous that mean, It needs 12volts available to run at its top speed,(maximum power watts?) and that it draws 0.15 of an Ampere (15% of an Ampere?). What implications does this have for the device supplying the power, say a transformer rated as the above or say, a nine volt battery. So if 0.15A is more than my transformer is rated for what is happening in the transformer, is the fan basically over pulling juice from the transformer or battery for instance, is this even the right way to think about it. I am really really bad at math so please take this into acount if answering my question, like if you were explaining to a very small child
Also im a sculptor and i want o make a peace which has a slowly pulsing light in it , An LED light would be perfect. I know there are ways to do this using the way a capacitor discharges and im sure i ussed to have abook somewhere with acircuit diagram in it i could use, i would really apreciate it if somone could help me with this as well.
Cheers. | |
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