How do I build simple circuits?

[DruidArmy]

Hi,
I've been trying to teach myself electronics. I have read a lot of introduction books and now want to build a circuit. However, I have not been able to find good books on how to assemble simple circuits. In other words how the parts (resistors, caps, coils, diodes, transistors) go together. I understand all the parts but need to learn to assemble circuits.

For instance, I want to plug into a 120v AC outlet and create an RLC circuit where the R is an incandescent light bulb inside the tank circuit. I figure by putting the light bulb inside the LC tank I will pass the same electricity thru the bulb multiple times and save on electricity consumption. I would somehow push a little more electricity into the circuit to maintain resonance.

Is this idea feasible? How do I get to the next step to building simple circuits? Any good books?

Druid

 

[Averagesupernova]

This website will not let me post the answer I want to since the single word "No" is not enough characters. Basically it cannot be done. You can't get more energy out than you put in.
-

BTW, the phrase "pass the same electricity thru the bulb multiple times" does not indicate to me that you 'understand all the parts' at all.

 

[NascentOxygen]

For instance, I want to plug into a 120v AC outlet and create an RLC circuit

No, you don't want to do that! You don't want to go anywhere near lethal voltages.

Start with circuits that operate off low-voltage batteries, so that you are not imperiling your life (and that of others who may try to extricate you from your experiment). There are plenty of perfectly safe circuits to construct, without cooking up something dangerous whose hazards you don't understand.

We value our PF members too much to not decry senseless risks through such misadventure!

Live long, live safely, and enjoy science.

 

[berkeman]

Hi,
I've been trying to teach myself electronics. I have read a lot of introduction books and now want to build a circuit. However, I have not been able to find good books on how to assemble simple circuits. In other words how the parts (resistors, caps, coils, diodes, transistors) go together. I understand all the parts but need to learn to assemble circuits.

For instance, I want to plug into a 120v AC outlet and create an RLC circuit where the R is an incandescent light bulb inside the tank circuit. I figure by putting the light bulb inside the LC tank I will pass the same electricity thru the bulb multiple times and save on electricity consumption. I would somehow push a little more electricity into the circuit to maintain resonance.

Is this idea feasible? How do I get to the next step to building simple circuits? Any good books?

Druid

Start with beginner electronics kits like these:

https://www.google.com/webhp?source...v=2&ie=UTF-8#q=electronics kits for beginners

You will learn a lot from putting together the kits and reading their "theory of operation" information that comes with them.

 

[DruidArmy]

Thanks for the safety concern. But can you answer the question as to if I put a light bulb inside the tank, Ie. between the capacitor and the coil, when the current (I) is at resonance maximum, the current flows back and forth between the capacitor and coil. The same electricity is surging back and forth across the filament. Is it not?

My supply would simply pulse in a small amount of current to maintain the state of resonance. Like a person pushing a swing analogy.

I'm not saying I would get something for nothing. What I'm saying is that in a conventional bulb the current only goes thru the bulb once, but with my technique, the current would oscillate across the bulb multiple times while in the tank. Perhaps DC would be easier to visualize.

 

[DruidArmy]

I have done several kits, but most are really weak when explaining "Theory of Operation". It's the why we put a capacitor here, why is a diode there, here's what's happening as the electrons flow around the circuit kind of stuff that I need more of.

It amazes me how ham operators,many of whom have no electrical engineering degree, can build a transmittor or radio from scratch. I wonder how they learned this field. I have hit a brick wall in trying to educate myself on this subject.

 

[berkeman]

I have done several kits, but most are really weak when explaining "Theory of Operation". It's the why we put a capacitor here, why is a diode there, here's what's happening as the electrons flow around the circuit kind of stuff that I need more of.

It amazes me how ham operators,many of whom have no electrical engineering degree, can build a transmittor or radio from scratch. I wonder how they learned this field. I have hit a brick wall in trying to educate myself on this subject.

Can you post what kits you've built so far, and what they and their docs look like? I'd like to get calibrated on what you've seen so far, and what may be the best thing for you to work with next.

And on the HAM Radio Handbook -- it's a good reference if you want to build legal transmitter/receiver units, but it's not a general EE development resource.

 

[Devils]

Start with beginner electronics kits like these:

https://www.google.com/webhp?source...v=2&ie=UTF-8#q=electronics kits for beginners

You will learn a lot from putting together the kits and reading their "theory of operation" information that comes with them.

I got a Radio Shack 150-in-1 kit when I was age 10. You learn a lot if you are fascinated with a subject!

 

[f95toli]

Thanks for the safety concern. But can you answer the question as to if I put a light bulb inside the tank, Ie. between the capacitor and the coil, when the current (I) is at resonance maximum, the current flows back and forth between the capacitor and coil. The same electricity is surging back and forth across the filament. Is it not?

My supply would simply pulse in a small amount of current to maintain the state of resonance. Like a person pushing a swing analogy.

No, because light bulbs use ENERGY not current. This is why they have a power rating (power in Watts is the same thing as energy per second ).
Setting up a resonant circuit does not "create" energy, it just means that the current reaches a maximum at a given frequency. If the quality factor of the circuit his high enough (which it won't be if you put a light bulb in there) you can also temporarily "store" some energy in the circuit but that energy still had to come from somewhere in the first place, meaning there is absolutely no way to save energy using a resonant circuit.

Also, remember that the power companies bill you for the ENERGY you use, not the amount of current and/or voltage.

 

[DruidArmy]

Can you post what kits you've built so far, and what they and their docs look like? I'd like to get calibrated on what you've seen so far, and what may be the best thing for you to work with next.

And on the HAM Radio Handbook -- it's a good reference if you want to build legal transmitter/receiver units, but it's not a general EE development resource.

I've got the Elenco 150 in one kit, I've done a radio kit, buzzer, etc. I got my Ham license and went thru all that training. I've read the ham radio handbook. It was way too technical for my level.

All the books I can find that are introductory just explain what a capacitor is, what resistor bands mean, parallel and serial analysis techniques, how batteries work, how inductors work, transformers , capacitive reactance, etc.

But now I want to build circuits of my own. For example, I want to create a circuit that outputs a signal at a particular frequency and voltage. Ideally one where I can vary the frequency and voltage of the output.

 

[milesyoung]

I've got the Elenco 150 in one kit, I've done a radio kit, buzzer, etc. I got my Ham license and went thru all that training. I've read the ham radio handbook. It was way too technical for my level.

All the books I can find that are introductory just explain what a capacitor is, what resistor bands mean, parallel and serial analysis techniques, how batteries work, how inductors work, transformers , capacitive reactance, etc.

But now I want to build circuits of my own. For example, I want to create a circuit that outputs a signal at a particular frequency and voltage. Ideally one where I can vary the frequency and voltage of the output.

If you have several electronic kits, does that mean you've actually built simple circuits with a low-voltage supply/battery, a bunch of resistors etc., and probed the voltages around the circuit to figure out how it all works?

Maybe used a breadboard before?

I would think that would be the very first step to getting into electronics.

 

[DruidArmy]

Yes, the kits include a breadboard. But mostly they are just putting pieces into place, with very little in the way of explaining in detail what is happening in the circuit.

For example, say I want to experiment with electrolysis, so I want to plug into a 120v AC main, then be able to change the output current to different frequencies, different voltages and be able to toggle from ac to dc output. Say i want to change the frequency from say 10hz to microwave frequencies to see if the electrolysis is more efficient at particular frequencies. If microwaves heat water better than lower frequencies, perhaps they will be more effective at electrolysis.

 

[milesyoung]

Yes, the kits include a breadboard. But mostly they are just putting pieces into place, with very little in the way of explaining in detail what is happening in the circuit.

That seems odd, if the kits are meant to teach you something about electronics.

Why not breadboard up some simple circuits with LED's, 555 IC's etc.? There's tonnes of neat stuff you can start out building. Do you like audio projects? Building small amplifiers and such is a great way to start out. Fiddle around with opamps, filters - all sorts of great stuff.

For example, say I want to experiment with electrolysis, so I want to plug into a 120v AC main, then be able to change the output current to different frequencies, different voltages and be able to toggle from ac to dc output. Say i want to change the frequency from say 10hz to microwave frequencies to see if the electrolysis is more efficient at particular frequencies. If microwaves heat water better than lower frequencies, perhaps they will be more effective at electrolysis.

This paragraph raises so many red flags, it's like you're intentionally trying to build something dangerous. High-voltage, low-impedance outputs, water, hydrogen/oxygen gas mixtures. As far as I know, electrolysis of water is only done using DC/pulsed DC. If you want to separate the hydrogen and oxygen gas, then generally you'd want to keep the polarities of the electrodes fixed, otherwise, if it even produces any reaction, you'll just end up with a mixture.

 

[jim hardy]

Thanks for the safety concern. But can you answer the question as to if I put a light bulb inside the tank, Ie. between the capacitor and the coil, when the current (I) is at resonance maximum, the current flows back and forth between the capacitor and coil. The same electricity is surging back and forth across the filament. Is it not?

My supply would simply pulse in a small amount of current to maintain the state of resonance. Like a person pushing a swing analogy.

I'm not saying I would get something for nothing. What I'm saying is that in a conventional bulb the current only goes thru the bulb once, but with my technique, the current would oscillate across the bulb multiple times while in the tank. Perhaps DC would be easier to visualize.

You ought to read up on resonance.
Search on "resonance Q"

http://ocw.mit.edu/courses/electric...pring-2006/lecture-notes/resonance_qfactr.pdf

http://en.wikipedia.org/wiki/Q_factor

Do you believe in conservation of energy ?
Q in a resonant circuit is the ratio of energy stored to energy dissipated every cycle.


Don't try to resonate at 60 hz because you need a big inductor and a big capacitor and you can easily kill somebody with such a resonant circuit.

There's plenty of Tesla coil plans that start with an old car or lawnmower ignition coil. You're not nearly so apt to kill yourself or a family member with one of those.
Tesla became obsessed by resonance and went bonkers, so be aware there's a lot of crackpottery about him on the internet. Resonance doesn't amplify power it just stores it.

I've been trying to teach myself electronics

Plenty of hobby sites on the internet.

amasci dot cm
discovercircuits dot com
sparkfun dot com

search on electronic hobby parts

 

[berkeman]

All the books I can find that are introductory just explain what a capacitor is, what resistor bands mean, parallel and serial analysis techniques, how batteries work, how inductors work, transformers , capacitive reactance, etc.

But now I want to build circuits of my own. For example, I want to create a circuit that outputs a signal at a particular frequency and voltage. Ideally one where I can vary the frequency and voltage of the output.

Take a look at this book when you get a chance:

The Art of Electronics by Horowitz and Hill: https://www.amazon.com/dp/0521370957/?tag=pfamazon01-20

Maybe you have a technical library nearby where you can check it out? It should be at a level where you can understand it, and if you read it cover-to-cover and build some of the circuits in it, you will be very far along in learning electronics, IMO.

 

[analogdesign]

This paragraph raises so many red flags, it's like you're intentionally trying to build something dangerous. High-voltage, low-impedance outputs, water, hydrogen/oxygen gas mixtures. As far as I know, electrolysis of water is only done using DC/pulsed DC. If you want to separate the hydrogen and oxygen gas, then generally you'd want to keep the polarities of the electrodes fixed, otherwise, if it even produces any reaction, you'll just end up with a mixture.

That paragraph makes me think this guy might be subtly trolling the forum.

To the OP: If you really want to "learn electronics" start with simple op-amp based audio projects or LED-flasher type things with a 555. These are fun, educational, and safe. Also, if you're being sincere, your RLC circuit won't work because any light you generate is due to power dissipation in the light bulb. Therefore, whatever energy you use to light the bulb will need to be supplied to the RLC circuit. You gain nothing.

 

[DruidArmy]

I may have confused the issue by mentioning resonance. I guess it is not necessary to be at resonance for this. Let me restate: Assume simple battery connected to 12 volt light bulb. The current flows thru the light bulb and the bulb dissipates some of the energy as light and heat. However, some of the energy of the current flows thru the bulb and is not used.

What I am suggesting is putting the bulb between a capacitor and inductor. Now as the first pass of the electric current thru the bulb,not all of the energy will be disippated, so it will go into the capacitor and stored as energy, then will be returned across the bulb and any excess energy still not consumed by the bulb with be stored as a magnetic field in the coil, then released back across the bulb as the energy sloshes back and forth between capacitor and inductor. Resonance is not necessary only LC tank. What am i missing?

 

[berkeman]

I may have confused the issue by mentioning resonance. I guess it is not necessary to be at resonance for this. Let me restate: Assume simple battery connected to 12 volt light bulb. The current flows thru the light bulb and the bulb dissipates some of the energy as light and heat. However, some of the energy of the current flows thru the bulb and is not used.

What I am suggesting is putting the bulb between a capacitor and inductor. Now as the first pass of the electric current thru the bulb,not all of the energy will be disippated, so it will go into the capacitor and stored as energy, then will be returned across the bulb and any excess energy still not consumed by the bulb with be stored as a magnetic field in the coil, then released back across the bulb as the energy sloshes back and forth between capacitor and inductor. Resonance is not necessary only LC tank. What am i missing?

No, you are just confused. All of the energy delivered by the battery is dissipated in the load in the single pass of current through the bulb.

 

[Devils]

That paragraph makes me think this guy might be subtly trolling the forum.

Either that or he is clueless & wants to kill himself.

 

[iScience]

you should really start with simple battery circuits before you start working with wall power.

 

[DruidArmy]

you should really start with simple battery circuits before you start working with wall power.

Okay, you have convinced me that I better work with 12v DC instead of 120v AC for safety reasons. I think the book recommended looks good - Of course it had to be a $110 dollar book :)

I will verify that my bulb uses 100% of the power sent to it - I still think much of the current passes thru the bulb without being used up as light or heat.

I'm not trolling, I'm confused and trying to learn. but the field is very challenging to learn on your own. All the sites I've found so far either assume you know nothing and just show the basics or assume you know a lot and get very technical.

I would like more of a mechanical explanation of circuits, ie. electrons come out from the negative side and go here, then they go there, etc.

Thanks for all the assistance.

Druid

 

[mishima]

Current is the movement of charge through an infinitely thin cross-sectional area, not the movement of charge through an arbitrarily long light bulb filament. In AC, current doesn't pass through anything; charges simply oscillate in place with a certain frequency (their mean location is constant).

Even in DC, it would take hours for a charge to make a complete loop around a circuit. They travel with velocities on the order of 10 micrometers a second. So why does the light come on the instant you flip the switch? Because energy is transferred through electric fields at light speed.

 

[davenn]

I will verify that my bulb uses 100% of the power sent to it - I still think much of the current passes thru the bulb without being used up as light or heat.

Power isn't sent to the bulb ... well not in the way you appear to be imagining

in a series DC circuit ... a bulb ( a resistor) across a battery, or other PSU, the current flowing in the circuit will be the same where-ever it is measured

lets take this circuit ...

it doesn't matter if its a resistor or a lamp

if you have got your ham license then you must know Ohms Law ?
you tell me what the current flow in that circuit is ... hint its going to be the same reading for both ammeters

Dave

 

[davenn]

Once you have worked out the current flowing in the circuit

Then using Power (Watts) = I (current) x V (Volts)

tell me what power is being used by the resistor

Dave

 

[DruidArmy]

I believe Ohms is I=V/R, so 1 amp will show for both meters since they are serially arranged. Power(watts)= 10 watts.

Now how much power is used by the resistor, hmm... Let's see, if the resistor was not there then 10 amps would be flowing assuming no resistance. Since only 1 amp is flowing after placing the resistance, I guess its using 9 amps of current. Therefore 1 amp is not used by the resistor.

As far as michima is concerned, current is the flow of electrons not charges. Unless u consider electrons as charges. All electrons are charged negatively. You cannot supercharge an electron to say -2 charges. Likewise, you cannot charge an electron positively. So please, get this straight, electricity is the flow of electrons not charges. Again, this ambiquity as to whether its charges or electrons is alarming.

 

[DruidArmy]

I don't really know if the resistor is using 9 amps of power. It is resisting the flow of electrons, so that only 1 amp is flowing. The other 9 amps are not actually being sent out of the battery. So there is no way its wasting 9 amps. So I don't really know how much power it is using.

 

[analogdesign]

Now how much power is used by the resistor, hmm... Let's see, if the resistor was not there then 10 amps would be flowing assuming no resistance. Since only 1 amp is flowing after placing the resistance, I guess its using 9 amps of current. Therefore 1 amp is not used by the resistor.

Now you're thinking about the circuit!

Remember Ohm's law, though. V = IR. V is set by a battery, so if the resistor were not there (R=infinity) there is no current flow. In the circuit davenn posted the only current path is through the resistor. See if you can figure out why. Every charge that comes out the top of the battery (we're being conceptual here) must find its way to the bottom of the battery (this is called "ground return"). The only way there is to return is through the resistor so all current is in the resistor.

So if we have 10 V and 10 Ohms, we have I = V/R = 1 Amp (just like you said).

But since I = 1 amp, and R = 10 Ohms, all the voltage must be dropped across the resistor and all the current must be used by the resistor. It can't possibly be 9 amps because only 1 Amp is coming from the battery as you said!

Power = IV, and manipulating Ohm's law you'll see power = (I^2)*R. In both ways of looking at it the power is 10 Watts and all of it is dissipated in the resistor. All of it. How do I know? Look at the equation. In a ideal wire, R = 0, so the power dissipated must also be zero.

and btw, current is the flow of charge. In most electronics that charge is electrons, but there are plenty of circuits that use ion flow (for example the neurons in your head that you're using to read this post).

 

[davenn]

analogdesign gave an awesome response and hopefully when you respond you will be able to confirm that you understood that

I believe Ohms is I=V/R, so 1 amp will show for both meters since they are serially arranged. Power(watts)= 10 watts.

yes

Now how much power is used by the resistor, hmm... Let's see, if the resistor was not there then 10 amps would be flowing assuming no resistance. Since only 1 amp is flowing after placing the resistance, I guess its using 9 amps of current. Therefore 1 amp is not used by the resistor

You missed the point of why I got you to figure out why both meters are measuring the same current.
If BOTH meters are measuring 1 Amp, then that is telling you that 1 AMP is flowing EVERYWHERE in the circuit including through the resistor.
It is the resistor that is limiting the current flow to 1 Amp.
Halve the resistance to 5 Ohms and you will double the current to 2 Amps. Double the resistance to 20 Ohms and you will halve the current to 500 mA ( 0.5 A)

If the resistor wasn't there ( a short circuit ) across the battery and the battery was an ideal supply, the current flow would be infinite.
But the battery isn't an ideal source because it has internal resistance and this will limit the maximum short circuit current ... how much current ? ... well that will depend on the type of battery and its internal resistance
A 12V car battery, for example, can supply 100's of amps under short circuit conditions
A car starter motor can draw upwards of 800 Amps during its brief bursts of use

cheers
Dave

 

[davenn]

Once you are happy with all that, we will move on to multiple series resistors
and maybe after that parallel resistors

looking forward to your replies

cheers
Dave

 

[DruidArmy]

Okay, I see that the resistors are using all the power in that circuit. I didn't realize resistors used up that much power. It makes me wonder if you plug a radio or any other device into a 110v A/C wall socket, does it use all the power delivered to it? I was thinking that if you had resistors to drop the voltage to say 5v, that the radio would only use 5v x I of power.


So can you tell me if I plug a 60 watt bulb into a 110v outlet, does it use all the power? How about a 100 watt bulb? I'm thinking you are going to tell me they both use all the power delivered. Then does it only draw as much power as it uses?

I think I can liken the behavior of resistors, to a garden hose of water. Each resistor could be represented by holes in the garden hose. The same volume of water would be present in each section of the hose, but the pressure would drop as each series of holes was encountered.

 

[NascentOxygen]

Devices 'take' only the power they need. All the power they take, they use. Much/most of the power used ends up as heat, one way or another.

If you connect a number of resistors (or light bulbs) in series, it might appear that each is taking only a fraction of the power and passing the rest on to the next. That is a confused (and confusing) view of what's going on. Power is volts x amps, and each is using all of the power it gets, though in the case of series connections, each is getting a fraction of the applied total voltage.

 

[eng90]

I don't really know if the resistor is using 9 amps of power. It is resisting the flow of electrons, so that only 1 amp is flowing. The other 9 amps are not actually being sent out of the battery. So there is no way its wasting 9 amps. So I don't really know how much power it is using.

I think you have a decent understanding of how each of the components in the circuit work. But I think you would benefit from learning about circuit analysis. If you look online there are free lectures that you can watch and gain the same knowledge. The link below is to MIT but there are plenty more available on the web.

http://ocw.mit.edu/courses/electric...tronics-spring-2007/video-lectures/lecture-2/

 

[DruidArmy]

Thanks for the lecture link. I've watched the whole MIT series before on physics with that funny professor who has now retired. Very good lectures. I liked it when he levitated a blow up doll using a simple winding and 110v house current, using induced eddy currents. On his final lecture he attached a fire extinquisher to his tricycle and rocketed off the stage. Ha Ha.

Yes, I'm going to build some circuits (12v) and test voltages around it. I'm not sure my water hose analogy is good. Cause if i had a series of holes in it, I'm not sure if the flow (current) would be the same across all sections.

hose= --------0-------00-----000-----> the holes represent different resistances

Still trying to figure out the mechanics of what's really happening inside the wire and resistors.

 

[f95toli]

Still trying to figure out the mechanics of what's really happening inside the wire and resistors.

Don't worry about that at this stage. There is -fortunately- no need to understand the underlying physics to understand circuit theory. It is better to think about the various components as "black boxes" with some functionality.
This is even more true later on when you start working with integrated circuits such as op-amps, where you -quite literally- have no idea what is inside and you have to rely on the manufacturers datasheet to understand the properties.

Also, feel free to use the water analogy if it helps, just remember that it is only works in the very simple cases and shouldn't really be used for anything but circuits with only voltage/current sources and resistors.