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Circuit JS?
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His circuit simulator got me through my electronics courses. It's better than any commercial simulator I've used.
Hijacking the top thread to post the best circuit tutorial I know
I am a chemist now being offered EE jobs because I played with this app a lot as a 20 year old. Thank you mr. Falstad, you helped make my future.
a resistor and a pin can drive an analog meter. can add buttons, rotary encoders, can drive a $4 lcd. switch things on/off with a mosfet/relay. detect the sun or dark, control $2 servos. i use my microntrollers to make meters and datalogging for rf.
edit:
Most of the crap I build, I don't even need to get out of my chair to get the parts for. A resistor and capacitor pack at radio shack and a misc assortment of common items and you're pretty much set. Buy a bin like this, organize your caps/resistors into it, throw some transistors, buttons, connectors in and you're set.. Majority of my time building is spent finding the right sized resistor fwiw.
This java electronic simulator {there's a java warning} is a valuable tool for testing out ideas on what to hook up to your GPIO. It's not full fledged like SPICE which is ridiculously complicated and time consuming to do anything, but it's a good compromise and especially easy to use to build some circuits (SPICE simulates wire gauge, distance to other wires, etc, which is good for high frequency stuff but we'll use low frequency or short-connections to avoid having to worry about this). The examples cover most things...
Nope. The capacitors are overwhelmingly biased in the correct polarity in this diagram. If you follow their negative terminals, it's almost a straight path to ground through the base-emitter of a transistor. They're positively charged while the LED is off, and discharged a bit while it's on.
Also, the two middle resistors should be connected to the top branches of the X, which makes the same circuit but more readable.
Like this: http://i.imgur.com/uVnb1.gif
Falstad emulation. Requires Java. I've changed the cap values to 1µf so it simulates faster. If you hover your mouse over the scope, you'll see the cap's voltage ramp between 2.9 and 7 volts.
EDIT: Emitter, not collector. Added modified image. Added simulation. I tend to edit a lot.
11 transistors for a simple XOR? You can do that with just 2 transistors, Falstad link.
The current doesn't only flow on the path of least resistance, rather it flows proportionally. That is, 10x current will flow through a 10ohm resistor compared to a 100ohm resistor.
Play around with this circuit simulator to visualize this
Ok, so, if you don't understand a little bit of transmission line theory, and you're trying to do really fast serial communications, it's going to bite you in the ass.
What you need to do is use cabling and connectors that maintain a constant characteristic impedance. You need to terminate them properly; this is part of what impedance matching means. For slower stuff (<50 MHz digital), you may be able to get away with just making all of your wires really short (a small fraction of 1/4 of a wavelength), but watch out for skew.
I did notice that you've got 75 Ω resistors. Depending on what sort of cabling you're using, this may be fine, or completely wrong. Different cables have different characteristic impedances. For example, CAT5 is 100 Ω, test equipment coax is usually 50 Ω, and TV/pro-AV stuff is usually 75 Ω. As I mentioned above, your connectors need to maintain the characteristic impedance of the cable, or you'll get all sorts of nastiness.
If you are a visual person, this may help you understand what's going on.
1: Paul Falstads Circuit Simulator. I taught myself basic and advanced electronics with this tool. Advantage: Runs interactively, i.e. you can modify stuff while simulating. Has ideal models of everything you need. No installation, runs in the browser. You can share circuits by generating a (very long) link.
2: LTspice. Takes a while until you get the hang of it. Advantage: much faster, allows much more advanced maths (both in simulation and in plotting), can use models of real devices.
You post in /r/Arduino - do you want to co-simulate your Arduino code and analog/digital peripherals? I don't know if there is a tool to do that.
If it's no knowledge at all, search around on the internet and figure out what the individual components (Resistors, capacitors, transistors, diodes, etc.) do, and try and 'analyze' some simple circuits and see if you can figure out why they work.
A lot of it is just experimenting and seeing what happens. There's wonderful simulation tools like Multisim or Falstad.
As for using that knowledge to make synths, Music From Outer Space and the circuits on that website helped me a ton! Just look around on it.
As for this build in specific, it didn't actually require that much electronics knowledge! Most of the work was already done because I bought the premade Doepfer DIY board. The reason I did this is because it's my first, and I really had no idea what to do. After being done with this, I feel like I'm more ready to make stuff from scratch and begin making my own modular :)
I don't know if this helped that much, feel free to ask more if you want to :)
I'd use a N-FET low-side switch and have the slide switch pull up the gate to 5V. Add a pull-down resistor and an electrolytic cap to the gate and choose the values of the resistor and cap so it stays on for another 10 secs or so after the switch is turned off.
You can then use the other switch contact (assuming it's an SPDT switch) to signal to the PI that it needs to shut down via one of the GPIO pins. I suppose a voltage divider between the switch and the GPIO pin of the Pi would be enough to bring the voltage down to 3.3V.
That's 5 components, or maybe 6 if you want to add a resistor to limit the inrush current of the electrolytic on the gate.
edit: simulation
The cap would probably have to be closer to 470µF in the real circuit, and you could also add an optocoupler between +5V and the MOSFET gate to allow the Pi to keep the gate pulled up via another IO pin until the shutdown has completed.
Hey, if we're going to list competitors, let's at least link to the good competitors! :-)
LTspice has a much larger symbol library than iCircuit.
Paul Falstad's Circuit Applet has a few less symbols but is the basis for iCircuit and is free
OrCAD Demo Pretty much the standard for circuit simulation, and it's free for small designs.
Here's an simulation showing where current is flowing in the oscillator (you can change the values). The capacitors determine the time the oscillator is on or off because they react in a time-dependent manner to the change in voltage. A larger cap will take longer to charge up, thus giving the oscillator a longer period on that side. Try using different cap values and see what happens (or just put two in parallel to double the capacitance).
To the people saying it's shorted, here's a diagram showing that if the resistance on the "short" is greater than or equal to the resistance through the LED, it'll still light up. I'm not saying 100% this is real, but it's definitely not impossible to replicate with conductive ink and LEDs.
Edit: I forgot to mention this, but you just need to click the open switch to see the circuit work.
Go to google and look up some mosfet schematic examples, then use an online circuit simulator to get some practice before taking it to the hardware. Here’s a like to a circuit simulator I use from time to time: http://www.falstad.com/circuit/
I'll give it a shot.
In a capacitor rapidly changing voltage passes through easily while DC is blocked. In real capacitors a small amount of DC will pass through, this is called leakage current.
Our skin protects us from DC up to a point, think of a 100kOhm resistor in parallel with the capacitor. Any DC must pass through that 100kOhms. The capacitive property of our body lets AC will pass through, bypassing that resistor.
This is a simulated circuit demonstrating the effect.
I pulled the values out of thin air, but it is roughly representative of a body. Think of the 100kOhm resistor as our skin, the 1uF capacitor as the capacitance of our body and the 1k resistor as our vulnerable internal organs.
Use the switch to go between voltage sources, both are 24V, but the top is AC oscillating at 60hz and the bottom is DC. Watch the current on the left side after the 1k resistor, that is the current going through the vital organs. When it is on DC it is just a few hundred microamps, but on AC it is peaking over 8mA.
If you want to learn the material: go through all the notes and make sure you understand every single derivation to the point where you have no doubts about any of the steps, no matter how small.
If you want to get a decent grade on the final: grind through every question on the practice exams over and over again until you don't even think about them anymore because you're just writing all the steps from memory. If you have time after that, then do the same for homework or in-class examples.
Those two options are independent. You can choose one, both, or none.
In terms of resources... Generally, the problems you'll find (except for circuits) are fairly standard, and you'll be able to find derivations of answers just by Googling the question with quotations around the most important words. For checking your answers for circuits (or investigating certain parts of them), use an online simulator.
This is the "correct" way to approach this, but for a hack like this, trying this simple analog circuit would be worth it IMO: https://i.imgur.com/GBxy0bh.png, assuming 5 V logic, with >2.5 V digital 1, and < 2.5 V digital 0. Check for yourself that it's not 3.3 V logic. try it here
After 17 ms, the test point node is < 2.5 V so it should register as a 17 ms pulse. You might need to slightly tweak the value of the 24k resistor.
If you don't need high precision you can always use a simple diode DC restoration and a voltage divider.
You can choose the capacitor value depending on your input signal frequency, the 1.2k resistor value affects the "0V" offset of the output, you can tweak it to achieve proper 0V with your designated signal.
If you want full amplitude on the input, just skip the voltage divider (replace with a single eg. 22k resistor and take the output of off the capacitor diode node.
Simulate it with something like this: http://www.falstad.com/circuit/
It's a great way to see the flow of current.
For the microphone try this model: https://www.circuitlab.com/circuit/w88e3e/jfet-based-electret-microphone-amplifier/
Or simply see what happens when you inject a voltage change where the microphone meets C1.
parallel diodes can act as analogue selector of the greatest V input if in common cathode (or the smallest in common anode).
https://gyazo.com/8109228bd170968a671f461679ba50e3
This can be used to build functions (linearize sensors):
https://gyazo.com/88afc14b17270f8959e765c7ab76d0ad
Go test some circuits yourself here:
Voltage divider, with a buffer if you think it's necessary.
Consider also the useful range of measurement, a car battery at 9v is dead so do you really care if it's lower that that, probably not, so use a differential amp (voltage subtractor) to remove that 9v before you divide it down otherwise you are throwing away most of your range.
Example in Falstad you'd probably want a better reference than a power sucking zener, but anyway. With a battery of 14.5v your output to the ADC is 3.3v, with a battery of 9v your output to the ADC is 0v.
Well, kinda. According to that page:
> Javascript version, posted 6/9/15. Huge thanks to Iain Sharp for the Javascript port. You can still use the original Java version.
Paul Falstad wrote the original Java version, and Iain Sharp (from <http://lushprojects.com/>, the site linked by OP) ported it to JavaScript. So, it's fair to say CircuitJS is originally from both sites, instead of only one.
^(Footnote: I just wanted to be informative, no offense intended!)
I love this one: http://www.falstad.com/circuit/
It's online and Java so you can use it from anywhere. It includes lots of sample circuits. It is also fairly accurate. I use it before breadboarding circuits to do some fine-tuning.
Can't agree more with allaboutcircuits.com, but don't get bogged down in a full-on SPICE. This is much quicker to get into and shows the basics better IMHO: http://www.falstad.com/circuit/ (warning, app is a java popup)
A MOSFET is the best bet here, because it doesn't draw any measurable current from the line being monitored. So... a MOSFET acting as a low-side switch, switching an LED on or off.
"File/Import" this into Falstad Circuit Sim:
$ 1 5.0E-6 10.20027730826997 50 5.0 50 172 112 208 112 176 0 6 3.1 5.0 0.0 0.0 0.5 Pin voltage 162 400 80 400 128 1 2.1024259 1.0 0.0 0.0 r 400 128 400 192 0 150.0 f 336 208 400 208 0 1.5 w 400 224 400 256 0 r 336 208 336 256 0 1000000.0 w 336 256 400 256 0 w 336 208 112 208 0 x 72 119 179 157 0 24 Pin to be\nmonitored g 400 256 400 272 0 R 400 80 400 48 0 0 40.0 5.0 0.0 0.0 0.5
The "Pin voltage" slider on the right controls the voltage coming out of the pin. Notice that the LED is off when the voltage is below 2V, and is on when the voltage is above 2.5V. In reality there will be some deviation from those voltages, due to the actual MOSFET you use having a slightly different "Vth" value. (Voltage where it begins to allow current to flow.) But even so, < 1V should be fully off and > 3V should be fully on.
You can use just about any MOSFET, but the easiest one to get will be a big honking power MOSFET:
http://www.radioshack.com/product/index.jsp?productId=2062618
This is way more transistor than this simple circuit could ever possibly need, but it will work fine and it's cheap, so why not.
Don't forget the 1 megaohm resistor between the MOSFET's gate and ground. The MOSFET may not turn the LED off correctly if you leave that out.
A typical red or green LED with a 5V power supply will be fine with a 150 ohm resistor, as shown. If you use a different LED (blue or white), you may need to change the resistor.
If you don't need high precision you can always use a simple diode DC restoration and a voltage divider.
You can choose the capacitor value depending on your input signal frequency, the 1.2k resistor value affects the "0V" offset of the output, you can tweak it to achieve proper 0V with your designated signal.
If you want full amplitude on the input, just skip the voltage divider (replace with a single eg. 22k resistor and take the output of off the capacitor diode node.
This is pretty good for trying stuff out. Note that you should not rely on it for testing exactly how something will work - as with any simulator, it will not behave exactly like the real thing - but it'll let you see in "slow motion" how circuits you draw behave.
The simulator you refer looks quite visual so here are some interactive simulators. I've never really used them, and I'm not sure of their price but check for yourself :)
http://www.partsim.com
https://www.circuitlab.com
http://www.falstad.com/circuit/
As already said, LTspice is an often used SPICE simulator made by LT. It might be a bit more abstract but I think it's the best free simulator available.
Use the resistance as half of a voltage divider to convert the resistance at empty to a voltage at empty. Then you can use a schmitt trigger to read the voltage and power the light. Like this (use the resistance slider on the right to adjust the resistance).
A schmitt trigger is great for this kind of application because it has a different "on" voltage than "off" voltage, so the light won't flicker when the fuel level is near the empty line.
You will need to choose the resistors in your voltage divider carefully to match the values the schmitt trigger expects.
You got it!
Just FYI, I'm about 99.99% sure it doesn't matter whether the resistors sit between the positive pins and the bus or the negative pins and the bus. I'm even 95% sure you can mix it up (some have the resistor on +, some have the resistor on -) and it will still work as designed.
Check out this example I mocked up in Falstad's circuit simulator. It uses capacitors instead of batteries, but the same principle applies.
When the simulation starts, both capacitors are charged (one to 16.8V, the other to 14V). When you click on the two switches, it disconnects the power source and connects the two capacitors together. The voltages then equalize gradually, even though the two capacitors have the resistor on the opposite terminal.
So you wanna be a cyberpunk eh?
You will get differing opinions here about what cyberpunk is.
Personally I feel it's more than just a look, it's an understanding of the tech. Making something yourself from whatever you may have lying around is kinda cyberpunk. /u/sexycyborg has some great examples, not only do they look fantastic but she made them herself.
If you wanna have something a bit more practical I recommend learning about electronics both digital and analog. There is a good cicruit sim here. I reccomend you learn and practice then make something that suits you.
Try to avoid anything that is a mass made high tech product, you learn nothing from them and they will more likely be a security risk.
If you are trying to make a 'universal 5V limiter' I believe a zener diode is the magic bullet you are looking for. Take a look at an example here: http://www.falstad.com/circuit/. (select Circuits>Diodes>Zener diodes>Voltage Reference)
Edit: Because reasons.
http://www.falstad.com/circuit/ is a great circuit simulator. It's not as powerful as the Spice variants, but it's much better at demonstrating concepts. http://www.falstad.com/circuit/e-index.html has explanations of all the example circuits.
http://www.adafruit.com/tutorials is also a good resource.
I'd suggest starting with one of the old Electronic Project Labs, if you can afford it. It covers both analog and digital electronics in pretty good detail. Plus, it gives good descriptions of simple circuits which you can then google for more information.
The problem is that it doesn't have a great deal of practical knowledge about designing circuits (no discussion of why bypass capacitors and the like are important). It also doesn't cover anything mechanical, and if you're looking into robotics, you probably want an understanding of motor controllers.
For making robots, you'll also want to learn about microcontrollers and how to use them. As much as I hate to say it, Arduinos are probably your best option here. They'll get you going with minimal configuration and hardware design, but they're not cheap. If and when you graduate from them, look into Atmel's AVR line, as they're nicer to program than Microchip's PICs.
One thing about typing part numbers into Google: append "filetype:pdf" to get datasheets instead of sites pretending to have datasheets. Datasheets are your friends; learn how to read them.
Above all else, I've found that it is most useful to have an intuitive understanding of what's going on in a circuit in terms of current and voltage. If you don't already have this intuition, look at the hydraulic analogy, which relates electrical current and voltage to fluid flow rates and pressures. Edit: If you're a visual person, check out this circuit simulator applet. Just don't try to simulate anything terribly complex; it sometimes blows up when you play with transistors.
Depends how good of an op-amp you want. Very basic working opamp can be made using 3 transistors with support for basically all topologies. If you don't mind limited topology support (very low non-inverting input resistance, low differential gain etc), then you can make an extremely crude opamp using just one transistor.
> I want to see when the switch cuts off in the fastest way possible
You can't get any faster than a single transistor. Connect the switch output to the base of an NPN transistor through a 1K resistor. Pull collector high to a second 5V source, separate from the original voltage source. Connect emitter to ground. The desired output is at the collector, will be high when switch is turned off, low otherwise.
Total time from switch cutoff to output going high will be Fall Time + Storage Time parameters given in the transistor datasheet. For 2N3904 it will be 50ns + 250ns = 300ns.
https://en.wikipedia.org/wiki/Hydraulic_analogy is enough for your first six months or so. It's a long way from perfect, and you'll have to abandon it at some point. But for just starting out and understanding the barest basics, it's fairly good.
> why in a parallel circuit the voltage is the same
Why is the pressure the same inside two pipes that are both attached to the outlet of a single pump?
> why a resistance can change the voltage in a point of the circuit
Why does water only dribble out of a pipe filled with gravel, but gush out of a pipe whose inside is clean?
Visualizing the flow of current as if it were water, can sometimes makes these things more intuitive...
A simulator is a good idea too. I wouldn't use LTSpice, though. Or any SPICE. Try http://www.falstad.com/circuit/. It's not perfect, and you can't even trust its results 100% of the time. But as a visualization tool it's fantastic.
So you have a mechanical switch you're sampling once per day?
Use a zener to clamp the ESD, and throw a super low pass filter on it: For example
You'd take your measurement across the cap.
That's called a "decade counter".
Short answer: The negative output of the bridge rectifier is not referenced to the point you labeled ground--they have an AC voltage difference between them. You measured the average of this AC voltage.
Here is a simulation of your circuit
On the left is your half-wave ground-referenced rectifier. On the right is your floating full-wave rectifier and the input capacitor to the buck converter. At the bottom is a scope connected where your multimeter read 23VDC--it was giving you the average of a sine wave spanning 3 to 37 volts.
Wow that site is actually pretty cool, I made demonstration of what I think he is trying to do: here
Please start here: https://us.reddit.com/r/AskElectronics/wiki/beginners
https://www.reddit.com/r/AskElectronics/wiki/education
> software that lets me "emulate"
>And then, this just occured to me, but there must be software for playing with circuits virtually yeah?
Yeah! A beginner friendly one is this simulator at falstad.com.
You can click through the example circuits, mess with them and see what's going on with each component. It's faster than swapping components on a breadboard and gives you a lot of info/feedback without needing to own/learn a 'scop.
This simulator was recommended on reddit in one of the electronics subs
http://www.falstad.com/circuit/circuitjs.html
Simulators are often not that accurate or can't understand certain things, so sometimes they will not be able to simulate a circuit that works perfectly, but they are a fun way to try out schematics you'll find online, and adapt them.
When you start experimenting, the module tester is a great help:
http://www.amazingsynth.com/module-tester-pcb/
also the breadboard friends
If you'd like a really beginners simulator, use the online circuit simulator. If you need anything better yet simple, i have used LT spice IV
If you are running this right off the GPIO pin then you need a resistor. Those pins are 3.3v.
Also be mindful of Amp limits on those pins. It's something like 15-20mA per pin and 50mA total.
If you are running many LEDs you may need to use a transistor to power them off the 5v rail. Though there may be an IC or something to help with powering many LEDs.
Depending on your needs, falstad circuit simulator does wonders for visualizing circuits. If you're looking to incorporate some common IC's it's probably not the best tool to use.
Okay, so you think that what you're doing is this.
What you're actually doing is this.
Are your oscilloscope and signal generator plugged into the same power strip? If so, they're grounded together, even if that ground isn't connected to earth. This is why most power supplies put the bridge rectifier after an isolation transformer like so.
Simulated. Note the importance of the blocking diodes.
The circuit you want to use is this. To make it work on one battery you'll need to use inverters that work down to 1V e.g. these and a mosfet with a threshold voltage low enough to be fully on at 1.1V, e.g. this one.
There's no way you're going to fit something in that space with through-hole components.
Hey man, good work. Using the current divider rule here is the correct way to go about it. I imagine you've got the right answer there judging by the description of your process.
Check out this circuit simulator applet, it's super handy to check your answers on questions like this.
Edit: Removed answers. Will post when OP shows his.
You mean something like this?
Yep. College. So much theory, no practice. Get thee to a makerspace.
Pick up some 7400 family logic and some buttons and leds. The pick one and make it. Don't worry about blowing it up. In fact buy a few to blow up so you are comfortable working with them. Play with this site too. http://www.falstad.com/circuit/
Happy hacking
Have you tried looking at this applet? It gives a very easy to understand visual representation of current flow in various circuits and you can even build your own!
EDIT: Here is an excellent one showing a simple common-emitter amplifier.
Imagine you want to turn a light on or off. You can take your hand and flip the switch between on and off and allow current to pass through or not. Now imagine you hook up a motor so that if you pass current through the motor one way it flips the switch up (on) and current passes through, and if you put current through the motor the other way, it flips the switch down (off) and current ceases to go to the light. Now you have a very complicated but effective electrical switching system.
What we realized (first with vacuum tubes, and then later with transistors) is that you can construct much much simpler switches where you have a voltage difference across two points, and then a third input voltage that allows the current to either go or not go.
Specifically, you can build AND and NOT switches: Suppose there's a voltage difference across points A and C, let's call C the low voltage, A the high, and B is your input voltage. One type says "if the voltage on B is high, then the current will be equal to the currents through A and B through, but if B is low, then no current passes through C (or very minimal current does at least)." This is AND. The other says "if B is high, then no current passes through C, and if B is low then the current going to C is the current from A to C." This is NOT.
For more I recommend this applet and this game
http://www.falstad.com/circuit/
this is great for understanding how everything works in detail, just browse through it and play with it.
There's also some things there that may be an inspiration for first basic projects (like led flasher).
Also http://en.wikipedia.org/wiki/Arduino may be good for you if you know any programming language. It's a good way to test your ideas before making proper board.
I discovered Falstad's simulator in high school. I've spent a few years playing around with it and using it to check my homework. It's helped a lot. I'm not an EE but circuits still seem very intuitive to me and I'm sure it's because of how much time I've spent there.
If it's just cosmetic you can bypass the LED with a resistor so that there's not enough of a voltage rise across it to turn on when the voltage is low. If it's important in some way you'll need to more seriously consider that as a requirement when designing your circuit.
Others have given you very good answers already but here's a visual demonstration of what people mean when they say your transistor will behave like a diode. Without that resistor you'd effectively be shorting the micro controller pin to ground. I actually had to put a small amount of resistance there otherwise the simulator would stop because there'd need to be infinite current.
Here is an example of a circuit which actually has a pulldown resistor. So you can see what that does.
Falstad's circuitjs is a super basic in-browser simulator with almost zero barrier to entry - but it's also quite easy to confuse.
LTSpice is a (free) rather better simulator with a horrendous UI - Windows exe, but works great in wine too.
https://www.allaboutcircuits.com/textbook/
They also have video lectures.
This might be useful for helping visualize what current is doing in a circuit. Can also be used to check dc homework problems http://www.falstad.com/circuit/circuitjs.html
Khan academy also has some circuits content that is decent.
Power supply, resistors, capacitors, inductors, solderless breadboard, gaussmeter, signal generator, multimeter, impedance analyzer, oscilloscope, vector network analyzer, spools of wire, steel laminations, soldering iron and solder, laser cutter, etc. Build whatever you are asked about and measure it.
I'm mostly joking, but if you had time, it might actually be useful to check your work on some resistor network problem by building it and testing it, and resistors are dirt cheap.
There are also free circuit simulators that are pretty easy to use for similar checking of your circuit analysis work. http://www.falstad.com/circuit/ is the most basic intro-level one.
You're looking for something in this ballpark. Another commenter posted a commercial solution (it's almost like other people have the same problem as you :D) but if you're intent on DIYing it that would be the trick.
Note that I may be totally wrong about the nature of your input current and simply loading it with a current sense resistor to convert it into a voltage might not be correct.
Also note the huge power dissipation through the power BJT. You will almost certainly need some pretty good heatsinking, depending of course on how much voltage drops across the valve.
Also note the huge burden voltage in the output current sense resistor, which may require tweaking resistor values depending on how much headroom the valve needs to see.
Note that if you tweak resistor values to the point where your current sense voltages end up very low, the specs of the op amp become more important. Rail-to-rail input, low offset voltage, and low noise for starters. The op amp may require compensation that requires additional components in the feedback loop.
Attach the computer reset to the button via a pulse generator (555 or RC), also attach the button directly to a GPIO line.
Ah ok, you made it sound like you had a very specific application in your OP (your counter doesn't have a strong enough output driver).
If what you're asking is:
> Is there any way to apply a single voltage to the top of multiple strings of LEDs, and still control them individually, with no other components?
In general, no. In pure theory, maybe? If you don't count resistors, and for some level of "control". I was experimenting with falstad, trying to get it to work with some sort of resistive / diode ladder and a current source but it doesn't quite work the way you want.
Practically speaking you just get four mosfets, one for each string of LEDs, and control them individually. Analog circuits are quite a bit tougher :p
Here is a way to test your answers.
You should find that your answers for i), iii) and v) are correct but the other two are wrong - double-check your application of Kirchoff's laws.
It's a good one.
I've done all of the analog exercises/labs and half of the digital ones. It's really done a fantastic job of filling in all the major gaps in my electronics knowledge and given me an opportunity to practice what I've learned.
As an aside, if you're not familiar with circuit design simulators, I've found this one on the web very good: http://www.falstad.com/circuit/circuitjs.html
It's helped me visualize a lot of analog circuits before trying to wire them up.
The heart of many oscillator designs is an LC tank circuit which is an inductor in paralell with a capacitor. In a tank, one plate of the capacitor charges up to the supply voltage until the voltage over the capacitor equals the supply. Then, once disconnected, the capacitor begins to discharge into the inductor. The inductor however does not like a change in current flow so it begins to store energy in its magnetic field. Once the capacitor is fully discharged (and therefore not supplying current to the inductor) the inductor begins to compress its magnetic field to induce a flow of charge through it since it does not like a change in current. This then charges up the other plate of the capacitor until it is fully charged and then discharges the other way into the inductor thus creating oscillations.
This is the basics of how an oscillator works but in reality you must have some sort of feedback network to sustain oscillations due to losses. Typically the tank circuit will no longer be a single inductor and single capacitor but instead 2 caps and an inductor (Colpitts Oscillator), 2 inductors and one cap (Hartley Oscillator), 3 capacitors and one inductor (Clapp Oscillator), and many more varieties. The reason for these added components is to create a voltage divider and a means for a feedback path with a transistor amplifier.
Here is a simple JFET Colpitts oscillator. Here we can see that the feedback is along the tapped capacitor and the source resistor forces Vgs to 0 thus putting the JFET in the 'on' position. You could try building the circuit here as well.
I hope this helps, let me know if you have any other questions.
if you are trying to do something with the signal like drive a motor, you need an active filter. if you are just measuring the output to show you can, passive is fine.
10x cut off frequency should be fine if you are just showing that you can. you can play with http://www.falstad.com/circuit/ to make the signal look like you want
A coil or any inductive load resists changes in current. If your SSR turns off suddenly and no current is flowing through the SSR, but current continues to flow through the coil, that will create a large voltage differential.
Think of water flowing through a turbine generator at a high rate of speed. Now if someone suddenly closes a valve to cut the flow of water, the turbine will start acting like a pump and continue to move water from the inlet to the outlet. The pressure behind the turbine will rise rapidly, and it's going to drop just as rapidly at the inlet, and that pressure spike may destroy the valves and/or pipes.
In this analogy the coil is the turbine and the transistor is the valve.
Here is how that looks in a simulation (use the switch at the bottom).
And it's this very effect that allows the ignition to work in the first place. With just a 12V supply you can get inductive voltage spikes of several thousand volts.
>I think I may be thinking of electron flow improperly or something simple like that. I just can't seem to wrap my head around where the electrons are going and why they don't go some ways or do go other ways. I'm very visual
I have the perfect site for you:
http://www.falstad.com/circuit/
Go through the example circuits and figure out how they work.
You can build things there too, but the build tools are a little clunky. You get used to them after a while.
Edit: There's even a visual simulation in the examples of 555 internals. It's like this site was made for you.
R4 is not shorted because the node at the top right of the diagram and the node on the bottom of the diagram are not the same. To help you visualize this, I've assembled your exact circuit in Falstad's simulator here: Circuit
In fact, R4 and R3 are in parallel, R1 and R2 are also in parallel.
Have you tried falstad's circuit simulator? While no replacement for real calculations/functional testing, it's fun and intuitive to play around with the circuit and get you in the right ballpark with values. A 555 timer oscillator should be a pre-made circuit option in the 'circuits' menu.
What everyone gave you is an example of something that can achieve similar results. There is no inverse of a BJT. The only inverse is the direction the currents go (NPN vs PNP). It will always require a little current one way to enable more current in another path.
A MOSFET is a voltage controlled device. A change in voltage turns the channel off or on. Changing the voltage will consume current as it acts like a capacitor. But the current input does not directly control the current output. The current input changes the voltage which affects the output.
Also, an inverter with a BJT is biasing the BJT so that when there is no current being input, current from the power supply is turning on the BJT. When you apply current to the input, you redirect that power supply bias current so it flows into/out of the inverter instead of the BJT, effectively turning it off. This is easily achieved with two BJTs. Here's a simple example (probably not the best biasing, but it gets the point across. Click on the H/L to change betwen current input on and current input off) Example BJT Inverter.
Just finished a basic circuits class. The thing I had most trouble with was capacitors and inductors in a circuit. Your best bet would be to just play around with some basic circuits in a circuit simulator. Look at how voltage division, current division work. Behavior of capacitors and inductors with respect to time etc. http://www.falstad.com/circuit/ This simulator is amazing for just basic understanding of circuits and easy to work with.
What you're probing is the voltage over the resistor, which is determined by the current flowing through it. Since there is no current flowing out, there is no voltage over it. Add a ground to the second terminal of the output resistor to see the triangle/square wave.
Working circuit: LINK
You could store more data per digit, but you'd need much more complicated circuitry to handle ternary logic, so you need more transistors per digit. This is a binary inverter (NOT gate). This is a ternary inverter. The ternary version has twice as many transistors.
There have been a few examples of ternary computers built, but nowadays it's extremaly rare to see anything other than binary used.
This. ~~Use a Rail-to-Rail opamp with enough output current capabilit and you con't even need a negative supply.~~ Most regular opamps will allow their output to go only as low as ~1.5V (above GND/Vee), but if you use a pass transistor and add a LED (or other way to drop the excessive opamp output voltage) between the opamp output and the pass transistor input, you can use any old opamp, even a not rail-to-rail.
Here's a link to a simulation of a possible application of a jelly-bean opamp driving a jelly-bean transistor through a jelly-bean LED.
Don't forget to apply capacitors to the input voltages.
You might want to give this a try:
http://www.falstad.com/circuit/
But seriously, learning how to read the graphs produced by LT Spice will tell you a lot more about what is going on in your circuits than the animations in the Falstad simulator.
Current always flows in loops. We call them circuits for a reason. When the diode is reverse-biased, the loop is blocked and so no current flows at all. This might help visualize what's happening.
It is a Java circuit simulator I like as you can quickly set things up and get a rough idea of what should happen. I have some doubts as to the numerical accuracy, but in my experience it has been "close enough" for simple circuits.
A diode and transformer would make sense. It could be a voltage amplifier if the cellphone battery isn't sufficient. If it's hooked up to the vibrator, then you have a rapidly square wave signal. That'll create a huge voltage spike in both directions if it's fed into a transformer, the diode allows it to charge the capacitor until it reaches the necessary voltage.
That was my first thought. Here is a thrown-together solution that uses a non-inverting summer.
Using the branch (another country so we might call it differently) method.
You can tell, by the current sources right away, that the current on the left branch is 10 A and going upwards. On the right side it is 15 A and downwards. Now look at the nodes. Draw them. Think of water hoses. On the top, the right (upwards) current goes into the left (downwards). 10 A go in, 15 A come out. Where did those extra 5 ampere come from? From the middle branch. So the middle branch has 5 A and is going upwards. In math talk it would be I1(left side current)+I2=I13(right side current)
Now we invoke Kirchhoff on the left hand circuit and we get +V[A]+2*5-12-6=0 V[A] = -10+12+6 V[A] = 8 (V)
Here is a pic of a software running the simulation to ensure that it is 8V. I really reccomend you using this app it will help you understand and verify your results.
Have fun!
Yeah, I love that app.
You can even export a link to a circuit. Check out this. Drag the Voltage slider to see the LEDs change.
A introduction into binary logic (truth tables, boolean login, simple circuit diagrams) would improve your understanding more.
This site has a nifty applet with some basic digital circuits where you can actually see what's happening with simple counters/adders and such.
I believe the solution to your problem would be trivial if I understood your setup better. As I understand it, you have a power supply, followed by a resistor, then three paralleled variable resistors, but after that your description is a bit murky. Are the LED's in series after their variable resistors? What do you mean when you say "turn the 3rd one on"? Is there a switch involved in this circuit? Are you saying that as one branch increases brightness, the rest decrease?
http://www.falstad.com/circuit/ is a great online simplified circuit simulator- play around with it a bit and chances are you'll find what you're looking for. Otherwise, mock up the circuit there and show us what exactly we're dealing with- it will make diagnosing the problem much easier.
This isn't really so much a source of information as a tool, but I feel like this java applet helped me understand some electronics components better. I especially liked it for things I'm curious about, like working with AC power, but which I have no desire to play with in person. And if you're into it, it has components like memristors the general public doesn't get to play with (although they seem to be heading down the pipeline lately). Of course, it does seem to let me get away with some things that would be a bad idea in real life, like hooking up an LED to large voltages with no resistor. But I feel like it really shines in giving you an idea what diodes/capacitors/etc will do in a circuit.
If you want to see an Arduino in a circuit simulated, this appears to do that, but I haven't tried it. It appears there are slight differences between the code for the physical arduino and this program's code, namely to do with how it handles typing. It's Windows only at the moment.
I tried that breadboard simulator and the very first chip I installed (the 74393) is mislabelled on pins 4 and 12. Not a good omen.
While this isn't a breadboard simulator, it's a pretty darn good circuit simulator: http://www.falstad.com/circuit/
i am using H(5V from arduino) or L(Ground for arduino)
This is just like using a digital output on arduino and setting it to HIGH(5V) or LOW(grnd)
The no compromises solution is to use both of the switch contacts and positive feedback debouncing, so you latch into the correct state on the first edge. link
Simulating it says that the LED drops 1.4V with a 10k resistor. Where did you measure the 4V?
I don't know how you wired the circuit board but in the simulator you need to swap the collector and emitter of bottom NPN transistor, I did a few changes.
That pulldown resistor is needed just to make PNP transistor conduct, it's enough if you have a current around 1mA. if you replace it with a 10 ohm resistor, depending on the hfe of transistor, resistor will draw ~2A! ohm's law...
Do the changes and also measure how much current goes to the motor white wire.
Is this circuit what you looking for?
It looks like the Q2 is slowly turned on as C1 is charged giving the soft flash effect.
Try this circuit with a mosfet. Need to elevate the source pin of the mosfet to (4V - Vth). E.g. if Vth of your mosfet is 3.3V then add one diode between the source and the ground. Make sure the diode can handle the current.