Project Summer - Page 1
Forum section: electronics / beginners

author: disco221
author_rank: Newbie
timestamp: April 28, 2022, 10:27:07 am
content: Hello all, I am student in my second year of studying electronics at my local uni. I don't think this summer I will manage to get an internship, so I would like to focus on projects. Specifically hardware projects, my dream position is to work in the analog ic domain. I am blessed enough to have enough money to buy an osciloscope+signal generator, and a dc power supply. I want to build all sort of circuits, analyze them, see the simulations in orcad, see the signals on the scope. How do I get about doing that ? The domain is pretty extensive, so I was thinking that I am going to need some books ? I was thinking about electronic devices by thomas l floyd for the components. On what type of projects should I focus ?Thank you for the attention!

author: Zero999
author_rank: Super Contributor
timestamp: April 28, 2022, 03:15:29 pm
content: How about a signal generator? You could go old school with an all analogue design, or use a microcontroller and get some experience with digital and programming.Various application notes can be found for free.

author: rstofer
author_rank: Super Contributor
timestamp: April 28, 2022, 03:33:05 pm
content: My only interest in analog circuits is for analog computing. It's pretty amazing what you can simulate with an op amp, resistor and capacitor.You can build a decent analog computer with just a few dozen parts:http://www.analogmuseum.org/english/homebrew/vogel/It only takes 2 integrators to simulate most equations of motion plus a couple of op amps for summers and such. The Vogel machine is entirely adequate. Damped harmonic motion is my favorite because we spent a lot of time trying to solve it analytically in school.You can also build up the integrators and summers with LTspice and get nice results. If you have MATLAB and Simulink, you can do a great job with no parts.You could also do some research on Lord Kelvin and his contributions to analog computing as well as the tide prediction computer. His solution based on putting the highest derivative (with the constants divided out) on the left side of the '=' sign and everything else on the right side is the basis of all analog computing. The '=' sign is magic! We start by assuming we have the highest derivative and integrate to get the lesser derivatives and then do some arithmetic to form the right hand side and feed it back to the input. Magic!

author: disco221
author_rank: Newbie
timestamp: April 29, 2022, 05:25:58 pm
content: I have never heard about the analog computer sounds really interesting, that is something that I will work on.. I was thinking about the same thing about OpAmps in LtSpice, it would be one of the things that I would be interested in doing, design op amps and then simulating them in LtSpice, then maybe seeing them irl. Is this something I should focus on ? If yes can you recommend me some resources, like maybe books ? or this is a too complex topic too start on ?

author: disco221
author_rank: Newbie
timestamp: April 29, 2022, 05:37:32 pm
content: A signal generator sounds like a really good idea. I was thinking to start with a small circuit, and then maybe really build like a full function generator. Thank you for the idea!

author: tepalia02
author_rank: Regular Contributor
timestamp: May 01, 2022, 10:49:42 am
content: You can try making a signal generator without any microcontroller. Using OMAMPs and other components only. You can try OPAMP based audio amplifiers also. Those are small and easy.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 01, 2022, 12:11:43 pm
content: Almost any (especially analog) piece of electronic equipment uses opamps, and there are thousands of variants, and that is because they all have non ideal properties. Building circuits on a breadboard to study the non ideal properties of different opamps is a hands-on way to learn more about electronics.Control theory and getting control loops stable is also an important skill.Working with spice simulators and designing PCB's are other relevant and important skills.I always find power supplies fascinating.First, they look deceptively simple. Some reference, potentiometer or DAC, then a few opamps and transistors. But if you design a power supply all parts have to work in harmony with each other, control loops have to be stable, etc.And when you've designed and build it, you have a useful piece of equipment for your lab.If you're into audio, designing and building a power amplifier could be interesting.Even if your main interest are in analog electronics, getting to know microcontrollers, a bit of programming, and interfacing them to the outside world is something you should also have done at least a few times.In fact, I'm a bit confused by your post. There are about a gazillion different ways to start with electronics and learn more on the 'net. The main part is to find something that interst you personally, especially if it's for holidays and having fun while learning.

author: devinatkin
author_rank: Contributor
timestamp: May 02, 2022, 02:42:36 pm
content: Someone currently working on getting their PhD in analog IC design here. Don't count yourself out of an internship yet, even if it is a bit late. Depending on the country you will need grad school in order to get into analog IC design, at least a masters, but likely a PhD.- Learn FPGAs. I know that's digital but mixed signal is the future so you should be good at both. Throwing some digital circuitry onto a primarily analog chip can help with all sorts of pain in the ass problems associated with getting consistent results.- Learn Magic and get involved with the Google Skywater runs. You probably want to start with digital and then move into the analog domain in order to make sure you get something useful.- Go and Talk to people in various labs at your university. If they're doing analog IC design they may be able to start you off bringing some silicon they designed up and running, then move you onto designing & testing.- Learn PCB design. The overall principals aren't THAT different from IC level design and you'll need to do some regardless to get your future chips up and running.Those are my initial thoughts

author: rstofer
author_rank: Super Contributor
timestamp: May 02, 2022, 04:46:47 pm
content: Quote from: disco221 on April 29, 2022, 05:25:58 pmYou'll have to Google around to find resources. You can also look for used books at alibris.comIn concept, analog computing is pretty simple. We build an integrator from an op amp like the 741 with the non-inverting input grounded and the input going to the inverting input through a 1 MOhm resistor. The 1 ufd feedback capacitor is also connected to the inverting input. This will result in an integrator with a 1 second time constant meaning the output can change from 0V to 10V (maximum signal voltage) in 1 second. Since this is just a dual supply op amp along with a resistor and capacitor, it is pretty easy to breadboard. We usually have 4 each 1 MOhm input resistors for separate inputs plus a 100 KOhm input resistor which effectively multiplies the signal by 10. You can see how it changes the time constant. This is useful because we only have potentiometers to reduce a signal, not amplify it. You can see this in the Vogel design I linked above.I have attached the MATLAB/Simulink project for a simple second order differential equation. You may have taken the Differential Equations course but, if not, you soon will. Note that the entire solution starts with the assumption that we have the second derivative available. This is likened to acceleration. We integrate once to get velocity and once more to get position. Then we scale these 3 signals and apply the constants, simplifying whenever possible (like assume m=1 in the example). Notice the Spring coefficient at 2.0. This means take the signal and drop it to 0.2 * the signal with a potentiometer and then wire it to the 10x input of the summer. The 0.3 Damping constant takes only a potentiometer.After applying a little scaling and summing we do actually have the second derivative, we just created it! All we do is feed that signal into the first integrator as the 2d derivative. We have Lord Kelvin to thank for that approach to solving DEs. Note the initial condition on the second integrator. This sets the initial displacement of the mass to -1. Note also that the first integrator has an initial condition of 0. No initial velocity.Since this is a Simulink example, the output of the integrator is not inverted. In a hardware design, the output of each of the op amps will be inverted. Not important, just something to remember when you are adding or subtracting values.Your op amp integrator actually produces the negative of the integral. Go ahead and breadboard it. If all you do is play with a single integrator, it will still be educational.You can change the time scale by using a 0.1 ufd capacitor with a 1 MOhm resistor and this capacitor with a suitable accuracy will be easier to find. You just have to remember that the time scale is 0.1 seconds. BTW, I wouldn't do this. We're only talking about 2 precision capacitors because only 2 integrators required.BTW: The signal range for these integrators is -10V .. 0V .. +10V even though it will use +-15V supplies. Make sure you come up with an accurate source for +-10V for input to the potentiometers. Check the Vogel design I linked above. Note that this machine has what is required to build a solution to a second order differential equation plus some additional features like the multipliers.

author: rstofer
author_rank: Super Contributor
timestamp: May 02, 2022, 05:34:01 pm
content: If all you did was breadboard a 5 input summer (4 ea 1 MOhm and 1 ea 100 KOhm input resistors with 1 MOHm feedback resistor (4 inputs will have a gain of -1 and the other will have a gain of -10) and a 5 input inverting integrator (same as summer but instead of the 1 MOhm feedback resistor there is a 1 ufd feedback capacitor) and played with various inputs while watching the output, it would be a productive summer. Doing the full Mass-Spring-Damper might be a stretch although you could emulate it with LTspice or MATLAB/Symlink {students get the software free}.The full project might also help with the Differential Equations course but just building and experimenting with the building blocks would be worth the time spent,Here's an interesting LTspice solution of a second order equation without op ampshttps://www.edn.com/a-virtual-analog-computer-for-your-desktop/There are other LTspice examples of analog computing.