Begginer exercises/challenges and DC to AC

[KTP]

Wow, nice video...even has a catchy soundtrack 

All of Hero999's suggestions are really the better way to do this, but when I made the circuit I wanted to only use what we were given in our tiny kit of lab parts for the intro EE class so that everyone else in the class could make the same blinky led with their parts.  The only semiconductor we had in the kit was the lowly 741 op-amp (ok, it was a really intro EE class...I made a 99.5 average ).  Too bad nobody else in the class seemed interested in doing the circuit or anything else other than the minimum homework problems to prepare for the tests.  I found a similar attitude in the mosfet class I just took.  Ah well, I think I had more fun than they did.

Good job, keep at it!  After you get comfortable making oscillators we can try driving a mosfet with it that is hooked up to an inductor with a catch diode and capacitor filter after.  This would be the start of a very crude open loop unregulated switching boost converter, which could turn the 9 volt battery voltage into 24 volts or even higher (for small loads).  Watch Dave's video on regulators when you get a chance.

[krd777]

Hi everyone!

Back again and sorry I didn't do the Schmitt Trigger simulation yet but I had a problem with my spare time and with LTspice too.

Posted by: shafri
HAHA! thats more like it. congratulation! welcome to EEVBlog for anyone interested in electronic design... for makers and "hackers" haha! Grin
next move? buy an oscilloscope and multimeter! if you still not own one, it will display some reality, not the simulated one.
and when you go advance, you can start looking for function generator, spectrum analyzer etc etc all those fancy gadgetries!

Well, since i can't afford to buy an oscilloscope right now, I'll use the ones i have available xD

First of all, here is a picture of the LM741 oscillator connected to an oscilloscope. It was working at 250 Hz with a 100 uF capacitor . I made a video of it working at around 2 KHz using a 10 uF capacitor which link is:

Posted by: Hero999
Good, I'm glad you've got it working.

Please note that the CMOS IC must be 74C14, if you use the 74HC14 you'll need to add a current limiting resistor for the LED and use a 3V to 6V supply.

Thank you Hero999!
Now for the Schmitt Trigger, I couldn't quite find the proper model in LTSpice to do as Mr. Hero999 said. I'll still search if there are any libraries with it.

Posted by: KTP
Wow, nice video...even has a catchy soundtrack  Grin

All of Hero999's suggestions are really the better way to do this, but when I made the circuit I wanted to only use what we were given in our tiny kit of lab parts for the intro EE class so that everyone else in the class could make the same blinky led with their parts.  The only semiconductor we had in the kit was the lowly 741 op-amp (ok, it was a really intro EE class...I made a 99.5 average Wink ).  Too bad nobody else in the class seemed interested in doing the circuit or anything else other than the minimum homework problems to prepare for the tests.  I found a similar attitude in the mosfet class I just took.  Ah well, I think I had more fun than they did.

Good job, keep at it!  After you get comfortable making oscillators we can try driving a mosfet with it that is hooked up to an inductor with a catch diode and capacitor filter after.  This would be the start of a very crude open loop unregulated switching boost converter, which could turn the 9 volt battery voltage into 24 volts or even higher (for small loads).  Watch Dave's video on regulators when you get a chance.

Yes, it happens. Some people just don't get a kick out of electronics right away. I think some start to have fun after a while.
Thanks! I'll still keep testing and trying new ones, see what I can get. Right now i want to test the Schmitt trigger Mr. Hero999 has suggested. Then I want to compare them. So for now, until I can't do the Schmitt one, I'll make this one on a PCB, so i can use it later easily for comparison.


P.S.: I know I know, my multimeter is a piece of $#%&/#/, but oh well, I didn't see the multimeter review videos before I bought it (I bought it around 6 months ago). It was around 30€, it was the best in the store I bought it, the next above it was a Fluke which costed +/- 300€   but yes, if it was now, I would prefer to buy a  BK Precision BK2709B which really got me on the video Mr. Dave just did about 100$ multi meters.

Bye for now everyone, I shall be back with the "war on" Schmitt Trigger !

[krd777]

nice osc you have there! your multimeter is a piece of $#%&/#/? ahhhh! its just a tool! i used to play with cheaper than anything shown here in EEVBlog.

Thanks Mr. shafri! Well, I say it based on the multimeter reviews from mr. Dave. Still this one does all I need for now, without auto-range xD

[Zad]

nice osc you have there! your multimeter is a piece of $#%&/#/? ahhhh! its just a tool! i used to play with cheaper than anything shown here in EEVBlog.

Quite right!

An awful lot of multimeter elitism has been generated over the past few months to be honest, and to a certain extent people have lost sight of reality. Bear in mind that one of the meters I use quite frequently is a 3.5 digit non-autoranging machine, made in the mid 1980s, and bought for something under £20 even back then. Im sure that if I were to present 240v across it, it would detonate and take out half the UK, and accuracy is outside 1% now, but it still does it's job fine. When comparing spec sheets and construction, I am as prone as anyone to want the ultimate meter, but eventually we have to realise what we are going to use it for.

[KTP]

Yes sometimes Dave seems to dink a multimeter a point or two if it will not survive a thermonuclear blast and he gets really pissy when it falls over, but in general the reviews look like a good way for a newbie or not so newbie to know what is out there in terms of value.

[krd777]

nice osc you have there! your multimeter is a piece of $#%&/#/? ahhhh! its just a tool! i used to play with cheaper than anything shown here in EEVBlog.

Quite right!

An awful lot of multimeter elitism has been generated over the past few months to be honest, and to a certain extent people have lost sight of reality. Bear in mind that one of the meters I use quite frequently is a 3.5 digit non-autoranging machine, made in the mid 1980s, and bought for something under £20 even back then. Im sure that if I were to present 240v across it, it would detonate and take out half the UK, and accuracy is outside 1% now, but it still does it's job fine. When comparing spec sheets and construction, I am as prone as anyone to want the ultimate meter, but eventually we have to realise what we are going to use it for.

Very true Mr. Zad. You don't buy an helicopter to just go get groceries from the local market. You also don't buy a car to travel quickly from Europe to Australia. xD But it still happens that some of us tend to buy a luxury car to go get the groceries and a private jet to go to Australia xP ahahah, I think this is the case. I may still use this multimeter of mine for quite a while (which I'll do for sure, since even college ones are the same model) but there's a tendency to look at such thing as the BK Precision BK2709B and say: I shouldn't have got that one instead! xD

But you and Mr. shafri are right for sure. No need to buy what we don't need!

Posted by: KTP
Yes sometimes Dave seems to dink a multimeter a point or two if it will not survive a thermonuclear blast and he gets really pissy when it falls over, but in general the reviews look like a good way for a newbie or not so newbie to know what is out there in terms of value.

Ahahahah, but that's something I like in the reviews! xD Like the Ideal Multimeter rant because it falls off due to balance problems in the design, or the "picking" on Extech's bad PCB layout xD

And yes, I find the reviews very helpful. Not that I buy multi meters every day but it allows to learn a lot about the kind of measuring equipment that is out there in the market.

[Mechatrommer]

Dave's review is very useful for somebody who already familiar and needing for an upgrade to more expensive DMM, as there are lot out there that sell crap at higher than cheapy price. But we cannot take it fanatically up to a point that we just blindly take what Dave has said, trust just one brand and trash another. We have to choose whats best and suitable for us.

I bought Uni-T DMM just due to some discussion raised by forum members, before the $100 shootout by Dave, but it turned out Uni-T got no big issue in the review. Quite glad to hear that, but... i can sense a switch in the trend that Dave made the review, he seems to make an attempt to equalize among all the DMM brand, carefully pointing the pros and cons for each model, and keep emphasizing that you should get whats suitable for you, quite matured review IMO, but sadly.... no more nasty rants that i used to like and makes me laugh the hell out loud.

[krd777]

Dave's review is very useful for somebody who already familiar and needing for an upgrade to more expensive DMM, as there are lot out there that sell crap at higher than cheapy price. But we cannot take it fanatically up to a point that we just blindly take what Dave has said, trust just one brand and trash another. We have to choose whats best and suitable for us.

I bought Uni-T DMM just due to some discussion raised by forum members, before the $100 shootout by Dave, but it turned out Uni-T got no big issue in the review. Quite glad to hear that, but... i can sense a switch in the trend that Dave made the review, he seems to make an attempt to equalize among all the DMM brand, carefully pointing the pros and cons for each model, and keep emphasizing that you should get whats suitable for you, quite matured review IMO, but sadly.... no more nasty rants that i used to like and makes me laugh the hell out loud.

Ahahah, so true Mr. shafri! So true. And yes, the rants are awesome xD

[krd777]

Ok, so I finally tried to make a simulation using LTspice's Schmitt trigger, but with no success due to an error I can't get rid of. Any suggestions?

PrintScreen attached.

[KTP]

right click on the transient analysis directive (the .tran thing). Set your maximum timestep to something reasonable (do you have it at 0 seconds or something?)  Try 10uS.

[krd777]

No, actually had it at 100 us, already tried 10 us, even 1 ms, no good. I found a question like this one on the net but can't quite get the answer.

http://www.electronics-related.com/usenet/design/show/56037-1.php


I can't find the trigger levels anywhere.

[jahonen]

Digital primitives are behavioral models, so no real devices are simulated. However there are number of parameters you can add to the gates to make the simulation a bit more realistic. See LTSpice help for LTspice/Circuit elements/A. special functions. Here is an example of schmitt-trigger oscillator which seems to run just fine after tweaking some parameters. These parameters can be entered in the "Value" attribute (right-click on the gate).

Regards,
Janne

[Zero999]

You need to get those parameters right, in order to ensure an accurate simulation.

The 74C14 typically has a positive and negative threshold of 3.6V and 1.4V respectively, when the supply voltage is 5V, so the correct value for Vh is 1.1V.

I don't know about the rise time, it does vary on the load (the higher the capacitive the longer the rise/fall time), 10ns seems a bit optimistic but I suppose it doesn't matter for a low frequency oscillator, anway I just set it to 50ns.

I don't know why some people seem to be obsessed with simulation anyway, don't get me wrong, it saves money and time but for simple circuits which have been proven to work, it isn't necessary.

Attached is the .asc file with the correct parameters.

[KTP]

I don't know why some people seem to be obsessed with simulation anyway, don't get me wrong, it saves money and time but for simple circuits which have been proven to work, it isn't necessary.

Simulating simple circuits which have been proven to work (and thus the outcome is predictable so you know if your simulation is working) is a great way to learn how to use the simulation tools.  I don't think the OP is trying to do this simulation in order to do a board run of 100,000 schmitt trigger oscillators...

[Zero999]

Yes, you're right of course, it's also best to start off with the basics.

This was just reminiscent of someone on another forum not wanting to use a CMOS crystal oscillator because they couldn't get it to work in some simulation program.

[krd777]

Digital primitives are behavioral models, so no real devices are simulated. However there are number of parameters you can add to the gates to make the simulation a bit more realistic. See LTSpice help for LTspice/Circuit elements/A. special functions. Here is an example of schmitt-trigger oscillator which seems to run just fine after tweaking some parameters. These parameters can be entered in the "Value" attribute (right-click on the gate).

Regards,
Janne

Thanks for the explanation Ms. Janne! Looks like these Schmitt Triggers are more complicated to simulate than OpAmps. or probably it's me not being used to LTSpice yet.

You need to get those parameters right, in order to ensure an accurate simulation.

The 74C14 typically has a positive and negative threshold of 3.6V and 1.4V respectively, when the supply voltage is 5V, so the correct value for Vh is 1.1V.

I don't know about the rise time, it does vary on the load (the higher the capacitive the longer the rise/fall time), 10ns seems a bit optimistic but I suppose it doesn't matter for a low frequency oscillator, anway I just set it to 50ns.

I don't know why some people seem to be obsessed with simulation anyway, don't get me wrong, it saves money and time but for simple circuits which have been proven to work, it isn't necessary.

Attached is the .asc file with the correct parameters.

Thank you very much again Mr. Hero999! It's a more complex piece for me at the moment. Didn't know about all those parameters when you advanced the idea of using a Schmitt trigger.
I wouldn't call it an obsession. Simulation is a part of my college work. I must prove my calculations with simulation. So everything I can get my hands on to simulate is great for training. Also is a great way to "see" the results without a physical circuit.

Simulating simple circuits which have been proven to work (and thus the outcome is predictable so you know if your simulation is working) is a great way to learn how to use the simulation tools.  I don't think the OP is trying to do this simulation in order to do a board run of 100,000 schmitt trigger oscillators...

As I said above xD. And yes, I could have stopped the simulations with the OpAmp idea, but was curious to compare both circuits and see if there were any significant differences in the output.

Yes, you're right of course, it's also best to start off with the basics.

This was just reminiscent of someone on another forum not wanting to use a CMOS crystal oscillator because they couldn't get it to work in some simulation program.

Still, trying something more advanced isn't too bad. the only problem there might be is that we may not get the results we wanted. But one always learns something I think.
And I thank you for sharing the concept and explanations here Hero999!


So yes, I consider the two questions I had answered! Thank you very much to you all!

Right now, and because I started reading on OpAmps because of this, I shall start a project where the objective is to select certain frequencies of a signal. And for each frequency "observed", there will be an action.
But this is a topic for another post xD.

Again, thank you very much everyone!