So as soon as I can catch my friend online again I'll be buying an Altera DE-2, which'll probably show up around the new year. Does anyone have any suggestions as for good sites or hopefully newb-friendly communities based around learning to use an fpga, preferably using Verilog?
Just got my arduino in the mail. After about 10 minutes i finally got it mounted in the sparkfun holder that came with it! :dance:
A little linear power supply I built while waiting for the parts for my oscilloscope:
[img_thumb]http://i.imgur.com/sMlm8.jpg[/img_thumb]
Voltage reference of 10v, uses a TIP 122.
[QUOTE=ddrl46;33764166]A little linear power supply I built while waiting for the parts for my oscilloscope:
[img_thumb]http://i.imgur.com/sMlm8.jpg[/img_thumb]
Voltage reference of 10v, uses a TIP 122.[/QUOTE]
Those terminal blocks, sex.
[QUOTE=DrLuke;33705906]I guess books
[editline]13th December 2011[/editline]
At the university I want to go to I will have the chance to specialize in high frequency electronics... it's really crazy shit, because you even have to consider the capacitance and inductance of the copper traces in a pcb to calculate proper frequencies etc...
Good thing we will have a few years before we have to choose a specialization![/QUOTE]
High Frequency you called? Don't wait till you attend uni, I'd start right away. It's a heavy branch of electronics just because it's so crazy. I have always liked HF and have been practicing it for 1,5 years now, yet a lot of things still look like MIT stuff. Not to mention things like VNA measuring and Smith charts.
[b]1000TH Post in this thread. Winner[/b]
oh god not the smith charts, they give me nightmares..
On the topic of HF...I've been taking a crack on my FM Band transmitter and its been a picky little circuit.
So far I have just the following two modules, the Audio Pre-Amp and the Oscillator/Modulator. Separately they work just fine, I input a signal from my MP3 into the Oscillator/Modulator it works just fine(As I did in my previous attempt: [URL="http://www.youtube.com/watch?v=F-m3M2yh5XM&feature=g-upl&context=G21be8f9AUAAAAAAACAA"]http://www.youtube.com/watch?v=F-m3M2yh5XM&feature=g-upl&context=G21be8f9AUAAAAAAACAA[/URL])
[IMG]https://sites.google.com/site/lonewolfscircuits/sitefiles/SingleTransistorFMTransmitter_DEMO.JPG[/IMG]
The Audio Pre-Amp I've also been working on for a while. Both in simulation and on breadboard it works well(Showed up amplified & clip-free on an O-Scope I borrowed a few months back):
[IMG]https://sites.google.com/site/lonewolfscircuits/sitefiles/Pre-Amp_Simulation.jpg[/IMG]
Main problem is connecting the two, the reason I included the Pre-Amp was to provide better impedance matching (32ohm Headphone output to the relatively high impedance of the modulator) & providing an even, line-level-like voltage to the modulator to make it easier to even out modulation. Not to mention that I have a microphone input as well which mixes in with the headphone audio input, so I need the mic amplified too.
So far I've concluded that I needed to change the biasing resistors on the Modulator & rethink the coupling capacitor between the two. They're still on the breadboard and I've tried grounding the backplane as best as I can. And as soon as I get this all straightened out and working I'll add in Harmonic Filters & the RF amp module. Any ideas?
Thanks
Looks like a plan you got there, keep it up, would like to see the results. Must be the simplest fm transmitter I've seen so far.
About a breadboard, I got rid of those - they cause parasitic capacitance and other side effects you would want to avoid.
I just started rebuilding my very very first transmitter, but this time decided to aim for a clean signal without spurious emmision, the first version was horrid. Mate of mine called it "A scrapheap". And it was.
Forgive my ignorance, but does impedance matching matter when you aren't trying to drive a passive load? I've only ever heard it come up when talking about maximum power transfer to speakers and such. It seems to me that in situations where you're going from amp to amp it would be more desirable to have R[sub]source[/sub] << R[sub]load[/sub], as that would result in the least attenuation of voltage.
Maybe it's a difference between FET/BJT circuits? Since FETs are voltage-controlled devices (I'm used to working with FETs), whereas BJTs are effectively current-controlled devices?
Well the first FM modulator circuit seems fine, although you could increase R1 & R2 a bit more, 47k I think would be a good value for both.
The second pre-amplifier has a few issues, firstly the output impedance is 10k which means you'll lose half the amplitude driving the FM modulator, this is at audio frequency so you do not need to match impedance, however 10k is still a good value for the collector resistor.
Also your setting the base voltage to roughly 1 diode drop this is [b]very bad[/b] since it will result in an emitter voltage of near zero giving you distortion of the input signal, it will also now has a very unstable bias that will shift will small changes in temperature, VBE and hFE.
How you should do it:
Pick a base voltage so you get at least 1V on the emitter (1V + 0.7V = 1.7V)
Adjust this so the input signal can swing fully negative (1.7+0.25V = 1.95V)
Pick R1 & R2 to get this voltage, but the parallel resistance must be less than hFE * RE (the emitter resistor) ideally 10x less to avoid attenuation.
Calculate the quiescent current for the given collector resistor (Vcc / 2) / Rc = 250uA
Pick the emitter resistor so it equals the quiescent current, (1.95V-0.7V) / 250uA = 5k
This will give you a stable bias at Vcc / 2 and allow for the full swing of the input signal.
The gain of this is RC / RE which is 10 or 20dB if you want to sound like a nerd.
If you desire a different gain you have to bypass the emitter feedback with a capacitor
and resistor, this gives you a separate AC feedback path.
If the next stage has an input impedance of anything under 100k (which it does) you will need an additional properly biased emitter-follower to provide a low impedance output to the FM modulator.
@ROBO
Matching impedance should only be done in certain situations where maximum power transfer is required, some obvious example are driving a speaker, electric motor or an electric heater.
This particularly applies to RF circuits where impedance mismatch can result in the transmission line or PCB trace suddenly looking more like an inductor or a capacitor which can severely effect the signal and ultimately reduce the power getting to the load, it's no good getting a RF signal with plenty of voltage but very little current.
But normally you want the voltage of a signal to be as high as possible so you try make the load impedance higher than the source impedance, I.E a voltage source.
In some cases you care more about the current than the voltage so you make the load impedance less than the source impedance, I.E a current source.
[b]Edit[/b]
Oh almost forgot, to properly size the capacitors use (1 / 2*Pi*R*C) this will give you the cutoff frequency (-3dB point) of a given capacitance and resistance, for example
the input capacitor, given your current value of the input bias resistors you will have a parallel input resistance of roughly 33.1k, using 10uF and this you can calculate the cutoff:
1 / 2 * Pi * 33.1k * 10uF = 0.48Hz, this is perfectly adequate, in fact you might want to decrease it to 1uF (4.8Hz) to reduce 1/f noise.
[t]http://i53.tinypic.com/14x1lza.png[/t]
Thanks for the thorough instruction Chryseus, I was jumping all over the place to balance it out the resistors. Managed to get a gain of 4 out of it in simulation, so off to the breadboard.. I'll get back with a report later
@DrLuke
HOW ABOUT A NICE GAME OF CHESS?
Currently making a Sawtooth + Square synthesizer. It's hard work! I'm terrible at electronics, but it's fun - especially when (if) you get the shit working.
[img]http://filesmelt.com/dl/IMG_04771.JPG[/img]
Got some nice equipment there
[editline]21st December 2011[/editline]
What the christ:
[img]http://i51.tinypic.com/6geazn.png[/img]
Rad, that is a sexy lab setup, beats the crap out of my workbench
it looks more like a university electronics lab than a home thing doesn't it?
[img]http://i56.tinypic.com/2a01g7r.png[/img]
I invented a new kind of DC-DC-converter, but it'll only work with a very special kind of capacitor with 3 plates instead of 2.
[QUOTE=Alcapwne;33833250]it looks more like a university electronics lab than a home thing doesn't it?[/QUOTE]
Exactly what it is.
[QUOTE=DrLuke;33833590][img]http://i56.tinypic.com/2a01g7r.png[/img]
I invented a new kind of DC-DC-converter, but it'll only work with a very special kind of capacitor with 3 plates instead of 2.[/QUOTE]
What's a DC-DC-converter?
[QUOTE=Rad McCool;33837715]Exactly what it is.
What's a DC-DC-converter?[/QUOTE]
Like a Transformer for DC voltages.
They're two types: Linear & Switch-Mode
Linear are just ones that step down voltages, the simplest you can think of is the 7805.
Downside is these are inefficient DC-DC converters.
Switch Mode types oscillate the voltage to change it, either up or down. And these are quite efficient.
A simple way is to use a 555 to invert the voltage to a 60Hz square wave which then can be used with a transformer to step up/down the voltage and then rectified back into DC.
A harder way is to use some sort of timer (Like a 555 or other clock source), to switch on/off a transistor to charge/discharge a capacitor or inductor, essentially creating a [URL="http://en.wikipedia.org/wiki/Charge_pump"]Charge Pump[/URL]
[QUOTE=DrLuke;33833590]it'll only work with a very special kind of capacitor with 3 plates instead of 2.[/QUOTE]
You can use two caps in series to do the same thing...
It's not even really new. What you drew is basically a charge pump.
I mean, if it really was new, you'd probably be better off patenting it instead of disclosing it on an internet forum.
[editline]22nd December 2011[/editline]
[QUOTE=LoneWolf_Recon;33837824]Like a Transformer for DC voltages.
Essentially, you can step up 5V DC to 20V DC.
A simple way is to use a 555 to invert the voltage to a 60Hz square wave which then can be used with a transformer to step up/down the voltage and then rectified back into DC.
A harder way is to use some sort of timer (Like a 555 or other clock source), to switch on/off a transistor to charge/discharge a capacitor or inductor, essentially creating a [URL="http://en.wikipedia.org/wiki/Charge_pump"]Charge Pump[/URL][/QUOTE]
You can also step down voltage to produce a high-current source.
You don't need to use a full transformer+rectifier, either. A single inductor and diode will do the trick. This circuit is called a boost or buck converter (for step-up or step-down, respectively).
[QUOTE=ROBO_DONUT;33837834]You can use two caps in series to do the same thing...
It's not even really new. What you drew is basically a charge pump.
I mean, if it really was new, you'd probably be better off patenting it instead of disclosing it on an internet forum.
[/QUOTE]
Jeez, get your buttplug out of your ass. The way I imagined it only works with a 3-plated capacitor as I want to change the plate's distance to increase to voltage. If you weren't busy fucking around you'd probably know that C = Q/U = E[SUB]0[/SUB] * A/d, so if you increade d, you also increase U as it's an equation. So by grounding the rightmost plane and toggling a switch that either grounds the middle plate or leaves it floating you should theoretically get a higher U than you charged the cap with. As I said, it doesn't work with just 2 caps in series, as they both have their own electric fields.
[QUOTE=DrLuke;33841438]Jeez, get your buttplug out of your ass. The way I imagined it only works with a 3-plated capacitor as I want to change the plate's distance to increase to voltage. If you weren't busy fucking around you'd probably know that C = Q/U = E[SUB]0[/SUB] * A/d, so if you increade d, you also increase U as it's an equation. So by grounding the rightmost plane and toggling a switch that either grounds the middle plate or leaves it floating you should theoretically get a higher U than you charged the cap with. As I said, it doesn't work with just 2 caps in series, as they both have their own electric fields.[/QUOTE]
Well, enjoy getting a 3 plate capacitor.
[QUOTE=DrLuke;33841438]As I said, it doesn't work with just 2 caps in series, as they both have their own electric fields.[/QUOTE]
It's literally the same thing.
I'm actually so distraught by how wrong you are I can't organize my thoughts properly or offer a coherent counter-argument.
[editline]f[/editline]
I get how it works (I [i]still[/i] get how it works, I understood it from the beginning). You don't need to break out the freshman physics. If you have two caps in series, with one end tied to ground and the middle 'floating', then the total capacitance is [i]C = 1/(C[sub]1[/sub] + C[sub]2[/sub])[/i]. When you short the middle to ground, then it becomes, simply, [i]C=C[sub]1[/sub][/i]. C increases, which changes the Q/V ratio, decreasing the overall voltage, and pumping the charge in from the previous stage. It's really just another way of building a charge pump. It's neat and all, but there's no reason you need any sort of special capacitor for it.
I feel like something's being overlooked here, though, and I'd like to see whether it actually works in practice.
Also, I didn't mean to be a jerk about it. You're looking at the problem from a different angle, which is never a bad thing. The overall idea is reasonable, but I really just honed in on that one detail that I think you got wrong.
[QUOTE=ROBO_DONUT;33841684]It's literally the same thing.
I'm actually so distraught by how wrong you are I can't organize my thoughts properly or offer a coherent counter-argument.
[editline]f[/editline]
I get how it works (I [i]still[/i] get how it works, I understood it from the beginning). You don't need to break out the freshman physics. If you have two caps in series, with one end tied to ground and the middle 'floating', then the total capacitance is [i]C = 1/(C[sub]1[/sub] + C[sub]2[/sub])[/i]. When you short the middle to ground, then it becomes, simply, [i]C=C[sub]1[/sub][/i]. C increases, which changes the Q/V ratio, decreasing the overall voltage, and pumping the charge in from the previous stage. It's really just another way of building a charge pump. It's neat and all, but there's no reason you need any sort of special capacitor for it.
I feel like something's being overlooked here, though, and I'd like to see whether it actually works in practice.
Also, I didn't mean to be a jerk about it. You're looking at the problem from a different angle, which is never a bad thing. The overall idea is reasonable, but I really just honed in on that one detail that I think you got wrong.[/QUOTE]
In practice it only works with a 3 plate capacitor, as 2 capacitors in series don't "use" the same electrical field.
[editline]22nd December 2011[/editline]
[img]http://i53.tinypic.com/29vmdzq.png[/img]
It's quite a difference in this case.
[editline]22nd December 2011[/editline]
[quote]DrLuke: u mad?
PlanetQQ: i just like how you can invent components[/quote]
:v:
Just replaced the grid lighting in the PM 3240 oscilloscope with some nice 30k mcd leds after finding out that buying new bulbs will cost 40 euros after shipping.
Installation with huge 3w 1k resistor in the bottom right corner:
[img_thumb]http://i.imgur.com/kNXaf.jpg[/img_thumb]
It works:
[img_thumb]http://i.imgur.com/yheE6.jpg[/img_thumb]
I might add some defusing in the future to get rid of that halo effect around the leds.
Love it! What was the previous grid illum colour? Orange-ish?
Meanwhile in the chezburger labs: every project either doesn't want to work from start or just randomly stops working. And I am running out of parts. total crisis.
[QUOTE=Chezburger;33866164]Love it! What was the previous grid illum colour? Orange-ish?
Meanwhile in the chezburger labs: every project either doesn't want to work from start or just randomly stops working. And I am running out of parts. total crisis.[/QUOTE]
It used two bulbs so I think it was yellow-ish.
[QUOTE=Chezburger;33866164]Meanwhile in the chezburger labs: every project either doesn't want to work from start or just randomly stops working. And I am running out of parts. total crisis.[/QUOTE]
Well, that sounds familiar. To add to that: my lab is a ridiculous mess right now. Can't find anything back 15 seconds after I've used it...
I forgot to tell, that was another symptom easily found in my lab aswell.
[editline]23rd December 2011[/editline]
We should define a medical term for this since more people "suffer" from it. lets call it, like laberitus or something.
[img]http://www.edn.com/photo/291/291880-Jim_Williams_in_his_lab_2007.jpg[/img]
[img]http://www.eetimes.com/ContentEETimes/Images/EELife/williams%20desk.jpg[/img]
You know you're an analog engineer when your desk looks like this.
Sorry, you need to Log In to post a reply to this thread.
