[url]http://www.adafruit.com/category/50[/url]
They've got quite a bit of EL stuff, dunno if they have tape though.
So I got this usb controlled display thing from Dad some months ago, and finally sat down to find the data sheet for the controller.
Well, I found it, all 334 pages of it. -sigh- that'll be fun to sift through.
In better news, my sample VFD shipped recently and it'll be here on the 15th! -is excited-
Making a square wave tone sound good is impossible.
[QUOTE=Chryseus;42493731]Hey that looks exactly like the solder I use, Stannol right ?[/QUOTE]
That's right.
[QUOTE=Nightrazr;42521139]That's right.[/QUOTE]
Another Midterm tomorrow! (on this thread relevant stuff)
[img]https://dl.dropboxusercontent.com/u/64514745/etc.png[/img]
etc
Mhh those are fun
My face hurts so I dug around some boxes because I couldn't sleep. Found a massive amount of LM386 and LM741 IC's. I don't remember ever buying these...
I looked up the data sheet on both and don't know how I'm supposed to use them.
If I wanted to make a radio amplifier with the LM386, what purpose do capacitors have in the circuit?
[QUOTE=false prophet;42530356]My face hurts so I dug around some boxes because I couldn't sleep. Found a massive amount of LM386 and LM741 IC's. I don't remember ever buying these...
I looked up the data sheet on both and don't know how I'm supposed to use them.
If I wanted to make a radio amplifier with the LM386, what purpose do capacitors have in the circuit?[/QUOTE]
Radio amplifier or do you mean radio receiver ?
The use of the capacitors will depend upon where it is in the circuit, almost certainly you will have at least one tuned LC tank circuit for tuning and some more to limit the low frequency gain of the op-amp.
If you're going to build a radio whatever you do try avoid building it on a breadboard, I've often picked up radio stations just from the parasitic inductance and capacitance of the breadboard but you may be able to get away with it particularly for AM long wave and strong local stations, in any case it's not really suitable for FM or short wave as the op-amp gain starts to roll off at 100kHz+, you could of course stack multiple stages which old TRF (tuned radio frequency) radios used to do but each stage needs to be preferably coupled through a matched LC tank circuit which requires significant alignment and a big multi-section tuning capacitor, the best sort of circuit you can aim for with just a single amplifier is a regenerative circuit where some of the output is used a positive feedback which gives a very very high single stage gain however requires constant tweaking to ensure the loop gain is just below unity to avoid oscillation (Barkhausen criterion) which is the major weakness of the regenerative receiver, better circuits such as the superhetrodyne mix the incoming RF with a local oscillator however as you'd expect these are more complicated.
op-amps are of minimal use for RF unless you pay a lot for a really high bandwidth op-amp, your generic good op-amp with a ft (transition frequency) of 100MHz is useless for FM, you'd actually need a ft on the order of 500MHz or better.
I'm starting to ramble so I will shutup now.
Not a receiver, just a sound amplifier. Like, for headphones or speakers taking a radio or mp3 as the input
[edit] or even a pitiful pocket guitar amplifier
[QUOTE=false prophet;42530605]Not a receiver, just a sound amplifier. Like, for headphones or speakers taking a radio or mp3 as the input
[edit] or even a pitiful pocket guitar amplifier[/QUOTE]
Ahh in that case things are a lot simpler, you can just use one or two op-amps in the standard inverting or non-inverting amplifier configuration, you might be able to power some headphones directly from the op-amp but for any decent level of output power there are two options open to you:
Firstly use an audio power amplifier chip designed for the application or build a simple class AB output stage using two NPN and two PNP transistors along with some diodes, although this does require a split rail supply which is easy enough if you're using batteries.
You could maybe use a simple class A output stage which might be fine for 1 or 2 watts of power, anything over that is going to need a real good bit of heatsinking as class A is highly inefficient.
Another slightly unusual method that most people don't consider these days is to use a class A output into an audio transformer (basically just a step down) which helps minimize power loss due to degraded beta at high current but this is not that important if you're using a darlington or sziklai output configuration it also needs a relatively high voltage.
You could also try a class D output stage but I've never experimented with those so I can't say much about their audio quality.
And finally you could use a MOSFET output stage which is not all that popular due to increased distortion and lower transconductance however it would reduce power dissipation even more, maybe making a pocket class A amplifier possible, although battery life would be a big issue.
Tell me what parts you have laying around besides the op-amps and I'll design you something.
I'm not really looking for schematics. I'm mainly just interested in what a capacitor does to the amplifier circuit. I've seen schematics that use the lm386 and have two or three capacitors involved, which is why I am asking what it affects.
30 second google suggests the caps are used to steady and smooth out power input.
[editline]15th October 2013[/editline]
*for the purpose of maintaining a stable current to prevent sound distortion I think.
[QUOTE=false prophet;42531170]I'm not really looking for schematics. I'm mainly just interested in what a capacitor does to the amplifier circuit. I've seen schematics that use the lm386 and have two or three capacitors involved, which is why I am asking what it affects.[/QUOTE]
[img]http://i.stack.imgur.com/jB4Lj.jpg[/img]
The lower capacitor 0.1uF cap marked Ci is the input coupling capacitor, it prevents the DC bias provided by the two 100k resistors from effecting the signal source, the value is chosen to ensure good low frequency response since it forms a high pass filter with the two input resistors and the input impedance of the op-amp, in practice you only care about the two resistors so Zin = 50k which with the given value of capacitance gives a -3db point of 31.8Hz (1 / 2 * Pi * R * C).
R1 and Rf form the feedback network that sets the gain, The upper 0.1uF capacitor marked Ci blocks DC current through R1 causing the gain at DC to be unity (1), since capacitors are considered open circuit at DC, while the AC gain is set by R1 and Rf except at low frequencies as discussed above.
Co is the output capacitor designed to remove any DC bias from the signal and would in practice be chosen based on the intended load impedance, for audio use they should at least be 1uF and up and for high power coupling several thousand uF is not unusual.
So, I have located a functioning PAL006A amplifier on a non-functional car stereo head unit. Googleing around reveals the part is long obsolete, but its a 50Wx4 power amp IC and I wish to use it since its on hand.
Unfortunately I can't find a reliable datasheet or pinout of it anywhere.
Know of any ways to determine its pinout/find its datasheet?
[QUOTE=S31-Syntax;42533364]So, I have located a functioning PAL006A amplifier on a non-functional car stereo head unit. Googleing around reveals the part is long obsolete, but its a 50Wx4 power amp IC and I wish to use it since its on hand.
Unfortunately I can't find a reliable datasheet or pinout of it anywhere.
Know of any ways to determine its pinout/find its datasheet?[/QUOTE]
If you can't find the datasheet then you may be out of luck, there are a few ways to figure out the pin out such as looking at the die or carefully injecting signals but nothing quick or simple.
If I could find the data sheet for a successor model or a known common replacement, would that possibly provide enough information to hazard a decent guess?
After tinkering with the lm386 for a million hours I finally got some sound out of it. But I only get noise. If I touch a bare wire, such as the positive speaker wire then I get crystal clear sound.
I did this on a breadboard. Anyone know whats up? Also when I touch a resistor I get some really wicked distortions.
Is that any bare wire, or just the positive speaker lead?
Post schematic.
[QUOTE=Chryseus;42531674][img]http://i.stack.imgur.com/jB4Lj.jpg[/img]
The lower capacitor 0.1uF cap marked Ci is the input coupling capacitor, it prevents the DC bias provided by the two 100k resistors from effecting the signal source, the value is chosen to ensure good low frequency response since it forms a high pass filter with the two input resistors and the input impedance of the op-amp, in practice you only care about the two resistors so Zin = 50k which with the given value of capacitance gives a -3db point of 31.8Hz (1 / 2 * Pi * R * C).
R1 and Rf form the feedback network that sets the gain, The upper 0.1uF capacitor marked Ci blocks DC current through R1 causing the gain at DC to be unity (1), since capacitors are considered open circuit at DC, while the AC gain is set by R1 and Rf except at low frequencies as discussed above.
Co is the output capacitor designed to remove any DC bias from the signal and would in practice be chosen based on the intended load impedance, for audio use they should at least be 1uF and up and for high power coupling several thousand uF is not unusual.[/QUOTE]
What do you need to form a mathematical relationship here?
I'm guessing either Laplace or phasors?
[QUOTE=Angus725;42541680]What do you need to form a mathematical relationship here?
I'm guessing either Laplace or phasors?[/QUOTE]
If you're talking about frequency response that can be done with some simple math, the gain is just [1 + Rf / R1), closed loop gain is of course ultimately limited by the op-amp itself and should fall to unity at the transition frequency or risk oscillation due to phase shift, most op-amps are internally compensated but driving capacitive loads creates another pole which can cause the phase shift to reach 180 degrees before the gain goes to unity.
It's usually easiest just to stick it a simulator or my preferred method stick it on a breadboard and sweep the input across the desired bandwidth looking for signs of instability.
[QUOTE=Chryseus;42541806]If you're talking about frequency response that can be done with some simple math, the gain is just [1 + Rf / R1), closed loop gain is of course ultimately limited by the op-amp itself and should fall to unity at the transition frequency or risk oscillation due to phase shift, most op-amps are internally compensated but driving capacitive loads creates another pole which can cause the phase shift to reach 180 degrees before the gain goes to unity.
It's usually easiest just to stick it a simulator or my preferred method stick it on a breadboard and sweep the input across the desired bandwidth looking for signs of instability.[/QUOTE]
Does the caps change any part of the frequency response? (Assuming only phase angle)
[QUOTE=Angus725;42542043]Does the caps change any part of the frequency response? (Assuming only phase angle)[/QUOTE]
The input, feedback and output capacitor determines the low frequency response, the feedback resistor isolates the feedback capacitor from the output so it should not create another pole ensuring the op-amp is stable, the capacitors are chosen to pass the lowest frequency of interest, the output phase is determined by the amplifier itself, the internal compensation network ensures the gain is below unity before the phase shift becomes severe enough to cause oscillation, that said if you stack up multiple op-amps you need to be very careful about applying global feedback since each stage will introduce some phase shift.
In audio applications 1uF to 100uF will usually do the job.
Hey guys,
Dont know if this counts....
But ive designed and im also selling Nikola Tesla t-shirts
£17 including P&P for the UK (if you want one, feel free to PM me)
[img]http://i.imgur.com/3naeh01.jpg[/img]
[img]http://i.imgur.com/VQu8Md4.jpg[/img]
What do you guys think of them?
Ive been planning a series of t-shirts themed around electronics and engineering.
That's not Tesla, where is the moustache ?
They're nice, but I don't think I'd pay £17 for one.
[editline]17th October 2013[/editline]
Just seen this on Amazon [url]http://www.amazon.co.uk/Buttons-Switches-Joysticks-COM-00097-Button/dp/B004OD8DXU/ref=pd_sim_ce_4[/url]
I don't buy electronic things on there anyway but £3.20 for one button?!
[QUOTE=S31-Syntax;42539579]Is that any bare wire, or just the positive speaker lead?[/QUOTE]
The positive speaker or an exposed wire on any of the pots. Or really, any exposed wire for that matter.
[QUOTE=Chryseus;42540857]Post schematic.[/QUOTE]
[url]http://www.ti.com/lit/ds/symlink/lm386.pdf[/url]
Page six, the very first schematic.
Could this be an issue with a breadboard?
[QUOTE=Leestons;42548200]They're nice, but I don't think I'd pay £17 for one.
[editline]17th October 2013[/editline]
Just seen this on Amazon [url]http://www.amazon.co.uk/Buttons-Switches-Joysticks-COM-00097-Button/dp/B004OD8DXU/ref=pd_sim_ce_4[/url]
I don't buy electronic things on there anyway but £3.20 for one button?![/QUOTE]
Considering the weight and the item description, it looks like a bag of such switches.
[QUOTE=Leestons;42548200]They're nice, but I don't think I'd pay £17 for one.
[editline]17th October 2013[/editline]
Just seen this on Amazon [url]http://www.amazon.co.uk/Buttons-Switches-Joysticks-COM-00097-Button/dp/B004OD8DXU/ref=pd_sim_ce_4[/url]
I don't buy electronic things on there anyway but £3.20 for one button?![/QUOTE]
Don't buy things like that from Amazon.
[url]http://www.bitsbox.co.uk/switches.html[/url]
[QUOTE=Leestons;42548200]They're nice, but I don't think I'd pay £17 for one.
[editline]17th October 2013[/editline]
Just seen this on Amazon [url]http://www.amazon.co.uk/Buttons-Switches-Joysticks-COM-00097-Button/dp/B004OD8DXU/ref=pd_sim_ce_4[/url]
I don't buy electronic things on there anyway but £3.20 for one button?![/QUOTE]
lol amazon
[QUOTE=Leestons;42548200]They're nice, but I don't think I'd pay £17 for one.
[editline]17th October 2013[/editline]
Just seen this on Amazon [url]http://www.amazon.co.uk/Buttons-Switches-Joysticks-COM-00097-Button/dp/B004OD8DXU/ref=pd_sim_ce_4[/url]
I don't buy electronic things on there anyway but £3.20 for one button?![/QUOTE]
Huh... that picture format looks familiar...
Oh yeah!
[url]https://www.sparkfun.com/products/97[/url]
[editline]17th October 2013[/editline]
Also I got my VFD, but I cannot for the life of me get the thing to light up at all. I've followed the pinouts, loaded the example code, supplied the specified 5v, and it stays dark.
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