[QUOTE=DrLuke;33842011]
[img]http://i53.tinypic.com/29vmdzq.png[/img]
It's quite a difference in this case.[/QUOTE]
DrLuke, based upon the drawing that you've provided & what you're saying. IMO, are you trying to the vary the capacitance based upon the charge applied to the middle plate? Hence creating a psuedo-varicap?
(Now I'm rambling :v:)
[QUOTE=LoneWolf_Recon;33872270]DrLuke, based upon the drawing that you've provided & what you're saying. IMO, are you trying to the vary the capacitance based upon the charge applied to the middle plate? Hence creating a psuedo-varicap?
(Now I'm rambling :v:)[/QUOTE]
Capacity is calculated by the following formulas:
C = Q/U and C = E[SUB]0[/SUB] * A/d (A = surface, d = distance of capacitor plates)
Therefor, when you spread the plates apart (increase d), the voltage (U) has to rise. Now as a mechanical movement is really impractical, I want to try to use the 3 plated capacitor by first grounding the middle plate, then leave it floating and ground the right plate. As there only is a charge on the leftmost plate, the electric field will go through the middle plate and to the right plate, effectively creating a capacitor that has less capacity but in the process the voltage rises. If you don't believe me, ask your physics teacher to take one of those huge old plate capacitors, charge it up and spread the plates apart. You'll see the voltage will raise.
[QUOTE=DrLuke;33874161]Capacity is calculated by the following formulas:
C = Q/U and C = E[SUB]0[/SUB] * A/d (A = surface, d = distance of capacitor plates)
Therefor, when you spread the plates apart (increase d), the voltage (U) has to rise. Now as a mechanical movement is really impractical, I want to try to use the 3 plated capacitor by first grounding the middle plate, then leave it floating and ground the right plate. As there only is a charge on the leftmost plate, the electric field will go through the middle plate and to the right plate, effectively creating a capacitor that has less capacity but in the process the voltage rises. If you don't believe me, ask your physics teacher to take one of those huge old plate capacitors, charge it up and spread the plates apart. You'll see the voltage will raise.[/QUOTE]
Please make it, id love to see it.
[QUOTE=Chryseus;33867349]*pics*
You know you're an analog engineer when your desk looks like this.[/QUOTE]
This man decided my fate, I am going to be an analog engineer.
[QUOTE=DrLuke;33874161]Capacity is calculated by the following formulas:
C = Q/U and C = E[SUB]0[/SUB] * A/d (A = surface, d = distance of capacitor plates)
Therefor, when you spread the plates apart (increase d), the voltage (U) has to rise. Now as a mechanical movement is really impractical, I want to try to use the 3 plated capacitor by first grounding the middle plate, then leave it floating and ground the right plate. As there only is a charge on the leftmost plate, the electric field will go through the middle plate and to the right plate, effectively creating a capacitor that has less capacity but in the process the voltage rises. If you don't believe me, ask your physics teacher to take one of those huge old plate capacitors, charge it up and spread the plates apart. You'll see the voltage will raise.[/QUOTE]
You're neglecting the fact that you're doing work in the 'mechanical' parallel-plate capacitor system.
Work is force over distance. The force here is the force of electrostatic attraction. The distance is the distance you're pulling the plates apart. There's energy going into that system. Simply grounding the center terminal of a three-plate capacitor isn't going to evoke the same behavior.
Woo, I got an autoranging multimeter with an IR temperature laser sensor on it! Awesome!
I am still working with some old thing that didn't cost alot. I am going for a fluke soon.
Quick question, what could be wrong with a device's display if it displays "ddddddd" instead of a number, but works perfectly fine other than that? Or in other words, would it be an easy fix. Mate of mine has the problem and I think I am underestimating the problem.
So, I hopped on the floppy drive music bandwagon for christmas, and it turns out to be fairly easy past staring at sheet music and tearing out my goddamn hair.
Hopefully I can expand this to two, and then maybe four drives, if I can find enough.
[video=youtube;oS3zd8GQxBg]http://www.youtube.com/watch?v=oS3zd8GQxBg[/video]
[code]/*
Floppy Drive Music: Twinkle Twinkle Little Star
Lapsus Antepedis
Dec 25 2011
Times are in microseconds
*/
// Constants
const int MAX_STEPS = 70;
int scale[20] = {7644,7214,6812,6428,6068,5728,5406,5102,4816,4546,4290,4048,3824,3608,3404,3214,3034,2864,2704,2550};
// Song, extra 0 or 1 at the start.
int note[] = {0,0,0,7,7,9,9,7,5,5,4,4,2,2,0,7,7,5,5,4,4,2,7,7,5,5,4,4,2,0,0,7,7,9,9,7,5,5,4,4,2,2,0};
int length[] = {0,4,4,4,4,4,4,8,4,4,4,4,4,4,8,4,4,4,4,4,4,8,4,4,4,4,4,4,8,4,4,4,4,4,4,8,4,4,4,4,4,4,8};
int songlength = 43;
int tempo = 100000;
// Variables
int curnote = 0;
int stepcounter = 0;
int dir = 0;
unsigned long time = 0;
unsigned long next_step = 0;
unsigned long next_note = 0;
unsigned long delaycalc = 0;
// Pins
int DriveEnable = 2;
int Direction = 4;
int Step = 3;
void setup()
{
pinMode(DriveEnable, OUTPUT);
pinMode(Direction, OUTPUT);
pinMode(Step, OUTPUT);
digitalWrite(DriveEnable, LOW);
digitalWrite(Direction, HIGH);
digitalWrite(Step, LOW);
// Zero the stepper
for (int i = 0; i < 100; i++)
{
digitalWrite(Step, HIGH);
delay(2);
digitalWrite(Step, LOW);
delay(2);
}
digitalWrite(Direction, dir);
curnote = 0;
next_step = micros() + 100000;
next_note = next_step;
}
void loop()
{
time = micros();
// Step handling
if (time >= next_step)
{
stepcounter++;
if (stepcounter >= MAX_STEPS)
{
stepcounter = 0;
dir = !dir;
digitalWrite(Direction, dir);
}
digitalWrite(Step, HIGH);
delayMicroseconds(1500);
digitalWrite(Step, LOW);
delaycalc = scale[note[curnote]];
next_step = time + delaycalc;
}
// Note handling
if (time >= next_note)
{
curnote++;
if (curnote >= songlength)
{
curnote = 0;
delay(10000);
}
delaycalc = length[curnote] * 100000;
delay(50);
next_note = micros() + delaycalc;
}
}[/code]
So this year I got $300, some misc tat and my sisters broken canon pixma ip2700 printer which yielded 2x 35v dc motors and a 24v psu.
Best christmas ever.
[editline]25th December 2011[/editline]
Tested the motors at 24 volts and they have some ompf to them. Considering building an RC tank or something.
Gonna order some boards and some more RF gear as soon as I sell these LVDTs:
[URL="http://www.ebay.com/itm/190617827946?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649"]http://www.ebay.com/itm/190617827946?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649[/URL]
Happy Holidays everyone!
[img]http://dl.dropbox.com/u/408914/DSC-0133.jpg[/img]
[img]http://dl.dropbox.com/u/408914/DSC-0130.jpg[/img]
so guys I made 5kv using a transistor and a old EEPROM I found
What, how
3 plate capacitor
[QUOTE=marcin1337;33921630]
so guys I made 5kv using a transistor [B]and a old EEPROM I found[/B][/QUOTE]
Wat.
Hello thread, I'm currently studying audio engineering, did some circuit bending, made some guitar pedals and little noise generators before.
Does anyone know where I can get an oscilloscope for a decent price ?
ebay is usually he best place to look for scopes, you should be able to get a good quality working analog scope for under £100 although delivery can be fairly costly, if you can find a seller locally then that will save you quite a bit.
As for what you should look for make sure you get a scope that has been confirmed working by the seller and has a clear screen with no or minimal burn in, you'll also want a decent bandwidth depending on what your doing, for audio use 5MHz should do but the more the better, I'd recommend 20MHz as the minimum for general use, 50 to 250MHz if you're interested in RF or have money to burn.
Other features to be on the look out for are: test signal for probe calibration, tigger holdoff, graticule illumination, beam finder, external trigger, slope triggering, XY mode and single shot sweep.
In particular brands such as Tektronix, HP (Agilent), Philips, Hameg and Hitachi are worth considering.
Finally make sure it comes with or buy a separate pair of good quality probes with switchable 1x and 10x attenuation.
I can sell you a scope for 60€ + shipping
It has 1 channel and can operate in XY mode. The only problem with it are some of the knobs are a bit wonky, they might need some treatment with anti-corrosive spray, but generally it's very well usable.
If you're interested I can send you some more pictures and infos of it:
[img]http://i56.tinypic.com/2wg65go.png[/img]
[editline]30th December 2011[/editline]
Oh it also comes without probes, but cheap 100 MHz probes from ebay should do the job.
FPGA should be arriving today! :dance:
One channel scopes are rather useless, sure if you just want to see the waveform they work but often you want to compare two waveforms in a circuit (or more).
[QUOTE=Chryseus;33963727]One channel scopes are rather useless, sure if you just want to see the waveform they work but often you want to compare two waveforms in a circuit (or more).[/QUOTE]
They certainly are not useless, he wants a scope for a decent price and 2 channel scopes on ebay etc. go well beyond 100€.
[QUOTE=DrLuke;33965062]go well beyond 100€.[/QUOTE]
Depends on brand and specs, I've seen many Hameg 20MHz scopes go for under £80, sometimes much less.
Also I doubt shipping from Europe to the UK would be cheap.
As for that scope 60 euro is a bit much considering it has a tiny screen, high input capacitance, 35ns rise time (350ns resolution), 10MHz bandwidth also since he lives in the UK which normally runs at 250V the scope is actually outside of its tolerance of 220V +10%.
E-bay will still be his best bet to find a decent-ish 2-channel scope. I was able to find one for $60, though it didn't come with probes or a power cable, but who doesn't have spare PSU cables lying around? And it's easy enough to make your own probes, too.
Oh right, you guys have a different voltage on the wallsockets...
[QUOTE=Chryseus;33965125]Depends on brand and specs, I've seen many Hameg 20MHz scopes go for under £80, sometimes much less.
Also I doubt shipping from Europe to the UK would be cheap.
As for that scope 60 euro is a bit much considering it has a tiny screen, high input capacitance, 35ns rise time (350ns resolution), 10MHz bandwidth also since he lives in the UK which normally runs at 250V the scope is actually outside of its tolerance of 220V +10%.[/QUOTE]
Our voltage is [i]meant[/i] to be 230V, which means the bulbs in the shops are rated at 230V.
The higher voltage at our sockets means that we go through bulbs really quickly, unless we switch to the energy efficient bulbs which take forever to warm up and even then are still pathetic.
[QUOTE=yngndrw;33969133]Our voltage is [i]meant[/i] to be 230V, which means the bulbs in the shops are rated at 230V.[/quote]
230V +-10% to be precise although most places I've lived in the UK have 240V or greater, my current house gets just over 250V.
Energy efficient bulbs work just fine, at least the newer ones do, if you buy cheap or old bulbs you're going to get poor quality.
So, I got my Arduino a few days ago and now I made a binary countdown for new year's eve:
[thumb]http://val.legtux.org/blog/img/blog-111230-dsc00005.jpg[/thumb]
Rate with Agree/Disagree
[QUOTE=Chryseus;33969269]230V +-10% to be precise although most places I've lived in the UK have 240V or greater, my current house gets just over 250V.
Energy efficient bulbs work just fine, at least the newer ones do, if you buy cheap or old bulbs you're going to get poor quality.[/QUOTE]
All the ones I've tried have been crap and perform the same, even the expensive ones.
I have found the CFL daylight bulbs (The ones designed for reptile enclosures) to be good through, seems as those are designed for their light output rather than being energy efficient.
I've personally started switching to fluorescent and LED lighting.
LED lighting is pretty awesome, if I had the time and money I'd convert my entire
house to low voltage LED lighting.
You can buy ready to go Led-"bulbs" on the internet.
I've ordered these for my under-kitchen-cabinet lights:
[url]http://www.ebay.co.uk/itm/White-5M-WaterProof-5050-300PCS-3-chip-SMD-LED-Strip-/220781466769?pt=LH_DefaultDomain_0&hash=item336799d491#ht_2642wt_1396[/url]
[url]http://www.ebay.co.uk/itm/LED-Driver-Transformer-12V-MR16-MR11-Light-Bulb-0-5-12W-/280784353358?pt=UK_HomeGarden_Lighting_Lamps_Lighting_SM&hash=item41600d384e#ht_1779wt_1396[/url]
I was also going to put some around the door of my cloak room / cupboard on a door-switch so it's lit automatically.
I have a 50Watt circular fluorescent light in the front room which is awesome and I was thinking of getting some ~10Watt LED flood lights for outside.
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