Electrical Engineering V3

[fpro]

I'm not spending a lot of money on this project, so I'm just going to use a computer power supply in case this experiment is a failure.

[AuntJimmy]

So I want to build a crappy universal remote

Is there any kind of witchcraft I can work if I want to send an IR signal to a TV but don't have an IR LED because I'm afraid of spending money

The red LEDs I have don't appear to be working, unless the TVs that I'm trying this on aren't responsive to universal remote signals

I have no idea what I'm doing help

[Quarternions]

[QUOTE=halofreak472;48838844]So I want to build a crappy universal remote

Is there any kind of witchcraft I can work if I want to send an IR signal to a TV but don't have an IR LED because I'm afraid of spending money

The red LEDs I have don't appear to be working, unless the TVs that I'm trying this on aren't responsive to universal remote signals

I have no idea what I'm doing help[/QUOTE]

IR Leds are like 5 to 10 cents ?

[No_Excuses]

[QUOTE=false prophet;48838793]I'm not spending a lot of money on this project, so I'm just going to use a computer power supply in case this experiment is a failure.[/QUOTE]
Well then you don't need a regulator or anything fancy.

[img]http://i.imgur.com/txon0Wrl.png[/img]

The value of the resistor will depend on the desired brightness/current handling of the LEDs.

[Leestons]

[QUOTE=quincy18;48839036]IR Leds are like 5 to 10 cents ?[/QUOTE]

And you can salvage them from old/broken remotes

[Zero-Point]

In a pinch, you can also salvage them from old computer mice if they have optical encoders, you'd just have to figure out which side is the emitter side and cut off the other.

[fpro]

[QUOTE=No_Excuses;48839199]Well then you don't need a regulator or anything fancy.

[img]http://i.imgur.com/txon0Wrl.png[/img]

The value of the resistor will depend on the desired brightness/current handling of the LEDs.[/QUOTE]

I guess that would work very well then. Would current be a big concern when using a computer power supply or would the resistors take care of it completely?

[paindoc]

[QUOTE=quincy18;48839036]IR Leds are like 5 to 10 cents ?[/QUOTE]

You don't realize how averse Halofreak is to spending money I thought he was gonna die after buying my old midi keyboard from me

[Chryseus]

[QUOTE=false prophet;48842875]I guess that would work very well then. Would current be a big concern when using a computer power supply or would the resistors take care of it completely?[/QUOTE]

Current is set by the resistors
I = (V - Vdrop) / R
R = (V - Vdrop) / I
Vdrop being the total voltage drop of each LED in series.
Power dissipation in the resistor is I^2 * R

[No_Excuses]

I've been duped! My zener diodes are looking a little capacitorish. Up side is I'll probably get to keep these for free but downside is another 3-4 week wait for the zeners.

[url=http://imgur.com/hcRlhwd][img]http://i.imgur.com/hcRlhwdl.jpg[/img][/url]

[Zero-Point]

[QUOTE=No_Excuses;48844518]I've been duped! My zener diodes are looking a little capacitorish. Up side is I'll probably get to keep these for free but downside is another 3-4 week wait for the zeners.

[url=http://imgur.com/hcRlhwd][img]http://i.imgur.com/hcRlhwdl.jpg[/img][/url][/QUOTE]

Noooo, ceramic-dip diode! Vely good build great from Cheapistan yes!

Also, one of my friends has a graphics card that is showing signs of a bad BGA connection, so I guess I'm forced to get off my ass and complete the Arduino Beginner's Trifecta:
1) Blink an LED - done
2) Say something on a 16x2 LCD screen - done
3) Make a re-flow oven

[iwancoppa]

[QUOTE=false prophet;48838793]I'm not spending a lot of money on this project, so I'm just going to use a computer power supply in case this experiment is a failure.[/QUOTE]

I've done this just recently, to make an aquarium light.

I've got an LM7805, a 9v linear wall wort scavenged from god knows where, and 30 10mm LEDs with current resistors, all from tayda. Total cost was something like $3 - I had to order a load more shit just to meet Tayda's $5 minimum order requirement.

Edit:

A little further information on Tayda's 10mm LEDs. They're ~14000 mcd with a 30 degree view angle, and have a forward current rating of 20ma. Depending on the color you'll get, you'll most likely need either 150 or 82 ohm 1/4 watt resistors, if using a 5v supply.

[Chryseus]

[t]http://i.imgur.com/R4nPTSs.jpg[/t]

I finished testing my low voltage boost converter, it was not really possible to meet my initial goal of 0.8V to 1.5V input so I decided to go for 1.5V to 3V using a combination of the 1.5V C cell in my meter and a small AAA cell which gives me an output of up to 40V at 50% duty, my initial estimate of ~95% duty was wrong since I forgot the switching transistor inverts the signal so really it was 5% duty which seems about right from my testing.
Next step is a PCB for it it with a classic op-amp regulator, I might use a 555 for the switching signal generator, and just brute force it rather than muck around with duty control, not like I need to give a tit about EMI in this application.
It works down to about 1.5V, 0.75V per cell so it's pretty efficient, we're only talking a current draw of a few hundred micro-amp at most.

[woidoi]

bought [URL="https://www.youtube.com/watch?v=zLr1Lpn69jI"]one of these tiny spy cams[/URL], but it was dead on arrival.

Turns out the battery was dead, and it seems to work now (an LED turned on, not much but more than before :v:)

[t]https://dl.dropboxusercontent.com/u/43645231/photos/electro/2015-10-08 19.35.15.jpg[/t]

My question is: can I risk running this on 3.3 V, which is quite a bit lower than the 3.7V the battery is rated at? It's a cheap LiPo and they tend to drop voltage when discharging, but do they even go as low as 3.3V?

[Chryseus]

[QUOTE=scratch (nl);48859028]My question is: can I risk running this on 3.3 V, which is quite a bit lower than the 3.7V the battery is rated at? It's a cheap LiPo and they tend to drop voltage when discharging, but do they even go as low as 3.3V?[/QUOTE]

3.3V should work fine.

[LoneWolf_Recon]

[QUOTE=scratch (nl);48859028]bought [URL="https://www.youtube.com/watch?v=zLr1Lpn69jI"]one of these tiny spy cams[/URL], but it was dead on arrival.

Turns out the battery was dead, and it seems to work now (an LED turned on, not much but more than before :v:)

[t]https://dl.dropboxusercontent.com/u/43645231/photos/electro/2015-10-08 19.35.15.jpg[/t]

My question is: can I risk running this on 3.3 V, which is quite a bit lower than the 3.7V the battery is rated at? It's a cheap LiPo and they tend to drop voltage when discharging, but do they even go as low as 3.3V?[/QUOTE]

I would hazard a guess that if you were to apply 3.3v through the battery lines it wouldn't do any damage but might not work. I assume that bit of electronics right next to the USB plug and battery terminals are battery recharging/power management circuitry which may or may not accept the 3.3v.

Unless you can read off the part numbers.

[woidoi]

It seems like 3.3V is too low. When I try to turn it on, an indicator led only goes on for a split second before turning off. From the little information that I could find, that seems to indicate an empty battery. I'll try it with something closer or at 3.7V when I can.

The camera itself works fine though. Once plugged into usb you can switch modes so that it'll work as a webcam, which it does without a hitch.

[Chryseus]

[t]http://i.imgur.com/FbTOO4f.png[/t]

Ready for PCB.

[No_Excuses]

I've been working on a power supply for a few weeks now...my first major project. Second I suppose, but my first was just a pure mistake. My ambition was far greater than my knowledge for that one. It's funny how it starts though. I just wanted a simple adjustable voltage source with a positive and negative rail. But if I'm going to use this for testing things I should have a current limit. After I figured out current limiting I realized it wasn't much harder to add a constant current mode. And since I have current limiting, voltage limiting shouldn't be much harder. And then I can add a soft start circuit, OVP and OVC LED's, volt and ammeters....

And since I'm going through a lot of design work (for me), there's no way I'm going to do it on a breadboard so let's design a PCB! So my simple idea has grown quite a lot. The PCB size is also very constrained so I have to stack two on top of each other to fit everything. Lots of learning on this one so I'm glad I decided to go all out on it.

[Cakebatyr]

[T]https://dl.pushbulletusercontent.com/AMuCql3GBrsH5RFmjHflBmgytYH8xxHg/IMG_20151010_162416.jpg[/t]

Bantennas for aa 800MHz trunked radio tracking system. Tape measure are the best.

[Leestons]

Nice wallpaper

[paindoc]

could i perchance make a small-scale microwave telescope? I haven't done the math yet on what exactly I can observe, but I'm trying to figure out if its financially feasible. Trying to think of something hardware related I can design and build for my upcoming A&A engineering application, I'm going to make a guidance computer (super basic) for software fun but need something hardware related.

[editline]11th October 2015[/editline]

[url]https://wiki.uib.no/ift/images/5/50/Ch10.pdf[/url] questioned answered now to study how to create software to analyze this and see if i can even get a dish somehow

I know the ESS department has one that you can plug software modules into and they like my club (3d printing) so maybe I need to go make some friends

[Cakebatyr]

For microwave you're going to need a [url=https://en.wikipedia.org/wiki/Horn_antenna]Horn antenna[/url] or [url=https://en.wikipedia.org/wiki/Helical_antenna]helical antenna[/url] and preferably a parabolic dish. If you can find one of those big [url=http://vancouver.craigslist.ca/van/ele/5249433122.html]old satellite dishes[/url] that would work fantastically.

Alternatively you can make stacks of Yagi-Uda antennas for pennies at microwave frequencies, check out [url=http://www.antenna-theory.com/m/antennas/main.php]this website[/url]. Microwave [b]receiving[/b] antennas are pretty easy and small, but you also need to be able to down convert that to a usable frequency for most receivers.

Edit: yeah that site works well. Also check out the Hydrogen Line at 1.421GHz with an RTLSDR. Don't get one of the oval dishes, they won't give you an accurate signal.

[TCWilliamson]

[url=http://i.imgur.com/xiSbLGb.png][img]http://i.imgur.com/xiSbLGbl.png[/img][/url]
[url=http://i.imgur.com/8lgSCTu.png][img]http://i.imgur.com/8lgSCTul.png[/img][/url]

3A Opto-isolated Gate driver boards on their way C:

[Chryseus]

[QUOTE=nuttyboffin;48887252][url=http://i.imgur.com/xiSbLGb.png][img]http://i.imgur.com/xiSbLGbl.png[/img][/url]
[url=http://i.imgur.com/8lgSCTu.png][img]http://i.imgur.com/8lgSCTul.png[/img][/url]

3A Opto-isolated Gate driver boards on their way C:[/QUOTE]

That should be Dual not Duel.

[TCWilliamson]

[QUOTE=Chryseus;48887509]That should be Dual not Duel.[/QUOTE]

... You say that, but just wait until those two Opto's accidentally turn on at the same time, connected to 600V 600A IGBT's and a 500V, 4700uF bus capacitor across them both.... + rectified mains or even 3 phase.

[LoneWolf_Recon]

Hey guys, I'm having some trouble with my buck converter. Needless to say the output voltage is dropping from my designed 8V (Which holds steady to about 300mA Load) to around 6.5V at +500mA. I've verified that the MOSFET is being driven fully into saturation and all my other specs are correct, however I think I designed the inductor too high at 33uH thus having a slow inductor current response time to power the load at the right voltage.

Should I just decrease the inductance or any other ideas?

Schematic ([URL="https://sites.google.com/site/lonewolfscircuits/sitefiles/8V_SMPS_Robot_Tether.asc?attredirects=0&d=1"]Spice Sim[/URL]):

[IMG]http://oi61.tinypic.com/rwknsg.jpg[/IMG]

[Dolton]

[QUOTE=LoneWolf_Recon;48889971]Hey guys, I'm having some trouble with my buck converter. Needless to say the output voltage is dropping from my designed 8V (Which holds steady to about 300mA Load) to around 6.5V at +500mA. I've verified that the MOSFET is being driven fully into saturation and all my other specs are correct, however I think I designed the inductor too high at 33uH thus having a slow inductor current response time to power the load at the right voltage.

Should I just decrease the inductance or any other ideas?

Schematic ([URL="https://sites.google.com/site/lonewolfscircuits/sitefiles/8V_SMPS_Robot_Tether.asc?attredirects=0&d=1"]Spice Sim[/URL]):

[IMG]http://oi61.tinypic.com/rwknsg.jpg[/IMG][/QUOTE]

[URL="http://cds.linear.com/docs/en/datasheet/1624f.pdf"]The datasheet[/URL] has a couple equations for inductor selection but generally, no reducing the size will not help. The size of the inductor has more to do with ripple rejection, and mode of operation (CCM vs DCM).

Do you have an oscilloscope to see what is happening at each node when the output voltage drops?

[DrLuke]

[QUOTE=nuttyboffin;48887252][url=http://i.imgur.com/xiSbLGb.png][img]http://i.imgur.com/xiSbLGbl.png[/img][/url]
[url=http://i.imgur.com/8lgSCTu.png][img]http://i.imgur.com/8lgSCTul.png[/img][/url]

3A Opto-isolated Gate driver boards on their way C:[/QUOTE]

Why no isolation slots?

[Nev]

Does anyone have any experience with EEGs for Arduino (or other platforms)? I want to make a simple sleep analyzer. Is it hard to make my own EEG? Or are there any cheap, ready-made kits?