Electrical Engineering V2

[Chryseus]

Playing around with the RTL SDR direct sampling software mod, decided to see how low it can go:

[t]http://i.cubeupload.com/aTvs9U.jpg[/t]

~800kHz not bad.

[Papkee]

Who's got the best affordable PCB service around? I've thought about OSHPark, but I would rather have something that's not purple. Also, I've tried Hackvana but they haven't responded to my emails.

I'm trying to get just a few copies of this arduino board made, and I'm really looking to spend the least I have to.

[DrLuke]

[QUOTE=papkee;46089220]Who's got the best affordable PCB service around? I've thought about OSHPark, but I would rather have something that's not purple. Also, I've tried Hackvana but they haven't responded to my emails.

I'm trying to get just a few copies of this arduino board made, and I'm really looking to spend the least I have to.[/QUOTE]

Hackvana takes some time to respond to the email. How long did you wait?

[Papkee]

[QUOTE=DrDevil;46089372]Hackvana takes some time to respond to the email. How long did you wait?[/QUOTE]

It's been about a week now. They say 48 hours.

[DrLuke]

[QUOTE=papkee;46089530]It's been about a week now. They say 48 hours.[/QUOTE]

Huh, that's weird. You should try again, as it's possible that Mitch (he runs Hackvana) missed your mail.
He had a really busy week because chinese Customs started screening each packet going into Hong Kong, resulting in PCBs getting stuck in some chinese office for days without anybody knowing where his stuff was (This mostly concerned delivieries with DHL Express).

[Chryseus]

ITEAD is pretty much the cheapest around, ~$14 for ten double layer 5x5cm PCBs including shipping (12 if you mark it as open source), pretty good quality if you don't mind a few weeks shipping.

[ben1066]

[QUOTE=Chryseus;46089613]ITEAD is pretty much the cheapest around, ~$14 for ten double layer 5x5cm PCBs including shipping (12 if you mark it as open source), pretty good quality if you don't mind a few weeks shipping.[/QUOTE]

Elecrow is about 14$ for 10 5x5cm but you also get to chose any silkscreen colour. I think they are cheaper for 10 10x10cm boards in green too.

[An Draoi]

[QUOTE=Chryseus;46088733]Playing around with the RTL SDR direct sampling software mod, decided to see how low it can go:

[t]http://i.cubeupload.com/aTvs9U.jpg[/t]

~800kHz not bad.[/QUOTE]

What does the program do?

[Chryseus]

[QUOTE=An Draoi;46090028]What does the program do?[/QUOTE]

It's for working with a software defined radio (SDR), I'm using a cheap RTL2832U which most TV tuner and digital radio dongles use, it can be used to listen / decode anything between 24MHz to ~1.8GHz, the list of things to do with it is pretty much endless.
If you don't have one I highly recommend getting one to play with, they can be had for under 20 bux.
[url]http://www.rtl-sdr.com/[/url]

[nikomo]

Making a little thing for my Pi, to control an RGB LED, a segment display and a button.
[t]http://i.imgur.com/YPU2q64.png[/t]

Damn the schematic looks awful.
PCB should look prettier.
And I still haven't figured out the resistors I need for the JFET because I still haven't been able to figure out how you're supposed to use them.

[An Draoi]

[QUOTE=Chryseus;46090238]It's for working with a software defined radio (SDR), I'm using a cheap RTL2832U which most TV tuner and digital radio dongles use, it can be used to listen / decode anything between 24MHz to ~1.8GHz, the list of things to do with it is pretty much endless.
If you don't have one I highly recommend getting one to play with, they can be had for under 20 bux.
[url]http://www.rtl-sdr.com/[/url][/QUOTE]

Sounds interesting. I'll look into it.

In other news, I've toyed with the multimeter, by setting it to continuity I managed to get the LED to flash a bit (It alternates colors so I've found) but the motor still eludes me. I have a battery pack with four AA batteries in it. It may be slightly disfunctional because of a thing I did with it last year which corroded a number of the wires... however it still can take a charge from end to end (I think. I get choppy readings on the multimeter, probably due to corroded/old solder. I'm going to try to clean the terminals with an iron). Regardless, the motor won't work even with a single batter, it won't react at all. It was suggested that perhaps more voltage would work but it doesn't appear to (unless the battery pack is indeed inoperable) and the motor fits in the palm of my hand, I could in fact hold a number of them in my hand. They're really small. Do you think they would react better to a number of batteries?

[Chryseus]

[QUOTE=nikomo;46092373]Making a little thing for my Pi, to control an RGB LED, a segment display and a button.
[t]http://i.imgur.com/YPU2q64.png[/t]

Damn the schematic looks awful.
PCB should look prettier.
And I still haven't figured out the resistors I need for the JFET because I still haven't been able to figure out how you're supposed to use them.[/QUOTE]

Err JFETs are not really used for switching, I think what your after is a MOSFET, also your circuit has more errors than I can count.
I'll draw you something later if someone doesn't beat me to it.

[QUOTE=An Draoi;46092744]Sounds interesting. I'll look into it.

In other news, I've toyed with the multimeter, by setting it to continuity I managed to get the LED to flash a bit (It alternates colors so I've found) but the motor still eludes me. I have a battery pack with four AA batteries in it. It may be slightly disfunctional because of a thing I did with it last year which corroded a number of the wires... however it still can take a charge from end to end (I think. I get choppy readings on the multimeter, probably due to corroded/old solder. I'm going to try to clean the terminals with an iron). Regardless, the motor won't work even with a single batter, it won't react at all. It was suggested that perhaps more voltage would work but it doesn't appear to (unless the battery pack is indeed inoperable) and the motor fits in the palm of my hand, I could in fact hold a number of them in my hand. They're really small. Do you think they would react better to a number of batteries?[/QUOTE]

6V might be too low to get a 12 or 24v motor going, also are you sure it's a DC motor, other motor types require a more complicated circuit to run them.

[nikomo]

[QUOTE=Chryseus;46093126]Err JFETs are not really used for switching, I think what your after is a MOSFET, also your circuit has more errors than I can count.
I'll draw you something later if someone doesn't beat me to it.[/QUOTE]

I want current limiting, not only switching.
Also yeah, I think I've figured out some massive flaws already myself.

Looks like I do actually want a MOSFET.

[An Draoi]

[QUOTE=Chryseus;46093126]Err JFETs are not really used for switching, I think what your after is a MOSFET, also your circuit has more errors than I can count.
I'll draw you something later if someone doesn't beat me to it.

6V might be too low to get a 12 or 24v motor going, also are you sure it's a DC motor, other motor types require a more complicated circuit to run them.[/QUOTE]

I'm not sure about any details on the motor. I took a broken toy that my little brothers wouldn't be using anymore and... ah... repurposed it :P

I got two motors and some LED's, as well as the original PCB (though I doubt that I could find a random use for that)

[r0b0tsquid]

[QUOTE=nikomo;46093181]I want current limiting, not only switching.
Also yeah, I think I've figured out some massive flaws already myself.

Looks like I do actually want a MOSFET.[/QUOTE]

The resistors do the current limiting, not the transistor.

MOSFETs:
[IMG]http://i.imgur.com/q2H7UGo.png[/IMG]

You could also do it with BJTs, you'd just want a base resistor of about 20x what you have in series with the LED.

[editline]28th September 2014[/editline]

[IMG]http://i.imgur.com/6LevWsi.png[/IMG]

[editline]28th September 2014[/editline]

If this is for an RPi, have you considered using a [URL="http://en.wikipedia.org/wiki/Shift_register"]shift register[/URL] on your board to control the LEDs? E.g. [URL="http://www.nxp.com/documents/data_sheet/74HC_HCT595.pdf"]74HC595[/URL]. You can chain shift registers up, so you could control all your LEDs with just 3 GPIO pins (you could get away with 2 to be honest, no need for the latch control pin for visual stuff) and it would make your project cooler.

A 595 could drive the LEDs directly, no need for transistors (although you would still need current-limiting resistors).

[DrLuke]

[QUOTE=r0b0tsquid;46093846]The resistors do the current limiting, not the transistor.

MOSFETs:
[IMG]http://i.imgur.com/q2H7UGo.png[/IMG]

You could also do it with BJTs, you'd just want a base resistor of about 20x what you have in series with the LED.

[editline]28th September 2014[/editline]

[IMG]http://i.imgur.com/6LevWsi.png[/IMG]

[editline]28th September 2014[/editline]

If this is for an RPi, have you considered using a [URL="http://en.wikipedia.org/wiki/Shift_register"]shift register[/URL] on your board to control the LEDs? E.g. [URL="http://www.nxp.com/documents/data_sheet/74HC_HCT595.pdf"]74HC595[/URL]. You can chain shift registers up, so you could control all your LEDs with just 3 GPIO pins (you could get away with 2 to be honest, no need for the latch control pin for visual stuff) and it would make your project cooler.

A 595 could drive the LEDs directly, no need for transistors (although you would still need current-limiting resistors).[/QUOTE]

You can even control the shift register with the built in SPI hardware.

[nikomo]

I have less than 8 weeks of working knowledge with electronics, so I'm constantly pushing against that wall.
I'll need time to think about all of that.

[DrLuke]

I've designed my first board in weeks:

[t]http://a.pomf.se/vnxbpd.png[/t]

It's a PWM LED strip driver based on an ATTiny.

[Leestons]

[QUOTE=r0b0tsquid;46093846]
[IMG]http://i.imgur.com/q2H7UGo.png[/IMG]
[IMG]http://i.imgur.com/6LevWsi.png[/IMG]
[/QUOTE]

Can I please ask what software you use for these?

[Fatfatfatty]

Update on my Playstation 2 resurrection project

The project was a failure

I got all the wires hooked up to my PSU +12V and ground to two wires, then i put the +12V against the +12V on the PS2 and GND to the GND on the mobo, there was a bit of arcing followed by a pop with a resulting smell of burnt capacitor. I killed my Playstation 2, I think it has to do with that the 12V out was labeled fucking 18 amps on my PSU

[video=youtube;2a4gyJsY0mc]http://www.youtube.com/watch?v=2a4gyJsY0mc[/video]

I should maybe read the power output and learn a little bit about that stuff before actually doing anything, oh well

[TCWilliamson]

[QUOTE=Fatfatfatty;46096558]Update on my Playstation 2 resurrection project

The project was a failure

I got all the wires hooked up to my PSU +12V and ground to two wires, then i put the +12V against the +12V on the PS2 and GND to the GND on the mobo, there was a bit of arcing followed by a pop with a resulting smell of burnt capacitor. I killed my Playstation 2, I think it has to do with that the 12V out was labeled fucking 18 amps on my PSU

[video=youtube;2a4gyJsY0mc]http://www.youtube.com/watch?v=2a4gyJsY0mc[/video]

I should maybe read the power output and learn a little bit about that stuff before actually doing anything, oh well[/QUOTE]

You do realise that it could have 20,000A and you would have the same thing happening, Voltage is the 'push' where as current is the actual force.

if you have a 12V power supply that can supply 20A and you put a 12W 12V light on it, it will draw 1A, at 12v, the voltage can only push 1A through that lightbulb.
It is far more likely you wired it up wrong.

[Fatfatfatty]

Well, I really am no electrical engineer, I am just a programmer. We all make mistakes due to inexperience. (next time i should read before I do, but now i have to pay the price of a broken main board, but i am sure i connected them correclty)

[TCWilliamson]

Look what i found! a plug with... an RFI coil in it? o.o
[img]http://i.imgur.com/lui8dNl.png[/img]

[r0b0tsquid]

[QUOTE=Leestons;46095783]Can I please ask what software you use for these?[/QUOTE]

I just use [url=http://www.falstad.com/circuit/]Java Circuit Sim[/url] and set the background to white and the resistors to European. For a more complex or precise schematic (i.e. with actual part numbers) I'd use Eagle :)

[Leestons]

[QUOTE=r0b0tsquid;46097457]I just use [url=http://www.falstad.com/circuit/]Java Circuit Sim[/url] and set the background to white and the resistors to European. For a more complex or precise schematic (i.e. with actual part numbers) I'd use Eagle :)[/QUOTE]

I've used that quite a bit and had no idea because of the white background. Thank you.

[Fourier]

[QUOTE=nikomo;46092373]Making a little thing for my Pi, to control an RGB LED, a segment display and a button.
[t]http://i.imgur.com/YPU2q64.png[/t]

Damn the schematic looks awful.
PCB should look prettier.
And I still haven't figured out the resistors I need for the JFET because I still haven't been able to figure out how you're supposed to use them.[/QUOTE]

You might be interested in PI-Blaster, a program that gives you 8 (eight) output PWM channels. (in GPIO), done via DMA controller.

[url]https://github.com/sarfata/pi-blaster/[/url]

[editline]28th September 2014[/editline]

[QUOTE=nuttyboffin;46096743]Look what i found! a plug with... an RFI coil in it? o.o
[img]http://i.imgur.com/lui8dNl.png[/img][/QUOTE]

I don't know why... why?

Current limit? Interference/filter?

[Cakebatyr]

[QUOTE=Chryseus;46090238]It's for working with a software defined radio (SDR), I'm using a cheap RTL2832U which most TV tuner and digital radio dongles use, it can be used to listen / decode anything between 24MHz to ~1.8GHz, the list of things to do with it is pretty much endless.
If you don't have one I highly recommend getting one to play with, they can be had for under 20 bux.
[url]http://www.rtl-sdr.com/[/url][/QUOTE]

Out of curiosity I looked into an SDR+RasPi. Whoa, [url=http://www.hardhack.org.au/ra_frequencies]amateur radio astronomy[/url]. And for the most part those frequency ranges fall neatly inside the RTL-SDR's tolerances.

This sounds like fun.

[Zero-Point]

[QUOTE=nuttyboffin;46096743]Look what i found! a plug with... an RFI coil in it? o.o
[img]http://i.imgur.com/lui8dNl.png[/img][/QUOTE]

[QUOTE=Fourier;46097988]
I don't know why... why?

Current limit? Interference/filter?[/QUOTE]

Just a noise filter. Might be a particularly sensitive device depending on what you pulled it out of.

[Chryseus]

[t]http://u.cubeupload.com/Chryseus/tVq5AH.png[/t]

Now for the fun part!
In case you haven't been keeping up it's a 24 bit audio ADC with USB isolation (up to 5kV), which I'm
going to use with my ECG, and perhaps a narrow band SDR.

[r0b0tsquid]

[QUOTE=Chryseus;46100479][t]http://u.cubeupload.com/Chryseus/tVq5AH.png[/t]

Now for the fun part!
In case you haven't been keeping up it's a 24 bit audio ADC with USB isolation (up to 5kV), which I'm
going to use with my ECG, and perhaps a narrow band SDR.[/QUOTE]

Looked up that ADC you used, it looks really nice, farnell has it for like £2.76 as well! I see that you've connected your signal to both inputs of the ADC, are you going to average the two results to get a better SNR? And is that better than having multiple input signals, like a full-on ECG in a hospital?

[editline]29th September 2014[/editline]

After a DX order failed to arrive, I've spent about 3 weeks trying to get hold of the right 5110 display for my board.

The driver chip and screen are identical, but for whatever reason there is a newer version of the board, with a different pinout - including things like [i]swapping VCC and GND[/i]. I've been trying to get one of the older boards (seeing as that is the pinout I have on my multimeter) but no one in the UK has one - a couple of sellers have photos of the old board but actually sent me the newer version instead, and then tried to be difficult when I asked for a refund. Oh well!

DX and a couple of Chinese ebayers are all sending old displays to my uni address, so hopefully they will be there when I move in. Until then, I'm breadboarding!

I've written a simple library for controlling 5110 LCDs, it uses that font that I drew by hand ages ago.

[img]http://i.imgur.com/gcQXB0X.jpg[/img]

I'll have different font, and a big font for the numbers further on down the line.

I forgot to include an Ohms symbol in the font when I drew it, this is the closest there was :v:

[img]http://i.imgur.com/cgu4qHn.jpg[/img]