Poopernickel posted:

When soldering wires directly onto traces or pads, it's always a good idea to tack down a little bit of glue right by the pad for strain relief. Otherwise you're just asking to lift the pad and the trace along with it.

Superglue is aces if you're sure you want to keep the wire there. If you want something a little bit less permanent, I'd recommend hot glue. I use it all the time in prototypes because it's somewhat flexible when dry and melts right off. Hot glue is also really good if you ever need to lift a pin from an surface-mount IC and solder to it. Without something for mechanical stability, your chances of ripping the pin right off of the IC increase significantly.

Here's what I usually do when I want "just a dab" of hot glue or when I need to put a little bit under a pin I've lifted. I cut off a tiny tiny piece of the glue stick and just put it wherever I want the glue to be. Then I dab it with a fine-tip soldering iron and it melts pretty much instantly. Since it melts at a much lower temperature than solder, you can do it without desoldering anything if you're careful.

Seriously, this is some protip poo poo right here

therunningman posted:

If the programming required is something that a reasonably intelligent person could be expected to slowly pick up, then it sounds like something for me.
I would be starting at "hello world", so any kind of early direction would be important to be put on the right track early.

Looking around briefly I keep seeing the name "Arduino". Good starting point?

clredwolf posted:

There should be a game called 'find the PIC'. Just rip something vaugely dealing with electricity apart and see how many PIC microcontrollers you can spot.

There's a good reason PICs and AVRs tend to be used a lot. They're incredibly rugged, easy to use processors. The other day, a friend of mine had a board that was powering up AVRs (Arduino Nanos actually) without anything connected on the 5V rail. Turns out he was pushing 24V into one of the analog pins, which was actually powering the part! He fixed the problem, and the analog pin still works correctly!

For a lot of applications, you really don't need much more than a PICAXE or Arduino. Both are nice due to their ease of use. Arduino happens to be open source, and I see a ton of projects out there for it. I happen to like the Arduino better, but both are perfectly reasonable starting points.

If you get an Arduino, I recommend starting with a Duemilanove. Those tend to have the most useful accessories, and most projects are based around them. The Arduino Nano is another good one, and it has the advantage of being able to fit right into a breadboard.

Corrupt Politician posted:

Fantastic thread here guys! I have a question that hopefully someone here will be able to answer:

I'm working on a project that requires me to control the output of somewhere around 100 3-color LEDs. The LEDs are the kind sold here (they are red/green/blue and draw around 20mA at 2-4V). I must be able to switch on/off each color of each LED individually, giving me 8 possible states per LED (pwm control would get me a lot more and would be ideal, but I don't really need it). The LEDs would be controlled by a PC, via USB or serial.

I've been searching on various electronics websites and most of what I've come up with are LED controllers that come with the LEDs attached, or that control a board of LEDs, neither of which work for me (the LEDs need to be completely separate from the controller and from each other). The only thing I've found so far is this 64-LED controller, which is a pretty cool gizmo, but is expensive ($92) and not big enough for my application (it's designed for 1-color LEDs, so I'd only end up with a 21-LED controller).

My question is twofold:
1) Is there some product out there that does exactly what I need?
2) If there isn't, then what is the best way to go about designing my own? I saw that some of you guys have designed LED controllers, but is there a relatively cheap way to make one for so many LEDs? (I have been working on this and have some Multisim pics that I'll upload if you're interested).

I would really appreciate any help on this. Also, sorry for the overly-wordy description.

Poopernickel posted:

Actually, this project is a prime candidate for an FPGA-based solution. You can buy FPGAs with hundreds of output pins, all independently controllable. With some careful work you could probably PWM every single pin as well (maybe with one PWM circuit shared between every 16 LEDs or something similar).

You could easily cook up a simple interface (maybe 7-bit LED address, 8-bit data, and a strobe pin) which you could load using your desired microcontroller of choice.

Looking around on Digikey, you can buy a Xilinx Spartan-IIE with 146 I/O pins for about $14. Three of those, an oscillator, some current-limiting resistors and a cheap microcontroller are all the circuitry you would need. Double-check the total drive capacity of one of those FPGAs though - I know each pin is rated for something like 30mA but it would be smart to check the overall power-sink capabilities.

I would recommend using an open-drain topology where the anodes of each LED are tied to the desired voltage rail and each cathode is connected (via current-limiting resistor) to the FPGA's output pins.

Obviously this method is somewhat hardware intensive, but you would get the best results by far (full PWM, any framerate you want, no worries about brightness).

Poopernickel posted:

verilog

ANIME AKBAR posted:

there are much easier ways than learning to use fpgas and using discrete components. One is ICs that are essentially shift registers whose outputs are configurable current sources. You can daisy chain any amount of them on the same serial bus, so you could operate them all with a single microcontroller.

here's a datasheet for one I've used in the past:
http://www.allegromicro.com/en/Products/Part_Numbers/6278/6278.pdf

Poopernickel posted:

I've never used a skillet so I can't comment on how well it works or doesn't work.

BattleMaster posted:

The cool thing is that everything the design needs is built right into the microcontroller except the SD card, audio amplifier, and the DAC crystal. If I used SMT components the design could be amazingly tiny but I'm not that good yet.

Exitlights posted:

I'm just making sure that when I do get a wireless connection going, I'll have a fast enough connection between whatever receives the video and my computer to be able to display the video in real-time. The COM port functionality provided by the Arduino, from what I can tell, maxes out at 115200 baud, which isn't enough to communicate video to my computer with any sort of framerate. Before I get to the wireless transmission part, I'd just like to interface my computer directly with a CMOS camera in real-time, ignoring the wireless part until I can at least get the camera to work.

BattleMaster posted:

The cool thing about the Microchip USB implementation is that it uses DMA to keep the peripheral fed while you do other stuff.

BattleMaster posted:

Pretty much for the same reason you'd run an RS232 cable to it, because you didn't read his posts. He needs to connect a wireless transceiver of some sort to a computer so he can control the boat using it.

Edit: Though in a hypothetical situation where you actually need to run a really long cable to a boat USB would win because the twisted pair differential signal is way more resistant to noise and the protocol has error correction built in

German Joey posted:

Does anyone have a suggestion on the easiest, quick-n-dirty way to send data from a .txt file to an MSP430? I have a .txt on my computer., generated with a perl script, filled with 0's and 1's, and I'd like to stream that through a MSP430 (a MSP430FG4618IPZ to be precise), bit-by-bit. Multiple bits at a time would be preferred, but bit-by-bit is fine. What would you guys recommend?

BattleMaster posted:

I can't speak for other brands but the internal oscillator in the PIC series isn't as accurate as an external crystal. This is important for things like accurate timing and asynchronous serial communication (USB, UART, etc.). I'm using a PIC18F26J50 in a design and its internal oscillator doesn't meet the frequency tolerance required for full-speed USB so it needs a crystal to work properly.

Keebler posted:

The old "True RS232" chip numbers are 1488 and 1489, the driver and transmitter are separate chips and require a bigger supply then the RS232 compatible chips. Maxim (and I'd imagine other companies like Intersil) do still make pin compatible versions of these. Maxim's is the MAX1488E and MAX1489E:

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1022

Digikey sells them for around $3 each in DIP form:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=MAX1488EEPD%2B-ND

catbread.jpg posted:

One solution would be to use a buck-boost converter, controlled to a fixed output voltage of 15V.

Voltage from the snowmobile-->rectifier-->filter-->buck/boost-->12V regulator.

That will work all the time.

ANIME AKBAR posted:

hahaha no

catbread.jpg posted:

Also why are you switching LEDs at 20 kHz?

Zuph posted:

This chip doesn't need nearly the external hardware that the other one does. This one's available SOIC, too, so it won't be impossible to solder.

Thinking about it more carefully, I suppose you're right. I'll just have to be careful with MAC address assignment. The filters on the ENC28J60 should safely ignore everything that I don't care about. Everything is simplified by assuming that these devices will be the only things on the network in question.

Zuph posted:

For this particular project, I'd want to run the wires outside, so I'd just use an old, crappy switch that I don't care about (Plus, my Gigabit switch cranks down to 10/100 if a 10 mbps device is attached ). I'll disregard anything but unicast packets, anyway. If I have the time and tenacity, I might set the master node up with a full TCP stack, so I can interface to a PC that way, instead of through RS232 or similar.

Metajo Cum Dumpster posted:

Half way to the end.

Delta-Wye posted:

The schematic is pretty much overkill - all you should need to reproduce is the three lines connecting the digital amp to the PIC (chip select [CS], serial clock [SCK] and slave out [SO]). The datasheet as all the info you SHOULD require, although deciphering a datasheet is a skill in-and-of itself. With such a simple SPI device (you're not even sending data to it) you can probably bit-bang it manually using digital ports pretty easy, although I'm not sure how much direct access an arduino would give you.

You pull CS low, and toggle the CLK line while reading the SO line as you go - as far as interfacing goes, it's super straightforward. Hell, with the CLK line (the clock is the major differences between synchronous and asynchronous communcation, aka SPI vs RS232) you should find that the timing can be fairly loose and still will work well.



(as an aside, I sometimes hate digikeys selection. They have lots of varieties of chips, sometimes hundreds with common chips like the 555, and very little information to differentiate them. Often times even the datasheet is mum on the differences between the small variations.)

Twerpling posted:

Anyone know of a cheap uC that possesses 2 UARTs, 2 PWMs, and does not require 3.6v or less? I am working on a project that requires one, everything is designed at 5V already and I don't want to go back and remake everything.

Hillridge posted:

you can cut down the length of wire by adding power resistors in series with it. A 10 ohm resistor rated for 20W (or more) will reduce the wire needed by about a foot, but almost 17W of your power/heat is going to come from the resistor instead of the wire.

Exitlights posted:

Got my Xbees and explorers from Sparkfun the other day from the free day, soldered on some pin headers, wired 'em up in a quick loop... and I got a wireless echo over my COM port! Extremely exciting. Now it's just a matter of putting the Xbees in place of the wired serial connection I was using before, and I'll have a digital, wireless R/C car controllable from my laptop.

It's a pretty newb project, but I'm pretty excited about it. I'll put up a newb video when I get the thing moving around

BattleMaster posted:

What's the trick to using an ADC and DAC with audio signals when the circuit only has a single positive supply? I've got a PIC with ADC, an SPI DAC, and an LM386 audio amp. I'd like to have the audio signal digitized by the ADC and recreated using the DAC but with the way I have it set up it only outputs varying high-frequency whines.

Popete posted:

So is this just saying that before the voltage/current re-enters the source it will equal 0? I just thought measuring voltage after it runs through a resistor still came out to a set voltage and not 0.

Cyril Sneer posted:

3) You need to either have the dongle/amplifier physically at the antenna, or you'll have to located the antenna in close proximity to your PC.

The Ferret King posted:

Any idea what these are?



They look like capacitors but they're labeled with things like "100 16S 2QN" and I couldn't find anything on Google that matches.

I'm salvaging and sorting parts from old electronics and I find that a lot of them have stuff not easily recognizable to me, even after consulting some how-to sites and guides.

Entone posted:

Hey guys. I'm currently in the process of restoring a 1940's Silvertone radio/45rpm Record Player. Here's the original photoshop of my idea. I'm adding the avr32 ngw100 board as my microcontroller, and on top of that I'm adding an homemade board that has a ac97 codec for audio. I'm going to add 6 IN-4 nixie lights for a clock, plus 4 IN-13 tubes for a vu bargraph. On top of that it will have rca out, plus a dual am and fm transmitter; so, I can play my mp3s to other antiques around the house.

You can view my updates @ http://epicdistraction.com





My question is: I accidentally broke one of the knobs/switches, and want to replace it with something that better fits its functionality. I'm trying to find a rotary switch that Single-Pole and two or three throw. I'm also looking for a near impossible feature. I want it to be self righting/center/neutralizing. So I can get knob that looks similar to an arrow and you can use it to go through the directory tree. I could get a SP3T rotary switch, but it would require manual effort to center the knob.

fake edit: should I make a thread over the project?

ludnix posted:

bolind posted:

Hello

I have an idea, that I'd like an informed opinion on.

I'm an emerging coffee/espresso nerd. I've already modified my espresso machine with PID temperature control, and now it's the grinder's turn.

My grinder is dumb as a box of rocks. One switch, one electric AC motor, that's it. Fancier, more expensive grinders have timers, so you set a given grind time (8.3 seconds, for instance), and you just push a button once, and the grinder runs for the specified duration. This results in the same amount of coffee for your espresso every time, which is desirable.

I'd like to modify my grinder to do the same. Does a component exist, that:

Runs on 230VAC only (12V or 24V is doable, but less desirable)
Let's me adjust the delay
Will close a relay (SSR maybe) for, say, ten seconds after a quick press of a button.

I think the power draw is around 300-400W.

Apologies if this is more of an "electrician" question and less of an "electronics" question.

dv6speed posted:

Instead of a relay you could also use a transistor and a triac and go the solid state route. The 555 should work fine for you coffee grinder needs. You will need to build a small power supply circuit unless you want to use batteries.

Scarboy posted:

The valve looks like it just a switch that opens when you give it 12V.