Electrical Engineering V3 - Developers

So I decided to fuck around with some old thermostats I saved from the dumpster at my old job. Set about figuring out what sort of information they were sending through their communications bus. Before I started I knew: 1) It used 2 wires. 2) It allowed multiple devices on the same bus without jumpers/device configuration. 3) It was mostly likely differential-pair signaling. So I hooked it up to my bench supply first to see if I could run these stats off of DC instead of AC (turns out I can, runs just fine on 14VDC and probably lower, means I don't have to fudge with an old 24VAC transformer and mains wiring). Next, I hooked it up to my scope and powered it on. Funny that they almost tossed this thing for "not communicating" as it was sending data just fine according to the scope. So I can see the data. Yay! Problem is it's RS-485 (confirmed by locating a MAX3443 on the PCB) and my scope can only decode parallel, RS-232, I2C and SPI. :surrender: I guess it's all for the best, not much use for this information as the stat has nothing to talk to so that it can generate useful information anyway. :downs: Now I just gotta figure out how to reverse-engineer the signals to these LCDs, as they're pretty nice little back-lit dot-matrix monochrome displays.

I needed a right angle db25 adapter and I needed it asap [t]http://i.imgur.com/TartfSrl.jpg[/t]

Hi, I'm doing a project where we are taking the motor and impacting mechanism from an off-the-shelf impact wrench, and, long story short, we are going to purchase a bldc controller for it, since we want to control it from a raspberry pi and have feedback control of speed. Therefore, we need to know whether the hall effect sensors in the stator are latching or analogue. Does anyone know how to find out, or if latched hall effect sensors are standard in this type of motor? Image of stator: [url]http://imgur.com/gallery/di8BV[/url] Any help would be greatly appreciated.

[QUOTE=bonnendaniel;52031461]Hi, I'm doing a project where we are taking the motor and impacting mechanism from an off-the-shelf impact wrench, and, long story short, we are going to purchase a bldc controller for it, since we want to control it from a raspberry pi and have feedback control of speed. Therefore, we need to know whether the hall effect sensors in the stator are latching or analogue. Does anyone know how to find out, or if latched hall effect sensors are standard in this type of motor? Image of stator: [URL]http://imgur.com/gallery/di8BV[/URL] Any help would be greatly appreciated.[/QUOTE] Your best bet is to hook up the hall effects sensor outputs to an O-scope and measure their waveforms while hand turning the stator. IIRC usually they're latching but I wouldn't recommend disassembling the whole motor assembly to find out unless by some random happenstance you could ask the manufacture for a Bill of Materials or Schematic. Also considering most Hall Effects have open drain outputs, you'll need to have a pull-up resistor to 3.3V on the RPi in order to properly use it (The RPi does have built-in pull-ups).

[IMG]http://i.imgur.com/TU7oQI4l.jpg[/IMG] You know you're working on something old when the instruction manual finds it pertinent to inform you that the device has transistors in capital italics. It's stereo so it's gotta be late 60's to early 70's. I can't find literally any information on it anywhere. Thing works perfectly well too, other than the fact I can't get it to play the first ~7mm of any record, works perfectly fine after that though. All I had to do was repair some speaker wire that was exposed and had a few busted strands. A little solder and shrink tube fixed it nice. The weird thing is that all the components inside the table were still good and nothing was bulging, burnt or weird.

What dates it for me is it refers to line frequency in cycles. I place it in the late 60's in the first real flood of germanium transistors.

[QUOTE=F.X Clampazzo;52033294][IMG]http://i.imgur.com/TU7oQI4l.jpg[/IMG] You know you're working on something old when the instruction manual finds it pertinent to inform you that the device has transistors in capital italics. It's stereo so it's gotta be late 60's to early 70's. I can't find literally any information on it anywhere. Thing works perfectly well too, other than the fact I can't get it to play the first ~7mm of any record, works perfectly fine after that though. All I had to do was repair some speaker wire that was exposed and had a few busted strands. A little solder and shrink tube fixed it nice. The weird thing is that all the components inside the table were still good and nothing was bulging, burnt or weird.[/QUOTE] Old stuff is pretty robust, I have some tube radios from the late 40's and early 50's that still mostly worked. As for your problem it's probably mechanical rather than electrical.

[QUOTE=F.X Clampazzo;52033294][IMG]http://i.imgur.com/TU7oQI4l.jpg[/IMG] You know you're working on something old when the instruction manual finds it pertinent to inform you that the device has transistors in capital italics. It's stereo so it's gotta be late 60's to early 70's. I can't find literally any information on it anywhere. Thing works perfectly well too, other than the fact I can't get it to play the first ~7mm of any record, works perfectly fine after that though. All I had to do was repair some speaker wire that was exposed and had a few busted strands. A little solder and shrink tube fixed it nice. The weird thing is that all the components inside the table were still good and nothing was bulging, burnt or weird.[/QUOTE] Friends dad had the exact same problems with his old phonograph from his young days. Turns out there were gunk buildup in various places of the mechanical engineer porn called the auto raise/lower mechanism of needle arm. And it also had a frayed internal cable for the output due to the cable being a little too long and slowly being rubbed by said mechanism. Cleaning the mechanism and relubing it, and replacing cable and it worked perfectly afterwards.

[QUOTE=Chryseus;52033700]Old stuff is pretty robust, I have some tube radios from the late 40's and early 50's that still mostly worked. As for your problem it's probably mechanical rather than electrical.[/QUOTE] Yeah, and unfortunately I can't risk breaking it to fix mechanical problems seeing as how I can't even find a wikipedia article on the thing. It's like it doesn't exist. I feel pretty lucky that the original needle and head still work seeing as how I can't seem to find even a generic replacement that takes a single screw through the top. I might be able to just replace the needle when it needs it, but I think it's going to be more of a display piece than actually used. Shit I might even sell it if I can figure out what it's worth. Edit: I found one website that sells the needles for it. That's all I've been able to find.

so i have a project for class where i need to use this micro controller with some sensors to do something. I want to be able to control a series of LED's in a shape on my breadboard using a light sensor/photoresistor. How should I start? Should I wire the LED's in series or parallel? How do I know what value resistor I need to use if needed?

[QUOTE=thefreemann;52035802]so i have a project for class where i need to use this micro controller with some sensors to do something. I want to be able to control a series of LED's in a shape on my breadboard using a light sensor/photoresistor. How should I start? Should I wire the LED's in series or parallel? How do I know what value resistor I need to use if needed?[/QUOTE] R = (V - Vd) / I Where V is the supply voltage and I is the LED current (5mA is probably fine) Vd is the LED voltage drop, about 2V. You'll want to use them in parallel so you can light them individually, or you could use [url=https://en.wikipedia.org/wiki/Charlieplexing]Charlieplexing[/url] if you want more LEDs than you have free GPIO pins for.

[QUOTE=Chryseus;52037127]R = (V - Vd) / I Where V is the supply voltage and I is the LED current (5mA is probably fine) Vd is the LED voltage drop, about 2V. You'll want to use them in parallel so you can light them individually, or you could use [url=https://en.wikipedia.org/wiki/Charlieplexing]Charlieplexing[/url] if you want more LEDs than you have free GPIO pins for.[/QUOTE] Er, I just need them to all light up at once, so I can just control them with one pin right?

[QUOTE=thefreemann;52037570]Er, I just need them to all light up at once, so I can just control them with one pin right?[/QUOTE] I'd use a appropriate N channel mosfet to control the negative/ground of the LED's, but yeah, if they all need to light up simultaneously then one output pin is enough.

[QUOTE=thefreemann;52037570]Er, I just need them to all light up at once, so I can just control them with one pin right?[/QUOTE] Ah I thought you wanted like display of the light level. [img]http://i.imgur.com/BYrf9to.png[/img] Don't exceed 20 LEDs on a single pin.

Hey, not sure if it's the right thread for it, but I've been working on a Nucleo shield for rocket flight data capture, and need to figure out a storage method. Last year I managed to get it up to a couple hundred Hz on a Uno using data buffering to an SD card, but it failed in flight, likely due to vibrations or launch Gs messing with the SD card. Was looking at FeRAM but it's not cost efficient for the larger amount of data being recorded, battery backed up RAM isn't gonna cut it as it just adds more risk when exposed to high Gs. Wondering if I should have on-board flash memory, or if there's some other solution for higher speed storage I haven't thought of yet.

The only two non-volatile solutions that'll work is FeRAM or MRAM, access time is the major bottleneck with Flash/EEPROM and you won't be able to store all your data as fast as you'd like before your buffer overflows. Go ahead and bite the bullet and buy FeRAM or [URL="http://www.mouser.com/Everspin-Technologies/Semiconductors/Integrated-Circuits-ICs/Memory/NVRAM/_/N-98xha?P=1yzs0cc&Ns=Pricing|0"]MRAM[/URL], you won't regret it later. Plus both are hardier against radiation than flash/EEPROM should you go high enough.

I had an oral exam about high power microwave engineering (so mostly magnetrons and gyrotrons), and afterwards the professor invited me to lunch. Turns out I am going to do work on a 2MW Gyrotron for Wendelstein 7-X for my bachelor thesis. I will be continuing the work from this paper: [url]http://sci-hub.cc/http://www.sciencedirect.com/science/article/pii/S0920379607003055[/url]

[QUOTE=paindoc;49072697]The same night I almost went on a eBay shopping spree I constructed a great wishlist of books I wanted for my birthday, and it includes [URL="http://www.amazon.com/gp/product/1449310664?colid=1QPSKLCVC0MS6&coliid=I10HW4OGVYRSCW&ref_=wl_it_dp_o_pC_nS_ttl"]this [/URL] It may be of some use to you, and the Kindle version is 3.50 and you can read these ond esktop. Look at the preview maybe and see if it helps a bit. There's a whole series of these books too. [editline]7th November 2015[/editline] Fluke has kitted out a makerspace on our campus fully, and when I was there last it had just opened. Its fully up and running now and holy shit you should see the test bench and the [URL="https://www.seeedstudio.com/fusion_pcb.html"]pcb fabrication[/URL] ahrdware they have. That and a box full of dozens of really nice Fluke Multimeters just sitting around for sale for super cheap to club employees and long-term members :o[/QUOTE] can't agree more.

I might of asked before but does anyone here have experience with solid-state relays? IE: -What kind of loads does it assume. Inductive? -Are they designed for continuous use? -While the Opto 22's I have say the switching voltage can be anything between 3-32v DC, will a 5v source from a USB port be reliable enough? -Mine are rated 25A. Is that momentary inrush current with a low running current or can I run at say 15A constantly and not have things catch fire?

[QUOTE=pentium;52074430]I might of asked before but does anyone here have experience with solid-state relays? IE: -What kind of loads does it assume. Inductive? -Are they designed for continuous use? -While the Opto 22's I have say the switching voltage can be anything between 3-32v DC, will a 5v source from a USB port be reliable enough? -Mine are rated 25A. Is that momentary inrush current with a low running current or can I run at say 15A constantly and not have things catch fire?[/QUOTE] If you're doing inductive loads, you'll want a surge-current rating higher than your running amp-draw. (so no, they don't assume inductive loads, but they're perfectly fine for resistive loads) [url=http://www.phidgets.com/docs/Solid_State_Relay_Primer#Choosing_an_SSR]Source[/url] They can be used continuously assuming you're not over-loading them and they have adequate heat-sinking. If 5V is within the rated switching voltage, then yes. 15A would be a safe bet if it's rated at 25A. Check the data sheet for more information.

The idea is that I have devices attached to servers (tape library and two disk arrays) that do not have power switches on the front and are in racks where I cannot access their switches or plugs from the back. If I turn the server on the USB goes live and the 5v engages the solid state relays and powers up said attached equipment.

If you have relays that are rated for the load, then that should work fine. *edit* If it's a heavy load, I would recommend some sort of heat-sinking, though.

Actually, scrap the relays. I realized I got much more appropriate toggle switches I can hide behind an inspection hatch on the side of the rack. Unrelated, I had to refurbish two streetlights today. [IMG]http://i11.photobucket.com/albums/a166/ballsandy/New%20Bucket/CGS_7520.jpg[/IMG] [IMG]http://i11.photobucket.com/albums/a166/ballsandy/New%20Bucket/CGS_7521.jpg[/IMG] [IMG]http://i11.photobucket.com/albums/a166/ballsandy/New%20Bucket/CGS_7522.jpg[/IMG] [IMG]http://i11.photobucket.com/albums/a166/ballsandy/New%20Bucket/CGS_7523.jpg[/IMG] Fucking ballasts.

I got a cheap little peltier/thermal couple module off ebay. The shit little laptop and SMF dell heat sinks wouldn't cool the hot side enough so I took apart an old HP Integrity rx2620 and found that it had these massive copper heat sinks ( over a pound of copper lol ) and they work fucking awesomely. [t]http://i.imgur.com/K3gheLN.jpg[/t] [t]http://i.imgur.com/ZDTm1vf.jpg[/t] Cold Side: [t]http://i.imgur.com/iQi8j6H.jpg[/t] Hot Side: [t]http://i.imgur.com/YFkg1Bu.jpg[/t] I also found that the redundant 600W+ power supplies in the server just slid into this module that turns them into convenient molex connectors that I should be able to easily mount all into a box and have a 12V 52A lab power supply. ( no pics of the power units themselves ) [t]http://i.imgur.com/ANAEep4.jpg[/t] [t]http://i.imgur.com/TTd5Bqt.jpg[/t] [t]http://i.imgur.com/Z0HVsWe.jpg[/t]

Are there any resources for reading about microelectronics? I need to write a report on it and I'm kinda lost. Don't know what to talk about in it.

Are you talking microelectronics like, how chips are made? The history of electronics? Because like we can talk for days about gates, buffers, latches etc. We're going to need far more information on your report than just microelectronics but I'd be willing to help you on the right track if you're truly lost. Personally a single report on it sounds kinda vague, seeing as how I've had weeks upon weeks of lectures on it down to individual chips and stupid shit I'll never remember simply because I can look in the god damned reference book/data sheets and get everything I need and more. Also, I repaired some kind of electronic bit for my brother's truck today. All I know about it is that it does something with tuning or some shit idk. The fucking bit that got me was that he somehow literally blew a board trace apart on the board but everything else checked out perfectly fine, had to take it to campus with me today so I could borrow the fancy equipment I only dream of affording. Only thing I had to replace was a resistor that, according to the company who makes the damn thing, was supposed to be 5% and was far more within a 10% range instead. Thing was about 8% below. Oddly enough the resistor wasn't even connected to the specific circuit I was fixing, so idk what that company is doing but damn do they suck.

[QUOTE=F.X Clampazzo;52086080]Are you talking microelectronics like, how chips are made? The history of electronics? Because like we can talk for days about gates, buffers, latches etc. We're going to need far more information on your report than just microelectronics but I'd be willing to help you on the right track if you're truly lost. Personally a single report on it sounds kinda vague, seeing as how I've had weeks upon weeks of lectures on it down to individual chips and stupid shit I'll never remember simply because I can look in the god damned reference book/data sheets and get everything I need and more. [/QUOTE] That helped a bit. I don't know what to talk about in my report, the theme my teacher chose is just "microelectronics". I'll take a look at Tocci's book, Digital Systems, and add some parts of it to my report.

That time of year again. [url=http://www.sphere.bc.ca/test/stuffday.html]You PNW'ers get your butts to Kelowna BC this Saturday. I buy lunch for the first FP'er who recognizes me.[/url]

[QUOTE=pentium;52091840]That time of year again. [url=http://www.sphere.bc.ca/test/stuffday.html]You PNW'ers get your butts to Kelowna BC this Saturday. I buy lunch for the first FP'er who recognizes me.[/url][/QUOTE] Fucking Canada, being all far away from me 'n shit. :disgust:

Hey guys quick question, I'm reading over this datasheet for the [URL="http://www.ti.com/lit/ds/symlink/lm3429-q1.pdf"]LM3429[/URL], and I'm wondering for SEPIC mode, can I have the sense resistor on the low side of the LED string? [IMG]https://my.mixtape.moe/qutzgy.PNG[/IMG] The HSP/HSN pins are connected directly to a difference op amp so I don't see any reason not too (provided I set HSN to ground).