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Solaron posted:mtwieg - you don't have PMs. Can I get in touch with you somehow about a few questions I had? You can shoot me an email: grantsd AT gmail.com. I had a few questions about the buzzer/locator thing I'm working on and I'd love to talk to you. mdt24 [at] case [dot] edu
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Jan 1, 2009 21:13
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babyeatingpsychopath posted:The electrical supply house has those buttons, too. I know because we had to get 8-10 of them for the current job. Red 2.5" Round Mushroom-head Momentary Contact switches labelled "emergency stop." They're stocked parts. Same way with Red Guard SPDT Toggle. The guard for the toggle switch is usually sold separately. ($7 on the internet, $1.50 at the surplus store.) My electronics-store friend got me one of these for Christmas. Unfortunately, I'm up to my ears in stopwatches, so I don't really need an egg timer. She says the alarm on it is really annoying, though. I'm thinking of adding it to the BRB box -- press button, lights count down, and then SKREE SKREE SKREE. It'd make the button a functional toy even if it doesn't do anything else! And I can use the extra switch I've already got in the box to select between the countdown/SKREE SKREE SKREE and the actually doing something as soon as the button is pressed! (Shameless plug: my friend/supplier/fellow goon is at Electronic Parts Outlet in Houston, if you're in the area.)
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Jan 2, 2009 06:48
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Bad Angus! Bad!
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Delivery McGee posted:(Shameless plug: my friend/supplier/fellow goon is at Electronic Parts Outlet in Houston, if you're in the area.) This doesn't mean you're going to get a goon discout, though. 
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Jan 2, 2009 06:50
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Karma Guard posted:This doesn't mean you're going to get a goon discout, though. Yeah, that's just for me  (seriously, don't annoy her. She has a mean left hook).
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Jan 2, 2009 06:56
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Delivery McGee posted:Yeah, that's just for me Oh god now goons will know which one is me  But in other news, the store I work at sells everything in the OP but the program that was mentioned. So if you're in Houston, you should just try and check us out. I know one of you was in here, I saw that City Name Sports Team shirt.
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Jan 2, 2009 07:00
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Grand_High_Took posted:I'd like to build a small and easily concealed electromagnet in order to trigger the induction based detector that sends a "car exiting" signal to the gate outside my apartment. Such a device is likely not possible. The electronics are likely callibrated so that a shift in inductance (or impedance, or current, or voltage, or resonant frequency - these are all equivalent effects) above a certain threshold is considered a "detection". From that, one can calculate how much voltage (or current) the detector loop must see. We know the area of the detector loop, so we could deduce how much external field must be present to induce the necessary voltage. Finally, if we posit the device to be placed on the ceiling of the garage, we can determine what kind of power we'd need in order to produce a sufficiently strong field.
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Jan 3, 2009 20:58
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Cyril Sneer posted:Such a device is likely not possible. I'm confused - you first say it's probably not possible, but then it sounds ilke you're saying that we CAN do it. We won't put the device on the ceiling of the garage -- assuming I can work out any power supply issues, my device should sit right on the ground, an inch or so from the detection loop. Does that change the analysis?
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Jan 5, 2009 01:11
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It's technically possible, but not likely to be practical - moreover, designing a solution would require more information on how the detector works (frequency and power, roughly, would be nice). Basically, you need pick an operating frequency for your transmitter then calculate how much power would be needed to induce a sufficiently-noticable change in voltage across the detector loop.
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Jan 5, 2009 05:14
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Cyril Sneer posted:It's technically possible, but not likely to be practical - moreover, designing a solution would require more information on how the detector works (frequency and power, roughly, would be nice). I think a bulk tape eraser (reasonably large AC electromagnet) sitting on the coil would work fine. Probably a 5lb lump of soft iron with a few hundred turns of wire on it and a few amps DC at 12V would induce more of a field than a bicycle would. Try a few different orientations. Really depends on how far away the thing is. I see that it's 4' from the edge of the road, plus width of sidewalk, so like 8' away, probably. I think this is a great project to just start making stuff and seeing if anything works, and from how far.
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Jan 5, 2009 06:05
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Where should I get started with microcontrollers once I get the very basics of electronics down? PIC v AVR? What's the difference? Do they have good beginner kits (I think PIC has PICKit 2).
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Jan 5, 2009 22:16
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Metajo Cum Dumpster posted:Where should I get started with microcontrollers once I get the very basics of electronics down? From personal experience if you already know some C, AVR is a good route to begin with. Their latest beginner kit/dev board is the STK600.
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Jan 5, 2009 23:18
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PICs are easier and faster to program in assembly language. You're not really going to miss out on a whole lot if you go with either product line, so you should go with whatever you like programming in better. If you go with PICs you might be better off just buying the ICD3 debugger*, making or buying a breadboard cable, and just build your circuits on breadboards. You won't miss out on much unless you want to work with SMT parts that you don't feel like soldering yourself. *Or just find a cheaper ICD2, I use one and it's good enough.
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Jan 6, 2009 00:22
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babyeatingpsychopath posted:I think a bulk tape eraser (reasonably large AC electromagnet) sitting on the coil would work fine. Probably a 5lb lump of soft iron with a few hundred turns of wire on it and a few amps DC at 12V would induce more of a field than a bicycle would. That's pretty much exactly what he'd have to do - just start making stuff and see if it works. But I was thinking this was something he was going to try and bury/hide - and I'm not sure a big lump of iron with, a few hundred turns, and a several-amped power supply would suit this purpose. edit: We need more RF talk 
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Jan 6, 2009 00:51
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Metajo Cum Dumpster posted:Where should I get started with microcontrollers once I get the very basics of electronics down? I've become a big fan of the Arduino board, which I found through the forums. Basically a $40 board that comes with a pre-flashed AVR that you can program using C. It's a very good stepping stone to programming AVRs that doesn't require any hardware other than a USB cable. (after you get comfortable with that, you can flash your own AVRs using a homemade cable made with three resistors, a piece of wire, and a sliced up parallel-serial adapter) edit: On the other hand, the only local AVR distributors sell them for about $10, while I've seen PICs for $3
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Jan 6, 2009 01:31
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Thanks guys. I still have a very limited knowledge of microcontrollers, so bare with me please. If AVRs use C, what language do PICs use? ante mentioned arduino boards, is this something similar to what you were talking about? http://www.sparkfun.com/commerce/product_info.php?products_id=666 all I need is a usb cable that fits the mini jack there to be able to program it? What program does it use? Is it in C as well? Whats the difference in the higher pin counts? Are all the chips 8-bit? Whats with the different "frequencies"? What else would I need with that arduino board mentioned above?
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Jan 6, 2009 04:29
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Metajo Cum Dumpster posted:If AVRs use C, what language do PICs use? They both get programmed in device-specific machine code. You can use assembly language, where each line translates directly into a single instruction for the CPU, or you can find a compiler for a language of your choice that turns that language into machine code. AVRs have a free official C compiler so that's a consideration if you already know C. You can always use Assembly but see below. The official PIC C compiler costs money and the third party ones also cost money or are incomplete. However, they are really easy to program with assembly language because all RAM and I/O peripherals are mapped as CPU registers so you don't spend time shuffling data around as you work with it. It takes more work than C, but you have much greater control over timing and the inner workings of the CPU. Edit: quote:Whats the difference in the higher pin counts? Are all the chips 8-bit? Whats with the different "frequencies"? 1. For the most part, more pins. Sometimes they get special peripherals that require more pins like microprocessor bus interfaces. 2. I believe all AVRs are 8-bit, and all PIC10/12/14/16/18s are 8-bit. The other PIC lines are 16 and 32-bit. 3. Clock frequencies, that is how many times the clock ticks per second. CPUs can do so much per clock tick (cycle) so a higher frequency means you can do more per second. BattleMaster fucked around with this message at 04:46 on Jan 6, 2009 |
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Jan 6, 2009 04:39
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Metajo Cum Dumpster posted:Thanks guys. I still have a very limited knowledge of microcontrollers, so bare with me please. Arduino has its own C compiler. The board and the official site make it really really easy to get into. You download the software, install the driver(just double click it!), and plug in the board. That's it. Other AVR setups or PICs may have advantages or disadvantages, but you're certainly not locked into the Arduino once you start using it, it's just a great way to learn. One thing I'm planning on doing in the near future is getting a few PICs and learning assembly with them. I'm going to need to be able to accurately control how many clock cycles everything takes for a project coming up. If I jumped right into that, it'd be pretty tough, though. Even wiring everything up can be a hassle sometimes, and it'd all be on breadboards.
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Jan 6, 2009 05:39
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ante posted:If I jumped right into that, it'd be pretty tough, though. Even wiring everything up can be a hassle sometimes, and it'd all be on breadboards. Broadboarding a microcontroller isn't that much more work than connecting stuff to a board like the Arduino. A voltage regulator, a crystal or two, a MAX232 if you're using a UART, and some breadboard adapters. Now I've wired up a system with a Z80 CPU on breadboards and that sure isn't pretty! I'm working on making a proper board before I do anything more complicated with it.
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Jan 6, 2009 05:54
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I'm having this problem. I have a PIC18F1320 ( http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010265 ) and I connected it to a MAX232 in order to do RS232 serial. Tx is connected to pin 9, Rx Pin 10 and nothing else except power and ground (I removed everything to figure out why this is happening). I connected a serial line from my computer and was planning on just using hyper term to communicate with the chip. I loaded up some test code and it loads up fine and seems to execute. I get data on hyper term but when I send something from hyper term to the chip nothing happens. I've hooked up my scope and logic analyzer and the signal is getting to the chip. I'm using the PICMicro C compiler by CCS to do this. Every thing works except receipt of data and it worked before. I've already tried a new chip and tried the simple test code that was provided by CCS. Nothing seems to work. Anyone have this problem? Is there a fuse I need to set?
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Jan 6, 2009 05:58
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Twerpling posted:I'm having this problem. I have a PIC18F1320 ( http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010265 ) and I connected it to a MAX232 in order to do RS232 serial. Tx is connected to pin 9, Rx Pin 10 and nothing else except power and ground (I removed everything to figure out why this is happening). Does the code set the RX pin's corresponding TRIS bit to input? I'm sure it does if it's someone else's code, but you never know.
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Jan 6, 2009 06:01
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Twerpling posted:I'm having this problem. I have a PIC18F1320 ( http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en010265 ) and I connected it to a MAX232 in order to do RS232 serial. Tx is connected to pin 9, Rx Pin 10 and nothing else except power and ground (I removed everything to figure out why this is happening). Make sure you have pullup resistors if you need them (I forget whether they're necessary for a normal max232).
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Jan 7, 2009 09:13
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hey guys I'm trying to find a specific type of connector but I don't know what it's called. It's similar to an IDC connector, but it fits on slightly larger wire, closer to hook-up wires than ribbon cable or wire-wrap stuff. It's usually used in pairs, and it has what looks like a normal female header on the end, the end fits snugly over normal header pins. the STK500 comes with a bunch of these little paired wires with this kind of connector. here are some pictures:    anyone know what it's called?
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Jan 7, 2009 09:32
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mtwieg posted:Make sure you have pullup resistors if you need them (I forget whether they're necessary for a normal max232). They're not. I don't know what to say. If the MAX232 is working and hooked up properly then maybe the demo code just doesn't work?
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Jan 7, 2009 18:18
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Decided I want to start with the Arduino as it's cheap, open, and want to practice my C. What should I get to start with? Also, what's with all the "shield" stuff?
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Jan 7, 2009 22:27
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Metajo Cum Dumpster posted:Decided I want to start with the Arduino as it's cheap, open, and want to practice my C. The Duemilanove is the basic one, just get that. The shields add functionality like bluetooth, internet(wtf), stuff like that.
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Jan 7, 2009 22:47
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Zaxxon posted:hey guys I'm trying to find a specific type of connector but I don't know what it's called. Doing a quick search I found these guys which are pretty much the same, except they have a locking mechanism so they're meant to be used with shielded headers, but will work fine on unshielded ones like on the STK500. However connecting them to wires can be a pain in the rear end unless you have a special tool called a crimper. Naturally, crimpers are abhorrently expensive.
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Jan 8, 2009 03:24
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mtwieg posted:ugh, searching for connectors is such a bitch. Makes having a catalog full of pictures worthwhile. I looked for the same exact thing (and also for the stk500) a while back. The general name for those types of connectors are rectangular. It's female, or rather a receptacle. And it's free hanging. The pitch is 0.1". it is such a bitch! And it's one of those things that seems like there would only be a few real standards in. I mean everything has the same kind of header pins, so why is is so drat hard to find connectors for them? those seem like they will do the trick. Don't let anyone tell you you aren't a hero. But yes searching for connectors is a colossal pain. I'm going to try my local salvage store (MC Howards for any electro goons in austin,) as they tend to have a fair amount of varied connectors or cables with connectors attached.
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Jan 8, 2009 04:51
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here are some without the locking mechanism. Now that I think about it the locking mechanism might make it impossible to connect two of them next to each other, so you should go with these simple ones.
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Jan 8, 2009 05:59
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You're just lucky the crimpers are under five grand!
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Jan 8, 2009 16:19
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mtwieg posted:here are some without the locking mechanism. Now that I think about it the locking mechanism might make it impossible to connect two of them next to each other, so you should go with these simple ones. I grabbed a bunch and some digital pots. also the no lead versions are a bit cheaper.
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Jan 9, 2009 01:33
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Can somebody please help me understand voltage? I understand the idea of amperage (eg. amount of electrons passing a specific point over a given amount of time) and I understand resistance but I just can't understand voltage. I'm reading All About Circuits and it says things like this in the first chapter: quote:If we break the circuit’s continuity at any point, the electric current will cease in the entire loop, and the full voltage produced by the battery will be manifested across the break, between the wire ends that used to be connected. quote:As before, with no flow of electrons, the entire potential (voltage) of the battery is available across the break, waiting for the opportunity of a connection to bridge across that break and permit electron flow again. Can anybody help me out? I'm also confused about how capacitors work in a circuit but that's a whole different discussion.
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Jan 9, 2009 19:08
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Vinlaen posted:Can somebody please help me understand voltage? I understand the idea of amperage (eg. amount of electrons passing a specific point over a given amount of time) and I understand resistance but I just can't understand voltage. The water analogy is very useful. Think of electricity as water. Current is flow rate. Resistance is resistance. Voltage is pressure. Pressure can only be measured in relation to something else, just like voltage. A battery is like a pump. When it's not connected to anything, the "pressure" between its terminals is some value. When it's pumping water through a closed loop, the pressure measured between the input and output is the same value, ideally. Same way with voltage. A battery has some voltage between its terminals. When it's providing current in a circuit, the voltage between its terminals is roughly the same value. If no current is flowing, the electrons at the battery's - terminal still want to get to the + terminal. Therefore, electrical pressure exists to any points connected to those terminals, thus, there's voltage between them. I feel it important to point out that voltage is a measure of electrical potential at one point relative to another point. The flu is addling my brain, so I can't think of any good examples, but someone else can.
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Jan 9, 2009 21:22
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I'll go through the analogy I use. Keep in mind that voltage is not an absolute value. It is a potential from one point to another, point A with respect to point B. Picture a mountain. On that mountain, imagine a single point. That point has an elevation, but elevation is not absolute. It's measured in metres above sea level. That's the height of the point with respect to the height of the sea. So, 300 metres above sea level, 10 volts from the positive terminal to the negative terminal. Same thing. On that mountain, there is a stream going from one point to another. It travels from the higher altitude to the lower one (+ voltage to -), and the amount of water going along that stream is the current. Pressure, I guess. Assuming ideal conditions, the source of the stream can supply infinite pressure, so don't worry about that part. Because of this, the pressure of the river depends on how wide it is. The wider it is, the lower the resistance, the more water flows along it. By the same token, the steeper the slope is, the more water will flow through. If you look at the mountain dead on, it'll look something like this:  The equivalent circuit is something like this:  The parts of the river that are very wide are wire, no resistance, no voltage drop across them. The drop in altitude/voltage across each element depends the familiar Ohm's law, and all that. If you get a break in the river, no water is flowing, so the potential to flow is the same all along that stagnant water. An open circuit is the exact opposite of a short circuit. With no resistance, the river is infinitely wide, so an infinitely large amount of water is try to push through.
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Jan 10, 2009 02:50
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Christ I had some bad luck with Jameco's misc and ttl IC grab bags. I got 28 UM82C88 bus controller ICs and a ton of empty plastic connectors amongst hundreds of tiny caps. And half of my 100 piece TTL grab bag are tiny SMDs I could never solder.
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Jan 10, 2009 17:15
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Has anyone ordered from Adafruit before? They have a nice Arduino starter kit bundle that goes with this Arduino beginner's tutorial. Wanted to see if they are reputable before I plop down $65 with some site I've never seen or heard of before.
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Jan 10, 2009 19:37
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Never ordered from there myself, but I have seen it discussed dozens of times over numerous forums and websites. From all I've read, it seems like a reputable place.
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Jan 10, 2009 20:34
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I've ordered there before. The shipping was a little slow because I got the cheapest shipping option, and she's pretty far away, but otherwise fantastic.
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Jan 10, 2009 21:02
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Metajo Cum Dumpster posted:I got 28 UM82C88 bus controller ICs and a ton of empty plastic connectors amongst hundreds of tiny caps. Haha. I'd buy a grab bag from them if it was guaranteed to have varying quantities of the entire 8080/8088 suite.
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Jan 10, 2009 22:10
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Metajo Cum Dumpster posted:Has anyone ordered from Adafruit before? They have a nice Arduino starter kit bundle that goes with this Arduino beginner's tutorial. Yes, lots of stuff, ladyada is great.
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Jan 11, 2009 16:27
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Metajo Cum Dumpster posted:Has anyone ordered from Adafruit before? They have a nice Arduino starter kit bundle that goes with this Arduino beginner's tutorial. yeah I got some spoke POV kits and a TVBegone. They are cool.
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Jan 12, 2009 18:49
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