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Man this economy must be bad if Bob Pease got the axe: http://www.edn.com/blog/1700000170/post/1030042103.html Dude is an analog circuit master Jedi. He invented the LM317!
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Mar 18, 2009 20:52
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oxbrain posted:Is there a reason I shouldn't file a new wedge point on my ancient weller tip? The local stores don't carry replacement tips, and I don't want to spend $10 on one from amazon. It'll probably be ok, but you'll want to keep it well tinned so it doesn't corrode. Worst case, you have to spend $10 on a new one.
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Mar 18, 2009 21:24
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Delta-Wye posted:So I'm building a multichannel light dimmer, and I need 5V for the PIC from AC, but I don't have space in the box for any of the transformers I have handy. Is there a neat trick to get regulated 5v from AC other than your typical transformer->rectifier->filter->regulator circuits? The wall to USB plug for the iPhone 3G is stupid small. Like amazingly tiny. Of course, knowing Apple it's probably also stupid expensive.
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Mar 20, 2009 16:14
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ANIME AKBAR posted:Overall I avoid using tantalum completely. We have a design standard at work that forbids using tantalums in anything other than well controlled, current limited circuits due to their failure mode of "catch on fire". I just skip them entirely as well.
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Mar 23, 2009 16:56
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BattleMaster posted:I thought that the option with the diode icon was the continuity test. It's to check the diode voltage drop, which is kind of like continuity for diodes. If you set it to that and put it across an LED, it will usually light it up slightly, which is a good way to figure out LED polarity safely.
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Apr 2, 2009 16:07
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I just tried out that circuit simulator, and it's pretty cool. Something seems to be a bit amiss though. I made this charge pump based negative voltage supply design, but I didn't expect to see a full -10V output.code:
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Apr 17, 2009 16:33
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ANIME AKBAR posted:uhh, that's not a charge pump. Charge pumps are much simpler. ok, technically the charge pump is just the 2 caps and diodes on the end with an AC source on the left. code:
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Apr 19, 2009 16:35
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ANIME AKBAR posted:no, a charge pump contains no diodes. What you're showing is more like a voltage doubler, but inverting. Charge pumps work using flying capacitors and analog switches. It really is the same thing, just implemented differently. From the wiki you linked: Another way to explain the operation of a charge pump is to consider it as the combination of a DC to AC converter (the switches) followed by a voltage multiplier. The op-amp produces the DC-AC, and a voltage multiplier is just caps and diodes. Charge pump may not be exactly the right term, but it's not totally wrong either.
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Apr 20, 2009 02:58
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Bush Ant posted:yeah i posted a similar circuit a few pages back, and someone was Fixed.
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Apr 27, 2009 16:51
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This may be a bit of a long shot, but do any of you know how gamma correction is done on a TFT/LCD at at very low hardware level? I know what gamma correction is for, but not quite how it's implemented in hardware. I have a raw LCD panel that needs 14 gamma voltage levels between GND and AVDD, all set by a big chain of resistors. I'm pretty sure the resistors are set by trial and error to iron out the idiosyncrasies in the gamma correction of that particular panel model, but I haven't been able to find any references as to how these voltages are used by the panel. I hope that makes sense.
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Apr 27, 2009 21:14
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It's not a full size LCD, it's a 800x480 7" display.
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Apr 27, 2009 22:33
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How do you plan to send the airflow data back to whatever is logging/processing it? This sounds like a good application for a Zigbee device.
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May 5, 2009 16:31
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ashgromnies posted:Are you sure that part number is what I want? I can't find anything about that behavior in the description and it only has five contacts on it - I'd think those would be left in, right in, left out, right out, ground? Or am I misunderstanding? I'm assuming there is a line that runs from the satellite receiver in trunk to the stereo in the front of the car at some point. If not, how is it setup exactly? If there is a line going to the stereo, then you will be splicing this into that line at the point where you want to plug in your iPod. Here's the way the pins are connected in the jack:  This is assuming the tip of the plug is L and the ring is R. You will need to cut at least the L and R wires. Pin 1: Connect to ground of the satellite receiver to stereo wire. Pin 2: Connect to the Stereo side of the R wire. Pin 3: Connect to the Sat side of the R wire. Pin 4: Connect to the Sat side of the L wire. Pin 5: Connect to the Stereo side of the L wire. When nothing is plugged in, pin 2 is connected to pin 3 and pin 4 is connected to pin 5, passing the satellite signal on to the stereo. When the plug is inserted, it breaks these connections and the signal on the plug comes out on pins 2 and 5 and goes to the stereo while the satellite signal goes no where. Hillridge fucked around with this message at 14:11 on May 8, 2009 |
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May 8, 2009 14:05
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scuz posted:For those that cared when I asked, I would up getting a Weller WES51 and it sorts rules compared to my old econoiron. However something else has reared its ugly head... Try to relax. You're probably trying too hard to keep your hand still. It may also help to find a way so that you can rest your hand/wrist on something and just guide the iron with your fingers. Not having a death grip on the iron is key. I've also found that I do better when I'm not loaded up on coffee.
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Jun 24, 2009 20:25
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What's on the board? He's saying that if you mirror the board, you will also mirror any footprints. For parts like ICs, this will mess up all the connections. The numbers below are the pins on an 8 pin IC, the dotted line is what they mirror over: code:There are a few cases of simple boards where this may not be true though, which is why I wonder what your board looks like.
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Jun 26, 2009 13:54
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I'm also confused as to why you would care about the q-current when you're only going to be ~27% efficient at 12V. Also why do you care about the drop out voltage if you're going 12V->3.3? Regardless, I've had a lot of luck with Micrel's products (both switchers and linears), most of which are available from Digikey.
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Jun 30, 2009 18:10
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SnoPuppy posted:This is true. And if it works for you, then don't fix what isn't broken. I edited the quote above. It may be a little nit-picky, but I think it'll help make things less confusing in the long run. You're explanation is spot on though. In general, I use linear regulators when: - I don't care about power consumption and I want a quick and easy solution - I don't need a lot of current on that supply - I need a very "clean" supply (switchers are more noisy than linears) - I'm doing a small voltage drop, like 3.3V to 1.8V If it's a big drop, or lots of current, a switcher is the way to go.
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Jun 30, 2009 21:40
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What's your input voltage? That may be actually be doable. Why does it need to be so light? Is it being shot into space or something?
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Jul 6, 2009 15:10
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Here's a nifty little chip I just started to use in some designs: NC7SZ57 and NC7SZ58 http://www.fairchildsemi.com/ds/NC/NC7SZ57.pdf It's a 6 pin configurable 2 input logic gate. Rather than having a bunch of different bins for simple gates, keep a few of each flavor of these around. Here's what it can do: code:The NC7Z57 uses this logic: Y= (I0')•(I2')+(I1)•(I2) The NC7Z58 uses this logic: Y= (I0')•(I2')+(I1')•(I2)
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Aug 5, 2009 15:49
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I may be teaching a one night a week program geared at middle to high school age kids (I can suggest an appropriate age group) interested in electronics, robotics, etc. I pretty much have free reign to come up with the course material, and I'd like to do something micro controller based, probably a PIC. I'm still roughing out exactly what I'd like to include, but here's a brief list: • Inexpensive hardware that the kids can take home to work on between classes and keep after the program ends. • Simple enough that this age group can get right into development without having to endure too much of a lecture beyond the basics. • The option for them to be able to expand on the hardware with ideas of their own. • Teaching soldering would be great, maybe tie that in with the previous point. • Hardware that is good enough to do "cool" projects. PIC makes an entry level board that has a small prototyping area, 4 LEDs, a potentiometer (for A2D), and a push button. It also has a header for additional IO. The whole thing is based on a PIC 16F690. It meets just about all the requirements, but I'm not sure how well it will hold interest. I've also considered getting one of the larger PIC development systems to keep in the class for people who want to do more. I'm open to any other suggestions as well, so if any of you know of a good fit, please share.
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Aug 26, 2009 21:21
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BattleMaster posted:Not suggestions, but a couple of questions. What hardware do you plan on getting to program the PICs with? Do you intend to teach the students assembly or are you planning on using a higher-level language? I was looking at this group of Starter Kits: http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en023805 They all come with USB programmers, and the prices are 25% lower than marked due to the academic discount. Now that I've looked again, I think the PIC18F4xK20 Starter Kit might not be such a bad idea. http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en535806 With the discount it's only $75, which I think is a reasonable extra cost considering the kid will get to keep it. It also isn't as restricted as the PICkit 2 Starter Kit ($37.50). I'm going to do a brief overview of assembly, and have them run through some of the simple lessons PIC includes. Since they would be able to take these home, they'll have plenty of time to experiment. After that I'm probably going to use whatever C compiler comes with the kit. Once they have the basics, I'd love to have the class evolve into the kids coming up with their own project ideas and then figuring out how to implement them.
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Aug 30, 2009 14:57
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I fixed a problem I've been having with loading the config data into an FPGA via my ASIC. I watched the whole process on a logic analyzer and everything met the spec for the FPGA. What they didn't bother putting in the datasheet was that you have to toggle the clock line a few more times after the last bit has transferred for it to work. On a completely unrelated note, does anyone know where I can find details on the old NES hardware? I remember someone asking an NES question a while back.
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Sep 22, 2009 02:25
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Basically I'm thinking about doing the same thing you are. Anyway, shoot me a PM if you want to toss some ideas around. Hillridge fucked around with this message at 15:23 on Sep 22, 2009 |
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Sep 22, 2009 15:21
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603's? Those aren't too bad - no scope or other optics required. Now these suckers made me get out the scope:  Ignore the filename, they are caps, not beads. They are pictured next to a dime and came out of my ipod touch. SnoPuppy - It's actually an Altera. I think I have it working without the extra cycles now too.
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Sep 28, 2009 15:34
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This place has some cool stuff for those of you who want to prototype, but can only find SMD parts: http://www.schmartboard.com/
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Oct 2, 2009 18:05
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Zaxxon posted:any of Yall use the mentor graphics "PADS" suite. I'm trying to make some part types and I'm having trouble with anything that's board layout isn't a pattern the wizard can make (QFNs DIPs or whatever.) I do. I'm more familiar with the schematic side of things, but I have a coworker who can probably answer your question.
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Oct 5, 2009 12:57
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I've been designing a touch screen LCD device for a while now, so I'm pretty familiar with the internals. You would have to open it up to check this out, but see if you can find where the 12V is going, and write down the markings on the chips. The panel itself probably uses 5V for the backlight and 3.3V for the logic. That 12V supply is most likely going to at least one switching buck (step down) regulator. In my experience most of these regulators can handle a wide input voltage, some as high as 40V. If you go with a battery technology that is over 12V when fully charged, chances are you will be fine. If you are using a charger to mount them, why not leave it intact so you can just plug them in while in the stedicam rig if you're on a break or something?
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Oct 16, 2009 12:48
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I had a broken development board returned to me and it turned out it had a short between 3.3V and ground. After troubleshooting all the typical problems and still having the short, I started pulling off anything connected to the 3.3V rail. I pulled off every single IC, including 8 SRAM chips, a Flash chip, and our ASIC, and still had a short. At this point I wasn't quitting until I found out the cause, so I moved on to my bypass and filter caps. I've never seen it before, but I had a 0.1uF 16V 0603 ceramic cap that had an internal short.  I'm in the middle of putting it all back together to see if that fixed it.
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Oct 16, 2009 18:18
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I just bought an old timing light that came with the original manual. I was wondering about how it worked and contemplating taking it apart, when lo and behold the manual has a complete schematic with BOM and assembly drawing! I was thinking it might be neat to modify this so that it can sense current via a clamp sensor around the wire rather than need to be connected directly to the spark plug. Since the spark wire goes right to the strobe, this may be a bit tricky though. Any suggestions?
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Oct 23, 2009 16:38
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Ha, amusingly enough, this ad was at the top of the page when I read your post:
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Oct 23, 2009 19:45
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You could certainly do it that way, but you would typically use a boost converter, which is a type of switching power supply. From that wiki page: The key principle that drives the boost converter is the tendency of an inductor to resist changes in current. When being charged it acts as a load and absorbs energy (somewhat like a resistor), when being discharged, it acts as an energy source (somewhat like a battery). The voltage it produces during the discharge phase is related to the rate of change of current, and not to the original charging voltage, thus allowing different input and output voltages. So in a way you are making the initial DC voltage into a sort of AC voltage then feeding it through an inductor and smoothing things with a cap. This is extremely generalized, and you would do better to read the wiki page on it. Don't worry if the theory behind it looks hard, practical use of these is pretty straightforward, and most manufacturers of boost ICs have sample schematics for typical uses.
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Nov 2, 2009 22:29
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Holy Diver posted:Alright circuit gurus, I'm looking for some help on a circuit I'm making. It needs to make a motor run in the positive direction for a number of seconds, hold for a number of seconds, and then run the motor in reverse. Here's how I have used logic signals to drive a 24V relay. This should work for a 12V relay as well. It's pretty close to what you were doing:
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Nov 4, 2009 18:52
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There are a few things to look at here. First of all, LED brightness is a factor of the current passing through them. If the LCD is limiting current to the LEDs, you may get some more brightness by lowering the resistance. The problem here, is that they probably limited current for a reason. Also, since you can dim it, the LCD probably PWMs the LED voltage. Replacing these LEDs with new ones is an option if the LCD can source enough current to power them. If you have a multimeter you can figure out the forward voltage of an LED pretty easily. At any rate, I doubt you will hurt super bright LEDs by powering them off of something designed for lower brightness parts. Do you have a model for the LCD screen?
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Nov 10, 2009 19:42
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If your multimeter has a diode setting, just stick the probes across the LED so that it lights up (dim is ok) and read the voltage. If it doesn't, put your LED in series with a large resistor (start with about 1.5k) and a 12V supply: 12V->LED->resistor->GND If it lights up, put the probes on either side of the LED and read the voltage. If it doesn't light up, decrease the resistance until it does. Hillridge fucked around with this message at 19:50 on Nov 10, 2009 |
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Nov 10, 2009 19:47
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This says it has a Cold Cathode Filament Tube for a back light, not LEDs. You probably won't be making this any brighter, but you may still be able to add the extra LEDs. Any luck on finding the forward voltage?
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Nov 14, 2009 04:38
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Is the lack of precision due to the bottles themselves, or the case holding them? If the latter, just make a filling rig that locks them in uniform positions, or make it work more like a factory where the bottles are fed in one by one and you have to manually place them in the case afterward.
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Nov 17, 2009 13:42
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you could just make a grid (wire, wood, plastic, whatever) that you pop over the top of the bottles to snug them up evenly to each other. That way all you have to do is put on the grid, the machine fills the bottles, you remove the grid and close the case. I still think the most tedious part of filling bottles is sanitizing them first. Especially if they were used as ashtrays 
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Nov 17, 2009 14:48
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The easiest way to do it is to look for a complete DC-DC module from a place like digi-key. It'll have a little pcb in it that has a switching regulator and all the associated parts on it and only brings out 3 pins - Vin, GND, Vout. These can be a bit pricey though. What is the voltage on the battery near the end of it's safe discharge range? If it is less than 12V you may want a buck-boost topology instead. As for your questions, Vripple is your maximum acceptable voltage ripple on the output. Since that is a switching regulator it will produce pulses which are smoothed by the inductor (L) and cap (C0) to create a DC-like voltage. Vripple is the amount of the pulses that don't get smoothed, and for some applications it is critical to keep this as low as possible. A Vripple of 100mV means that your 12V output will be a 100mV (peak to peak) AC voltage on top of a 12V DC offset. Switching frequency can also affect parts of a circuit, so that other box is for setting your target minimum. Typically, a faster switcher means a smaller L and C is needed to smooth the output. Vout isn't just a pin per se, as the output of this chip needs to go through inductor L before it can be used. You can see Vout in the lower right of that picture, where the inductor and Cap meet.
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Nov 18, 2009 12:20
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Edit: Oh god I resized the image but not the background. Can a mod please delete this? Sorry I missed your message last night. Your resistors are close enough. A few things though: 1. Check your breadboard to make sure the + and - buses run the whole length. Some boards stop in the middle and need to be jumpered. 2. The cap i circled in blue can just be stuck on one side of the power buses, no need to span the board. 3. Change the green wire from - to + like ante mentioned 4. I think you are shorting the + to the - in the back there where I drew the ?, but I can't see for sure. It looks like the yellow wire goes to the first row, which is jumpered to the first row on the bottom by that red wire, then to ground by the green wire. Hillridge fucked around with this message at 15:55 on Nov 19, 2009 |
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Nov 19, 2009 15:50
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No, but make sure you don't have your resistor backwards, or it could fail unexpectedly.
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Dec 13, 2009 14:37
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