|
Simplest method is to low pass the pulse train, giving a DC voltage equal to the average output of the train. Compare that with some threshold and connect the output to a FET. A comparator would make things easy. You can pick up an lm339 at radioshack. Otherwise you could fudge a comparator or schmitt trigger out of transistors. there are other ways too but they would be have to be finely tuned. Would you be willing to use a comparator IC?
|
#
?
Nov 18, 2008 19:36
|
|
|
|
| # ? May 22, 2024 08:41 |
|
|
Still putting together my starter electronics kit; What should I do for the ICs (4000s/7400TTLs) if I don't know which ones I'd need, should I get one of this expensive grab bags or would it be smarter to just go through and individually pick them out? http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=135280& http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=17996& and a socket bag.
|
|
#
?
Nov 24, 2008 02:52
|
|
|
If you have a decent idea of what kind of circuits you want to make, go ahead and pick them yourself. I'd recommend at least getting basic cmos logic gates (nand, nor, not), some cmos analog switches (cd4066), and some multistable vibrators (cd4538), and probably some gates and latches too. cmos stuff is nice for the extended voltage range, but if you're looking to make fast digital systems, TTL is more cost efficient.
|
|
#
?
Nov 24, 2008 13:26
|
|
|
Ok, I have a bunch of disposable camera flashes I want to discharge at the same time. My question is, if I wire up say 5 of them to go off on one switch, would I be able to replace all 5 capacitors with one larger adjustable cap to alter the output of the flash brightness? Here's what I'm working on. http://www.diyphotography.net/studio-diy-disposable-camera-ring-flash I can get you guys detailed info on the camera's (with pics) if you need it when I get home. By the way, one of those capacitors hurts like gently caress all when they blow on the back of your hand (and they make a sound like a screaming woman, that might have been me though)
|
|
#
?
Nov 24, 2008 20:42
|
|
|
|
|
#
?
Nov 27, 2008 02:29
|
|
|
I've been thinking about learning to program a microcontroller. I've been thinking about one of these, a USB ICSP, a breadboard, and a power supply. I'd like to program ATMega 328Ps. Is there any reason this shouldn't work?
|
|
#
?
Nov 27, 2008 04:43
|
|
|
Coppied from the AV thread http://forums.somethingawful.com/showthread.php?threadid=3022754 Gainclones, a $100 amp that can compete with the likes of much more expensive 2 channel amps. You can read more about them... http://en.wikipedia.org/wiki/Gainclone Build some kits from here http://www.chipamp.com/ And learn more about them here http://myweb.tiscali.co.uk/nuukspot/decdun/gainclone_psu.html So anyways, about 5 years ago I decided to try and save some money and build a 2 channel gainclone amp.  It turned out really and it sounded excellent. I had it hooked up to my PC but it was loving loud and it buzzed from the PC noise(now that is fixed with the MSI 7411), I added some pots and it reduced the noise. The case is a mess but its been utterly reliable and like I said before delivered great sound. Well during the order I rationalized that if I was building a simple two channel gainclone a 7 channel would work great, and hay while were at it lets bridge the front to two channels(so I would have 9 gainclones in there).   Problem is I really don't know how to do this from the wiring and the power supply perspective. Reading electrical engineering diagrams were a bit difficult with me for some darn reason. Looking at the beginers guide for gainclone I get this for the power requirements quote:As this is a 'dummies' guide, I am going to pass on that one and give you some general guidelines instead. For each channel of a chip amp, I suggest a minimum of 80 VA. Gainclones work off of a rectifier bridge, currently my two channel has a single rectifier bridge and I have heard that you can run more then two off a single bridge but am uncertain about this as I figure something could go wrong. What I was figuring I could do is get the 800 torroid and get a couple of terminal blocks(I think they are multiple tap) and connecting the 5 recitifer bridges up to them. If anyone would be able to give me some help that would be great.
|
|
#
?
Dec 1, 2008 22:29
|
|
|
Paul MaudDib posted:I've been thinking about learning to program a microcontroller. I've been thinking about one of these, a USB ICSP, a breadboard, and a power supply. I'd like to program ATMega 328Ps. Is there any reason this shouldn't work? Otherwise it seems like a decent cheap development board. With the Arduino you wouldn't need to have a the programmer, but I think if you wanted to get rid of the bootloader and use a standard C compiler or assembly you would need a programmer. Also, the arduino uses at atmega168 which is the same line as the 328 so it is pin for pin compatible with the 328. I've personally just put together my AVR circuits on breadboards or on protoboards. I came across these, which seem like a cheap and quick way to throw together a breakout board. In other news I got at AVR Dragon the other day. Mostly because I want to play with the JTAG, and it says it supports atmega devices with up to 32k of flash.
|
|
#
?
Dec 4, 2008 06:36
|
|
|
Phew! I've crawled through the entire thread over the past two weeks, and I wanted to say thanks for all the great information in here (mtwieg - your OpAmp/Comparator article was especially informative). I have a plan for my first 'real' project, though I need a little advice on how exactly to go about it. I'd like to make a battery-operated, analog electronic thermometer. Basically, the output would just be a line of LEDs of various colors, each corresponding to a minimum temperature (I'm hoping for an LED for each 5'c, from -20'c to 45'c). I've got a 10k Thermistor and all the LEDs I need (as well as various assorted resistors, capacitors, transistors, and diodes), however I'm not 100% on how I should set it all up yet. My plan was to effectively have two 'units'. First, the temperature probe, which would have as intput a supply voltage, would contain the thermistor in parallel with a resistor (from what I had read this can help to provide a linear voltage output over the target temperature range). This voltage output would then be fed into the 'display', which I think would essentially be like a LED VU-meter: A cluster of comparator-LED circuits in parallel, each taking the probe lead as input and a differing reference voltage depending on the desired temperature the LED is supposed to correspond to. The other end of the LEDs would go to the power supply, via a ballast resistor for each LED (is there a better way to do this?) Does this sound like a reasonable approach? The basic circuit I had in mind looks something like this (All resistor values arbitrary ATM; pretend one of the ones on the left is the thermistor):  One other optimization I was thinking of would be to have the power to the LEDs be pulsed instead of always hot so as to save battery power. I have a bag full of 555s I could use, or would this be overkill? I'm still not 100% sure that I know how to drive an arbitrary number of LEDs in parallel and produce consistent current across each...
|
|
#
?
Dec 5, 2008 18:59
|
|
|
You need to make a voltage divider with the thermistor and a resistor, not a parallel circuit. If you match that 10k thermistor with a 10k resistor, the output should be VCC/2 at the optimal temperature. Edit: Okay, now that you added a diagram I can see that's what you were already doing. The tricky part is that the thermistor increases or decreases its resistance on a curve rather than linearly so you need to compensate for that somehow. The typical way to do it would be to use a microcontroller with a conversion table in software, but that doesn't seem to be what you want. Edit: I see now that you don't really need it to be very accurate, with only three LEDs. You would probably prefer using an LM35 temperature sensor, which accurately outputs 10mV per degree Celsius. The datasheet for the LM35 also includes an application note that tells you how to make a bar graph thermometer, but it uses a couple of ICs designed for that task which is probably not as do-it-yourself as you'd like. I was looking at the datasheet for the bar-graph LED driver and you might want to borrow the design shown in the block diagram if you can't get yours to work. BattleMaster fucked around with this message at 21:10 on Dec 5, 2008 |
|
#
?
Dec 5, 2008 20:48
|
|
|
BattleMaster posted:You need to make a voltage divider with the thermistor and a resistor, not a parallel circuit. If you match that 10k thermistor with a 10k resistor, the output should be VCC/2 at the optimal temperature. Edit: Okay, now that you added a diagram I can see that's what you were already doing.  But would a micro-controller really matter? Since I'm looking for thresholds ("Temperature greater than X for LED1, greater than Y for LED2," etc) can I just have my reference voltages scale non-linearly along with the curve of the thermistor? Either way, yeah I'm probably looking at 5'c per LED, so I don't need too much accuracy -- I'm mostly just struggling with getting the reference voltages right and the LEDs to not explode on me at this point.This page was where I got the impression that I could just use another resistor to make the Thermistor circuit roughly linear -- is that not correct? quote:You would probably prefer using an LM35 temperature sensor, which accurately outputs 10mV per degree Celsius. The datasheet for the LM35 also includes an application note that tells you how to make a bar graph thermometer, but it uses a couple of ICs designed for that task which is probably not as do-it-yourself as you'd like. That's cool, I may look into that (if not for this, than for the next evolution of the project). e: quote:Edit: Holy poo poo, edits galore! I was looking at the datasheet for the bar-graph LED driver and you might want to rip off the schematic of its internals for your project. Hubis fucked around with this message at 21:07 on Dec 5, 2008 |
|
#
?
Dec 5, 2008 21:02
|
|
|
Hubis posted:Well, that was just a reduction, because I didn't want to put 15 OpAmp/LED circuits down there You don't really need a microcontroller for a circuit like this, it just makes compensating for things like the thermistor curve way easier when you can feed the number into a lookup table. You can just forget I said that because it's not a very do-it-yourself solution. Down the road, though, if you want to do something like displaying the temperature in numerals on a seven-segment display, it will make it much easier for you if you can stomach the programming. If that method in that link works, go right ahead and use that. I honestly got fed up with thermistors when I found out than an LM35 is only a little more expensive and a lot more accurate. BattleMaster fucked around with this message at 21:14 on Dec 5, 2008 |
|
#
?
Dec 5, 2008 21:06
|
|
|
Another way to do a VU thingy is to use a clock source, counter, an R/2R A/D tree, one comparator, and a latch. You have your clock feeding the counter, which outputs to your D/A converter (usually an R/2R tree) which feeds your comparator. The other input of your comparator is your input signal. When the comparator turns on, you latch your counter value into your LEDs. It's not really cost-effective for a small number of LEDs, but for 15 or 20, you're looking at a good cost savings. The R/2R A/D chain also means you only have to buy two values of precision resistor. Say you want 16 values. That's 8 dual opamps and 16 different precision resistors. Or 4 ICs (latch, counter, opamp, clock [555]), and 16 resistors of one value and 19 of twice that value.
|
|
#
?
Dec 6, 2008 05:31
|
|
|
I'm looking for the smallest IC/speaker to make a beeping noise. I'd like to mess around with making something (similar to the keyfob on a car where you push a button and a receiver beeps). The item I'd be using this on is rather small, so I'm trying to find my options. If I'm confusing (which is quite possible), PM me for details. Here's what I've found, which should work actually: http://www.sparkfun.com/commerce/product_info.php?products_id=7950 Can I run this from a small battery, like a watch battery? I wouldn't have connected power. Solaron fucked around with this message at 21:16 on Dec 10, 2008 |
|
#
?
Dec 10, 2008 21:06
|
|
|
Solaron posted:I'm looking for the smallest IC/speaker to make a beeping noise. I'd like to mess around with making something (similar to the keyfob on a car where you push a button and a receiver beeps). I don't know for sure how long the battery will last, but I think should be fine. Watch batteries can be either ~1.5v or 3v. Make sure you get the 3v variety. The buzzer also needs an AC input, so maybe look into a low power 555 timer, or a couple transistors in an oscillator circuit.
|
|
#
?
Dec 11, 2008 01:25
|
|
|
Solaron posted:I'm looking for the smallest IC/speaker to make a beeping noise. I'd like to mess around with making something (similar to the keyfob on a car where you push a button and a receiver beeps). magnetic transducers are definitely your best bet. You can get smaller than that, but as size decreases you're generally forced to use higher frequencies and dissipate more power. That sparkfun part is probably a good compromise.
|
|
#
?
Dec 11, 2008 03:39
|
|
|
The goal is to eventually have something that fits in a 6mm tube, but at least getting the components tested and working will be a great start; I don't even know if any viable options exist to make a complete circuit in a setup so small. Thanks for the info - I'll grab that part from sparkfun and try it out. EDIT: Is that even possible? I'm still looking as I ordered parts, and I'm not seeing anything small enough to fit within the 6mm requirement. Does anyone have any links/resources where I could find such small components? Solaron fucked around with this message at 19:04 on Dec 11, 2008 |
|
#
?
Dec 11, 2008 04:06
|
|
|
Solaron posted:The goal is to eventually have something that fits in a 6mm tube, but at least getting the components tested and working will be a great start; I don't even know if any viable options exist to make a complete circuit in a setup so small. Here's another buzzer which is as close as you'll probably get. That's 6.6mm in diameter, so your 6mm spec may be simply infeasible.
|
|
#
?
Dec 12, 2008 18:01
|
|
|
A while back I mentioned that sodar ranging project I was working on. It's done and, according to my team, working beautifully. The final tech report is due tonight, so I'll have more information on it then (I'll likely make another thread for it). With their consent, I'll post the whole document.
|
|
#
?
Dec 12, 2008 18:03
|
|
|
^^^ This sounds cool - I'd be interested in seeing it. mtwieg posted:another buzzer which is as close as you'll probably get. That's 6.6mm in diameter, so your 6mm spec may be simply infeasible. 6.6mm would actually work, barely. The issue is still power - I was hoping to find some sort of batteries to work, but that may not be possible. I don't know enough to know for sure, either, is the problem. If anyone wants to PM me and answer some questions, that would be awesome. Depending how much I end up bugging you, I can throw you  or something.
|
|
#
?
Dec 12, 2008 18:35
|
|
|
Solaron posted:6.6mm would actually work, barely. The issue is still power - I was hoping to find some sort of batteries to work, but that may not be possible. I don't know enough to know for sure, either, is the problem. Also if you want some kind of rf receiver, that might require significant power too. What kind of communication were you thinking of (just an on off signal or something else)? quote:If anyone wants to PM me and answer some questions, that would be awesome. Depending how much I end up bugging you, I can throw you
|
|
#
?
Dec 12, 2008 19:22
|
|
|
I found this tiny buzzer. It's piezo, which needs a driver, but I think a single-transistor oscillator should work fine. Now there just needs a voltage source. It's rated "10Vp-p" with an operating range "1~30Vp-p" @ 5mA max. Is it feasable to drive the oscillator that drives the piezo element with a voltage multiplier? Using tiny SMD caps and diodes on a chip of PCB, I bet you could make one pretty small. In fact, SMD on all of this stuff with a double-layer PCB could be made very small.
|
|
#
?
Dec 12, 2008 19:49
|
|
|
Can anyone suggest a simple tranceiver chip (or receiver/transmitter combo) that would allow me to send an RF signal about 150 meters? I doesn't need to have high bandwidth. It doesn't need to do error correction. It really doesn't need to do much except respond to a pulse on a designated frequency, and that's it. Here's the application: I live on the third floor of a walkup building in an apartment complex surrounded by a fence. The complex will not hook up the gate buzzer to allow people to call me and get buzzed in because I don't have a landline, which means that every time I order a pizza or have people over, I have to go downstairs and walk 125m or so to open the gate for them. This is stupid and annoying. I have a keychain fob with a button that opens the gate, but its range is limited to about 10m. I've looked at the datasheet for the transmitter chip it contains, and I don't think it would be at all trivial to emulate its signal in a way that would be accepted by the receiver (it transmits an encrypted and unique identifying code each time the button is pressed - *might* be possible to hack because it cycles eventually, but would take quite a while I think). Plus, I think it would be easier to make a transmitter from whatever off the shelf parts I can find and use the receiving end as a relay to trigger the keyfob device I already have, than it would be to try to make one that uses the same frequency as the receiver unit. So, I want a simple chip combo that will passively wait for a signal and simply notice when it receives one. A simple 1 or 0 is fine and it doesn't need to be complex -- I'm just using it to trigger the transmit circuit on the keyfob. Any thoughts?
|
|
#
?
Dec 12, 2008 23:57
|
|
|
quote:I found this tiny buzzer. It's piezo, which needs a driver, but I think a single-transistor oscillator should work fine. Now there just needs a voltage source. It's rated "10Vp-p" with an operating range "1~30Vp-p" @ 5mA max. I believe it's too large around, am I reading that correct? 10mm? Length is no issue, but diameter is, sadly. quote:Just post them here. Worst case scenario is you get ignored, but as long as you're not too vague and your questions are reasonable you shouldn't be. If it gets to the point where you want exact designs or extensive consultation, then we'll talk money. Awesome, that works. I have no problem messing around with different scenarios and components, but I don't know enough to know exactly what I need. I just don't want to get yelled out of here since I'm clueless compared to 99% of you. It would definitely need to have power self-contained to beep when triggered by a button elsewhere. It's basically a glorified keyfinder for a specific application that's got some annoying size constraints. Would the extra allowable length I can have (up to 12" if necessary) help in this case at all, to offset the 6/6.5 mm restriction? (I don't have an exact measurement yet. It's ~.25")
|
|
#
?
Dec 13, 2008 02:34
|
|
|
Grand_High_Took posted:Any thoughts? Some apartment buzzing systems don't need a valid number on the landline, just the phone itself. Someone I know has a phone in his apartment with no plan or anything on it, its sole purpose is to buzz people in. I'd look into that, first. If you have to hack the hardware could you post a link to the datasheet of the chip you have to emulate?
|
|
#
?
Dec 13, 2008 02:38
|
|
|
Solaron posted:I believe it's too large around, am I reading that correct? 10mm? Length is no issue, but diameter is, sadly. are you trying to make a locator for your car or something? Do you want it to be directionless (doesn't matter which way it's pointing)? What's the desired range/reliability? Are you making your own transmitter as well? Where will the receiver be located? ANIME AKBAR fucked around with this message at 03:40 on Dec 13, 2008 |
|
#
?
Dec 13, 2008 03:33
|
|
|
ante posted:Some apartment buzzing systems don't need a valid number on the landline, just the phone itself. Someone I know has a phone in his apartment with no plan or anything on it, its sole purpose is to buzz people in. Unfortunately, mine insists on the landline. As far as the hardware, that's the whole point -- I don't want to have to emulate the chip. I'd rather just get around it entirely by applying the appropriate current to the chip I already have, and letting it do its job. If I can't find a suitable tx/rx pair, I will post the datasheet for the chip and work on cracking its code -- but I'd prefer to avoid it if I can.
|
|
#
?
Dec 13, 2008 05:37
|
|
|
Solaron posted:I believe it's too large around, am I reading that correct? 10mm? Length is no issue, but diameter is, sadly. Ok, I found this one 6.5mm x 3.5mm. I can't find any suppliers, though. Then there's this from digikey. 6.6mm dia. x 3.5mm. These are magnetic; 80mA @ 1.5VDC, and I think you still need some kind of oscillator to drive them.
|
|
#
?
Dec 13, 2008 06:18
|
|
|
Hi-- I do some circuitbending, and I was thinking it'd be nice to have alligator clips that lead directly to a standard quarter-inch or 3.5 mm audio output (male or female). Some quick searching didn't turn anything up... do these exist?
|
|
#
?
Dec 14, 2008 01:26
|
|
|
YO MAMA HEAD posted:Hi-- I do some circuitbending, and I was thinking it'd be nice to have alligator clips that lead directly to a standard quarter-inch or 3.5 mm audio output (male or female). Some quick searching didn't turn anything up... do these exist? If you don't mind me asking, how do you do circuit bending? I think I get the idea, but I'm not really sure.
|
|
#
?
Dec 14, 2008 02:47
|
|
|
Get something that makes a noise, like a child's toy, short circuit stuff, see what happens!
|
|
#
?
Dec 14, 2008 03:12
|
|
|
Yeah, basically. You just do it and see what happens. I just mess around with poo poo, I've only tried putting one thing back together and adding dials etc. to the casing. It's fun, but I don't know anything about electronics so I just mess around. e: http://www.youtube.com/watch?v=QXOmHM1RiG0 I wish I had made this, though.
|
|
#
?
Dec 14, 2008 03:18
|
|
|
YO MAMA HEAD posted:Hi-- I do some circuitbending, and I was thinking it'd be nice to have alligator clips that lead directly to a standard quarter-inch or 3.5 mm audio output (male or female). Some quick searching didn't turn anything up... do these exist? Buy a 3.5mm plug or socket with some solder terminals and make your own? Max cost is probably $2 or $3
|
|
#
?
Dec 14, 2008 08:30
|
|
|
Yeah, I know. I guess I'll just do that with what I have, it would have been nice to have something a little better quality though. Thanks anyway!
|
|
#
?
Dec 14, 2008 17:40
|
|
|
My radio got stolen a while back, and I really miss it. I'm not keen on just replacing it with a new one, because it will probably just get jacked again. SO, instead I would like to keep a big gaping nasty hole in my dashboard that says, "you already hit this one", and then hide a sound system somewhere else. I have a really awesome Sansa mp3 player with FM radio, and the speakers in my car are really great. I just need some way to amplify it. Can I just buy a car amplifier at Best Buy or wherever and hook it up to the headphone jack on my Sansa? I feel like this would be too easy and there is more work to be done, so I am hesitant to try it.
|
|
#
?
Dec 15, 2008 02:50
|
|
|
Well many car radios/cd players include auxiliary input jacks into which you can plug any device that would normally go to headphones or a stereo or whatever. But as for something that does only that without the radio/cd player, I'm not sure if there is such a thing. I'm not big on car audio. As for making one yourself, I doubt it would be too hard. What kind of load does it need need to drive (or rather, what do normal radios and such output on the car's audio lines)? I doubt it needs to drive the speakers directly, so it doesn't have to be powerful. I imagine it just takes each stereo channel, buffers it and puts some gain on in, along with whatever signal conditioning you want (maybe you don't care?). Such a thing could be built with a few op amps and resistors.
|
|
#
?
Dec 15, 2008 18:42
|
|
|
And also I wanted to post the sodar project, but I don't know a decent way to share a 15MB PDF. Any suggestions?
|
|
#
?
Dec 15, 2008 19:41
|
|
|
http://www.scribd.com/ could help. That's the only website I can think of that can host PDFs. There might be a quick way to turn all the pages into jpegs, as well, but that would probably take too long to post.
|
|
#
?
Dec 15, 2008 19:53
|
|
|
mtwieg posted:And also I wanted to post the sodar project, but I don't know a decent way to share a 15MB PDF. Any suggestions? Does your school give you any web space for projects? I know mine did, at least while I was still a student. Or a google doc - I think they can import PDFs, but there might be a size restriction. If you cut out images you might be able to shrink the size a good deal.
|
|
#
?
Dec 15, 2008 20:54
|
|
|
|
| # ? May 22, 2024 08:41 |
|
|
Or I could host it. If you e-mail it to nerobro at gmail dot com, I'll put it up on my webspace for ya.
|
|
#
?
Dec 15, 2008 21:14
|
|
