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So, this is what I have working right now. I have the onboard LEDs set up to display the number of light -> dark switches detected, while integrating over something like 0.25ms. Depending on the speed of the motor the speed the counter fills up varies, so it seems to be working. What I still want to do is reduce the integration time back down to 1 microsecond, pulse the laser using the FPGA, and try to use an opamp instead of a comparator since that should simplify setting the trigger level. I also am thinking about alternatingly intergrating the signal with the laser on and off to determine background noise level and the offset due to line delay. E: And a pulldown on the FPGAinput probably wouldn't hurt, I just had the breadboard unplugged and the FPGA was counting away due to noise. Ika fucked around with this message at 21:03 on Sep 21, 2014 |
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Sep 21, 2014 20:59
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Stupid question: since jumpers are cheap as gently caress on amazon is there any reason I shouldn't just go ahead and use some of my male-male jumpers for making easy connect/disconnect connections on a prototype board by soldering one end in place?
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Sep 22, 2014 10:59
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Parts Kit posted:Stupid question: since jumpers are cheap as gently caress on amazon is there any reason I shouldn't just go ahead and use some of my male-male jumpers for making easy connect/disconnect connections on a prototype board by soldering one end in place? As long as you're not expecting the same durability and current rating as you'd get from higher quality stranded wire, and you're not melting the plastic in a way that's problematic, go for it.
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Sep 22, 2014 14:39
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Cool, thank you. I figure I can just take a male-male and nip it in half and strip the two new ends for an easy quick connect.
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Sep 22, 2014 18:37
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Speaking of which, what part do I need to look for to find the individual end pins of those jumper wires? I've got a number of misc. LEDs I want to add wires and pins to.
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Sep 22, 2014 19:11
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Is there a recommended starter kit for this sort of thing? I've recently become interested in playing around with circuits and trying to electrocute myself to death an early age. I've been doing lots of reading, but of course the story is always that it's best to learn hands on. I was wondering if there is a recommended starter grab bag of components for general loving around. Eventually I wanna make a couple of guitar pedals, so I've been looking at places like DIY stompbox and I like that Small Bear has some breadboard kits to play around with, but that's not my only goal and I'd like to understand what exactly I'm doing rather than just insert x part to y socket and solder. Is something like this okay? Or am I just getting some junk? http://www.amazon.com/JAMECO-VALUEP...ronics+grab+bag
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Sep 22, 2014 19:55
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Ika posted:Speaking of which, what part do I need to look for to find the individual end pins of those jumper wires? I've got a number of misc. LEDs I want to add wires and pins to. Assuming you're talking about the connectors I think you are: Crimp pins and sockets Female headers The above two items are also available in a kit. Crimp tool unless you want to use pliers like a scrub If those prices seem high you can try your luck searching a distributor like Newark or DigiKey. I'm sure that connector type has a name but I can't remember it. Nativity In Black posted:Is something like this okay? Or am I just getting some junk? Looks like a bunch of junk to me. I would be concerned about ending up with a bag of random parts that have potentially hard to read / no identifiers on them and therefore zero documentation available to tell you their specs.
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Sep 22, 2014 23:14
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Speaking of bags of crap, is there any reason not to buy a cheap resistor or capacitor kit from eBay or dealextreme?
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Sep 23, 2014 00:09
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BrainParasite posted:Speaking of bags of crap, is there any reason not to buy a cheap resistor or capacitor kit from eBay or dealextreme? It might not arrive? But really, eBay or DX vendors usually are selling overstock or discontinued parts. For a hobbyist, where 1000 resistors will last you years, go for it. For a garage door clicker manufacturer, not so much.
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Sep 23, 2014 00:26
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BrainParasite posted:Speaking of bags of crap, is there any reason not to buy a cheap resistor or capacitor kit from eBay or dealextreme? Go nuts Nativity In Black posted:Is there a recommended starter kit for this sort of thing? I've recently become interested in playing around with circuits and trying to electrocute myself to death an early age. I've been doing lots of reading, but of course the story is always that it's best to learn hands on. I was wondering if there is a recommended starter grab bag of components for general loving around. I don't think that's a bad idea, if a little trial-by-fire. US-based kits like JAMECO ones are probably 10x the price of Aliexpress/dealextreme ones, though
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Sep 23, 2014 01:25
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PDP-1 posted:I see now that I phrased the problem pretty poorly - the intention was to filter the AC component to 1-2% of its original amplitude (i.e. -40dB at 10Hz) regardless of what the DC component happened to be, while replicating the DC component only at the output (0dB at 0Hz). The DC component can range from -10V to +10V, so it could be 0V and then the AC component is the entire input signal and we don't get to use the 0.2V/10V=2% trick. I know I'm a little late to the party on this topic, but microcontrollers are great at doing this kind of thing! Particularly when you're talking about such low frequencies, it's easy to implement all kinds of fancy filters on the right micro. A small microcontroller can actually wind up being cheaper and use less board space than a 3rd- or 4th- order analog filter with such a low frequency.
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Sep 23, 2014 09:24
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DethMarine21 posted:Assuming you're talking about the connectors I think you are: Thanks. I actually meant 1x1 male connectors, which would match these connectors, but the kit contains both male and female crimp thingies so they should exist. I can't use that site since they won't ship to me but I should be able to find what I am looking for now that I have a name. Ika fucked around with this message at 09:31 on Sep 23, 2014 |
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Sep 23, 2014 09:28
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The best crimper for those DuPont connectors is still the $9 one from Radio Shack. It's labelled a DSub crimper and works really well.
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Sep 23, 2014 14:08
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Ika posted:Thanks. I actually meant 1x1 male connectors, which would match these connectors, but the kit contains both male and female crimp thingies so they should exist. I can't use that site since they won't ship to me but I should be able to find what I am looking for now that I have a name. I just got an order from newark with those pins. Small-lot price is 4.3 cents per. More than 250 is 3.8 cents. I got a whole stack of stuff. 1x2, 1x3, 1x4, 2x2, 2x3, 2x4 and 250 pins, with shipping, for $20. And since one of the hubs is just down the road, my order was completed at 9pm and showed up at 9am the next day.
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Sep 23, 2014 15:07
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BrainParasite posted:Speaking of bags of crap, is there any reason not to buy a cheap resistor or capacitor kit from eBay or dealextreme? I bought a 1206 resistor + capacitor kit on eBay and it's pretty great, only thing it didn't have is super high capacitance X5Rs. Bags are labelled decently which is nice for the caps, resistors are pretty clearly labelled by themselves.
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Sep 23, 2014 16:15
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Not sure if this is the right place, but does anyone recognize this display? I'm trying to source a replacement screen for a Hilti PD4 laser range meter. Unfortunately, the display is completely free of any identifying marks. However, I did find a picture of a Hilti PD30's screen that does have a part number, though that lead no where. (COG-CHM1068-02 I believe) The display without the plastic bracket measures 35.20x32.75mm with 28x31mm viewable. I believe it is a cog graphic display with the 5 pin interface likely being i2c. Batron makes units that look similar, although none with the same dimensions. Click the picture for the imgur album. 
ThinkFear fucked around with this message at 16:23 on Sep 23, 2014 |
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Sep 23, 2014 16:17
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BrainParasite posted:Speaking of bags of crap, is there any reason not to buy a cheap resistor or capacitor kit from eBay or dealextreme? IMO those are the only way to go; especially for SMD capacitors and resistors (seriously, the price of a 603/805 resistor kit from a reputable supplier is outrageous when you consider that you could buy the parts as separate line items for about $10 from the same store).
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Sep 23, 2014 16:45
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Cunning Plan posted:consider that you could buy the parts as separate line items for about $10 from the same store). Eh, but the summer interns have left and I'd have to pull them off the reels myself...
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Sep 23, 2014 17:38
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Cunning Plan posted:IMO those are the only way to go; especially for SMD capacitors and resistors (seriously, the price of a 603/805 resistor kit from a reputable supplier is outrageous when you consider that you could buy the parts as separate line items for about $10 from the same store). Semi-related, how well do ceramic caps age? I recently got a huge 1/4 metal film resistor kit, and an equally huge electrolytic cap kit, since for most of what I do, I'm gonna be using medium-large electrolytics. It seemed overkill to order an entire kit of ceramic caps though, since they wouldn't see enough use to justify it. Is my current strategy of "pull them off old boards as needed" not-stupid? I'm not talking about like 1950s TVs here but the gear sure ain't new and I wouldn't re-use an electrolytic off these boards.
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Sep 23, 2014 19:53
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babyeatingpsychopath posted:I just got an order from newark with those pins. Small-lot price is 4.3 cents per. More than 250 is 3.8 cents. I got a whole stack of stuff. 1x2, 1x3, 1x4, 2x2, 2x3, 2x4 and 250 pins, with shipping, for $20. And since one of the hubs is just down the road, my order was completed at 9pm and showed up at 9am the next day. Makes me wish still lived in the US. Their price here is over double what you guys pay even before factoring in the exchange rate. But that is exactly what I was looking for, and the hardest part is often figuring out part numbers / names, now I just need to search for DuPont connectors here.  And someone at work suggested I just solder my cables to some of these, which I happen to have, so I will use that as an interim solution. Ika fucked around with this message at 20:16 on Sep 23, 2014 |
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Sep 23, 2014 20:04
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Does anyone know if there's a way to spoof an SD card with hardware and software? I'm looking to intercept the data being written to an SD Card from a device, probably using this https://www.sparkfun.com/products/9419. There are some comments about using it instead of a real card, which would be ideal. I've got plenty of hardware to run code on, but I'm not sure if spoofing an SD Card is even doable.
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Sep 24, 2014 04:12
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sharkytm posted:Does anyone know if there's a way to spoof an SD card with hardware and software? I'm looking to intercept the data being written to an SD Card from a device, probably using this https://www.sparkfun.com/products/9419. There are some comments about using it instead of a real card, which would be ideal. I've got plenty of hardware to run code on, but I'm not sure if spoofing an SD Card is even doable. Look at the "SDIO Simplified Spec" at https://www.sdcard.org/downloads/pls/simplified_specs/ and spoof away
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Sep 24, 2014 04:24
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Do any of you use field solvers when doing layouts? I would like to step up my SI game but at an a bit of a loss as to which tool to look into - initially, at least.
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Sep 26, 2014 18:13
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Delta-Wye posted:Do any of you use field solvers when doing layouts? I would like to step up my SI game but at an a bit of a loss as to which tool to look into - initially, at least. I can't say what is the accepted standard in planar work, but I know that HFSS is king in the 3D world. I imagine the ADS layout tools see some use due to its dominance in the design arena.
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Sep 26, 2014 23:20
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Delta-Wye posted:Do any of you use field solvers when doing layouts? I would like to step up my SI game but at an a bit of a loss as to which tool to look into - initially, at least. Hyperlinx is very common for general si analysis. It's a step below a full field solver but includes tools for most common board scenarios - termination, stack up impudence, power plane analysis etc.
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Sep 26, 2014 23:48
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I have a bunch of 5M RGB LED strips and amplifiers so I can connect them all together. I want to run them around a rectangular room, so if I get some of these right angle connectors then all I have to do is cut my strips at the designated spots, connect them to those? Will there be any power loss or anything with those? I've ordered 5 power supplies, 5 RGB LED strips, four amplifiers, and a controller. Everything I ordered more than one of had at least one thing that didn't work. Thanks eBay sellers! They are all very prompt with sending replacements though, so that's cool.
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Sep 27, 2014 03:09
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Delta-Wye posted:Do any of you use field solvers when doing layouts? I would like to step up my SI game but at an a bit of a loss as to which tool to look into - initially, at least. In the past I used Hyperlynx pretty extensively - it's really easy to operate, but it makes some approximations. For example, it assumes reference planes are perfect. Which is true much of the time, but it means that non ideal situations aren't always modeled well (i.e. changing reference planes and stitching via location). As long as you know the limits though, it can be pretty effective. It's good for estimating trace impedances and tuning termination though, especially when you want to bend the rules. You can also start modeling stuff in about 2 minutes, which is nice. Mentor has a 3D solver add on as well, but I haven't used it. Other tools tend to get more complicated (and expensive) from there, and are geared towards the higher speed designs (> ~3 gbps). AWR Microwave Office is good for 2.5d/3d planar modeling, but I found it annoying for modeling digital systems. It does a decent job modeling for printed RF designs without having too much of a learning curve. I've also briefly played with CST for full 3d modeling, but it's pretty complicated and will take much longer to use effectively. It also takes forever to run a decent sized model, but the results are quite accurate. I don't have direct experience with HFSS or SIwave, but I've heard good things about them. They're both from Ansys - HFSS is the dominant player in the 3D EM modeling world, and SIwave is their 2.5D planar tool.
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Sep 27, 2014 06:47
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Dohaeris posted:I have a bunch of 5M RGB LED strips and amplifiers so I can connect them all together. I want to run them around a rectangular room, so if I get some of these right angle connectors then all I have to do is cut my strips at the designated spots, connect them to those? Will there be any power loss or anything with those? I've ordered 5 power supplies, 5 RGB LED strips, four amplifiers, and a controller. Everything I ordered more than one of had at least one thing that didn't work. Thanks eBay sellers! They are all very prompt with sending replacements though, so that's cool. Are you trying to frame a bulletin board, or just worried about the corners of the room? If it's just the corners of the room, you should be fine with just the flex in the strips.
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Sep 27, 2014 20:03
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n0tqu1tesane posted:Are you trying to frame a bulletin board, or just worried about the corners of the room? If it's just the corners of the room, you should be fine with just the flex in the strips. Basically corners of a room, however I want to lay it flat along the wall. The walls in the room in question have a metal power box strip that runs around the room at like waist level. This is a classroom so it's a great height for kids to be able to see the strips and talk about how they work and stuff as well, I just need to get them in a rectangle.
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Sep 28, 2014 00:40
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Here's a quick question. If I have a 5v source, and a 3.3v source, powering 5v devices and 3v devices respectively, do I have to keep their grounds separate from one another? Is there a situation where I'd want to do that? It looks like everything works fine regardless of what ground they're connected to, but I don't want to blow any components up.
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Sep 29, 2014 01:53
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Keep the grounds common until you know you're not supposed to. Generally the skillset that answers "separate the grounds" supersedes this question
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Sep 29, 2014 02:02
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Along the same lines (but for safety!), if I have AC going into a transformer and then being rectified to ~80VDC, should my power switch make/break the AC live, neutral, or both? I'm thinking just live.
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Sep 29, 2014 03:04
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I picked up an antique fan today that needs some restoring but I'm a bit confused about one component of the wiring. It's some type of resistor but not like any I've seen. It's a non-conducting board wrapped in a heating element wire which is then sandwiched between 2 silica wafer boards. It's all parts I've seen in hair dryers before. So when you turn this fan on the lower of the 2 speed settings, it runs the current through the heating element which is screwed to the frame and uses it to slow down the motor, but heating the frame up in the process. I want to rewire this fan with new wiring but I'm wondering if I should try and keep this resistor thing or just swap to a modern resistor. Any suggestions? Also, how should I figure out which AC resistor I need? I've got a multimeter but I'm not sure how to use it to figure out exactly how much resistance this thing is providing.  
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Sep 29, 2014 04:23
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I've seen the same thing under a car dashboard used to control the HVAC blower motor. As a car ages the resistor pack gets damaged and the fan will only work at high speed where it is bypassing the resistors and seeing the full 12V. Of course the car is DC but voltage dividers work for AC, too. You'll have to choose a new resistor that can handle the wattage. http://hyperphysics.phy-astr.gsu.edu/hbase/electric/vdivac.html
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Sep 29, 2014 15:30
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bred posted:I've seen the same thing under a car dashboard used to control the HVAC blower motor. As a car ages the resistor pack gets damaged and the fan will only work at high speed where it is bypassing the resistors and seeing the full 12V. Huh, perhaps this is why the lower two fan settings on my 98 cavalier shitbox don't work. Good to know!
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Sep 29, 2014 21:59
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I don't have enough experience to figure out what that is trying to tell me. I've looked at it on and off today with not much luck. However, using the circuit simulator in the OP I built this which seems to help. It looks like I just need to figure out what the resistance across the existing heating element resistor is, and wire it in place of it.
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Sep 30, 2014 03:57
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ante posted:Along the same lines (but for safety!), if I have AC going into a transformer and then being rectified to ~80VDC, should my power switch make/break the AC live, neutral, or both? Typically only the live is switched. If you've got a ground in the cord, you can switch both if you want. If it's a 240V device, you must switch both wires (and also must have a ground, so you're good). SpartanIV posted:I don't have enough experience to figure out what that is trying to tell me. I've looked at it on and off today with not much luck. Get a modern dimmer and wire it into the fan. Resistive stuff is for people without extremely cheap solid-state devices. babyeatingpsychopath fucked around with this message at 04:24 on Sep 30, 2014 |
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Sep 30, 2014 04:19
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babyeatingpsychopath posted:Get a modern dimmer and wire it into the fan. Resistive stuff is for people without extremely cheap solid-state devices. Almost no type of common dimmer, household, theatrical, or otherwise, is going to do well with an inductive load. And by not do well I mean like I hope you have insurance. There's a real good reason fans have Hi-Med-Low settings as opposed to just a knob you can set to whatever intensity you want. Controlling inductive loads is a nightmare.
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Sep 30, 2014 05:00
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SoundMonkey posted:Almost no type of common dimmer, household, theatrical, or otherwise, is going to do well with an inductive load. And by not do well I mean like I hope you have insurance. I saw some dimmer switches at Lowes today labelled "Fan dimmer" made by Lutron. $20 instead of all the other $10 dimmers. I know normal dimmers are just a single triac with phase-angle firing, or something slightly more complicated for CFL/LED dimmers. Apparently another $10 gets you enough other stuff inside to properly control inductive loads.
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Sep 30, 2014 05:48
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babyeatingpsychopath posted:I saw some dimmer switches at Lowes today labelled "Fan dimmer" made by Lutron. $20 instead of all the other $10 dimmers. I know normal dimmers are just a single triac with phase-angle firing, or something slightly more complicated for CFL/LED dimmers. Apparently another $10 gets you enough other stuff inside to properly control inductive loads. I guess IGBT dimmers could do it but I'm still not sure I'd trust it hugely. Inductive loads are real funky, and even the hot-poo poo dimmers I use at work (2x2.4kW Strand CD80 modules, 48 per rack) are incredibly specialized (as in, you need a different one for a 0-full relay module, a different one for low-current applications since their SCR-based modules don't work so well for that, etc). Anything inductive or reactive makes them poo poo the bed, at $900/module no less. SoundMonkey fucked around with this message at 07:25 on Sep 30, 2014 |
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Sep 30, 2014 05:55
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