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Cyril Sneer posted:If it was for work the fee would be a non-issue, but I have absolutely no need to get these parts fast. And they could literally all fit in a standard letter envelope. Argggg. AliExpress works for really common parts. Never ever ever use them for work or something where semiconductor quality actually matters, though.
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Jan 29, 2016 05:01
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Cyril Sneer posted:If it was for work the fee would be a non-issue, but I have absolutely no need to get these parts fast. And they could literally all fit in a standard letter envelope. Argggg. If it's no rush then just wait for when you need enough parts that the $8 shipping is no big deal
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Jan 29, 2016 05:34
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I've been reading about electronics and Arduino for a while, without having a good project to practice it on. Eager to make a start with it, I have a problem that I hope I can build a solution to. Yes, I'm noting how similar it is to the one on the previous page. I keep two small nocturnal marsupials, and currently I have to front end their feed at the beginning of the night, but ideally I'd like to hold some back until later in the night. So I was thinking about a device that, when set to a certain time, opens (not unlocks), a small box I could keep in there with them with food in. I was thinking I would probably want a non-Arduino solution because I don't want to commit it to that job full time, I would want to use it for other things. So I thought about hacking an alarm clock to have the buzzer connection in fact lead to a construction which then opens or lowers from the top of the cage when the alarm goes off. Does anyone have any experience of something like this or any tips? I've seen a fair few cat and dog feeders, but they are usually much bigger than I need and are for feedings at set times when people are out.
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Jan 29, 2016 19:12
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Fat Turkey posted:I've seen a fair few cat and dog feeders, but they are usually much bigger than I need and are for feedings at set times when people are out.
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Jan 29, 2016 20:06
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Also you can get an Arduino clone for like 3 bucks so don't worry about 'wasting' one in a full-time job like this.
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Jan 30, 2016 00:00
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I'm not sure about these aquarium feeders but from the sound of it its wet food? This would be for the main diet of fresh fruit and veg, so solids. Yes I see, I can use my Uno to design I and use a clone to run it? But I would need a clone with time telling properties and for it to always be plugged in right? Either way it will be fun designing something for this, any further tips appreciated.
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Jan 30, 2016 02:45
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Fat Turkey posted:I'm not sure about these aquarium feeders but from the sound of it its wet food? This would be for the main diet of fresh fruit and veg, so solids. The clone will be the same as the "real" Uno in every way but price. For this, I'd consider using a cheap servo, which is a controllable motor that turns to a specific angle between 0 and 180 degrees on command. I'm imagining a servo stuck to the side of a little box so that it can rotate a cover in and out of the way:  The code would be really simple, something like "when the button is pressed, set servo to 0 degrees (close box), wait 10000 seconds, then set servo to 90 degrees (open box)". Little 9g servos cost $1.50 shipped from China or $4 domestically. Bigger cheap servos exist, too ($4.60 from China, $6 U.S.).
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Jan 30, 2016 06:15
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That diagram is really useful, I think I need to structure it so that the lid actually exists the cage to give them more room. Not sure where you can get such cheap Arduino clones but they're obviously available. What the 9g of the servo indicate? Those links are great, buy I should have mentioned I'm UK based. Still, you've shown the spec so I'll just hunt on our eBay, i think we may have a local supplier nearish me anyay. Hopefully I'll make some progress now. 
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Jan 31, 2016 02:07
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Fat Turkey posted:That diagram is really useful, I think I need to structure it so that the lid actually exists the cage to give them more room. Not sure where you can get such cheap Arduino clones but they're obviously available. Cheap arduinos (as with all cheap electronics) come from ebay or aliexpress. I'm not sure on the 9g on the servo -- one might guess 9 grams, but that's not the right unit for torque, and it's also really low...maybe it was once a model number, but those servos have been cloned by 900 manufacturers now. Yeah, your domestic prices should have similar markup versus China with similar improvements in ship time. For projects, I just pipeline, buying from China for the next few projects while working on current ones. Shipping is slow and random enough that it makes going to the mail a fun lottery.
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Jan 31, 2016 02:47
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9g is the actual weight of the servo
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Jan 31, 2016 06:53
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peepsalot posted:9g is the actual weight of the servo I always thought it was how much the servo could... um... lift? How the hell is the weight of the servo at all useful?
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Jan 31, 2016 08:15
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Parallel Paraplegic posted:I always thought it was how much the servo could... um... lift? How the hell is the weight of the servo at all useful? The torque is also usually specified, but cheapass chinese listings aren't known for their detailed/accurate specs *shrug*
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Jan 31, 2016 09:09
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peepsalot posted:The weight is useful if you make very lightweight RC planes, which is sort of their intended use. I think 9g is also sort of used as a shorthand for that form factor, basically any 9g servo should be interchangeable. Oh that makes a lot more sense, thanks. That's confused me since I first joined robotics club in highschool 10+ years ago and I never bothered to look it up 
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Jan 31, 2016 09:29
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peepsalot posted:9g is the actual weight of the servo 
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Jan 31, 2016 20:11
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Fat Turkey posted:I'm not sure about these aquarium feeders but from the sound of it its wet food? This would be for the main diet of fresh fruit and veg, so solids. Aquarium feeders are for dry food, flake or pellet, and are intended to hold many days worth of food. Fresh fruit and vegetables would be a really bad idea for one of these. You want something that'd be easy to clean and store no more than a day's worth of food at a time.
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Jan 31, 2016 22:42
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In case anyone missed it, looks like FTDI is up to their old tricks: http://www.eevblog.com/forum/microcontrollers/ftdi-gate-2-0/ New driver pushed through Windows Update renders counterfeit chips worthless (transmits only "NON GENUINE DEVICE FOUND!").
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Feb 1, 2016 14:45
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Zuph posted:In case anyone missed it, looks like FTDI is up to their old tricks: http://www.eevblog.com/forum/microcontrollers/ftdi-gate-2-0/ I read it a bit until that moron defending FTDI's behaviour made me too annoyed to continue. Did it say what version of windows? We use SO many of the Aten UC232a devices and it makes my blood run cold if some of them happen to have counterfeit ftdi chips which could happen very easily.
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Feb 1, 2016 16:56
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The defenders seem to think that counterfeit FTDI chips are labelled "COUNTERFEIT" and are sold explicitly as counterfeits and that people and manufacturers specifically seek out counterfeits.
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Feb 1, 2016 21:48
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BattleMaster posted:The defenders seem to think that counterfeit FTDI chips are labelled "COUNTERFEIT" and are sold explicitly as counterfeits and that people and manufacturers specifically seek out counterfeits. Yes exactly. I don't think they realize how easy it is for fakes to get into legitimate supply chains with no one being aware. Fakes have been found in all sorts of aerospace equipment ffs and that is hopefully somewhat well tracked. Well at least we'll have an idea of what to look for if our usb uarts start going freaky deaky.
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Feb 1, 2016 22:10
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The last time I really argued the point people came back with "well, when I was in an onshore 13485 medically certified product line, we didn't have this problem??" as if every CE product can meet those standards.
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Feb 1, 2016 22:20
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BattleMaster posted:The defenders seem to think that counterfeit FTDI chips are labelled "COUNTERFEIT" and are sold explicitly as counterfeits and that people and manufacturers specifically seek out counterfeits. Well, now the chips literally shout IM A COUNTERFEIT, so problem solved
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Feb 3, 2016 05:37
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Slanderer posted:Well, now the chips literally shout IM A COUNTERFEIT, so problem solved Well I mean sure, after you've paid for it and soldered it to your board
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Feb 3, 2016 05:49
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Yeah and after passing through a half dozen middlemen so good luck actually tracing where the gently caress it came from. It does suck for FTDI too I'll give them that, although it is strangely ironic because you can pretty easily use a FTDI part in $25 worth of BOM parts to build your own SPI programmer instead of paying Cheetah $500 or whatever it is they charge. priznat fucked around with this message at 06:31 on Feb 3, 2016 |
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Feb 3, 2016 06:28
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Also not every application displays what's coming in from the UART so you might not even know that a counterfeit part is why the product isn't working until you hook up a logic analyzer. I understand why FTDI is frustrated with counterfeit parts but they're running a serious risk that people will stop using their chip knowing that they risk having a bum product if the supply gets contaminated.
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Feb 3, 2016 06:35
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BattleMaster posted:Also not every application displays what's coming in from the UART so you might not even know that a counterfeit part is why the product isn't working until you hook up a logic analyzer. Like there are other decent options... They need to step up production and work with resellers to identify counterfeit components, not alienate the entire EE community. I'm sure we'll see a video from Dave Jones about this, again.
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Feb 3, 2016 17:53
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priznat posted:Yeah and after passing through a half dozen middlemen so good luck actually tracing where the gently caress it came from. Again I think if they just made a tool for quick-checking if a particular batch of chips are counterfeit they would actually get a lot of manufacturers willing to check before a production run, but no instead they just gently caress up end users who really have nothing to do with it.
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Feb 3, 2016 21:08
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I hope this might be the right place for this electrical question! I have a camper van I've built out of an old Ford cargo van. It has a battery bank and solar power system. I'm trying to figure out if my voltage drop behavior under heavy loads is normal or the sign of a bad battery/cell. I have four 6v deep cycle flooded lead acid batteries connected in two series pairs parallel, for a total rated 406ah at 12v. They have purchase stickers of 04/15 and 05/15 so they are less than a year old. They came with the van; the prior owners charged them only with the alternator of the van, and they used them with a mini fridge so it is entirely possible that they were drained too low at some point and never really topped off until I got the solar hookup in fall of 2015. I have an inverter attached to the batteries for AC power. The inverter is a cheapo 1000w modified sine inverter that I will probably replace soon with a nice little Morningstar SureSine 300 pure sine inverter. Until then, this inverter is connected with a very short run of #0 cables. I have a little 200w AC space heater plugging into the inverter (after maybe 10ft of romex to the outlet) that makes a decent amount of heat for the small space I'm working with. I noticed, however, that when it is running the voltage of my batteries (as shown on my battery monitor, which shows the inverter drawing about 20 amps falling to 16-17 amps) drops down to 11.5v within a few seconds, dimming the DC lights I have noticeably. When the inverter is switched off, the batteries recover to their resting full voltage of 12.6-7v. For kicks I plugged in a 1300w space heater and fired it up, since the inverter should be able to handle that much for a short period before it shuts down due to overheating. It did indeed run the larger space heater, but it was making a terrible buzzing noise and going much slower than usual. When I looked at my battery monitor, I saw that (in addition to drawing 100 amps... good thing I used that #0 cabling!) my battery voltage dropped to 10.5v. The battery voltage recovered again to 12.6-7v when I switched the heater off. It seems like my batteries are simply unable to supply that much current that quickly, which makes sense since they are deep cycle batteries rather than starter batteries with a CCA rating. However, I hear many other campervan/RV people talking about their 2000w+ inverters running big loads like hair dryers without running into similar problems. Are they using other types of batteries most likely? Or are my batteries possibly shot? If not, I can't see how deep cycle batteries could possibly work with a 2000w+ inverter. I do plan on picking up a hygrometer and testing the specific gravity of each battery cell. Man_of_Teflon fucked around with this message at 21:23 on Feb 3, 2016 |
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Feb 3, 2016 21:20
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Man_of_Teflon posted:I hope this might be the right place for this electrical question! That is a poo poo ton of current, but with that capacity that is only like 0.25C discharge rate, so I would think they might be able to handle it. Is your battery monitor measuring the voltage right at the battery terminals, is located by the inverter? If it's the latter, check for a bad connection somewhere (which could be increasing the series resistance of the battery, leading to higher power draw since the inverter is a constant-power load). If not, definitely break out the hygrometer, since that seems off.
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Feb 3, 2016 21:34
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Slanderer posted:That is a poo poo ton of current, but with that capacity that is only like 0.25C discharge rate, so I would think they might be able to handle it. Is your battery monitor measuring the voltage right at the battery terminals, is located by the inverter? If it's the latter, check for a bad connection somewhere (which could be increasing the series resistance of the battery, leading to higher power draw since the inverter is a constant-power load). If not, definitely break out the hygrometer, since that seems off. The solar charger/monitor combo (SC-2030 and TM-2030) are wired with a shunt on the negative end of the battery bank per the manufacturer instructions:  I used #0 from battery bank to shunt too since everything goes through the shunt, including the inverter. I will try to check with a hygrometer tonight... I wonder if I overfilled a cell when I was topping them off with distilled water. edit: i suppose it probably doesn't help that this was done with the batteries around 40 degrees F. Man_of_Teflon fucked around with this message at 23:24 on Feb 3, 2016 |
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Feb 3, 2016 23:15
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Man_of_Teflon posted:The solar charger/monitor combo (SC-2030 and TM-2030) are wired with a shunt on the negative end of the battery bank per the manufacturer instructions: If the batteries have been in the same series/parallel configuration since install, it's likely that one or more has become unbalanaced. Find a 6V charger and condition each battery individually then wire everything back up and see if it's better. In general, a "battery conditioning" is approximately the following procedure: discharge battery at a constant current to a specific voltage, then constant voltage charge until current stabilizes, then discharge, then charge at constant current to a specific voltage, then constant voltage float charge until current (once again) stabilizes. That last charge should give the correct number of amp-hours in the battery. The "specific voltage" changes for 6v/12v/24v batteries, and the "specific current" changes based on the C rate of the battery, but is (in general) C/10, where "C" is the number of amps the battery can deliver from full charge for one hour before reaching a cutoff voltage of 1.5V/cell. Source: TECHNICAL MANUAL -- NAVY AND AIR FORCE AIRCRAFT AND AIRCRAFT SUPPORT EQUIPMENT STORAGE BATTERIES (NA 17-15BAD-1/TO 8D2-62-1) babyeatingpsychopath fucked around with this message at 00:32 on Feb 4, 2016 |
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Feb 4, 2016 00:25
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Man_of_Teflon posted:I hope this might be the right place for this electrical question! 6V ("golf cart" probably) are right for your application (they're often used for marine "house banks" as well). Your batteries sound like they're doing fine it's your inverter that's struggling. Maybe a higher power inverter will deal better with the voltage drop. Dropping to 10.5 under that type of load doesn't sound unreasonable. You should also double check the voltage right at the inverter. The wiring may be worse than you think and could easily be dropping another volt. Remember that it's not the rating that matters in these applications, it's voltage drop which dominates when dealing with 12V power. You try to keep it less than 3%, which isn't much. And remember to multiply the distance by 2 for the return path.
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Feb 4, 2016 04:32
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Here are two youtube videos: https://www.youtube.com/watch?v=3FpjcOWwiI4 https://www.youtube.com/watch?v=Snibt3CNqBA I would appreciate any insight regarding the materials donned by the performers.
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Feb 4, 2016 07:11
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DreadLlama posted:Here are two youtube videos: It's just steel mesh clothing, here's a site about it: http://www.teslamad.com/faraday/faraday.html EDIT: The guy in my link makes his out of chainmail but I've seen them made out of steel mesh too, I can't tell which one it is in the videos you linked though. Here's a random piece of steel mesh I found on amazon as an example: http://www.amazon.com/Stainless-Unpolished-Standard-Tolerance-E2016-06/dp/B00CNM1K3E Shame Boy fucked around with this message at 08:18 on Feb 4, 2016 |
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Feb 4, 2016 08:09
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What's the smallest writable 125kHz RFID chip I can get? I wanna clone a bulky HID fob and incorporate the result into something else that I carry, like my phone or car remote. I've been looking on Ebay, Ali, and other places, but all I find is a) knockoffs of the ordinary HID fobs/cards and b) read-only RFID stickers for inventory management. I guess I could order another fob and a card and try opening them up or dissolving them in acetone to extract just the RFID components, but it would sure be nice if I could buy an entire batch of them wholesale without paying for the plastic finishing.
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Feb 6, 2016 00:47
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Eikre posted:What's the smallest writable 125kHz RFID chip I can get? I wanna clone a bulky HID fob and incorporate the result into something else that I carry, like my phone or car remote. I've been looking on Ebay, Ali, and other places, but all I find is a) knockoffs of the ordinary HID fobs/cards and b) read-only RFID stickers for inventory management. Do they even make sticker-type 125kHz RFIDs? Or are their antenna coils too big? You can easily get affordable NFC type 2 tags in sticker format, though, which lends credence to my insane "antenna hypothesis"
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Feb 6, 2016 02:30
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DreadLlama posted:Here are two youtube videos: It looks like mesh suits with some breakout points in the hands, feet, and head so they can direct the sparks a bit while dancing around. For some Tesla coils you don't even need that - I occasionally get roped into doing Tesla coil demos for our lab's educational outreach events and we have a 250kV unit with a low enough duty cycle that we can put our hands directly in the arc Sith Lord style. The high frequency sparks cause a small current to flow on the outermost layers of your body so the only place that really feels any effect is the tips of your fingers where the arcs are concentrated and leave pinpoint-sized patches of singed skin. It doesn't hurt at all, but after doing the demo repeatedly for several bussloads worth of kids your hands start to smell like burned hair. Makes for a good show tho. Your wouldn't want to pull that trick with coils that have a higher duty cycle like the ones that can modulate music - they dump sufficient energy to cook the spark entry point to the pain threshold... or so I've been told.
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Feb 6, 2016 04:56
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Slanderer posted:Do they even make sticker-type 125kHz RFIDs? Or are their antenna coils too big? No, you're right, I only glanced as far as "read only" on those search results and didn't realize they were also on the wrong frequency. There are offers for all-but-naked apparatus stuck to the back of foam adhesive disks which seems to be as close to component form as I'm gonna get. Surprisingly, they're more expensive per unit than fobs. Economy of scale is some crazy poo poo. As long as I'm on the subject, a tangential inquiry: Do you suppose you could put multiple chips on the same antenna coil and still get viable reads? They would cause each other interference and strain the power transference, so I imagine it would top out with two or three, but it seems feasible, right? I don't suppose there's a RFID platform that stores several IDs and transmits them each in turn, as a way of acting like a keychain, is there? I just realized one of my other tags is also 125kHz.
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Feb 6, 2016 09:43
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I had an idea for a device to mount under a stove top vent hood. I want to point a ir thermometer at the stove top, and project the temperature(of the pan) onto the pan(or maybe just next to the pan). Everything seems really straightforward\easy except the projecting... I know I could just use a regular display, but he projecting part is the real novelty of the project for me. The first thing that came to mind was that dinky little 'portable keyboard' that actually projected the keyboard onto a surface for you to use http://www.amazon.com/AGS-Wireless-...jector+keyboard I can't find anything better than some pretty expensive projector dev boards from TI. Any ideas?
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Feb 6, 2016 18:33
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They make alarm clocks that project the time on a wall. You might be able to find a dirt cheap one on eBay or somewhere and use it for parts. From the small amount of research I did it looks like one of the easiest ways to make such a projection display is to put a super bright LED behind an LCD screen and add some lenses to focus the light. Some cheap piece of junk like this might be enough to get you started.
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Feb 6, 2016 19:04
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DethMarine21 posted:They make alarm clocks that project the time on a wall. You might be able to find a dirt cheap one on eBay or somewhere and use it for parts. From the small amount of research I did it looks like one of the easiest ways to make such a projection display is to put a super bright LED behind an LCD screen and add some lenses to focus the light. http://www.amazon.com/Electrohome-Projection-Temperature-Smartphones-EAAC601/dp/B003WGRUQQ Here's one that even claims to support temperature display by default (though maybe not enough digits) And if you're looking to start more from scratch, here's a project I found on hack a day that might get you started and give you some ideas: http://web.media.mit.edu/~stefanm/TinyProjector/
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Feb 7, 2016 00:38
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