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Cyril Sneer posted:Lets say I wanted to run 400mA DC through a 28-awg wire, insulated, and part of a larger bundle...reasonable? I'm okay with "some" heating, and the 400mA is the absolute maximum which would not occur continuously. This violates the power transmission rating (225mA or so), but my understanding is this basically means no heating at all. Any idea for average current/duty cycle?
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Jul 23, 2014 04:02
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Cyril Sneer posted:Lets say I wanted to run 400mA DC through a 28-awg wire, insulated, and part of a larger bundle...reasonable? I'm okay with "some" heating, and the 400mA is the absolute maximum which would not occur continuously. This violates the power transmission rating (225mA or so), but my understanding is this basically means no heating at all. Those charts are typically de-rated heavily but also don't forget voltage drop. If you're trying to transmit low voltage power it can add up.
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Jul 23, 2014 04:50
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Aurium posted:Any idea for average current/duty cycle? Really hard to say - its ultimately driving a motor whose load changes dynamically. It certainly won't be at 100% for any extended periods of time. I'd estimate maybe something like ~200mA 2/3rd of the time + 400mA 1/3rd =~ 266mA average.
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Jul 23, 2014 05:02
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asdf32 posted:Those charts are typically de-rated heavily but also don't forget voltage drop. If you're trying to transmit low voltage power it can add up. It's only about 3 feet, so < 0.5 ohms. At 400mA, that's a power dissipation of 0.08W, which isn't much.
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Jul 23, 2014 05:05
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Cyril Sneer posted:It's only about 3 feet, so < 0.5 ohms. At 400mA, that's a power dissipation of 0.08W, which isn't much. Well I was talking about voltage drop. If you have 0.5 ohms on each wire, positive and negative, then it's 1 ohms total for a drop of 0.4V at 400mA. That may not be insignificant if you're working with 3.3 or 5V. (Looking at actual numbers it looks like you're at just about 0.5 ohms total for 6' of 28awg)
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Jul 23, 2014 05:23
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At 5 volts, 6 feet of 28ga aluminum wire will drop about 0.5 volts, yeah. If you go up to, say, 22ga you're down to 0.1 volts drop. What's the reason you have to use the tiny stuff? Is it already wired into a harness or something?
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Jul 23, 2014 17:51
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How would I convert 450 VDC into 240 VAC with 95% efficiency while handling up to 2 kVA loads in less than 40 cubic inches? I'm asking for a friend...
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Jul 24, 2014 02:09
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Cyril Sneer posted:Really hard to say - its ultimately driving a motor whose load changes dynamically. It certainly won't be at 100% for any extended periods of time. I'd estimate maybe something like ~200mA 2/3rd of the time + 400mA 1/3rd =~ 266mA average. These estimates make it sound fine. Is this a one off? Can you build it up and take some data?
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Jul 24, 2014 02:32
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Stabby McDamage posted:How would I convert 450 VDC into 240 VAC with 95% efficiency while handling up to 2 kVA loads in less than 40 cubic inches?
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Jul 24, 2014 03:06
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A parsec is a unit of length, not time.
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Jul 24, 2014 03:12
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Stabby McDamage posted:How would I convert 450 VDC into 240 VAC with 95% efficiency while handling up to 2 kVA loads in less than 40 cubic inches? I know the answer, but for a million dollars I'm going to keep it to myself.
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Jul 24, 2014 03:27
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Stabby McDamage posted:How would I convert 450 VDC into 240 VAC with 95% efficiency while handling up to 2 kVA loads in less than 40 cubic inches? While I'm fully aware that "that's not how poo poo works", I'm also looking at my 3400W audio amplifiers, which have absolutely no trouble feeding you a pure sine wave at 60Hz forever... ...except they weigh 40 pounds. Still, 3-4U rackspace.
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Jul 24, 2014 05:23
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I'm thinking about entering it actually, similar to my graduate research where I built a 10kW model -- but that was purely industrial and based around SiC JFETs. I've got the hardware I want to use for this in mind already to boot... Don't know if I can afford the development solo though, the test equipment needed will be pretty expensive.
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Jul 24, 2014 05:37
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Sagebrush posted:At 5 volts, 6 feet of 28ga aluminum wire will drop about 0.5 volts, yeah. If you go up to, say, 22ga you're down to 0.1 volts drop. What's the reason you have to use the tiny stuff? Is it already wired into a harness or something? Yeah, it's part of an already existing custom cable bundle, and it would be preferable not to have buy new stuff.
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Jul 24, 2014 13:00
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Hi guys, sorry if this is the wrong place for this. Are Weller soldering irons still the way to go? What's the functional difference between this and this? If it helps, I need this to assemble an ErgoDox keyboard although I occasionally find myself with projects that involve soldering.
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Jul 24, 2014 14:32
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Mr. Glass posted:Hi guys, sorry if this is the wrong place for this. Are Weller soldering irons still the way to go? What's the functional difference between this and this?
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Jul 24, 2014 14:41
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Ah, so the station part of the WLC100 is just a glorified lamp dimmer?
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Jul 24, 2014 14:45
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Mr. Glass posted:Ah, so the station part of the WLC100 is just a glorified lamp dimmer?
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Jul 24, 2014 14:49
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Mr. Glass posted:Ah, so the station part of the WLC100 is just a glorified lamp dimmer? Yes, it is. That said I've used one and they're as good as that style gets. The wes51 is definitely worth the upgrade though. Hakko is another good brand. The fx888d is beloved. They don't sell one with analog control anymore though.
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Jul 24, 2014 15:22
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Looks like the choice is between the FX888D and the WES51, then. Thanks for the info.
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Jul 24, 2014 15:44
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I'm a Metcal purist, but we only have Wellers at work (WES50 and WES51) and they actually are not /that/ bad. The exact temperature control can be nice for certain operations.
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Jul 24, 2014 17:29
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I bought the Aoyue iron that the thread recommended earlier, and it's been quite nice.
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Jul 24, 2014 18:00
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Mr. Glass posted:Looks like the choice is between the FX888D and the WES51, then. Thanks for the info. I've been quite happy with my Hakko, though I don't have the digital version.
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Jul 24, 2014 18:56
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Aurium posted:Yes, it is. That said I've used one and they're as good as that style gets. The wes51 is definitely worth the upgrade though. I have a Hakko FX-888D and I do, in fact, love it.
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Jul 24, 2014 19:14
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poeticoddity posted:I've been quite happy with my Hakko, though I don't have the digital version. Are you me, did I post this? Because, I agree. It's awesome if not fischer-price colored.
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Jul 24, 2014 20:53
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Mr. Glass posted:Looks like the choice is between the FX888D and the WES51, then. Thanks for the info. For what it's worth, if you're in a 240v country, just go with a Weller. Genuine 240v Hakkos are expensive, for no good reason. Also if you like digital display + analog knob, don't overlook Weller's wesd51. I wish Hakko did that with the 888d. movax posted:I'm a Metcal purist, but we only have Wellers at work (WES50 and WES51) and they actually are not /that/ bad. The exact temperature control can be nice for certain operations. Interesting, usually you see Metcal at work and something else for personal. What one do you have? (and what did you pay for it, if you don't mind) I often see decent deals on ebay for the STSS.
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Jul 24, 2014 23:49
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Aurium posted:Hakko is another good brand. The fx888d is beloved. They don't sell one with analog control anymore though. Yeah, because it was too badass for this world.  That's an iron that says "no we don't need any fuckin' bright colors or L-E-D displays or buttons or garbage like that. It has a dial, you turn the dial to where you want, and it goes there and it stays there and you don't need any more poo poo than that. Comes in any color you want so long as it's black." I love my 936.
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Jul 25, 2014 04:53
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Aurium posted:For what it's worth, if you're in a 240v country, just go with a Weller. Genuine 240v Hakkos are expensive, for no good reason. Also if you like digital display + analog knob, don't overlook Weller's wesd51. I wish Hakko did that with the 888d. Yeah, it's weird -- I keep asking them to buy a Metcal and they keep refusing and spending money on other stupid poo poo, like overnight shipping stuff because they don't understand the meaning of 'schedule'. Anyways - I have the MX500 myself, it's really solid. I've been meaning to pick up the tweezer attachment off eBay for awhile now.
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Jul 25, 2014 06:45
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Hooly poo poo, $500
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Jul 25, 2014 06:50
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movax posted:Anyways - I have the MX500 myself, it's really solid.
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Jul 25, 2014 07:03
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Aurium posted:Genuine 240v Hakkos are expensive, for no good reason. This pisses me off no end. It costs £125 (~$200) for an FX888D that sells for what, $90 in the US? It's cheaper to buy a 110V US iron, ship it to the UK, then buy a replacement 240V transformer from a Hakko distributor than it is to just buy a 240V iron to begin with.
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Jul 25, 2014 11:50
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I have a specific question about sourcing a part that I think may have a more general answer. I'm looking for an 8-to-3 priority encoder like an MC10H165 that doesn't use an absurd amount of power like an MC10H165 does (the thing has a supply current of ~140 mA  ). I assume the Right Answer is to find an analagous 74HC part. Is there any bijection between 10H-series and 74-series parts? Or is there a better way to look for this stuff than googling or trying to wrangle Digikey's unwieldy-for-this-purpose parametric search?
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Jul 25, 2014 14:06
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The 74xx148 is an 8-to-3 priority encoder. There doesn't seem to be any correlation between 74-series part numbers and the ECL 10K-series unfortunately.
Sweevo fucked around with this message at 16:03 on Jul 25, 2014 |
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Jul 25, 2014 16:00
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Oh, it looks like TI's SN74HC148 draws 80 uA and runs off a reasonably low supply voltage too. The inputs and outputs are active-low but that's easy enough to fix. Perfect!
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Jul 25, 2014 16:07
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I've been meaning to compile a cheat sheet for the TI logic families for awhile now, but here's a good basic PDF that goes over the differences between LVT, LVC, AUP, AVC, LVTH, LVCZ, HC, ABT, AUC, etc and how to pick whichever one you need (TTL inputs, CMOS inputs, speed vs. power, etc).
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Jul 25, 2014 17:30
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What's the best way to learn how to SPICE? I want to model out some circuits using parts that aren't available in that Java applet (what I've been using up through now), but SPICE is a bit overwhelming for me.  I swear, this hobby moves super quick from "ok yeah, I understand how this works and what's going on" to "holy poo poo this is over my head"
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Jul 25, 2014 18:15
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COOL CORN posted:What's the best way to learn how to SPICE? I want to model out some circuits using parts that aren't available in that Java applet (what I've been using up through now), but SPICE is a bit overwhelming for me. Try LT-Spice. It's graphic, it'll simulate most any basic circuit you need and it's free. If money is no object, Multi-sim is balls awesome for anything that doesn't have an MCU that needs to be emulated (although it can do a basic PIC or 8088).
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Jul 25, 2014 22:58
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Not many people seem to know about it but my favourite is Micro-cap. It's GUI super-intuitive to use - much better than LT Spice IMO.
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Jul 26, 2014 03:49
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I've got a kind of specific question, I'm hoping someone else can see what i'm missing. I've got a 4033 7 segment decade counter/decoder hooked up to 2 4 digit 7-seg leds. Instead of having a bunch of 4033s cascading, i've got one with it's a-g outputs hooked to all of the inputs on both displays. I then have a plain jane 4017 decade counter with it's clock attached to the carry out of the 4033. I am driving all of this with an Arduino, and I'm really trying to keep the pins down because I eventually want to use an Arduino Trinket to drive this display and sensors. Anyway, everything is fine on boot. The arduino sends a Reset pulse, the right most digit displays a zero, everything is peachy keen. The 4033 COut is high at this point. When I send a high pulse to the 4033 clock, the decade counter advances to the next digit, and the digit shows a 1. This digit then counts it's way up to 0, then when it rolls over to 1 it advances to the next digit. The next 6 digits all work exactly the same. I put in an LED on the COut of the decoder, and it goes HIGH when the digit goes from 9 to 0, BUT the decade counter does not advance. According to the data sheet, it should click over on the high side. It's probably something really stupid that i'm not seeing because i've been staring at this breadboard for too long. I'll post some schematics too while I'm at it. Ignore the LEDs on the right side, i'm using ExpressSCH and it doesn't have 7-seg displays. 
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Jul 26, 2014 07:30
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A bit late to the party but I have an 888D and it is absolutely awesome (and unlike my previous idiot trash iron, I don't have time to go have a beer while it heats up). Apparently (according to the salesman at the store who made REAL drat SURE I knew this) its one downfall is that if people don't read the giant warning and turn it on without the iron plugged in, it fucks it up. Not sure by what mechanism it fucks it up, but apparently that's a thing.
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Jul 26, 2014 23:52
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