[QUOTE=Tobba;50596069]Running the math on potting this thing in epoxy, I'm carrying 5A over a 3000 mils long 60 mil trace. I'm getting that with 1oz copper, it'd generate 600mW of heat and reach 30C above ambient sitting under 1cm of epoxy (assuming 1.5 W/(mK)), I feel like that calculation is wonky at best though, and since it's sitting inside a pretty hot area (it drives a heater) it seems that it might become an issue.
Can't really figure out if I should bother with 2oz copper for this kinda current, it'll take OSHpark up to a month to get them here. I'm starting to feel like 1oz will be fine though, anyone got any experience with this?[/QUOTE]
You say it drives a heater, but where in the heater will it be located? In my experience scrapping old heaters/furnaces, they're seldom potted, unless it's the kind that has all the controls inside the blower motor.
[QUOTE=Tobba;50596069]Running the math on potting this thing in epoxy, I'm carrying 5A over a 3000 mils long 60 mil trace. I'm getting that with 1oz copper, it'd generate 600mW of heat and reach 30C above ambient sitting under 1cm of epoxy (assuming 1.5 W/(mK)), I feel like that calculation is wonky at best though, and since it's sitting inside a pretty hot area (it drives a heater) it seems that it might become an issue.
Can't really figure out if I should bother with 2oz copper for this kinda current, it'll take OSHpark up to a month to get them here. I'm starting to feel like 1oz will be fine though, anyone got any experience with this?[/QUOTE]
Nah, your equation is spot on and the trace/epoxy will get warmer if there is a hotter ambient generated by the heater. You can use [URL="http://www.daycounter.com/Calculators/Heat-Sink-Temperature-Calculator.phtml"]this heat sink calculator[/URL] and pretend your trace is an IC with the epoxy on top as the package (Using your already provided thermal resistances).
Then just bump up the ambient temperature to its max that you would like/generated by the heater before the temperature of the trace is too hot for the epoxy.
Personally, I would widen that trace or make some duplicate path if I wasn't willing to wait on the 2oz copper. Because 607mW is way too much heat IMO for a trace to be dissipating.
[QUOTE=Zero-Point;50598201]You say it drives a heater, but where in the heater will it be located? In my experience scrapping old heaters/furnaces, they're seldom potted, unless it's the kind that has all the controls inside the blower motor.[/QUOTE]
It's separated from the interior by a rather flimsy piece of aluminum, but the air inside isn't gonna get terribly hot (IR heaters), so I'd guess the ambient in the control part ends up at 40-50C at worst.
Real reason for potting it (other than that I feel like doing it) is that I'll probably be running it with the cover off / working on the control board a lot, so I don't want it sitting hot glued somewhere with mains poking out everywhere. If it wasn't a one-off there's really no point in doing it.
[QUOTE=iwancoppa;50584328]Edit: After having a look at pricing for eagleCAD :nope:, I think it's time to switch before I get too comfortable with it. KiCAD is looking good; any suggestions?[/QUOTE]
I use KiCad. I like it. It works. The stable version that came out like 6 months ago, has proven to be rock solid. UI might need a bit to get used to, but the board layout side is great.
There's a guy doing this board with KiCad right now, so it definitely handles even more complex stuff.
[t]http://i.imgur.com/fY50h22.jpg[/t]
Decided to copy some quick blink code off the internet to test my AVR, so that I couldn't possibly fuck it up myself.
Should've known better, apparently setting the entire port D to output is a terrible fucking idea on an ATmega168, since the reset pin is on there :v:. There goes an hour and a good few erase cycles.
I made a bit of progress on the rover
[vid]https://dl.dropboxusercontent.com/u/43645231/photos/electro/2016-06-26 20.22.07.mp4[/vid]
didn't do much to it, but I got manual driving to work.
USB gamepad (dualshock clone) > python (using pygame) > serial > rover
Main reason for manual is so I can test stuff easely. I can just drive it back incase it doesn't want to drive automatically for whatever reason :v:
[QUOTE=scratch (nl);50599473]snip[/QUOTE]
Please tell me you're going to add IR sensors to that([URL="http://www.taydaelectronics.com/sensors-transducer/optical-sensor/tcrt1000-reflective-optical-sensor-950nm-tcrt1000.html"]These are good[/URL])
probably yeah, the ultrasonic sensor (that's not yet in use) alone won't be capable of doing a whole lot on it's own. I atleast want some IR sensors to prevent it from driving off a table or down the stairs.
I've also made a board to program an ESP8266, but I ran into an issue.
I previously made a board that sat on an arduino which did the job, but was pretty garbage and occupied the arduino which is a waste.
For the new one I'm using [URL="http://www.dx.com/p/usb-to-ttl-ch340g-converter-module-adapter-for-arduino-and-stc-418846"]one of these[/URL], and it kinda works. I can upload a program succesfully, However, when the ESP8266 leaves programming mode, the converter keeps disconnecting repeatedly from my PC. The test program I uploaded sends a message every second, and I can see the LED on the converter indicating it received said message.
I'm assuming that the issue is that the 3.3V supply of the converter can't handle the high current draw from the ESP8266 when not in programming mode, could this be correct?
One pretty big hint to this is that the power LED on the converter dimms a bit randomly while the disconnecting is happening.
So today I found out female RJ45 connectors meant for ethernet aren't just dumb connectors, they actually work like this:
[img]http://i.imgur.com/nwSIlbw.png[/img]
Which made the ones I bought completely useless
I got it fixed, I got a voltage regulator that uses the 5V supply for 3.3V (regulator has 1V dropout so it's fine) as it's beefier than the 3.3V supply :v:
[QUOTE=Goz3rr;50604758]So today I found out female RJ45 connectors meant for ethernet aren't just dumb connectors, they actually work like this:
[img]http://i.imgur.com/nwSIlbw.png[/img]
Which made the ones I bought completely useless[/QUOTE]
Only some of them does, others doesn't have the galvanic insulation built-in and needs it added separately (if required)
Was a problem with a batch of Raspberry Pi's that were assembled with RJ45 connectors without the transformers built-in
[QUOTE=Goz3rr;50604758]So today I found out female RJ45 connectors meant for ethernet aren't just dumb connectors, they actually work like this:
[img]http://i.imgur.com/nwSIlbw.png[/img]
Which made the ones I bought completely useless[/QUOTE]
Don't know where you got them, but Digikey has them clearly demarcated with [url=http://www.digikey.ca/product-search/en/connectors-interconnects/modular-connectors-jacks/1442740]Modular Connectors[/url] and [url=http://www.digikey.ca/product-search/en/connectors-interconnects/modular-connectors-jacks-with-magnetics/1442739]Modular Connectors with Magnetics[/url]
This laptop has a cool battery but it's at like 5V. So around 1.65V per cell. It refuses to let the me charge it. Need to find way to manually charge the cells and try to revive the thing. It's just been sitting too long.
[QUOTE=gjsdeath;50613934]This laptop has a cool battery but it's at like 5V. So around 1.65V per cell. It refuses to let the me charge it. Need to find way to manually charge the cells and try to revive the thing. It's just been sitting too long.[/QUOTE]
Don't bother charging the whole thing. Take it apart and see if individual cells are still good.
[QUOTE=DrDevil;50614372]Don't bother charging the whole thing. Take it apart and see if individual cells are still good.[/QUOTE]
Wish it were that easy. The thing is like glued/welded together. Trying not to destory it in the process.
[t]http://i.imgur.com/hq0LzQO.jpg[/t]
First PCB design and fab I've done - 10 watt, 1 amp dummy load. I also managed to get the jack the wrong way around in the schematic, and promptly discovered the pain associated with a cheapo chinese electrolytic cap exploding from reverse polarity. :goodjob:
Thankfully I included a 9v battery snap option, which is working admirably.
I finally got around to [url=http://www.vcfed.org/forum/entry.php?621-Bringing-the-Model-33-to-the-21st-Century-Part-1]publishing the full writeup to that Teletype modem project I spent all that time on.[/url]
I still need to figure out a serial buffer.
[t]http://i.imgur.com/tr7e506.jpg[/t]
An hour wasted googling and re-reading the ADC section of the datasheet over this breadboard design stupidity. :incredible:
Man, OSHPark are still holding strong as my favorite PCB fab company:
[QUOTE]Hi! We had some free room on one of our Super Swift Service panels,
so we took the opportunity to give you an upgrade.
Your affected orders are:
* 0QHBmJqq - EL Driver 2016 A
The Super Swift Service drops your expected fabrication time from 12
calendar days to just 5 business days. The same fabs manufacture the
Super Swift panels as our normal panels, so you can expect the same
excellent quality.
Only fabrication time is affected, so the shipping times and method will
remain the same.
Thanks for using OSH Park![/QUOTE]
[url]http://www.avsforum.com/forum/155-diy-speakers-subs/2100354-inuke-6000dsp-filter-mod-guide-less-low-frequency-rolloff.html[/url]
[img]http://s24.postimg.org/hmn3jltth/6000_DSP_filtermod_filtermod_complete.jpg[/img]
You have the wire. You have the shrink tube. Yet you use the jumper plugs anyways. Is it really that hard to solder shit in? :pudge:
[QUOTE=iwancoppa;50649848][t]http://i.imgur.com/tr7e506.jpg[/t]
An hour wasted googling and re-reading the ADC section of the datasheet over this breadboard design stupidity. :incredible:[/QUOTE]
I had the same problem with that breadboard. They are a right bitch.
I have been working on creating a ticker display and i spent the evening trying to figure out why it would not draw anything on the display.
For the nodeMCU, it can only do SPI on certain pins......
The only reason I found out what was happening was by breaking out a cheapo ebay logic probe and seeing that latch was not change like it needed.
[IMG]https://dl.dropboxusercontent.com/u/30521593/20160706_012159.jpg[/IMG]
Hey everyone check out this completely ordinary space heater:
[url=http://imgur.com/cWDDzVG][img]http://i.imgur.com/cWDDzVGl.jpg?1[/img][/url]
Hold on there's something on the side....
[url=http://imgur.com/SRmfxjH][img]http://i.imgur.com/SRmfxjHl.jpg?1[/img][/url]
What are all these doing here?
[url=http://imgur.com/JPcosHb][img]http://i.imgur.com/JPcosHbl.jpg?1[/img][/url]
Well hello there.
[url=http://imgur.com/dhMG8qZ][img]http://i.imgur.com/dhMG8qZl.jpg?1[/img][/url]
This is my dummy load I've wanted to slap together for so long. Two sets of 16, 8, 4 and 2 ohm jacks. The colors mean nothing, they're just what I had lying around. I figure I can get around 1300W (15A) at 8 ohms if I parallel the two 16 ohm loads.
Also bonus EC3 to banana plug connectors I made for charging some NiMH batteries. They replace the top one there which is kind of nasty.
[url=http://imgur.com/BegSKWB][img]http://i.imgur.com/BegSKWBl.jpg[/img][/url]
I am trying to find a replacement for a SM2B41. I can't seem to find anything with similar specs as the it has. Here is the datasheet: [url]http://www.datasheets360.com/pdf/660794047310665779[/url]
If I go with something exactly the same specs, would it matter much?
[QUOTE=pentium;50654620][url]http://www.avsforum.com/forum/155-diy-speakers-subs/2100354-inuke-6000dsp-filter-mod-guide-less-low-frequency-rolloff.html[/url]
[img]http://s24.postimg.org/hmn3jltth/6000_DSP_filtermod_filtermod_complete.jpg[/img]
You have the wire. You have the shrink tube. Yet you use the jumper plugs anyways. Is it really that hard to solder shit in? :pudge:[/QUOTE]
Maybe they want to be able to change the values as needed to play with the sound
I hope it's worth to ask here, but here goes.
I've got a cheap (2.50 euros!) USB desk fan which had a shitty wire, so I went and got an old variable adapter that scales from 1.5v to 12v, and decided to use that as its power supply. I was surprised to find out it doesn't seem to have a problem with more than double the voltage when at 12v, except for the blades slightly bending when you crank up the power adapter to 12v.
Now another thing I want to add to this thing is a potentiometer on the back so I can control its speed much easier rather than having to reach out behind the adapter and fiddle with its switch.
What type of potentiometer would I need to let it scale up to 12v DC at 800mA?
Thing is I'm sort of a beginner with this yet, so yeah that's why I hoped to ask it here.
For the sake of reference, here's the spec label on the rear of the adapter I use:
[T]https://f.lewd.se/SPdg6Q_chrome_2016-07-07_16-21-17.png[/T]
[QUOTE=false prophet;50661243]I am trying to find a replacement for a SM2B41. I can't seem to find anything with similar specs as the it has. Here is the datasheet: [url]http://www.datasheets360.com/pdf/660794047310665779[/url]
If I go with something exactly the same specs, would it matter much?[/QUOTE]
Here's something similar ([URL="http://www.mouser.com/ProductDetail/STMicroelectronics/ACST610-8T/?qs=sGAEpiMZZMuAO0%252bGuNbnQsr3mj90O844iTi82rb5GUE%3d"]ACST610-8T[/URL]), its a more robust, but has lower gate trigger voltage/current
[QUOTE=Merijnwitje;50663975]I hope it's worth to ask here, but here goes.
I've got a cheap (2.50 euros!) USB desk fan which had a shitty wire, so I went and got an old variable adapter that scales from 1.5v to 12v, and decided to use that as its power supply. I was surprised to find out it doesn't seem to have a problem with more than double the voltage when at 12v, except for the blades slightly bending when you crank up the power adapter to 12v.
Now another thing I want to add to this thing is a potentiometer on the back so I can control its speed much easier rather than having to reach out behind the adapter and fiddle with its switch.
What type of potentiometer would I need to let it scale up to 12v DC at 800mA?
Thing is I'm sort of a beginner with this yet, so yeah that's why I hoped to ask it here.
For the sake of reference, here's the spec label on the rear of the adapter I use:
[T]https://f.lewd.se/SPdg6Q_chrome_2016-07-07_16-21-17.png[/T][/QUOTE]
At that kind of power (~10W) it becomes quite unwieldy in both size and power dissipated by a potentiometer. You could attempt to do this with a Rheostat or Rotary Dimmer for home lighting (You can pick this up at any home improvement store).
Fans like those don't really scale to well with current (Brushless fans are better scaled by voltage), thus I'd recommend getting a [URL="http://www.ebay.com/itm/DROK-DC-Step-Down-Variable-Voltage-Regulator-36V-to-24V-12V-5V-3-3V-3V-Buck-C-/231952610121?hash=item360173f349:g:FLIAAOSwU1FXQV4i"]variable buck converter[/URL], and wire up as follows:
Variable adapter -> Buck Converter -> Fan.
You can mount the variable buck converter inside the fan, and either get a larger potentiometer to replace the one currently on it (The blue trimpot) or just leave a small opening for you to adjust the voltage with a screw driver.
I suppose I could try to get a larger potentiometer on the board, yeah. A small one like that isn't really easy as I'd have to reach out with a screwdriver the whole time just to quickly change the speed. I just hope it will fit qua space.
[T]http://i.imgur.com/AWTbImj.jpg[/T]
[QUOTE=Merijnwitje;50664178]I suppose I could try to get a larger potentiometer on the board, yeah. A small one like that isn't really easy as I'd have to reach out with a screwdriver the whole time just to quickly change the speed. I just hope it will fit qua space.
[T]http://i.imgur.com/AWTbImj.jpg[/T][/QUOTE]
Maybe look at using a PWM signal and mosfet or such to control the voltage. It would let you have a pot and shouldnt be too big.
Something like [url]http://www.ebay.com/itm/3V-35V-12V-24V-DC-Motor-PWM-Speed-Control-Controller-Speed-Switch-LED-Dimmer-FAN-/171911081847[/url]
There's basically no reason to do it this way, but I mean who doesn't like options.
[url=http://imgur.com/t3xKAdz][img]http://i.imgur.com/t3xKAdzl.png[/img][/url]
Pros:
-Simple
Cons:
-Fan will only get about 10.5V max
-TIP31A needs a reasonable sized heatsink
is The Art of Electronics worth getting? It gets a lot of praise for being straight to the point, which is something that does sound quite interesting to me as well.
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Electrical Engineering V3
