Electrical Engineering V2 - Developers

I'm looking to buy about a dozen 3.5mm female audio jacks for headphones(actually only need one, but just in case) but nothing I find on ebay seems to really be for stereo. Does anyone with experience know of any decent sellers on ebay? The closest I found to what I want are: [url]http://www.ebay.com/itm/141083775380[/url] But I only see 2 pins on this, which tells me thats not really stereo, unless I'm missing something? I'm building a radio on a breadboard, and want to later put it in an acrylic case.

[QUOTE=false prophet;44911012]I'm looking to buy about a dozen 3.5mm female audio jacks for headphones(actually only need one, but just in case) but nothing I find on ebay seems to really be for stereo. Does anyone with experience know of any decent sellers on ebay? The closest I found to what I want are: [url]http://www.ebay.com/itm/141083775380[/url] But I only see 2 pins on this, which tells me thats not really stereo, unless I'm missing something? I'm building a radio on a breadboard, and want to later put it in an acrylic case.[/QUOTE] Two pins plus the body of the connector (ground) makes three. You're probably better off getting the plastic pcb mount jacks if you plan on using it on a breadboard I guess.

[QUOTE=false prophet;44911012]I'm looking to buy about a dozen 3.5mm female audio jacks for headphones(actually only need one, but just in case) but nothing I find on ebay seems to really be for stereo. Does anyone with experience know of any decent sellers on ebay? The closest I found to what I want are: [url]http://www.ebay.com/itm/141083775380[/url] But I only see 2 pins on this, which tells me thats not really stereo, unless I'm missing something? I'm building a radio on a breadboard, and want to later put it in an acrylic case.[/QUOTE] Look for TRS (Tip, Ring, Sleeve) connectors, they're the stereo ones. Unless you want a data/mic signal, like your phone has, then it'd be a TRRS.

If i had a friend offering a KEITHLY 5.5 digit multimeter that is used and has been tested working: [img]http://i.imgur.com/CNtCPCV.png[/img] [img]http://i.imgur.com/OCkJ4Sl.png[/img] Should i buy it for £120?

To be able to switch off my dashboard entirely without unplugging my arduino, what should I use? Right now switching off my psu just means the shift registers still draw 5v from the headers that drive them. Is this a good place to use optocouplers or not?

[QUOTE=nuttyboffin;44911729]Should i buy it for £120?[/QUOTE] Rather overpriced imo, I would pay no more than £80 for that, don't forget if you want accuracy you will have to get it calibrated as well otherwise you might as well buy a brand new one for that price.

Im Creative :D I don't have any sheet router or a pcb etching kit, so i just moved my pillar drill up and pressed the pcb against it to cut into it [img]http://i.imgur.com/MxLyVou.jpg[/img]

Look what the postman delivered [img]http://puu.sh/93dRa.jpg[/img] And after a trip to the riglol web app: [img]http://puu.sh/93dUO.jpg[/img]

UPS delivered my chips from farnell, so i got to have a little play with them: Built a nice little 10V (under load) PSU [img]http://i.imgur.com/jmmNljC.jpg[/img] [img]http://i.imgur.com/Cr4FThH.jpg[/img] Draws near no current when no load. I didn't really plan it out or do any designs so it isn't that great load wise, but it still works! I would show you a picture of the scope waveforms but the damn thing flashes because of how the IRS chip works.

Testing the capacity of a pair of 18650 cells ripped form a laptop battery. [img]http://puu.sh/93u23.jpg[/img] Here's a link to the spreadsheet so you can watch me enter data LIVE! [url]https://docs.google.com/spreadsheets/d/1T02lNdZ84AwtOJ4UdTYXLbGrHIH9jAv124EK00h7prM/edit?usp=sharing[/url]

[QUOTE=chipset;44923293]Testing the capacity of a pair of 18650 cells ripped form a laptop battery.[/QUOTE] Those batteries are awesome for projects that need a lot of current, the ones I have can deliver several amps each when shorted. Just be careful how you store them or you could end up with them venting :v: Capacity is usually around 1-2Ah

[QUOTE=Chryseus;44923343]Those batteries are awesome for projects that need a lot of current, the ones I have can deliver several amps each when shorted. Just be careful how you store them or you could end up with them venting :v: Capacity is usually around 1-2Ah[/QUOTE] I have a bunch more in a box that are stored in appaling conditions, I really should order battery boxes from ebay. I'm don't really need any kind of an accurate figure here, mainly just wanna see if they're healthy. I'm mostly just taking a load of data points so that I can graph it later, for science or something like that.

[QUOTE=chipset;44923293]Testing the capacity of a pair of 18650 cells ripped form a laptop battery. [img]http://puu.sh/93u23.jpg[/img] Here's a link to the spreadsheet so you can watch me enter data LIVE! [url]https://docs.google.com/spreadsheets/d/1T02lNdZ84AwtOJ4UdTYXLbGrHIH9jAv124EK00h7prM/edit?usp=sharing[/url][/QUOTE] Dat live data acquisition. :v:

Round two of testing battery capacity just started, join me in the spreadsheet for LIVE data entry! [url]https://docs.google.com/spreadsheets/d/1T02lNdZ84AwtOJ4UdTYXLbGrHIH9jAv124EK00h7prM/edit?usp=sharing[/url] This time using 2.2A instead of 0.5A load current, so hopefully it shouldn't take 8 hours. Edit: Test completed, at 2.2A load the two cells had a combined capacity of 916mAh from full charge to 3.0V. i.e a little over 400mAh per cell. I'll do another test at 1A tomorrow and compare the results. Edit: Test done at 1A load, result about 2.5Ah for the two cells in parallel, so 1.25Ah per cell. Not sure if it's because of these cells in particular, their age or if it's normal, but the reduction in capacity from 1A to 2.2A load is quite astonishing.

Hello, one quick question! I need to use NTE152 in my circuit (transistor), but I don't have it. Can I use IRF530n (mosfet)? NTE152 is used by 555 for pulsing

[QUOTE=HeatPipe;44960416]Hello, one quick question! I need to use NTE152 in my circuit (transistor), but I don't have it. Can I use IRF530n (mosfet)? NTE152 is used by 555 for pulsing[/QUOTE] depends what the circuit is.

[QUOTE=nuttyboffin;44960679]depends what the circuit is.[/QUOTE] I know. 555 is just making constant pulses

[QUOTE=HeatPipe;44960416]Hello, one quick question! I need to use NTE152 in my circuit (transistor), but I don't have it. Can I use IRF530n (mosfet)? NTE152 is used by 555 for pulsing[/QUOTE] I don't see why not, in fact that's a upgrade substitution.

[QUOTE=LoneWolf_Recon;44961904]I don't see why not, in fact that's a upgrade substitution.[/QUOTE] Yeah I guess. In circuit, there is resistor between base and 555 output, I should remove that resistor right?

[QUOTE=HeatPipe;44962565]Yeah I guess. In circuit, there is resistor between base and 555 output, I should remove that resistor right?[/QUOTE] You can if you want, but its good practice to pull the gate up or down with atleast a 10k. (If you do leave the original resistor in, do check to make sure that the voltage across the 10k is atleast the threshold voltage of the mosfet, or else it won't fully turn on)

[QUOTE=LoneWolf_Recon;44963015]You can if you want, but its good practice to pull the gate up or down with atleast a 10k. (If you do leave the original resistor in, do check to make sure that the voltage across the 10k is atleast the threshold voltage of the mosfet, or else it won't fully turn on)[/QUOTE] Ok, cool :) Will run it, measure with oscilloscope if it functions fully and then add resistor accordingly (pull up/down)

So I've been poking around on eBay, looking for a DSO. I figured for shits and giggles I'd get one that needs fixing (because what's the worst that can happen?). Problem is I can't seem to decide which one I want to get, as they're all <$150 in this state usually. [url=http://www.ebay.com/itm/Agilent-HP-54501A-Digital-Oscilloscope-100-MHz-4-channel-/181087063033?pt=BI_Oscilloscopes&hash=item2a29a14bf9]There's this one[/url], but it seems like a craps-shoot because there's 4 of them, each with different problems (I'm sure you can't pick and chose which one you want). [url=http://www.ebay.com/itm/Agilent-HP-54111D-Digitizing-Oscilloscope-1GS-s-500MHz-2CH-/221401124218?pt=BI_Oscilloscopes&hash=item338c890d7a]Then there's this one[/url], which might be easy, but who knows and it's only 2-channel (which is fine, but if I'm gonna get a deal on one it might as well be 4-channel so I'm not out there buying ANOTHER 'scope in the future when I need more channels). [url=http://www.ebay.com/itm/HP-AGILENT-54100-CLASS-HP-AGILENT-54100D-DIGITIZING-OSCILLOSCOPE-/230830197650?pt=BI_Oscilloscopes&hash=item35be8d4b92]This one[/url] might not even need repairs at all according to the page, but since the user's manual I could find for it dates to a revision in 1984, and that's the latest, it might not be worth the trouble. [url=http://www.ebay.com/itm/Tektronix-11801A-Digital-Sampling-Oscilloscope-50GHz-8ch-Opt-1C-1R-2D-4D-/141302862381?pt=BI_Oscilloscopes&hash=item20e64e922d]And then there's this sucker.[/url] If it turns out to be an easy repair then it'd be a hell of a steal, buuuut then I'd need to get those modules to even use the thing, and I doubt I'd find any of those for cheap that were worth buying. [url=http://www.ebay.com/itm/LeCroy-7200-Precision-Digital-Oscilloscope-7242-Timebase-Plug-in-500MHz-1Gs-s-/251486205978?pt=BI_Oscilloscopes&hash=item3a8dbef81a]This one is...[/url] Eh, if it's stuck booting, there's no telling what the issue is. The knob could be an easy fix though. So many choices!

The danger is that you can buy one that requires replacement of custom ICs, and the chance of you getting your hands on those is next to nil unless you buy another one and hope that that very IC is still working in there. Also make sure that you get one that has a self-test that actually displays errors, that should narrow down your search effort.

[QUOTE=DrDevil;44972818]The danger is that you can buy one that requires replacement of custom ICs, and the chance of you getting your hands on those is next to nil unless you buy another one and hope that that very IC is still working in there. Also make sure that you get one that has a self-test that actually displays errors, that should narrow down your search effort.[/QUOTE] Yeah, that's the other main thing holding me back on this. Even if it's "only" $150, it's not good at all if all I can get out of it is scrap parts.

[QUOTE=Zero-Point;44972853]Yeah, that's the other main thing holding me back on this. Even if it's "only" $150, it's not good at all if all I can get out of it is scrap parts.[/QUOTE] If it's your first DSO, I suggest just buying a lower end DSO for the same money. Afterall fixing a DSO without another DSO would be a pretty hard task aswell.

[QUOTE=DrDevil;44973469]If it's your first DSO, I suggest just buying a lower end DSO for the same money. Afterall fixing a DSO without another DSO would be a pretty hard task aswell.[/QUOTE] I wasn't aware you could get a new DSO for <$150. :v:

[QUOTE=Zero-Point;44973674]I wasn't aware you could get a new DSO for <$150. :v:[/QUOTE] A used Rigol DS1052e might go for that price.

All the used ones they have listed on eBay are $320 minimum. Oh well.

Gotta mow more lawns then!

[QUOTE=DrDevil;44973853]Gotta mow more lawns then![/QUOTE] but muh allergeez Eh, I'll think it over. Worst-case if I end up buying one to fix and I can't fix it, I can just turn right around and sell it again right? :v: