[QUOTE=Tobba;41039526]I need an USB to Serial (as in UART) with adjustable voltage
Any idea where I can get this, I can ghetto it up by hooking up an arduino for 5V stuff and another board that does 3.3V but its large, hacky and unpractical[/QUOTE]
You can get some model with built-in function to switch between 5v and 3.3v (and sometimes also 1.8v) all with the flick of a switch.
[editline]15th June 2013[/editline]
[IMG]http://www.hobbytronics.co.uk/image/data/tutorial/mosfet_level_converter.jpg[/IMG]
Schematic for a single line bi-directional level converter.
My first pick and place manufactured board!
[img]http://i.imgur.com/NbwEUSY.jpg[/img]
I need to get some MAX7219's. I'v looked at ebay and found this: [url]http://www.ebay.com/itm/10PCS-IC-MAX7219CNG-MAX7219-DIP-24-DRIVER-LED-DISPLAY-8DGT-NEW-GOOD-QUALITY/300739928460?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D261%26meid%3D8486634252860574137%26pid%3D100005%26prg%3D1088%26rk%3D5%26sd%3D130733916831%26[/url] While Farnell and Sparkfun sell those for over 10$. The question now is what's wrong with the IC's on ebay? Are they rejects, faulty or some shit?
[QUOTE=alexaz;41093458]I need to get some MAX7219's. I'v looked at ebay and found this: [url]http://www.ebay.com/itm/10PCS-IC-MAX7219CNG-MAX7219-DIP-24-DRIVER-LED-DISPLAY-8DGT-NEW-GOOD-QUALITY/300739928460?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D261%26meid%3D8486634252860574137%26pid%3D100005%26prg%3D1088%26rk%3D5%26sd%3D130733916831%26[/url] While Farnell and Sparkfun sell those for over 10$. The question now is what's wrong with the IC's on ebay? Are they rejects, faulty or some shit?[/QUOTE]
It seems to be a fake, if [URL="http://www.planetarduino.org/?cat=432"]this[/URL] is accurate on what the real ones look like.
[QUOTE=alexaz;41093458]I need to get some MAX7219's. I'v looked at ebay and found this: [URL]http://www.ebay.com/itm/10PCS-IC-MAX7219CNG-MAX7219-DIP-24-DRIVER-LED-DISPLAY-8DGT-NEW-GOOD-QUALITY/300739928460?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D261%26meid%3D8486634252860574137%26pid%3D100005%26prg%3D1088%26rk%3D5%26sd%3D130733916831%26[/URL] While Farnell and Sparkfun sell those for over 10$. The question now is what's wrong with the IC's on ebay? Are they rejects, faulty or some shit?[/QUOTE]
Maybe the seller bought them in bulk for a lower price.
Most common chips have Chinese clones, they certainly work but you cannot be 100% sure they will have the same performance and reliability of the real thing.
However in my experience these are generally fine, the only thing I would really avoid buying are cheap capacitors and power transistors as these can ruin your day if and when they fail.
[QUOTE=Chryseus;41093867]Most common chips have Chinese clones, they certainly work but you cannot be 100% sure they will have the same performance and reliability of the real thing.
However in my experience these are generally fine, the only thing I would really avoid buying are cheap capacitors and power transistors as these can ruin your day if and when they fail.[/QUOTE]
Agreed... however i admit i do that alot xD
probibly why i have so little circuits that work....
How would I connect a RGB LED Roll to a Raspberry Pi?
[thumb]http://mitchtech.net/wp-content/uploads/2013/01/raspi_rgb_led.png[/thumb]
I'm trying that but when I connect the ground to the Raspberry Pi it all dies. It starts working again if I unplug the cable from the MOSFET to the Raspberry Pi GPIO pin and touch it. If I don't touch it it does not turn on, what could be causing this? The MOSFET? And how do I fix it so it works :P
By the looks of it, those aint MOSFET, those are NPN darlingtons. I'd add a resistor to the base of the transistor to limit the current, because it seems like you draw too much current from the GPIO.
[QUOTE=alexaz;41116151]By the looks of it, those aint MOSFET, those are NPN darlingtons. I'd add a resistor to the base of the transistor to limit the current, because it seems like you draw too much current from the GPIO.[/QUOTE]
So this is the wrong thing to have? [url]http://www.ebay.co.uk/itm/2-5-10Pcs-IRFZ44N-IRFZ44-Power-Transistor-MOSFET-N-Channel-49A-49-amp-55V-New-/400434258667?ssPageName=ADME:L:OC:GB:3160[/url]
Oops. Do I need the NPN Darlingtons or can I do something with the MOSFETs to fix it?
[QUOTE=jamie1130;41117256]So this is the wrong thing to have? [url]http://www.ebay.co.uk/itm/2-5-10Pcs-IRFZ44N-IRFZ44-Power-Transistor-MOSFET-N-Channel-49A-49-amp-55V-New-/400434258667?ssPageName=ADME:L:OC:GB:3160[/url]
Oops. Do I need the NPN Darlingtons or can I do something with the MOSFETs to fix it?[/QUOTE]
They should work as is, are you powering it all from USB, or from USB and an external power supply?
Do you have current limiting resistors for the LED's?
I could be batshit wrong here, but when the RPi supplies 3v3 to the gate, it saturates the FET causing the power supply to trip, since the circuit is nothing but diodes. However when you touch the gate there's just enough charge to put it in active state and limit the current through the diodes.
[QUOTE=alexaz;41118263]Do you have current limiting resistors for the LED's?
I could be batshit wrong here, but when the RPi supplies 3v3 to the gate, it saturates the FET causing the power supply to trip, since the circuit is nothing but diodes. However when you touch the gate there's just enough charge to put it in active state and limit the current through the diodes.[/QUOTE]
I have no idea :(
[QUOTE=alexaz;41118263]Do you have current limiting resistors for the LED's?
I could be batshit wrong here, but when the RPi supplies 3v3 to the gate, it saturates the FET causing the power supply to trip, since the circuit is nothing but diodes. However when you touch the gate there's just enough charge to put it in active state and limit the current through the diodes.[/QUOTE]
It's connected via USB to the plug socket the Pi that is, and then I have a 12V power supply which goes to the VCC on the 4 pins of the LED thing. I'm a bit confused but I know that what I'm controlling is not the power it's the "ground" if that makes any sense
[QUOTE=jamie1130;41118629]
It's connected via USB to the plug socket the Pi that is, and then I have a 12V power supply which goes to the VCC on the 4 pins of the LED thing. I'm a bit confused but I know that what I'm controlling is not the power it's the "ground" if that makes any sense[/QUOTE]
As alexaz said you should have a current limiting resistor on each LED (between the middle pin of each transistor and LED), I suggest using 1k or the nearest value.
If that does not solve the problem I can think of a few other possible causes, the 3.3V not being high enough to turn on the mosfets (datasheet specifies max of 4V at 500uA drain current) or there being an earth ground loop with you 12V supply and the USB.
Also you can think of a mosfet as a very large resistor when off and a very small resistor when on allowing current through it.
The RPi is rather sensitive with its low level GPIO, the max current quoted on average is ~15mA per GPIO with a maximum of ~50mA for the entire GPIO array. Add some 1K+ resistors between the bases of the Darlingtons and the GPIOs to reduce the current to about 2mA per GPIO.
Like so (The yellow boxes are the resistors, since they are darglington transistors, you may use a variety of resistors ranging from 1K to 100k for adequate brightness of the LEDs, depending upon the resistors on the LEDs):
[IMG]http://oi41.tinypic.com/2ztkscy.jpg[/IMG]
[QUOTE=LoneWolf_Recon;41118890]The RPi is rather sensitive with its low level GPIO, the max current quoted on average is ~15mA per GPIO with a maximum of ~50mA for the entire GPIO array. Add some 1K+ resistors between the bases of the Darlingtons and the GPIOs to reduce the current to about 2mA per GPIO.
Like so (The yellow boxes are the resistors, since they are darglington transistors, you may use a variety of resistors ranging from 1K to 100k for adequate brightness of the LEDs, depending upon the resistors on the LEDs):
[/QUOTE]
He's using mosfets, read up a few posts.
Also that would not really limit current in any case since darlington transistors have a very high and unpredictable beta.
Better solution would be both base and collector resistors.
Probably need a Mosfet driver circuit, designed to drive 5v logic level Mosfets, but itself operate on 3.3V logic level (with low current consumption ofcourse)
[QUOTE=Van-man;41119151]Probably need a Mosfet driver circuit, designed to drive 5v logic level Mosfets, but itself operate on 3.3V logic level (with low current consumption ofcourse)[/QUOTE]
However that doesn't explain his Pi going on the fritz when he connects it, it sounds like leaky MOSFETs if it immediately shuts off current when he removes his finger from the Gate.
Can we see your setup? And the outlet plugs for both your USB supply and 12V supply?
Hey guys, a question.
Is there some sort of a board that can generate and measure digital and analog signals on multiple ports, while being controlled by a program running on a computer ([b]without[/b] uploading the program to the board)?
I'd love to just write some gibberish in Lua from the comfort of my desktop and see some LEDs flicker or something to that effect.
[QUOTE=Nikita;41123696]Hey guys, a question.
Is there some sort of a board that can generate and measure digital and analog signals on multiple ports, while being controlled by a program running on a computer ([b]without[/b] uploading the program to the board)?
I'd love to just write some gibberish in Lua from the comfort of my desktop and see some LEDs flicker or something to that effect.[/QUOTE]
An ADC and DAC with a USB microcontroller or USB -> UART
My monitor began flickering a while ago, and now it's gotten to a point where it was more or less constant, so I decided to open it up and see what was going on, seeing as it was already FUBAR and I had nothing to lose.
Even with my limited knowledge of EE, I think I can safely say that capacitors are NOT supposed to look like this:
[img]https://dl.dropboxusercontent.com/u/68611/20130621_105201.jpg[/img]
Turns out that leaking capacitors is a very common problem with Samsung monitors.
The good news is that this gave me an excuse to finally order a soldering iron!
[img]http://img.dxcdn.com/productimages/sku_191967_1.jpg[/img]
Just brought my first working oscilliscope, currently waiting for delivery....
cost me £299
Its a 100Mhz 2 Channel 'scope
Brought it here:
[url]http://dx.com/p/gwinstek-gds-1102a-u-5-7-tft-lcd-100mhz-25gsa-s-2-channel-digital-storage-oscilloscope-grey-191967[/url]
[QUOTE=Dr Magnusson;41123931]My monitor began flickering a while ago, and now it's gotten to a point where it was more or less constant, so I decided to open it up and see what was going on, seeing as it was already FUBAR and I had nothing to lose.
Even with my limited knowledge of EE, I think I can safely say that capacitors are NOT supposed to look like this:
[img]https://dl.dropboxusercontent.com/u/68611/20130621_105201.jpg[/img]
Turns out that leaking capacitors is a very common problem with Samsung monitors.
The good news is that this gave me an excuse to finally order a soldering iron![/QUOTE]
this is fantastic, same thing happenned to me (it happens to most LCD monitors, mine's from '08 and it died completely)
I looked up the manual used by the people who put them together and used the pictures to figure out how to pop it open, took down the values of all the large capacitors and bought them for ~$5, replaced them
I'm quite new to the whole electronics side of things, so having it work 100% right after closing it up and hooking it together again was quite a good feeling
couple of weeks later, I get $50 for doing the same for someone else's monitor up the road!
your capacitors are laid out much better than mine were, so it should be even easier
[QUOTE=Em See;41124449]this is fantastic, same thing happenned to me (it happens to most LCD monitors, mine's from '08 and it died completely)
I looked up the manual used by the people who put them together and used the pictures to figure out how to pop it open, took down the values of all the large capacitors and bought them for ~$5, replaced them
I'm quite new to the whole electronics side of things, so having it work 100% right after closing it up and hooking it together again was quite a good feeling
couple of weeks later, I get $50 for doing the same for someone else's monitor up the road!
your capacitors are laid out much better than mine were, so it should be even easier[/QUOTE]
I googled around a bit and found 2 amazingly detailed guides on how to do it for my specific monitor, so replacing them should be a breeze. The hard part was finding a vendor that was willing to sell capacitors with the right specs to private persons, and in smaller lots than 100's or 1000's :v:
oh, that part is easy, just go on ebay, or farnell or wherever and order them up, its not like they are huge ones. (ones i deal with can be like 450v @ 3300uf)
Not terribly thread related, but I just finished my Electronic Engineering masters degree with a 2.1 I feel like a proper engineer now.
[QUOTE=metallics;41124705]Not terribly thread related, but I just finished my Electronic Engineering masters degree with a 2.1 I feel like a proper engineer now.[/QUOTE]
Neat, my mathis is so bad i cant even get into do a degree,
the only A-level thats going really well for me is electronics (A-A*)
next year im doing A2 and btec engineering 2 year course
Same here I don't really have enough to take EE, also I can't imagine sitting through 2 years of stuff I already mostly know.
[QUOTE=nuttyboffin;41124693]oh, that part is easy, just go on ebay, or farnell or wherever and order them up, its not like they are huge ones. (ones i deal with can be like 450v @ 3300uf)[/QUOTE]
We don't have Ebay here, or at least it's not very big, and Farnell only ships to companies who can provide a Central Company Register-ID. It's a tax thing.
ive never had that problem. and what do you mean you dont have ebay o.o
China ships anywhere.
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