1. Post #281
    Gold Member
    Chryseus's Avatar
    February 2009
    2,405 Posts
    So... How should I power them? I got the 12v 5a power supply from adafruit, and it has a connector that I don't think I should just wrap a wire around and stick in the led strip. And doesn't the board have overcurrent protection?
    You make use of a transistor like this:


    Maximum pin current is 40mA. Small LEDs can draw 20mA each.
    600*20 = 12000mA.
    12000 > 40
    They are probably in mixed series / parallel configuration with reduced current such as 4mA per branch.
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  2. Post #282
    Gold Member

    March 2005
    3,028 Posts
    There's no load resistor on that LED...
    You make use of a transistor like this:
    [img]They are probably in mixed series / parallel configuration with reduced current such as 4mA per branch.
    Using a 12V supply, you can have no more than 6 in series, which means 100 strands in parallel.
    That's still well over 10 times the rated current.
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  3. Post #283
    Gold Member
    Chryseus's Avatar
    February 2009
    2,405 Posts
    There's no load resistor on that LED...
    Good job spotting that I just quickly grabbed an image from Google.
    This is more like it:


    Actual value for the base resistor depends on load, you can work it out as follows:
    1. Find the maximum load current
    2. Find the required base current (Iload / 10) {10 is a good low current gain as might be expected in a average transistor}
    3. Using the base current work out the resistor size ((Vpin - Vbe) / Ibase)
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  4. Post #284
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    bobthe2lol's Avatar
    July 2007
    1,370 Posts
    Maximum pin current is 40mA. Small LEDs can draw 20mA each.
    600*20 = 12000mA.
    12000 > 40

    Hope you had a nice big FET driving those LEDs.

    No, because you shouldn't be powering anything through an I/O pin. They're strictly for signalling.
    You need a power transistor to switch larger loads.
    Well, I'm not very good at electronics and math, but I did follow the tutorial, and it involved using 3 MOSFETS (whatever those are) and connecting the 12v line of the led strips to Vin on the board, so I wasn't powering them via the I/O pins. I belive I had the left line of the mosfet connected to the pwm pins for brightness modulation.

    I wired it up like in the picture here:

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  5. Post #285
    Gold Member

    March 2005
    3,028 Posts
    Well, I'm not very good at electronics and math, but I did follow the tutorial, and it involved using 3 MOSFETS (whatever those are) and connecting the 12v line of the led strips to Vin on the board, so I wasn't powering them via the I/O pins. I belive I had the left line of the mosfet connected to the pwm pins for brightness modulation.
    It sounds like you had everything set up right. Your board shouldn't be damaged. Perhaps it's a software issue?
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  6. Post #286
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    bobthe2lol's Avatar
    July 2007
    1,370 Posts
    It sounds like you had everything set up right. Your board shouldn't be damaged. Perhaps it's a software issue?
    What sort of software issue? The only thing I can think of is that the bootloader got corrupted, and I can't really fix that without some piece of equipment right (or another arduino, I kind of want a Mega... more pins)?
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  7. Post #287
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    Xera's Avatar
    November 2006
    3,097 Posts
    You're better off posting on the Arduino forums.
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  8. Post #288
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    March 2005
    3,028 Posts
    What sort of software issue? The only thing I can think of is that the bootloader got corrupted, and I can't really fix that without some piece of equipment right (or another arduino, I kind of want a Mega... more pins)?
    You can reprogram AVRs using the parallel port and three resistors.
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  9. Post #289
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    Lapsus's Avatar
    June 2006
    1,075 Posts
    You can reprogram AVRs using the parallel port and three resistors.
    Well, here's hoping that he actually has a parallel port on his motherboard, if that's the case.

    @bob2thelol: do you get any different results if you unhook everything from the arduino and just use it from USB power with something simple like the blink sketch? It's a long shot, but it can't hurt.
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  10. Post #290
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    bobthe2lol's Avatar
    July 2007
    1,370 Posts
    Well, here's hoping that he actually has a parallel port on his motherboard, if that's the case.

    @bob2thelol: do you get any different results if you unhook everything from the arduino and just use it from USB power with something simple like the blink sketch? It's a long shot, but it can't hurt.
    That was one of the first thing I tried. I thought, is something shorting out, or are some of the pins shorting, or doing something else wierd? So I unplugged everything, let it sit for a bit, then plugged in USB only and tried the blink sketch. Same result. :(

    And nope, I don't have a parallel port. Heh... damn.
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  11. Post #291
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    Zero-Point's Avatar
    March 2006
    7,368 Posts


    I was not expecting this when I lifted the mystery SOIC part, has to be one of the more
    unusual things I've found.
    Ah, the joys of SMD chokes.
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  12. Post #292
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    Chryseus's Avatar
    February 2009
    2,405 Posts
    Added new supplier to the list, RSH Electronics they have some good bargain packs and ship international for 4.00
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  13. Post #293
    q3k
    Gold Member
    q3k's Avatar
    October 2009
    921 Posts
    Just a quick question: what would be the best way of powering a 5V microcontroller off a 12V AC power supply? Just build a diode bridge, slap on some capacitors and use a linear regulator (7805)? Or is there a better way?
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  14. Post #294
    Gold Member
    Chryseus's Avatar
    February 2009
    2,405 Posts
    Just a quick question: what would be the best way of powering a 5V microcontroller off a 12V AC power supply? Just build a diode bridge, slap on some capacitors and use a linear regulator (7805)? Or is there a better way?
    That's pretty much as simple as you can get.
    If you have an op-amp and transistors laying around you can build your own regulator which would save you the cost of a 7805 if you don't already have one.
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  15. Post #295
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    March 2005
    3,028 Posts
    That's pretty much as simple as you can get.
    If you have an op-amp and transistors laying around you can build your own regulator which would save you the cost of a 7805 if you don't already have one.
    You still need a voltage reference, which would generally be some sort of diode (preferably zener). You can also drop the op-amp circuit and use a single transistor like a voltage follower with the zener diode at the input. I think the op-amp probably adds some stability, though.
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  16. Post #296
    www.bff-hab.de
    Dennab
    February 2009
    7,832 Posts


    I was not expecting this when I lifted the mystery SOIC part, has to be one of the more
    unusual things I've found.

    Gotta wonder what the machine building these looks like.
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  17. Post #297
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    Vbits's Avatar
    April 2010
    1,186 Posts
    Looks like was just inserted nearly complete into the package and then sealed.
    I don't know anything about IC production but that is just a guess.
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  18. Post #298
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    Chryseus's Avatar
    February 2009
    2,405 Posts
    Gotta wonder what the machine building these looks like.
    This probably:


    Edit
    My new article on resistors and potentiometers is done, http://chryseus8086.co.uk/?p=176 hopefully someone will find it useful.
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  19. Post #299
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    Nikita's Avatar
    April 2005
    1,913 Posts
    Curiosity: how would you go about recording a radio-frequency unfilitered signal, gathering data from it inside a windows program, then generating a new arbitrary signal and outputting it?

    Unfiltered as in, all frequencies, both input and output.
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  20. Post #300
    Gold Member

    March 2005
    3,028 Posts
    Curiosity: how would you go about recording a radio-frequency unfilitered signal, gathering data from it inside a windows program, then generating a new arbitrary signal and outputting it?

    Unfiltered as in, all frequencies, both input and output.
    You can't record raw wideband RF in real-time without some really fancy hardware.
    You can, however, bring a specific band down to an intermediate frequency (IF) by mixing (or sampling) it with a local oscillator. Your IF can be low enough that you can sample it with an ordinary sound card. You can find lots on this topic by searching for software-defined radio. Jeri Ellsworth recently did a bunch of videos where she builds and debugs a quadrature sampling detector.
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  21. Post #301
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    Mr.T's Avatar
    August 2010
    2,691 Posts
    Is Farnell a good supplier? Or is it expensive?
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  22. Post #302
    Gold Member
    ddrl46's Avatar
    October 2007
    3,675 Posts
    Is Farnell a good supplier? Or is it expensive?
    Farnell is great, but ordering there as a consumer can be a pain in the butt.
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  23. Post #303
    Gold Member
    Nikita's Avatar
    April 2005
    1,913 Posts
    Another thought: How hard would it be to use real meat as an actuator?
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  24. Post #304
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    March 2005
    3,028 Posts
    I am intrigued and slightly terrified by this query.
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  25. Post #305
    Gold Member
    ryan1271's Avatar
    February 2008
    1,126 Posts
    Another thought: How hard would it be to use real meat as an actuator?
    I would imagine it would need to be freshly dead although alive would be more ideal. After that it shouldn't be very difficult, just hitch the meat to something and apply a current to or near the nerves.
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  26. Post #306
    q3k
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    q3k's Avatar
    October 2009
    921 Posts
    I would imagine it would need to be freshly dead although alive would be more ideal. After that it shouldn't be very difficult, just hitch the meat to something and apply a current to or near the nerves.
    Or use soy sauce.

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  27. Post #307
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    Nikita's Avatar
    April 2005
    1,913 Posts
    I would imagine it would need to be freshly dead although alive would be more ideal. After that it shouldn't be very difficult, just hitch the meat to something and apply a current to or near the nerves.
    If muscle tissue is supplied with ample oxygen and ATP, in theory it should stay alive, right?
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  28. Post #308
    q3k
    Gold Member
    q3k's Avatar
    October 2009
    921 Posts
    If muscle tissue is supplied with ample oxygen and ATP, in theory it should stay alive, right?
    ATP is only created for fractions of a second. What you're looking for is muscles that are rich in myoglobin (the muscle-bound equivalent of hemoglobin), commonly called "red meat".
    However, it still doesn't mean you will be able to repeatedly trigger contraction in a muscle, as I'm not sure whether ion pumps (powered by ATP, used to depolarize "triggered" neurons by re-balancing ions) and myosin (proteins that, combined with actin, form muscles and allow contraction, also powered by ATP) will be able to function properly. You'll have to ask a biologist about that.
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  29. Post #309
    Gold Member
    Chryseus's Avatar
    February 2009
    2,405 Posts
    Is Farnell a good supplier? Or is it expensive?
    Farnell is excellent, however a minimum order applies (at least in the UK) including a small delivery charge, if you open a trade account however you get free delivery and no minimum order which is awesome.
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  30. Post #310
    Gold Member
    Lapsus's Avatar
    June 2006
    1,075 Posts


    Just ordered some MSP430 stuff, the watch going on sale made for the perfect excuse to actually place an order, ended up ordering another watch and launchpad for a friend also.
    Here's the deal site if you're interested, saw it on hackaday.
    I can't wait to start messing around with an entirely different microcontroller, instead of my Arduinos, it should make for a nice change of pace.
    Also, seeing as the TI store is a pain in the ass, if you want to know more, Watch, Touch thing, Launchpad.
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  31. Post #311
    Gold Member
    ddrl46's Avatar
    October 2007
    3,675 Posts


    Just ordered some MSP430 stuff, the watch going on sale made for the perfect excuse to actually place an order, ended up ordering another watch and launchpad for a friend also.
    Here's the deal site if you're interested, saw it on hackaday.
    I can't wait to start messing around with an entirely different microcontroller, instead of my Arduinos, it should make for a nice change of pace.
    Also, seeing as the TI store is a pain in the ass, if you want to know more, Watch, Touch thing, Launchpad.
    I hope TI ships their products a bit faster now, I had to wait almost two months to get my Launchpads.
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  32. Post #312
    Gold Member
    Lapsus's Avatar
    June 2006
    1,075 Posts
    I hope TI ships their products a bit faster now, I had to wait almost two months to get my Launchpads.
    Well, here's hoping. I saw some other posts online about their shipping taking ages, but really, for $40 including shipping so long as they show up at all I'll be happy.
    On the plus side, I just got an order status update, apparently the estimated ship date is now today, so here's hoping they've got things sorted out.
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  33. Post #313
    Gold Member
    Xera's Avatar
    November 2006
    3,097 Posts
    I hope TI ships their products a bit faster now, I had to wait almost two months to get my Launchpads.
    The only reason they took so long was because a ridiculous amount of people ordered them. My last order for 2 launchpads and the FRAM board took a week to get to me in the UK.
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  34. Post #314
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    Nipa's Avatar
    June 2006
    1,095 Posts
    The TI watch deal expired. Annoyed me, as I saw it in the evening and was going to buy it in the morning, but was confronted with DEAL EXPIRED. How the hell does it go to August 30th if it ends in 8 hours!?
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  35. Post #315
    q3k
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    q3k's Avatar
    October 2009
    921 Posts
    Parts for my next project have arrived!

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  36. Post #316
    Gold Member
    Chryseus's Avatar
    February 2009
    2,405 Posts
    Parts for my next project have arrived!
    What is this next project ?
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  37. Post #317
    q3k
    Gold Member
    q3k's Avatar
    October 2009
    921 Posts
    What is this next project ?
    Making my fence door openable by a 125KHz RFID tag.
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  38. Post #318
    Gold Member
    Lapsus's Avatar
    June 2006
    1,075 Posts
    Massive what the fuck moment, apparently the watches are arriving today, but they've split the watches, the launchpads, and the booster pack into three separate shipments.
    I'm going to be massively pissed off if I have to pay customs and import fees on three separate packages, but on the plus side, watches!

    Edited:

    Or apparently the watches JUST ARRIVED, quite literally as I was typing that post, with no customs fees. I'm so confused. Will be back with pictures.
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  39. Post #319
    q3k
    Gold Member
    q3k's Avatar
    October 2009
    921 Posts

    Well that works.
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  40. Post #320
    Hearts
    Agent766's Avatar
    July 2007
    3,179 Posts
    I was trying to think of a clever flaw with the RFID. Then I realized one could just jump the fence.
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