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  • question

    cassiel replied on August 09, 2009 12:03 to the question "Multiple BlinkM I2C/Arduino, several metres?" in ThingM:

    cassiel
    There's a line in hardware/libraries/Wire/utility/twi.h - look for TWI_FREQ - but to be honest I'm not sure that reducing the speed actually made a huge amount of difference in the end. For that project we're currently just power-cycling to kick off a preloaded startup sequence.
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  • question

    cassiel asked a question in ThingM on August 08, 2009 19:34:

    cassiel
    How many BlinkM/MaxM units on a single Arduino regulated power pin?
    We're building an 8-unit Arduino-controlled BlinkM/MaxM installation, and I'm doing some testing with an Arduino Mega and a pair of BlinkM/MaxM combos. For the full installation we'll source a decent power supply for the entire setup, but in the meantime, I'm wondering if I can get away with driving two BlinkM/MaxMs directly from the Arduino's regulated supply?

    I've seen a few setups with one BlinkM/MaxM, but even when I do that the small IC next to the Arduino's power socket (presumably the voltage regulator) gets very hot. Do I risk blowing the regulator with two BlinkM/MaxMs (or even with one)?

    I'm using an external PSU of course - not USB. The PSU is rated at 500mA unregulated, but if that burns out I'll buy another one. I'm less keen on wrecking the Arduino or either of the BlinkMs. Should I just buy them their own external PSUs and be done with it? :-)
  • problem

    cassiel replied on July 16, 2009 08:39 to the problem "Red LED dead" in ThingM:

    cassiel
    Thanks for the reply. The scripting problem appears to be 100% pilot error at this end - I messed up and duplicated part of the command syntax I'm using between host and Arduino. (Memo to self: "play script" is not the same as "cut power.")

    I'm still finding fade time setup to be a little unpredictable - two BlinkMs fresh out of the box apparently fade at different times, and response to setFadeSpeed seems sporadic - but that's probably an initialisation issue I need to fix here...

    Thanks again.
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  • problem

    cassiel replied on July 15, 2009 20:40 to the problem "Red LED dead" in ThingM:

    cassiel
    We're currently powering the BlinkMs from the regulated 5V on the Arduino Mega. It's possible we over-voltaged one (we were also pulling in a second regulated 5V from elsewhere to power some other kit) but losing two or three is slightly worrying. We'll try to work out if there's a pattern.

    As I said, we had one unit lose its green LED after a few minutes. I currently have another BlinkM that will accept RGB messages but refuses to run scripts...! Am currently investigating...
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  • problem

    cassiel replied on July 15, 2009 16:04 to the problem "Red LED dead" in ThingM:

    cassiel
    One of our batch of BlinkM's had a green LED die after a few minutes of use... We have also completely lost two additional BlinkM's. We're trying to be careful with power regulation, but even so, they seem to be extraordinarily delicate...
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  • question

    cassiel replied on July 15, 2009 16:01 to the question "Multiple BlinkM I2C/Arduino, several metres?" in ThingM:

    cassiel
    OK... we've run a couple of 20-metre cables with BlinkM's on the end and things seem to be fairly stable, although I've slowed down the I2C clock speed a lot.
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  • question

    Nick Rothwell asked a question in ThingM on July 14, 2009 10:07:

    Nick Rothwell
    Multiple BlinkM I2C/Arduino, several metres?
    Firstly, thanks for the comments on the other topics about I2C bus length...

    We're building a display system with several (14) BlinkMs in individual casings wired in a star from an Arduino Mega. The cable run to each casing is potentially several metres. The star arrangement is so that a single cable per casing can be used for power requirements as well as I2C connection.

    First question: will it work? Or should we really be going for a single bus chaining all the casings (which means an additional cable run).

    The other topics mention some solutions. Might there also be any gain in running the I2C clock slower? Can I hack the clock speed in wire.h down to some arbitrary value and have the BlinkM's still talk to the bus correctly?

    Thanks...!

  • Nick Rothwell started following the question "Length of I2C bus" in ThingM.