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Member Since: August 14, 2009

Country: United States

  • This is a CURRENT regulating supply. It is different from what you may be used to which is a Voltage regulating supply.
    It is fixed to drive 350 mA through whatever is attached to it. This is really nice for high power LEDs because you can put an arbitrary number of LEDs in series and it will drive them all to the same brightness without a current limiting resistor.
    Note that putting 7 50mA LEDs in parallel is NOT equivalent to putting 1 350mA led on the driver. That is because the forward drop voltage of the LEDs in parallel may not be exactly the same, meaning one LED will go active, burn out (LEDs driving voltage drops when they turn on), and then the next will do the same, and so on.
    These are for VERY bright LEDs in Series such as the ones listed in SMD in the LED section. a typical LED operates on

  • Not that Sparkfun carries it, but I’m looking at the BK precision 1550 which is available from a number of reputable retailers for about the same price and is bipolar.
    It’s a digital single output.
    My experience with BK is that they work pretty well, but I’ve only used 2 of them in the past.

  • Great question!<br />
    <br />
    Looking at the UART Spec its worth noting that the inactive (IDLE) state is with the register pulled high. <br />
    <br />
    Noting that it is the Slave’s responsibility to pull the TX line down (and sink the Master RX channel’s current)should explain the diode direction and operation. <br />
    <br />
    In IDLE every slave is able to keep his own TX high irrespective of what the masters RX channel is at. A particular slave can transmit by pulling his TX down without affecting the TX on other slaves.<br />
    <br />
    Seems to me that the master would need to pull up the RX line (which I do not think is common since this is how masters often detect if a device is connected). Also, though this is not that big of a deal, but the Vd of the diodes needs to be chosen sufficiently small to allow reliable switching. Germanium diodes would be much better than silicon diodes.

  • Interesting tutorial, but maybe a bit misleading. I agree with Quazar in that the common ground is a problem. Without a isolator, it is essential that there is a shared ground. Maybe that was the intention symbolically (since what is drawn, in eagle would result in a common VCC and GND), but it is unclear.<br />
    <br />
    Additionally, It is NOT necessarily true that bus contention will occur. On MSP430s at least, it is not difficult to make the bus go into HiZ when not transmitting (tri-state registers), allowing data to be transmitted from multiple slaves. This means that a UART cannot act in a truly asynchronous fashion, but with time-slicing and some user generated code for arbitration, this is possible. <br />
    <br />
    For instance, I have a set of devices that could not implement SPI, so I instead implemented a scheme where the host sent a message and device 1 got 30ms to transmit and go HiZ, then device 2 did the same, and then 3 the same.

  • Does it ramp or does is PWM?:<br />
    It outputs a PWM. You are relying on your motor to be the low pass filter. Almost all DACs work like this at some level. <br />
    <br />
    Do I need this?<br />
    Nope! but you can do 4 motors with this in 1 direction each!, so thats pretty cool. All YOU need is one Mosfet. Tie one terminal to gnd and the other to the FET, and just switch that. <br />
    <br />
    Are we protected against back EMF?<br />
    Nope… if you are using something like LiPo/LiIon battery I would definitely be worried about this. If you are using a sealed lead acid or alkaline, don’t worry about it unless you have super inductive loads, all you will do is recharge the battery. You will have to use your own judgement for NiCAD, NiMH etc.

  • Bit of a late reply, but yes, the H bridge will switch anything down to 4.5 V (and up to 15V) as a motor supply. You can likely go quite a bit lower, but you may not get reliable switching. For instance, if you were to use a 3V supply you may get a slow rise time. <br />
    <br />
    Just be sure you use the 6V for the VM only and not the VCC or signal levels.

  • Does anyone have any experience with feedback of this motor? What is the backlash like in the output shaft (how many deg can you wiggle the shaft w/o turning the motor)? Is there space enough to get a hall effect (sparkfun variety in there for gear tooth counting?)

  • The passcode is 1234, red (slowly blinking) means that the module is ready to receive. I don’t have access to OSX, but in Linux you have to use rfcomm to setup a Pico-net, and then you get a device on /dev/rfcomm0 that you can do what you want with. I suspect things are not that complicated in OSX

  • Hey I wanted to post a few RTFM issues with these modules since you literally have to read all the documentation to get these modules to work.
    The key is is ‘1234'
    For 2-wire serial (TX-RX-GND) you must connect CTS and RTS (shorting the pins)
    The module defaults to 9600 baud, 8N1 and H/W flow control. (I tried it at 115200 and had trouble (but I was still hacking then, so maybe that works too)
    For Arduino users
    You CANNOT program the Arduino through this interface
    If you are having connectivity problems try this:
    Unplug USB and power externally.
    Transmit and receive from Hyperterminal or some other terminal. The Arduino serial port terminal sometimes drops the bluetooth port.
    I found that the intel integrated bluetooth in my laptop kept resetting the connection, but a belkin dongle worked just fine.
    Also worth noting: Breadboards seem to act like Faraday cages and completely shield the signal in one direction, so be careful monitor your signal strength!
    Also consider swearing at it… that seems to help too;)
    Hope this helps!

  • This could really use a “not” gate on one of each of the “InA” and “inB” lines. Like a Not-AIn1 and Not-Bin1, so that people not interested in the braking function can use the controller by running one logic line to both In1 and In2. I suspect that there are a lot of people with low-pin count uC’s who would appreciate not having to use 2 more GPIO’s and not having to add extra logic.
    Otherwise, this is one of the best “hobby motor controllers” I’ve found at this price. (in case anyone is interested) It gets kinda hot running Tamiya gearboxes, but it works!

No public wish lists :(