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Member Since: October 9, 2008

Country: United States


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  • I’m also having this problem during test, running the motor at 12v, it’s incredibly hot. It seems to be working, but I wonder, if is miswired, etc? Is there a way to verify that it’s wired properly?

  • For high precision stuff you really need a flat notch. Most of these motors don’t come with a shaft that has a notch, but fortunately, they’re not too hard to add. There are lots of tutorials online on how to do this, but basically tape off all holes with masking or gaffers tape, clamp the shaft into a vice or something (so it doesn’t rotate while you file it), and then just take a metal file to it (slow and steady wins the race) – when satisfied, remove the clamp/vice, shake off all the metal dust (taking care that none falls into the motor), remove the tape.

  • SparkFun sells an AVR serial programmer for like $12 (https://www.sparkfun.com/products/14 – I think it’s the same schematic as the “PonyProg”, http://8051expert.com/index.php)

    I bought the SparkFun one (as opposed to building it myself) and tried it with a USB->Serial converter and it works fine in both Windows and Linux for me with the AVR Dude software (YMMV).

    (I also bought the crazy expensive USB Flash drive programmer that SparkFun sells, it’s a bit faster with AVR Dude, but I was never able to make the “USB flash drive” functionality work, it definitely was not worth the ~$70 USD. lol, Get the cheap one, you won’t regret it.)

    However, if you’re going this route already, you may want to ask yourself if you really need the Arduino platform. GCC / WinAVR / etc gives you an open-crossplatform-toolchain to develop with, and you’re already doing everything manually anyway – no reason to tie yourself down with Arduino.

    Also, once you learn one part, you can start ordering application specific parts – why spend $18 on an Arduino for every project, when your project might be able get away with a smaller $4 ATTINY2313, and for the big projects spend the $8 and get the ATMEGA324/ATMEGA64 etc…? ;-)

    (One piece of advice: Navigating the data sheets can be a bit of a hassle, especially when it comes to programming the fuse bits – for those, just Google for a website that does pre-calculated fuse bits for you – there are a ton, and make sure it has the chip you’re working with, and try it out – and don’t lock or write protect the device (or program the reset pin to be an IO pin!!!!) if you plan on flashing the device again, because once you do any of those, the chip is pretty much done.)

  • Thanks for all the help. I did find this application note about floating inputs http://www.ti.com/lit/an/scba004c/scba004c.pdf – and it explains the input transition rise/fall rate stuff, and why it’s a bad idea to transition slowly (at least I hope this is related!).

    I do see the 29 MHz spelled out explicitly in the datasheet now that I inspect it closer (derp!) – However the math still seems weird to me, using the tPd for 6V still gives me like 31 MHz instead of 29 (It’s Megahertz not Mebihertz, right? lol).

    As for the tutorial, I did see the original SparkFun tutorial on reading datasheets, but it was extremely basic – a lot of the terms are still black magic to me.

    As for the device losing data if I go “too slow” – is that only if I transition the voltage between Vss and Vcc (and versa-vice) too slowly or is that if I provide the clock pulses too slowly?

  • Hey, thanks for the reply!

    I guess this leaves me a little bit confused on a couple of counts:

    • Where does the 29 MHz number in the description come from?

    • It is the maximum rise fall time (at 6 volts), which I understood to mean (and please correct me here) that the chip could sometimes take up to 400 nano seconds to transition to it’s new output state based on the input I send it (is that incorrect?) – As in: it could go faster, but there isn’t any indication from the chip when it does, so if I change it’s state and try to read it’s outputs faster than 400 nano-seconds (at 6 volts), doesn’t this mean that sometimes I will get the old (or possibly undefined) data?

    • The note at the bottom is specifically related to voltages, not timing – it says that if I power it in the range of .5 volts to 1.5 volts that it could cause double clocking and incorrect data / undefined states.

    Apologies for being a bit of a newb about this. Clearly, there’s something here that I’m missing.

  • Yeah but, all of that could have been done with another $1 of parts… – and normally – I’m all for throwing micro-controllers at things – it’s fun – but he didn’t do that either, did he? He through an Arduino at it. If he was dead set on using a micro, he could have at least used an ATTiny and not been so wasteful – heck it would have fit on the body of the tweezers making a compact and elegant part.

    Also, he does loose a bit of functionality here versus the coin cell – in that, if the leads are clipped on the LED, he’ll never know which one is positive.

  • Or… just a watch battery. I mean quickly is definitely a lie here – because you’re never going to have all of those things where and when you need them – instead if you just have watch batteries floating around in your various kits, you’ll always have one handy and wham, there it goes.

    At the worst if they wanted to make fancy tweezers that ran the LED in both directions (alternating), they could just build an astable-multivibrator circuit (2 transistors, a couple caps and resistors) and then you have the polarity issue solved.

  • One of these three are wrong: The description, the datasheet, or me.

    Datasheet says that the fastest* “input transition rise/fall time” is “400 ns”.

    Description says you can run it up to 29 MHz.

    My math says 1 / (400 * (10-9)) = 2,500,000 Hz (or 2.5 MHz) – that’s more than an order of magnitude slower.

    • is assuming 6V, which appears to be the maximum voltage / max-speed.
  • At 100 units for $12, this is cheaper than Digikey. :)

  • Uhh, I’m not seeing any though hole 1N4007s on Digikey that a cheaper than $0.11 (that you can buy in quantities as low as 100). There are several that you can get 1000/~$80 … but that’s a bit much for me. ;)

    Edit: Ahh, I misspoke. When you buy that one in a package of 100, it becomes $0.0649/part – or $6.49/100. Nice.