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Re: Discovering the frequency of an RFID: a foosball story

 by wiml ¦  Mon Sep 17, 2012 9:46 pm ¦  Forum: SparkFun Product Questions ¦  Topic: Discovering the frequency of an RFID: a foosball story ¦  Replies: 2 ¦  Views: 484

Is there any writing or marking at all on your office keycard that says who made it? Mine has the brand name ("i.CLASS") on the end in small letters, and from that you can usually find out what standard it uses. Otherwise, I think the vast majority of keycards fall into three categories. The old thi...

Re: Digital AC Dimmer Module

 by wiml ¦  Sat Jul 07, 2012 5:18 pm ¦  Forum: New Product Ideas ¦  Topic: Digital AC Dimmer Module ¦  Replies: 7 ¦  Views: 4591

The PowerSwitchTail people have some products along those lines. (Annoyingly, it looks like you need to buy the zero-crossing detector and the SSR switch as separate "tail"s? Whose idea was that?) Maybe SF could carry them.

Olimex OLinuxIno?

 by wiml ¦  Sat Jul 07, 2012 1:26 am ¦  Forum: New Product Ideas ¦  Topic: Olimex OLinuxIno? ¦  Replies: 0 ¦  Views: 773

The OLinuxIno looks pretty nice — in the RaspPi-BeagleBone space (more open than the RaspPi, cheaper than the BeagleBone). Sparkfun is one of Olimex's listed US distributors. Any chance SF will be carrying these? (I assume it'd end up cheaper for me to buy them through SF than to have them shipped i...

Your favorite small connectors?

 by wiml ¦  Thu Mar 22, 2012 5:28 pm ¦  Forum: SparkFun Product Questions ¦  Topic: Your favorite small connectors? ¦  Replies: 0 ¦  Views: 299

I love the venerable 0.1" header connectors, they're cheap and simple and flexible. But sometimes they're the biggest thing on a small board and I want something less bulky. What kinds of connectors do you use when you want a general purpose multi-pin connector that is small ? There are smaller vers...

 by wiml ¦  Fri Jan 08, 2010 12:23 pm ¦  Forum: Terms of service and best practices ¦  Topic: Spammer List ¦  Replies: 690 ¦  Views: 142651

I also got Novak's iTunes PM spam :?

 by wiml ¦  Fri Jan 01, 2010 1:22 pm ¦  Forum: Terms of service and best practices ¦  Topic: Spammer List ¦  Replies: 690 ¦  Views: 142651

Yup, I just got a PM spam from Gargrave as well.

 by wiml ¦  Thu Oct 22, 2009 11:40 pm ¦  Forum: AVR Microcontrollers ¦  Topic: Issue with Open source for AT91SAM7s ¦  Replies: 8 ¦  Views: 2352

Take a glance through the .map file that gets generated, and also try running arm-elf-size on the main.out file (which should be an ELF file and therefore examinable using 'size'). The map file should tell you what bits of code are getting placed at what addresses. (This is controlled mostly by the ...

 by wiml ¦  Fri Oct 09, 2009 12:09 pm ¦  Forum: Everything ARM and LPC ¦  Topic: address of structure element ¦  Replies: 2 ¦  Views: 751

I agree, gcc is probably padding the structure members so they're aligned for more efficient access. You can use a gcc attribute or pragma to affect this, though I usually prefer to do the offset calculations myself and not rely on the compiler to generate a specific memory layout for a structure.

 by wiml ¦  Thu Oct 08, 2009 2:39 am ¦  Forum: Wireless/RF ¦  Topic: BlueSMiRF Communication Issue ¦  Replies: 1 ¦  Views: 542

I had a problem like that which I couldn't track down (except in my case it would stop working after an hour or two). I'm pretty sure it was due to a bug in the software on the computer the module was talking to, because it didn't occur with other host computers. Frustrating.

 by wiml ¦  Thu Oct 01, 2009 2:00 pm ¦  Forum: SparkFun Product Questions ¦  Topic: Constant Current Driver question ¦  Replies: 17 ¦  Views: 4029

(Also note that the voltage-gain register is also used to manipulate the LED current, indirectly by adjusting the voltage applied to Rext; and it has 128 steps, instead of the 2 settings that the current-gain setting gives you. Take a look at pages 22–23.)

 by wiml ¦  Thu Oct 01, 2009 1:53 pm ¦  Forum: SparkFun Product Questions ¦  Topic: Constant Current Driver question ¦  Replies: 17 ¦  Views: 4029

The Iref is almost certainly part of a current mirror circuit. The data sheet makes sense to me if I go into it expecting a constant-current LED driver to be built around a current mirror; otherwise, it is awfully vague. I like MrPotatoHead's idea of varying the voltage to which Rext is attached. Ju...

 by wiml ¦  Thu Oct 01, 2009 1:35 pm ¦  Forum: SparkFun Product Questions ¦  Topic: FT245R Bitbanging on Linux ¦  Replies: 1 ¦  Views: 1342

Possibly they get set to inputs-with-pullups briefly? Maybe the best solution would be to wire the relays so that they're activated by a low output (eg: 5v→relay→ft245, instead of gnd→relay→ft245). It's always a good idea, if you can, to design things so that the default/reset/initial states of the ...

 by wiml ¦  Thu Oct 01, 2009 1:13 pm ¦  Forum: SparkFun Product Questions ¦  Topic: reliable wire-to-board connections ¦  Replies: 8 ¦  Views: 1482

I'm with TheDirty — I don't understand whether your problem is that your wires are pulling out of the connectors (or breaking off), or whether your connectors are disconnecting? If the latter, you can get locking connectors. Or are they simply not making good contact despite not coming apart? I've n...

 by wiml ¦  Sun Sep 27, 2009 6:11 pm ¦  Forum: SparkFun Site Questions/Comments ¦  Topic: Constant Current Diodes ¦  Replies: 12 ¦  Views: 9206

Mouser does have a selection of current-regulator diodes up to 6.5 mA, and they do sell in small quantities.

But for what you described I'd probably just use an LM317 (or LM317L), since I have those lying around already.

 by wiml ¦  Sat Sep 26, 2009 1:27 pm ¦  Forum: Everything ARM and LPC ¦  Topic: FreeRTOS & AT91SAM7S256 ¦  Replies: 4 ¦  Views: 1485

I took a stab at using FreeRTOS on the AT91SAM7S64 board, but ran into enough difficulties like yours that I put it aside. :( I might come back to it later (or eCos or Nut/OS) once I start doing more complicated things, but for now I'm just using a hand-rolled scheduler+timer loop kind of thing.

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