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• That has got to be the coolest punpkin I've ever seen! Love the idea!
  

  Posted by: ve2vfd on October 21, 2006 at 8:02 AM

• That's so awesome!

  Posted by: Mattyfu on October 21, 2006 at 2:49 PM

• Interesting circuit, but you might want to learn about microcontrollers.

  You could replace everything but the LED's with an 8-pin PIC12F629 costing about $1, and greatly simplify your assembly process as well as reducing the parts cost. By controlling it in software you can also add a lot more functionality, such as several flash patterns controlled by a button.

  Posted by: Oracle1729 on October 21, 2006 at 2:58 PM

• I learned about microcontrollers (I spent every day this week programming one), but I like to do things the easy and cheap way. =)

  If you already have a microcontroller setup with a programmer and a working code base, I agree that it's a very good way to go. Otherwise, this is one of those unusual cases where a microcontroller certainly does not save you time or money-- assuming that you're only making one board. The two chips used for this circuit (4017 & 555) only cost $0.80 together. Whether you use discrete logic or a microcontroller, the controller is the cheap part of the circuit. It's the other parts (like the protoboard, LEDs, battery connector, and so on) that drive up the cost.

  As far as microcontrollers go, the PIC12F629 is actually a great choice for this application, with its six high-current output pins. You could program the outputs with a PWM signal to emulate the low-pass filter, giving that cheesy incandescent look; it would be tiny and great. One caveat, however: most microcontrollers (PIC12F629 included) cannot run directly off of 9 V like this circuit does. I like using the 9 V because it's compact and convenient. It also lets the circuit drive four bright LEDs in series (2 V each). To do that with a micro, you would still need the output drive transistors as well as a voltage regulator.
  

  Posted by: Windell_Oskay on October 21, 2006 at 4:12 PM

• I built this circuit a few years ago... I have yet to have started into programmable microcontrollers - my biggest hold up is buying a programmer.... any recommendations for to build one? Or what I should look for if buying one?

  Posted by: trebuchet03 on October 21, 2006 at 9:10 PM

• When I got started in microcontrollers there weren't a lot of programmer options, the homemade and cheap ones were basically parallel port adapters that didn't work well, so I bought the Picstart Plus. It's quite nice and still available, but it's $200.

  These days there's a lot of very good options for PICs. A couple I've heard good things about are Wouter's WISP628, which is open so you can build one or a complete kit is $23.30 plus shipping (from Europe).

  At the more commercial end is the MELABS programmer which is around $90.

  I've never used either of these though, or anything but the picstart.

  Posted by: Oracle1729 on October 22, 2006 at 1:44 AM

• Windell, the 12F629 only has 5 output pins. I was talking about driving the 6 LEDs through multiplexing 3x2.

  Posted by: Oracle1729 on October 22, 2006 at 1:48 AM

• The question of which microcontroller to use is really an excellent one, and one without a clear winner. It's a lot like choosing a car; most have the same basic set of features, but you can pick the options. Do you want the sunroof (er, A/D)? The V8 engine (32-bit)? Do you want 8, 32 or 496 pins?

  To me, the most important thing in choosing a system is probably not the micro itself, but:
  (1) Availability of free and mature cross-platform development tools
  (2) Availability of inexpensive development and programming hardware
  (3) Range (size, power and cost) of the product family that can be programmed with those tools.

  With platforms like Arduino, PIC, AVR, and the Make controller, as well as excellent options from TI, Freescale, Analog Devices and others, the choices can indeed be difficult to evaluate. Without going back to look, I can recall articles in Make and Craft that described projects based on the first four of those systems. Perhaps the editors of Make, in a future issue, will bless us with a comparative review of these systems for those of us that don't want to support several separate platforms. =)

  Posted by: Windell_Oskay on October 22, 2006 at 1:54 AM

• Oracle1729,
  According to the family description for the PIC12F629, there are "6 I/O pins with individual direction control." I thought that that meant that you could set it up with six outputs. However, looking at the datasheet (4.8 MB PDF), it becomes clear that you're right: only five of those can be used for output. (I was tricked!)

  I suppose that my error here underscores how difficult it can be to pick a microcontroller!

  Posted by: Windell_Oskay on October 22, 2006 at 2:18 AM

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