# Dirt Cheap and Tiny Micro Controller



## halstaff (Nov 18, 2009)

In order to take my Skeleton Fish Prop - http://www.hauntforum.com/showthread.php?t=25364 to the next level, I needed to reduce the size of the controller for the servo. With Fritz's help, we were able to cut the already small 08 Picaxe down by almost half as well as bring the cost of the controller and chip under $4. It now will fit inside a film canister. It also allowed me to animate my $20 prop challenge entry and still meet the cost limit.
After several revisions, this is the final result -



It includes a download circuit and 2 headers. I plan to connect a PIR to trigger the board to one and then add either a motor or servo to the other one.


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## HalloweenRick (Nov 25, 2005)

That's amazing! How do you power the board?


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## halstaff (Nov 18, 2009)

I'm using a regulated 5V wall wart that I got from Electronic Goldmine for .79 each on their Deal of the Day. I wish I could have ordered more but the limit was 10. Now they're out of stock.


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## Mr_Chicken (Nov 26, 2008)

I see your fish, but, in general terms, what does it do and how do you use it?


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## halstaff (Nov 18, 2009)

Well I guess the fish doesn't do much, just flip around on the line so that it looks alive. I guess it's subtle but since this part of my haunt is for my parties and people are there for awhile, I like having some props that don't just jump right out at you.
I have a pirate fishing in the jacuzzi and he's just caught the fish. I'm planning an adding another one that he's already caught that also is animated.


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## Mr_Chicken (Nov 26, 2008)

Sorry, not the fish, the controller. I do dig the fish, I'm just trying to grasp what the controller does.


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## halstaff (Nov 18, 2009)

Sorry I misunderstood your question. I tend to take things to literally. Just ask my wife!
The controller is what runs the servo that makes the fish move. You can't just plug a servo into a power supply like you can a regular motor. You program the chip with a free editor and that sends the commands to the servo. With 2 header pins, I can control 2 servos or use one of the header pins and connect a trigger to it. I have some props being animated with servos that run continuously, like the fish, so I only use one header. However, I like to have some of them triggered when someone approaches, they run for 20 seconds or so, shut off and wait for 60 seconds or so before they can be started again. In that case, you'll need 2 headers. 
This controller was specially designed for applications that require a very small controller or where you want a VERY cheap controller. I used this controller for my $20 prop entry so that I could meet the cost limit. If I need more than the 2 headers because I'm controlling more servos or an audio device or lights, I use Fritz's Very Low Cost controller http://www.ipprofessional.com.au/VLC%20Servo%20Controller.pdf which also utilizes the 08 Picaxe but has the ability to control 4 devices.
You could also use this to control a wiper or vent motor with the addition of a couple of components. See my thread here - http://www.hauntforum.com/showthread.php?t=25829
Please feel free to ask any questions and I'll be happy to try and clear up any confusion.


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## RoxyBlue (Oct 6, 2008)

You and Fritz have done something very impressive (at least to me)


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## halstaff (Nov 18, 2009)

Here's the schematic for those that expressed interest -



Really a very simple circuit.


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## halstaff (Nov 18, 2009)

Here's a picture of the finished micro controllers. They each have a download header and 2 output headers. I'll be using one for a trigger and the other to run a servo or motor.



I played around with several different layouts and could make them a little smaller if the need ever arose.


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## Frighteners Entertainment (Jan 24, 2006)

very cool.


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## niblique71 (Dec 2, 2009)

Frighteners Entertainment said:


> very cool.


Nah... that SUPER COOL!!!


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## Frighteners Entertainment (Jan 24, 2006)

I stand corrected! lol


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## Otaku (Dec 3, 2004)

Well, I have no excuse now. Looks like I'm gonna have to find a reason to build a few of these. Thanks, Steve, for the cool schematic - very easy to read.


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## halstaff (Nov 18, 2009)

Thank you but I am still but a grasshopper learning at the feet of my teachers, especially Master Otaku and Master Fritz!


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## pshort (May 6, 2008)

FWIW, I've now got a PCB design that would be suitable for home-etching. It's very similar to halstaff's design (at the schematic level), except it has two more I/O connectors to bring out the unused PICAXE pins. The board is 0.8" x 1.0", using physically smaller resistors than halstaff's design.

If there is any interest, I can upload a pdf file that could be printed out and transferred to a PCB for etching.


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## halstaff (Nov 18, 2009)

pshort said:


> FWIW, I've now got a PCB design that would be suitable for home-etching. It's very similar to halstaff's design (at the schematic level), except it has two more I/O connectors to bring out the unused PICAXE pins. The board is 0.8" x 1.0", using physically smaller resistors than halstaff's design.
> 
> If there is any interest, I can upload a pdf file that could be printed out and transferred to a PCB for etching.


I would like a copy of the file. I've never tried to etch my own board but am interested in learning how to do it. I guess that's something else I need to add to my to do list.


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## JeffHaas (Sep 7, 2010)

This would be a good idea for a group buy - put a bunch of copies of the PCB into one of those inexpensive board-making services. It might be possible to get the cost way, way down.


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## Otaku (Dec 3, 2004)

Wonder if Jeff at SCB would like to quote? He can easily do that board.


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## fritz42_male (May 5, 2009)

Nice! Can I get a copy please -preferably in the format of the software you used to draw it.


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## pshort (May 6, 2008)

Here is the pdf file. Page 3 is the mirrored image that you will need if you are using the toner transfer method. There is a video in the "How-To's" section of the doityourselfchristmas.com forum that shows a method for home-etching PCBs, and there are undoubtedly lots of other sites on the web.

I think that it would be a good idea to wait and see if there are any critiques or suggestions before etching this board. One thing that might be an issue is that there are a few places in the design where the clearance between adjacent copper areas is .010". I've not had a problem with this in the past, but ymmv.

Fritz - I've sent you a pm.


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## halstaff (Nov 18, 2009)

Here's the layout of the circuit -



I hope this is my final design modification. It uses the Radio Shack printed circuit board (276-150) cut in half and with the sides trimmed off. I use a Dremel with a cutoff wheel. It has a download header and utilizes 3 of the output headers which will allow a trigger and 2 additional connections for servos, motors, etc.


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## hpropman (Jul 27, 2008)

Nicely done gentleman! I will have to make some of those boards I might also be interested in a group buy. I also have someone that might be able to make and sell the boards on their website for us. I will ask him.


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## mickkell (Jan 16, 2009)

Oh that would be nice,I'd like to buy some of those.
Let me know Please.


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## pshort (May 6, 2008)

I think that your best bet would be to use halstaff's approach. The board that he uses is available at Radio Shack.


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