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Free Line Following Robot Platform


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Just found out that Target has a really cool christmas giftcard this year. Between Target and Bestbuy, you can always get nice free stuff.
 
The "Draw and Go" Giftcard at Target is a Line following robot, shaped like a bone car. post-44-0-10991300-1356828017_thumb.jpg

 

It has four LR44 batteries (two for 3v to the driver, two for 3v to the motors), two infrared transmit leds and receive leds, a few j3y smd transistors, two metal weights a unlabled 8 pin soic chip (Comparator? MCU?) and two independently geared and controlled motors in a single package.

 

This thing is perfect as a little robot car platform. Or get two or four and bolt them together to make a bigger car. (To get it open, you need to make a hole on the three bottom pegs that cover the screws as you can see in the picture. I stabbed them with a small jewelers screwdriver). You can easily replace the controller with a msp430.

 

And the kicker, it's free. Well, you need to put at least five dollars on the gift card, but you can use it right away.  I had to buy some groceries anyway. No limits.

 

They should have them by the registers, or the greeting card aisle. If anything you can always ask them were they are. These are christmas related, so once they run out, they won't restock them.

 

In the last few years, Target has had glowing led cards (wii, and generally very often christmas ones), led and sound (xbox), usb flash drives in credit card shape (speed racer), digital camera and mp3 players (50 dollar gift card required), RC cars, legos, all sorts.

Bestbuy has had some of the same, including usb color changing leds, and usb hubs, and you only had to put 1 cent on them. None this year though.

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Thanks Abe! 

 

I ordered 4 online with only $1.95 shipping.  With my big truck, it probably would have taken more than that in gas to get to Target.

 

Should've ordered more and made it a group buy. ;)

 

Or maybe I should've waited to post the link since my wife works there and gets discounts (up to 15%) on things she buys: she once paid $12.75 + tax for a $15 Verizon pre-paid card.

But she's sleeping now since she has to be in store at 4am (it's 8:55 pm here now) so I can't prod more information out of her as to whether or not that is possible.

 

I'll look into it, if people are interested... but then there's the cost of shipping from here to there to consider too so I don't know if the discount would be enough to offset shipping....

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Best method. You can buy regular target giftcards... with Target giftcards. Only exception printed on the card is buying Prepaid Creditcards or prepaid cards (i.e. cell phone top off cards). Today I got 4 of the Draw and Go's, using a single fiver (buy one with the five, buy the second with the first, rinse lather repeat) then used the last card to buy some green tea. Bestbuy is easier, since the minimum is 1 cent.

 

 

Honestly though, it's worth it just for the batteries alone. Also, Christmas clearance should go to 60 or 75% tomorrow sunday. So even more reason to get one.

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Should've ordered more and made it a group buy. ;-)

 

Or maybe I should've waited to post the link since my wife works there and gets discounts (up to 15%) on things she buys: she once paid $12.75 + tax for a $15 Verizon pre-paid card.

But she's sleeping now since she has to be in store at 4am (it's 8:55 pm here now) so I can't prod more information out of her as to whether or not that is possible.

 

I'll look into it, if people are interested... but then there's the cost of shipping from here to there to consider too so I don't know if the discount would be enough to offset shipping....

These are regular target giftcards, not exactly regular products, I doubt the discount applies on the giftcards. 

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So I decided to ignore sleep. Drew out the schematic of the board.

 

post-44-0-12570100-1356963676_thumb.png

 

And a mostly accurate representation of the physical board (the Rev 1.2 board I have is single layer, no jumpers/bottom layer. Really more for neatness and readability.) It is nicely split with all the right side parts on the the right side and left on the left side.

 

post-44-0-21491400-1356963667_thumb.png

 

Still no idea what the 8 pin chip is, but it has two unused free pins.

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Any markings on the chip? Power pins match PIC, MSP430G22x0 and maybe ATtiny too.

 

Can't be a MSP430 in there already, but it looks like MSP430G2230 could work with a few mods. The motor drive is on test/reset so that would have to change.

Nope, no markings. I picked up a few more (with some free dirty looks too) but I figure they will all be rev 1.2 boards because I got them from the same location. Maybe the chip will be marked in one one or two.

 

If anything, can always cut the trace and run a small jumper wire.

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It doesn't match the Attiny series very well, VCC and GND are diagonal on the Attinys rather than both at one end. It (attinyizing) could be done with liberal trace cutting, though it'd be easier to use something that matched up better, or to simply have a floating brainboard that jumper wired to the original chip's pads. Or a MSP as said before. Programming an Attiny in place on that board with be a pain too, no single/double pin JTAG, it's ISP/ICSP or forget it.

 

I'd guess it's probably either custom, or a couple comparitors.

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Yea it's weird. I still don't understand how the photosensor diode works (Assuming R3 is a weak 30k pull-up connected to Q1's base, the photosensor anode is connected to ground while is cathode is connected [reversed bias??], IC Pin 4 has a pull-up to Q1's collector, so when the photosensor conducts, the base is pulled down, q1 stops conducting, so the IC reads logic high, when the photosensor stops conducting, the weak pullup enables the transistor so the IC reads logic low.) (Okay, maybe I understand it).

 

I need to first measure the voltage drop on the photosensor, then ditch it, so I can directly drive q1/q2. If I can do that, how the rest of the circuit works is easy enough. 

 

I'm wondering if toggling pin 3 will toggle pin 5 as well.

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