Synopsis: Inexpensive introduction to "smart" technology by using infrared light for guidance. All that is required to complete this kit are basic soldering skills and two AA batteries. The only issue I have with this kit is the wheels do not always begin turning when they should (see troubleshooting).
I recently received a D2-3 Tracking & Obstacle Avoidance Smart Car DIY Kit from ICStation. The kit arrived nicely packaged to avoid the bumps and bruises one might expect when receiving items in the mail from China.
When I opened the package and I found the Printed Circuit Board (PCB), two motors, battery holder, parts package, and the instructions(pics 2, 3 & 4 above). .
Hmm, the included instructions were going to be a little bit of an issue for me - they are written in Chinese and of all the languages I know (one) it's not Chinese. These is a tiny bit of English in the instructions, the parts list does include the PCB location (ie: R2,R3,R4,R5) and the values (ie: 5.1K) for the components. I maybe able to assemble the kit with just this information, but I currently have nothing to explain the functionality or programming for the kit.
Well, let's get started and see how far we get!
ICStation, in appreciation for this Instructable, has provided the following discount for my fellow Instructable users.
15% off any item*, use code "gr8ics" during checkout
*one discount per user, maximum discount $300.00, expiration date 3-31-2017
Gee, I've never had a discount code created for me before!
Step 1: Assembly (resistors, Capacitors, Trim Pots)
Once I took closer look at the PCB I realized that assembly shouldn't be an issue. The board is extremely well labeled. The component locations are marked as you'd expect, but what's very helpful is the value for each component is also marked on the board (see pic 1).
The kit comes with carbon film resistors (see pic 2) which you may not be familiar with. These are those blue resistors you try to avoid because its harder to read their color bands to determine their value. Or maybe that's just me and my old eyes. Anyway, you determine the value of a carbon film resistor the same as you would a more typical carbon composition resistor (the tan colored ones), by looking at the color bands. Just set your resistor calculator to five (5) bands instead of four (4). If you haven't downloaded a resistor calculator yet, I'd recommend doing so. There are a ton of free resistor calcs out there, I use one from MoyerElectronics on my Windows PC, look for the "free software" tab on their site. And I use the one included in Electronic Tool Box Pro ( by Marcus Roskosch) on my iPad, an app I highly recommend with over 40 different tools and reference sections in one place.
The assembly order below is laid out to avoid some "gotchas" I found while assembling mine. For instance, you'll want to solder the motor wiring to the board and motors prior to mounting the motors. Good luck wiring the motors when they are already mounted!
The fixed resistors supplied with this kit are: (pics 3 thru 6 above should help identify the correct resistors)
# of.....Value............Color Bands.................................PCB Location
(5).....10K............Brown, Black, Black, Red.................R11, R14, R17, R20, R22
(4).....5.2K...........Green, Brown, Black, Brown............R2, R3, R4, R5 (note: the instructions and PCB identify these as 5.1K resistors)
(4).....1K..............Brown, Black, Black, Brown.............R6, R7, R8, R9
(4).....510 Ohm...Green, Red, Black, Black.................R12, R15, R18, R21
Identify and install the fixed resistors at this time. NOTE: (see pic 7) There are four 10k resistors (R2,R3,R4&R5) that share a common ground path. The solder pads on the PCB for those should connect to each other (the ground legs only). This is true for the common ground shared by R20 & R15 as well.
The variable trimmer resistors supplied with this kit are: (pic 8 above)
# of.....Value.....PCB Board Location
(4)......103.........R10, R13, R16, R19
Identify and install the variable trim resistors at this time.
Note: apply just enough pressure to ensure the legs of these trim resistors "pop" into place and all three legs are protruding through the PCB for soldering.
The capacitors supplied with this kit are:
# of....Value.....Type.............PCB Location
(3)......104........ceramic........C2, C4, C5 (pic 9 above)
(1)......47uF......electrolytic...C1 (pic 10 above) NOTE that polarity matters (positive and negative) with electrolytic capacitors)
Identify and install the capacitors at this time.
At this point your board, with the above components installed, should look like picture 11 above.
Step 2: Assembly Continued (Transistors,switches,carriers,header Pins)
The Transistors supplied with this kit are: (pic 1)
# of.....Value..........IC Board Location
2.........8850...........Q1 & Q2
Identify and install the transistors now. Note: the graphic on the PCB shows the correct orientation that the transistors should be installed in (match the flat side)
There are two switches supplied with this kit, one will be used for power ON and OFF. The other as a mode selector for tracking or avoidance. There's a quick PDF file (pic 3) that explains how a single pole, double-throw switch (like these) function.
Install the two switches at this time.
Next I installed the two Integrated Circuit (IC) Chip carriers (pic 5) Note: You MUST pay attention to the small indent you will find at one end of each carrier. These carriers need to be installed with that indent matching the graphic on the PCB.
The Header Pins (pic 6) were installed next. You will need two rows of eight pins and one row of four. Install those so that that longer section of each pin is facing up.
With these installations completed your board should look like pic 7 above.
Step 3: Assembly Continued (LEDs, IR Tx, IR Rx)
It's time to install the LEDs! This kit contains:
(2) Red LEDs
(4) IR (Infrared) LEDs - transmit (TX) infrared light (two installed on top, two installed on bottom of PCB)
(4) IR Photodiodes - receive (RX) infrared light (two installed on top, two installed on bottom of PCB)
NOTE: All LEDs are polarized, meaning that positive and negative matters! The LED graphic symbol on the PCB is your guide for installing the LEDs correctly (see pics 1, 2 & 3).
Let's start with the easy ones, the Red LEDs. After checking pic 3, install those at D1 & D2
Next install two (2) IR LEDs (Tx) at D5 & D6 and two (2) IR Photodiodes (Rx) at D8 & D10. When installing these DO NOT mount them flush to the board. Keep them raised of the board at least 1/8th of an inch to allow them to be bent into their forward facing position. (see pic 4)
After those LEDs are installed, install the "caster". That's the large bolt that goes through the hole at the front of the board. Place the screw in from the top of the board, secure it with the nut, then screw the nut with the rounded over top onto the end of the screw. Doing this now makes installing the rest of the LEDs a little easier.
With the caster in place install the other two (2) IR LEDs (Tx) at D3 & D4 and two (2) IR Photo Diode Sensors (Rx) at D7 & D9. BIG TIME NOTE: these Tx and Rx LEDs are installed from the bottom of the PCB and should extend down from the board to be about an 1/8th of an inch from touching the surface. (see pic 4)
Your PCB should now look like pic 4 above.
Step 4: Assembly Continued (battery Holder, Motors - Wiring & Mounting, Wheels)
Install the battery holder (see pic 1) at this time. Solder the red (positive) wire to 3v + and the black (negative) wire to 3v on the PCB - (see pic 2).
Wiring the two (2) motors with their attached gearboxes attached (see pic 3). These will be installed with the drive shaft facing out. NOTE: DO NOT mount these exactly where the PCB board graphic indicates. You'll want to mount them slightly forward to avoid wheel rub (see pic 4).
To begin, cut the two wires included in the kit in half, strip 1/16th of an inch or so off the newly cut ends, solder one end of each wire to each contact on both motors (see pic 5).
Now, before soldering the motor wires to the PCB we need to determine which wire goes where. The PCB has two locations, with two holes each, marked MG1 & MG2 (motor 1 & motor 2). We are going to use a AA battery and the shape of the soldering tab on the back of the board to determine the correct wires.
Hold one wire from a motor to the positive end of a AA battery, hold the other wire from that motor to the negative end of the battery, note which way the drive shaft is moving. You need to determine if the drive shaft, when the motor is mounted, will be moving in the forward direction. If it is not, switch the positive and negative wires on the battery. Once you have determined the drive shaft is moving in the correct direction note which wire is on the positive end of the battery. That will be your positive wire for the PCB and should be soldered to the square solder pad for that motor (see pic 6).
One last note, if you didn't already, trim the leads from the On / Off switch so the motor isn't held up by those.
With the motors wired they can now be mounted to the PCB - remember, slightly forward (pic 4).
Time for some wheels. Each wheel is made up of two parts, a plastic wheel and a rubber O-ring (see pic 7). Check each wheel for any left over molding material in the slot the O-ring will sit in (see pic 8). Clean out any you may find with a small file. This step allows the O-ring to fit on the wheel without any bumps in it.
With the wheel cleaned up, slip the O-ring into place around the wheel (see pic 9). Using one small screw per wheel attach them to the drive shafts (see pic 10).
Pic 10 shows the completed PCB up to this point.
Step 5: Assembly Continued (IC Chip Installation)
Remember those IC chip holders we installed way back when (see pic 1), now it's time to install the chips into them. Let's be very careful and gentle while we do this.
These chips need to; 1. Go into the correct holder, 2. Go into the holder in the correct direction (see pic 2)
When we installed the chip holders we had to pay attention to the indent in the case of the holder as well as the indent on the PCB graphic, making sure those indents lined up.
The same holds true for the chips themselves. There is an indent at one end of each chip's case, guess what that indent needs to line up with. You smart! Yes, the indent in the holder and the indent in the chip must be at the same end. (see pic 2)
Prior to installing the chips look carefully at all of the pins, are they straight and lined up with each other? Then place the chip on it's holder (in the correct direction) and make sure all of the pins are correctly positioned to be inserted into the holder. Gently press the chip into it's holder - watching those pins closely as you do. Make sure those pins are going into the holder and not just being bent out of the way.
Picture 3 above shows the completed installation of the chips.
That's it folks! Assembly is completed.
Step 6: Test Drive
Time for a test drive. Grab a sheet of white paper, or white something you can hold in front of the forward facing (avoidance) LEDs.
NOTE: Normal light (light bulbs, sunshine, etc.) will also be picked up by the photodiodes in this kit, testing and adjustments should be made in an environment where the lighting is consistent. For instance, not in a room were sunshine or a light will significantly change the amount of light being received by the photodiodes as the car is in motion.
Push the power switch to the OFF position and the MODE switch to avoidance (see pic 1).
Adjust all of the variable trimmers to their center position (see pic 2).
While holding the car up and off of any surfaces, cause those wheels should start turning, push the power switch to the ON position. (it can take up to five (5) seconds or so before the car responds)
Use the white paper to test the avoidance LEDs by holding the paper in front of one set of LEDs at a time. The car should respond by stopping one wheel while maintaining power to the other wheel (which will turn the car to avoid the obstacle).
Move the MODE switch to tracking and test those LEDs in the same manner.
If the car is not responding correctly at this time please see the troubleshooting step.
To adjust the sensitivity (range) of the LEDs use the variable trimmers for the MODE you are in (see pic 2).
A good starting point is to turn the variable trimmers for until the red LED lights up, then back off the trimmer until the LED just goes out (maybe even flickers a little).
Understanding how the car responds to the adjustments made to the variable trimmers is a matter of play time. The more you play, the more you will understand. If things get out of control simply return the variable trimmers to their center positions and play some more.
Good luck and thank you for reading this Instructable. As always if you find any errors or omissions please do not be shy about letting me know. I'd rather fix an error than let it live for eternity on the internet!
There are two additional steps in this Instructable, troubleshooting and definitions should you require them.
Step 7: Troubleshooting
1. Car not responding correctly:
a. Are the IR emitters working? That can be hard to tell with infrared light being invisible to the human eye and all. However, infrared light can be seen by most cameras, including your smart phone's camera. I have an iPad 2, iPad Pro and iPhone 6 Plus that I can use to see the infrared light. BUT, I can only see it in the rear facing (selfie) cameras on all three devices, it is not visible in the forward facing cameras.
Go to a dark location, and use your camera to look at the IR emitters. You should see a faint violet/purple color in the emitter if it's working. (see pic 2)
b. Are the Photodiodes working? You can find out with a flash light, or other bright source of light, even a lightbulb. Shine the flashlight at one photodiode, any reaction? Put the car in avoidance mode (mode switch to the right), With the front of the car facing away from you, turn the trimmers for avoidance mode (the two outside trimmers) all the way counterclockwise. PS: using a flashlight is a fun way to "drive" the car
2. Wheel(s) won't turn on their own, meaning you have to turn the wheel a little by hand to get it started. This appears to be a common issue with this kit. I did two things to solve this issue;
a. opened the crankcases and lubricated with a spray silicone
b. removed the 1k resistors at R6 & R7 and replaced them with 510 ohm resistors
After the above two items where done the reliability of the wheels turning on their own, when they should, went up to about 95%.
3. Rubbing on Wall, runs along a wall or the side of an obstacle but stays in physical contact with the wall or object, actually rubbing it's way along.
Adjust the forward facing (avoidance) LEDs so that they are not only pointing forward but a little to the side as well.
Step 8: Definitions (very Basic)
Capacitors (cap) - store and release electrical current
Header Pins - provide a dedicated path to a specific location (IE: each pin of an IC chip)
Integrated Circuit (IC) - (or chip) a single component containing a miniaturized set of electronic components and circuits. A single chip could contain millions, even billions of really, really, really, small components.
Infrared (IR) - invisible radiant energy, meaning - in this case - light we can not see. The light is there, but it is outside of the visible light spectrum the human eye can see
Infrared LED - (or IR emitter) emits infrared light when the correct voltage is applied
Light-emitting diode(LED) - emits light when the correct voltage is applied
Photodiodes - absorb light and produce current
Printed Circuit Board (PCB) - supports and connects electronic components
Resistors - limit/regulate the flow of current in a circuit
Transistors - amplify or switch current in a circuit
Variable Trimmer Resistors (potentiometers) - (or pot) an adjustable resistor