Bargain UNO Bot project

06/08/2016
Here's an inexpensive robot kit we found on ebay or Amazon for around $40

Search Amazon or ebay using the phrase "Avoidance Tracking Motor Smart Robot Car Chassis Kit Speed Encoder" and you'll come up with results. (choose the 2WD kits for just under $40)
(Edit: on 10/20/17 found kit on ebay for < $20)

This is a good collection of parts to get you started with a simple avoidance tracking robot.

It is NOWHERE NEAR A COMPLETE KIT and comes with only the briefest of instructions for attaching the motors and wheels.
(in chineese of course so most of us must rely on the pictures alone)

That being said, this could be the basis for "standard starting package" that a club or group could get, enabling

everyone to start from the same base parts list and see what could be built from it.

Perhaps a rule that limited additional parts expense to that of the original kit (around $40) could be established

as a guideline. Simple tasks could be proposed like following a wall or line or exiting a room or maze.

A few things to note:

1. You CANNOT get away without some soldering or drilling. To do more than just basic moving about you'll need

to add a few more sensors and that will require some additional fabrication for mounting them.

You could make most of the necessary connections if you had a bunch of "dupont" style jumper wires with

femail pin connectors on each end.

2. The "kit" comes with encoder disks that mount to the motor shafts but NO SENSORS to read them.

I happen to have a bunch that fit this project (after fabricating a retaining bracket)

3. Using 4 AA batteries as a power supply is just barely sufficient to run the motors and the Arduino and only

with a very fresh set of batteries. I'd suggest going with 6 or more AA cells or even better

an 11.7v LiPo battery pack (these can be found for around $12 on ebay. another $12 or so for a charger)

More details to be added soon. for now just download the attached powerpoint slideshow.

7/4/16 Update:

Not being happy with the mouting parts for the servo motor that came with the kit I decided to design my own

mount for the servo and ping sensor. I used an old plastic DVD case. It was easy to cut with scissors or a razor knife.

This assembly is just pressed into the existing holes in the chassis (no screws or glue, but it seems to stay put).

There is a connector on the shield labled URF01 that appears to be designed for the ping sensor.

They connect to pins A0 & A1 along with VCC and GND. I made a connector and added a pushbutton between

the GND pin and the A0 pin (Trig signal on the sensor) I'm assuming I'll not need to read the pushbutton while

distance measurment is happening so it's pretty safe to share the I/O pin as they will get used up pretty fast.

I found a small speaker, looks like it's from a phone, and made another connector using pin#8. Now the Bot can

beep at different tones perhaps to signal some sort of status or error situation. Right now it beeps when the

button is pressed.

7/5/16 Update:

Had a Major OOPs tonight!

I decided to add another connector so I could replace the 4 AA battery box with my 11.1v LiPo Battery.

When I plugged in the LiPo cell and switched it on the servo went nuts and the right wheel went to full speed.

What I learned is the the big connector on the lower left side of the sensor shield labeled GND & VCC is NOT

connected to VIN (unregulated 6-12v input) but instead connected to the regulated 5V supply (VCC, like it says, duh..).

This mistake toasted my UNO and the PING sensor. I have spares of both so progress will continue but I'm not feeling too brilliant tonight.

Apparently the 6V from the 4 AA battery pack will not harm the electronics but anything greater is not good.

8/13/16 Update:

Working on programming mostly now. When driving the wheels I found it's good to send a short burst of

power to the wheel motors (maybe 10-50ms of full power) to get the motors started. Do the same

(maybe a bit shorter in duration, like 10-20ms) but in the reverse direction to stop the motion and prevent drifting.

I Added a shot of my new LiPo battery and the clip I fabricated to hold it in place. The clip is made from a scrap

piece of plastic that I heated with a heat gun and bent in the "S" shape.

I also uploaded a schematic of how things are connected so far.

8/14/16 Update:

Added a connector for an HC06 Bluetooth Module then ported code from another similar robot project.

Now pressing the select button 5x puts the bot in Bluetooth demo mode and it can be driven around like an

RC Car using the Joystick bluetooth Commander app on my phone. Updated the schematic with this addition.

NOTE: if you add this you must remove the bluetooth module before programming the Uno since it shares the

only serial port.

8/25/16 Update:

Added some VERY SIMPLE code to get folks started with the UNO Bot. (see UnoBotTest.zip attached below)

Make sure the defined HBLOCK_A1 - HBLOCK_A4 values match the signal pins going to your motor driver inputs.

(see UnoBot_Schematic.pdf)

8/29/16 Update:

Uploaded another version of the test code. (see UnoBotTest3.zip attached below)

This has some very simple routines to check the wheel encoder sensors.

Please note that this is simple test code just to get folks up and running with something to play with.

There's many better ways to do all of this stuff but I'm trying to keep things very simple.

Then menu options are different from the previous version especially option#3 which will now

run the wheels at FULL speed and only stopping when you select option #4.

(this is to allow you to maybe get a scope on the encoder signals and see what's going on)

Enjoy!

Note: To get a larger view of the images below, right click on the image and select "Open image in new tab", then select the new tab.

Download Link Details:

Bargain UNO BOT Kit.pptx Powerpoint showing assembly steps
UnoBot_Schematic.pdf How I wired my Bot.
UnoBotTest.zip Simple test code to get your bot wheels moving
UnoBotTest3.zip Expanded version of the test code with wheel encoder test routines.