Line Following Robot

It's a cold -30 degree Celsius P.A day off school, so Brodie and I decided to pick up a Weekend Project and start his Line Following Robot kit.

The Line Following Robot is a DIY kit that once complete, follows a line. You achieve this buy assembling, soldering and troubleshooting through the schematics and some mechanical aspects. It works utilizing photosensors and LED's to determine where the dark line is, then counters its movement to stay on track.

This kit was his introduction to soldering and schematics, so we took some time discuss some safety tips about soldering irons and electrical components.

Saftey discussion

Soldering irons are hot! They often reach temperatures of 200-300 degree Celsius, so avoid touching any of the metal or placing on things that could burn or catch fire.

While it's best to use none toxic whenever possible, the solder and paste produce a smoke or fume. Avoid inhaling it by having an extraction fan, or what I always do is hold my breath and lightly blow as I solder a point.

Electrical components such as resistors, IC's, transistors and so on, may contain lead or other checmicals - so while working with them, avoid touching your face, rubbing your eyes or putting your hands in your mouth. Wash you hands immediately after you lab is complete, or you have your mid lab snack.

Getting started

Brodie began sorting the components as I pulled up the instructions. While the kit was nicely organized with resistor locations, the resistors were not labeled. This gave us an opportunity to discuss resistors and how we can identify their resistance by using the lines (bands) on them with a tool such as a band calculator found here:

  https://www.allaboutcircuits.com/tools/resistor-color-code-calculator/

Once we determined the values, we labeled them so we can quickly identify for installation.

With everything now sorted, we followed the schematic and resistor labeling on the PCB and began installing our components. When installing component leads, it's often helpful to bend the lead ends outward to help the component remain in place for soldering. 

When pushing components in, be sure to keep fingers clear of the leads. The are stiff, pointy and can easily peirce skin!

Brodie discovered pulling them after they were slightly inserted was easier that trying to push and avoided bending them.

Once you have a manageable amount of leads through, you can begin soldering them. Soldering requires paste to help displace oxygen, so Brodie used a paint brush to brush paste on to the back side come component leads.

Soldering is kind of tricky. It is also helpful to have a solder stand with alligator clips to hold your board, keeping both hands free for soldering. We worked together with Brodie working the soldering iron, while I fed the solder.

We washed up and had some lunch while observing what we just assembled.

It wasn't all smooth sailing. The right side top LED which would help tune it wasn't working. It turns out, the board point had peeled off the PCB. This could be a defect, or we applied heat for too long on this particular point. To fix it, we used a cut lead piece to jump points and get it working.

To tune the photosensors we propped the wheels up and centered the front bolt on the black line, and watched how the LED's reacted as we moved side to side. We used a screw driver to adjust the potentiometers until the reaction looked balanced and less erratic.

We noticed the one the one photosensors was not level with the other, so we hit it with the soldering iron to lower it and got much more consistent responses from both photosensors.

We also played with shielding the LED's from the photo sensors to see if it improves our robots movements.

While doing so we discovered that electrical tape was the same width as our printed track included within our kit. That really changed things for us.

Once it was going, Jamie joined us to discuss what was happening and how it worked. 

We played with a few more ideas for courses to do for another day.

Here is an 8:40 video of it following a course we made. Which way will it go?

Thanks for reading!