Resources for the book Robot Building for Beginners and Sandwich, the Line-Following Robot

Sandwich’s printed circuit board


This secret page is for owners of the book, Robot Building for Beginners. Thank you for buying the book.

Second Edition Errata

(If you have the original book, see first edition errata)

So far, I have not been informed of any errors in the Second Edition. Please email me if you discover any errors or unclear portions in the book.

Source Files

Sandwich Parts List

Excel file of Sandwich parts and prices PDF file of Sandwich parts and prices

Click either of the icons above for a complete list of parts and prices for Sandwich, along with an example supplier for most items. This list doesn’t include the price of tools or experiments from the book.

Sandwich Printed Circuit Board

File for Sandwich’s circuit board

Click the icon above for the printed circuit board layout for Sandwich. (For your private use only. Do not create more than 10 circuit boards a year.) You can obtain the free application that reads the file. Of course you can modify the circuit if you desire.

You can save a lot of money by buying a board from Solarbotics (part #SandPCB) for $12. This board has silkscreened part numbers and part outlines, as well as a solder mask, making it easier for beginners.

Alternatively, you can etch and drill your own PCB at home. Make sure the board prints to exactly 3.8 inches by 2.5 inches or the parts won’t fit.

In any case, there are detailed instructions on stuffing the circuit board with electronic parts.

If you decide to etch your own, you only need to etch a single side: the bottom layer. You will then need to use wire or leftover component leads to make three connections, marked ①, ②, and ③ in the photo below.

Blue single sided PCB with several jumper wires instead of second layer traces

Blue single sided PCB with several jumper wires instead of second layer traces.

There are a few other optional wires that are used for test points (9V, GND, TP1, TP2). Loop them a little bit above the board (rather than flat) so that you can connect a test clip from a multimeter. Note that ③ is both a trace connection and also the test point for the second set of sensors.

The single-sided board doesn’t support the tiny six-pin onboard line-following switch Ⓐ. Instead, you'll need to use the four-pin connection Ⓑ to an off-board DPDT center-off switch.

Hsiang Neng HN-GH12-1324Y Motor Mounting Hole Template

Visio file of motor mounting template

Here’s the motor mounting hole layout for Sandwich’s motors. If you have Microsoft Visio it’s better to download the file, as the application will try to make sure the scaling is correct when it prints. Otherwise, copy the image below or print it using your browser.

Motor mounting template


Because LEGO kits change regularly, here’s a more reliable source to obtain the specific LEGO pieces you want, at a low cost.

  1. Go to
  2. Click the Search tab (toward the top of the window).
  3. Under Containing Keyword, type “black technic axle”. Under Sort By, select “Description”.
  4. The search will find hundreds and hundreds of lots. Unfortunately, I can’t figure out a way to refine the search further. Specifying “3” or “6” to select the axle length reduces the search list to no items, so something is obviously wrong with their search engine at the present.
Sample Brinklink page with 3-length black axles
  1. You’re looking for axle size “3”. Size “6” is fine if you don’t mind cutting it in half. Frankly, because they’re so inexpensive, you might want as well buy a variety of lengths from the same seller (within their shop, the category is usually “Technic, axle”). In any case, buy enough axles so you have extras in case something goes wrong.
  2. Bricklink is an auction site. The sellers are all independent people across the world. The seller lists how many they have of the item, where the seller is located, where they’re willing to ship, and the minimum total order $$$. You should click on the seller’s name to see what payments they accept (under the Store Policies tab). Click on the number following the seller’s name to see what other buyers think about the seller. I haven’t had a bad transaction myself, but I suppose it happens, so buyer beware.
  3. While you’re at it, find the tires for Sandwich by searching for “VR”. You should be able to find “Tyre 49.6 x 28 VR” and “Wheel 49.6 x 28 VR”. Some sell the tire and wheel together.